Production Note Cornell University Library pro- duced this volume to replace the irreparably deteriorated original. It was scanned using Xerox soft- ware and equipment at 600 dots per inch resolution and com- pressed prior to storage using CCITT Group 4 compression. The digital data were used to create Cornell's replacement volume on paper that meets the ANSI Stand- ard Z39.48-1984. The production of this volume was supported in part by the Commission on Pres- ervation and Access and the Xerox Corporation. Digital file copy- right by Cornell University Library 1991.CORNELL UNIVERSITY LIBRARY GIFT OF Mrs. Welles G. Catlin ENGINEERINGWorks of Prof. Robt. H. Thurston, MATERIALS OF ENGINEERING. A work designed for Engineers, Students, and Artisans in wood, metal, and stone. Also as a TEXT-BOOK in Scientific Schools, showing the properties of the subjects treated. By Prof. R. H. Thurston. Well illustrated. In three parts. Part I. THE NON-METALLIC MATERIALS OF ENGINEERING AND METALLURGY, With Measures in British and Metric Units, and Metric and Reduction Tables. 8vo, cloth, $3 00 PartH. IRON AND STEEL. The Ores of Iron; Methods of Reduction ; Manufacturing Processes; Chemical and Physical Properties of Iron and Steel; Strength, Ductility, Elasticity and Resistance; Effects of Time, Temperature, and repeated Strain; Methods of Test; Specifications. 8vo, cloth, 4 00 Part m. THE ALLOYS AND THEIR CONSTITUENTS. Copper, Tin, Zinc, Lead, Antimony, Bismuth, Nickel, Aluminum, etc.; The Brasses, Bronzes ; Copper-Tin-Zinc Alloys ; Other Valuable Alloys ; Their Qualities, Peculiar Characteristics; Uses and Special Adaptations; Thurston’s “Maximum Alloys”; Strength of the Alloys as Commonly Made, and as Affected by Special Conditions ; The Mechanical Treatment of Metals.........................8vo, cloth, 3 00 *' As intimated above, this work, which is soon to be completed, will form one of the most complete as well as modern treatises upon the Materials used in all sorts of Building Construc- tions. as a whole it forms a very comprehensive and practical book for Engineers, both Civil and Mechanical.”—American Machinist. “ We regard this as a most useful book for reference in its departments; it should be in every Engineer’s library.”—Mechanical Engineer. MATERIALS OF CONSTRUCTION. A Text-book for Technical Schools, condensed from Thurston’s “ Materials of Engi- neering.” Treating of Iron and Steel, their ores, manufacture, properties and uses; the useful metals and their alloys, especially brasses and bronzes, and their “ kal- chords ”; strength, ductility, resistance, and elasticity, effects of prolonged and oft- repeated loading, crystallization and granulation; peculiar metals; Thurston’s “maxi- mum alloys ” ; stone ; timber; preservative processes, etc., etc. By Prof. Robt. H. Thurston, of Cornell University. Many illustrations..Thick 8vo, cloth, 5 00 “ Prof. Thurston has rendered a great service to the profession by the publication of this throrough, yet comprehensive, text-book. . . . The book meets a long-felt want, and the well-known reputation of its author is a sufficient guarantee for its accuracy and thorough- ness. "—Building. TREATISE ON FRICTION AND LOST WORK IN MACHINERY AND MILL WORK. Containing an explanation of the Theory of Friction, and an account of the various Lubricants in general use, with a record of various experiments to deduce the laws of Friction and Lubricated Surfaces, etc. By Prof. Robt. H. Thurston. Copiously illustrated................................................8vo, cloth, 3 00 ‘‘It is not too high praise to say that the present treatise Is exhaustive and a complete review of the whole subject.”—American Engineer. STATIONARY STEAM-ENGINES. Especially adapted to Electric Lighting Purposes. Treating of the Development of Steam-engines—the principles of Construction and Economy, with description of Moderate Speed and High Speed Engines. By Prof. R. H. Thurston. 12mo, cloth, 1 50 “ This work must prove to be of great interest to both manufacturers and users of steam- engines.”— Builder and Wood-worker. DEVELOPMENT OF THE PHILOSOPHY OF THE STEAM ENGINE. An Historical Sketch. By Robert H. Thurston..............12mo, cloth, 75 CONVERSION TABLES Of the Metric and British or United States WEIGHTS AND MEASURES. With an Introduction by Robt. II. Thurston, LL.D., Dr. Eng......8vo, cloth, 1 00 A MANUAL OF STEAM BOILERS, THEIR DESIGN, CONSTRUC- TION, AND OPERATION. For Technical Schools and Engineers. By Prof. R. H. Thurston. Numerous illustrations. 686 pages...................................8vo, cloth, 6 00 STEAM-BOILER EXPLOSIONS IN THEORY AND IN PRACTICE. Containing Causes of—Preventives—Emergencies—Low Water—Consequences— Management—Safety—Incrustation—Experimental Investigations, etc., etc., etc. By R. H. Thurston, LL.D., Dr. Eng., Director of Sibley College, Cornell Univer- sity. With many illustrations............................12mo, cloth, 1 50 “Prof. Thurston has had exceptional facilities for investigating the Causes of Boiler Explosions, and throughout this work there will be found matter of peculiar interest to Practical men.” —American Machinist. BAND-BOOK OF ENGINE AND BOILER TRIALS. A Practical Work. By Robert H. Thurston. 8vo, cloth. In Press. . Will be Mailed and Prepaid on the receipt of the price. PUBLISHED AND FOR SALE BY -TOTTISr WILEY SONS,A HANDBOOK OF Engine and Boiler TRIALS, AND OF THE Indicator and Prony Brake. FOR ENGINEERS AND TECHNICAL SCHOOLS. BY R. H. THURSTON, M.A., LL.D., Dr.Eng’g ; Director of Sibley College, Cornell University ; Past President Am. Society Mechanical Engineers; Author of “Materials of Engineering,” “Friction and Lost Work,” “History of the Steam-engine,” “ Manual of Steam-boilers,” etc. etc. NEW YORK: JOHN WILEY AND SONS. 189c.Copyrignt, 1890, BY Robert H. Thurston. Drummond & Neu, Electrotypers, 1 to 7 Hague Street, New York. Ferris Bros., Printers, 326 Pearl Street, New York.PREFACE. This little treatise on methods of testing engines and boilers is an attempt to meet what has seemed to the Author a long- existing want. Hitherto, every engineer doing work of this kind has been compelled to do that work without a standard of reference, and the results of trials of engines and of boilers which have found their way into the record have been presented in such various ways as to be difficult of comparison, and such as to offer to the engineer desiring to do his work in an accepta- ble and permanently useful manner no generally accepted cri- terion. But the work of a committee of the American Society of Mechanical Engineers, of the German engineers, and of one or two individual and recognized authorities among experts, at later dates, has led to such a general concurrence among mem- bers of the profession that it is now possible to at least provi- sionally offer a system of testing both engines and steam-gener- ators that may be accepted as satisfactory. That this system will be steadily and constantly improved cannot be doubted, and the methods in vogue among the best practitioners to-day will not be precisely those in use among such experts a year hence ; but the processes now adopted most generally will probably only be modified in detail, and the im- provements will now mainly consist, it may be safely pre- sumed, in the application of the most recent and accurate methods of precise measurement, as customarily applied in laboratories, to the determination of the quantities sought in such trials. The main outline of the scheme of trials to-day will be the substantial representative of similar operations later. A time has thus arrived when it is possible to put in permanent iiiIV PREFACE. form, and to publish for general use, the schemes of trials which have just taken definite shape. This is what the Author has attempted to do in this treatise. It is proposed to present here those methods of trial of heat- engines which have become standard ; to exhibit the processes of their application ; to describe the best forms of apparatus used to date in conducting them and in securing the data sought; to illustrate their use and their various capabilities ; and, finally, to present examples of the reports made by distinguished engineers on important work of this character, and thus to give good exemplars of their form, and of the data and results deduced from them in the case of the better classes of machin- ery and apparatus. It is intended that the apparatus in com- mon use shall be described, as well as the method of its appli- cation to its purposes ; its capabilities in the direct or indirect procurement of data ; the processes of computation of the latter ; the method of arrangement and tabulation of results ; and the final compilation and report on the essential quantities which are required to give basis for the determination of the economy and efficiency, physical or commercial, of the machinery em- ployed for the development of power. The system of boiler-trial described is that proposed by the committee above referred to, and which has since become con- ventionally standard throughout the United States, and largely abroad. It is more complete and more satisfactory, in the opin- ion of the Author, than any other yet published, and seems to have been found sufficient to meet every ordinary requirement. The special precautions advised by the several experts on the committee are also quoted, and the forms of blanks and records found best adapted for use in such work are given. Some con- sideration is given to the methods of determining the character and value of the steam supplied by the boiler; and the forms of calorimeter generally used are described. It was shown by the results of a trial made by the Author for a committee of the American Institute, in 1871, that the best boilers, worked under ordinarily satisfactory conditions, give practically dry steam ; but the necessity is none the less imperative to make certain, at every important trial, that this is the case with the boilers under test. A trial made without such determination of the qualityPREFACE. V of the steam would, to-day, be regarded by the most expert among the profession as comparatively valueless. The text adhered to in this account of the standard boiler- trial is that of the committee, as published in the transactions of the society. References are given in all cases in which the subject is such as would justify the reader in looking up origi- nal sources of information. The chapter on the indicator is a brief and simple account of that wonderful instrument and its capabilities, as well as a description of the usual and best ways of handling it. No attempt has been made to elaborate to any great extent the study of the diagram; but the better forms of diagram, and those wrhich are most likely to be met with in the best, as well as those taken from some defective, engines, are illustrated. For further information upon this exhaustless subject, the reader will consult the special treatises on the steam-engine indicator, of which a number exist, each, from that of Porter, the first workmanlike presentation of the subject, up to the latest ex- tensive work published, having its own special field and its own peculiar characteristics. All give information of real value. It has been endeavored to give some idea of the shape and of the signification of the more usual and familiar forms of “ card,’' and to show just how they bear upon the adjustment, the pro- portions, and the working of the engine ; while singular and rare forms, which, however, so greatly interest every engineer, are generally left to be described by the writers of the special trea- tises on the indicator. In this respect, the published writings of several specialists of great experience and ability in the hand- ling of the instrument will be found peculiarly rich. In the chapter on the measurement and computations of the indicator diagram will be found a description of the methods usually considered best and most exact, and of the processes leading to the more important of the results attainable by the use of the instrument. These are mainly well known and stand- ard among the best practitioners ; but a few are of recent appli- cation and comparatively unknown, and are here for the first time introduced into a treatise of this kind. Such are the appli- cations of the chronograph, applied, probably for the first time, in the manner exhibited in the frontispiece, by Professor W. A.VI PREFACE. Anthony, and used for various purposes by a few engineers when seeking to obtain precise measurements of minute and rapid variations of engine-speed. The use of the timing-fork, employed for some years past in the work of the Author, is another novel and hitherto undescribed method of securing a record of the variations of velocity of parts of the engine, and one which promises to be of great value in investigations of the character described in illustration of its use in this chapter. The application of the Prony or dynamometric brake is still another no less important and rarely described process of securing what are now universally recognized as essential meas- urements in the determination of the real efficiency of the engine* The several best-known modern forms of brake are here de- scribed, and their theory and the mode of their application are given in sufficient detail, it is hoped, to enable any one to prop- erly apply them. The transmitting dynamometer is also often now used and finds its place in the text. Standard methods of engine-trial are as essential to the satisfactory work of the engineer as are standard boiler-trials. There exists no such precisely formulated standard for engine- as for boiler-trials ; but the text includes descriptions of such methods as are, in the opinion of the best authorities, likely to give, on the whole, most satisfactory, complete, and exact re- sults. The schemes of competitive trials as customarily con- ducted are presented, and examples of special methods and re- sults are given. The work is completed by the introduction of a series of valuable reports written by a number of the ablest jnembers of the profession as exemplars and models of most admirable summaries of data, and of conclusions derived from their study and from the computations made therefrom. One example of each of the most important classes of engine is studied in this manner ; and the series should enable any engineer unfamiliar with such work by earlier experience to secure results thoroughly satisfactory to himself and to his clients. All essential con- stants and tables are given in the Appendix, and should others be desired in special cases, they can be readily found—usually in the table-books which cover the desk of every engineer and every student of engineering.PREFACE. vii The Author has sought to compile a concise, accurate, and satisfactorily complete account of the apparatus and methods of the time, as familiar to the most experienced and accurate specialists. But even as the book is going through the press, new methods are being devised and old ones improved ; while new instruments are being invented and the familiar apparatus of physical measurements are being applied to new purposes. Only the careful watch of current periodical literature will enable the engineer, young or old, to keep fully up with the progress of the age; it is nevertheless hoped that this compi- lation may prove of service to many, both young and old, and may be found to include enough of the most modern and the best practice to enable its reader to attain, in his own work, satisfactory results both as to accuracy and completeness.CONTENTS CHAPTER I. OBJECTS SOUGHT IN TEST-TRIALS. ART. PAGE 1. The Purposes of Trials—Efficiencies of the Steam-engine—Terms de- fined, .................................................. . i 2. Specifications of Performance—Engine Duty—Boiler Power, . . 2 3. The Various Objects Sought in Detail,..........................5 4. The Maker and the Method of Trial, ...... 7 5. Character of Report demanded, . .............................8 6. Instruments needed, . 9 7. Methods of Application of Instruments,.........................9 8. Data needed and Computations required,.........................10 9. Trials to determine Economy,.......................................10 10. Steam-boiler Efficiencies, . . . ............................... 11. Efficiency of Heating Surface,...................................13 12. Effective Development of Heat, ..................................19 13. Efficient Utilization of Heat, ..................................23 14. Measurement of Power and Capacity—Actual Boiler Power, . . 27 15. Quantities measured—Results computed—Usual Values, ... 29 16. General System of Test-trial, ........ 33 17. Steam-boiler Trials, .......... 34 18. Steam-engine Trials, .......... 36 19. Engine and Boiler Trials, ...........................................36 20. Apparatus of Engine and Boiler Trials,...............................37 CHAPTER II. STEAM-BOILER TRIALS. 21. Purposes of Boiler-trials,............................................38 22. Test of Value of Fuel,...............................................39 23. Determination of Value of Boiler,....................................39 24. Evaporative Power of Fuels, . . . . , . . .39 25. Analysis of Fuels,....................................... 40 26. Efficiency and Economy of Fuel,......................................41 ixX CONTENTS. ART. PAGE 27. Relative Values of Boilers...............................42 28. Variation of Efficiency with Consumption of Fuel and Size of Grate, . 42 29. Relation of Area of Heating Surface to Economy, .... 43 30. Combined Power and Efficiency, ....... 43 31. Apparatus and Methods of Test,........................ . 43 32. Standard Test-trials,.......................................45 33. Instructions and Rules for Standard Method, ..... 46 34. Precautions—Blanks and Record, . . , . . . -55 35. Heating Power of Fuels, . . .......................61 36. Specific Heats—Stored Energy in Steam,......................71 37. Latent and Total Heats computed—Water required, . . . -73 38. Factors of Evaporation—Boiler Horse-power, . . . . . 74 39. Regnault’s Steam Tables and other Constants,.............75 CHAPTER III. RESULTS OF BOILER-TRIALS—APPARATUS. 40. Results of Test-trials—Illustrations,.......................76 41. Quality of Steam, .......... 84 42. Form of Barrel Calorimeter and Use,......................86 43. Theory of Calorimeters, . . 88 44. Records—Errors, .......... 94 45. The Coil Calorimeter, ......... 95 46. The Continuous Calorimeter,.................................98 47. Analysis of Gases—Form of Apparatus, ...... 105 48. Draught-gauges—Test-gauges, . . . . . . . .110 49. Sample Trial—Methods and Results,..........................113 CHAPTER IV. THE STEAM-ENGINE INDICATOR. 50. The Indicator and the Dynamometer,.........................128 51. Construction of Indicators, . .129 52. Essentials of a good Indicator, ...........................129 53. Forms of the Indicator, ......... 130 54. Standardization, ........................................ 142 55. Attachment of the Indicator—Indicator Motions, . . . . 159 56. Uses of the Indicator—Precautions.................. . . 179 CHAPTER V. INDICATOR DIAGRAMS INTERPRETED. 57. Indicator Diagrams.........................................182 58. Typical Diagram—Nomenclature, . . . . . . .182CONTENTS. XI ART. PAGE 59. Modified Forms,...............................................186 60. Interpretation of Diagrams,...................................189 61. Compound-engine Diagrams, . 194 62. Special Applications—Valve Adjustments,.......................203 63. Pump Diagrams—Air Pumps and Compressors, .... 204 64. Peculiar Forms of Diagram,..................................208 CHAPTER VI. MEASUREMENTS OF DIAGRAMS; COMPUTATIONS, APPARATUS, AND METHODS. 65. Apparatus and Methods of Measurement,.........................212 66. Measuring the Diagram,........................................212 67. Planimeters and their Use,...................... . . .219 68. Computing Power—Counters; Chronographs; Timing-forks, . . 223 69. Heat, Steam, and Water Consumption,...........................237 70. Curve-tracing—Hyperbolic Curves—Clearance,....................248 71. Cylinder-condensation and Leakage,............................253 CHAPTER VII. ENGINE FRICTION—DYNAMOMETERS-— THE PRONY BRAKE. 72. Engine Friction—Efficiency of the Machine,....................262 73. Indicated Power—Dynamometric Power,.....................262 74. Gross and Net Power—Transmitting Dynamometers, . . . 264 75. Calibrating the Transmission Dynamometer,.....................267 76. Prony’s Dynamometric Brake, ........ 269 77. Designing a Dynamometric Brake—Various Forms, .... 272 78. Data derived by Use of the Dynamometer,.......................282 CHAPTER VIII. STANDARD METHODS OF ENGINE TRIAL. 79. Standard Methods of Engine Trial,...........................285 80. Engine and Boiler Trials,.....................................287 81. Fitting up Engine for Trial—The Two Systems of Trial, . . . 294 82. Methods of Trial,.............................................296 83. The Farey and Donkin System,..................................298 84. Trials of Gas-engines,........................................303 85. Simple and Binary Vapor Engine Trials,........................304 86. Special Conditions of Gas and Vapor Engine Trials, .... 305 87. The Scheme of the Trial,......................................309 88. Competitive Engine-trials—Regulations,........................310 89. Regulations for Competitive Boiler and Pump Trials, . . . 316 90. Standard Boiler-trials,............................ . . .322CONTENTS. Xl 1 ART. gi. Quality of Steam—Smoke Prevention, . page: • 323 92. Examples of Special Methods, . 323 CHAPTER IX. EXAMPLES OF ENGINE-TRIALS—METHODS AND REPORTS. 93. Examples of Engine and Boiler Test, . • 331 94. Examples of Stationary Engine Test, . • 332 95. Deductions and Conclusions, • 346“ 96. Portable Engine Trials, .... - 35h 97. Conclusions therefrom. .... . 361 98. Reports on Locomotive Trials, . . 364 99. General Results and Conclusions, . 375 100. Marine-engine Performance, ... • 376- 101. Graphical Records—Deductions, • 393 102. Pumping-engine and Boiler Tests—Centrifugal Pump, . 404 103. Illustrations of the Farey and Donkin System, . 424 104. Gas-engine Trials and Reports, . • 436- 105. Vapor-engine Trials, ..... 106. General Conclusions—The Outlook, . . 45s APPENDIX. Table I. Numerical Constants; Circles; Areas; etc., . 464 II. Logarithms, Common and Natural, • 477 III. Mean Pressure Ratios, . 480 IV. Terminal Pressures, .... . 481 V. Heat Transfer and Transformation, . 482 VI. Thermometer Scales, . . ' . . 484 VII. Volumes and Densities of Water, . 486 VIII. Metric Steam Table, .... . 487 IX. Metric Steam and Work Table, . 490 X. Steam Tables—British Units, . 492 XI. Stored Energy in Steam and Water, . . 499 XII. Formulas for Properties of Steam, . 501 XIII. Factors of Evaporation, . 503 XIV. Composition of Fuels, .... . 504 XV. Horse-power Constants, . 506ENGINE AND BOILER TRIALS CHAPTER I. REASONS AND PURPOSES. I. The Purpose of Test-trials of engines and boilers, is, commonly, the verification of the claims of the builder to complete fulfilment of his contract, and more especially as to the power and economical working of his apparatus. When- ever a motor, whether an air, a gas, or a steam or other vapor engine, is constructed for a proposing purchaser and user, the builder is expected to bind himself by a carefully drawn con- tract to supply apparatus capable of developing a stated amount of power and with a specified consumption of fuel, and, sometimes, of other supplies. A test-trial is demanded, when the machine is set up and in normal operation, to ascertain whether such contract and its specifications have been com- pletely fulfilled. In other cases, a trial is made to satisfy the proprietor that his machinery is doing good work; in still other instances, he desires to ascertain whether variations of the usual methods of operation and rules of management may be expected to give improved results ; sometimes, he desires to test the skill of his men, or the character of the fuel employed. In all cases, what- ever the main purpose of the operation, certain data are sought to be obtained as a basis for computation of the results needed, either to give a measure of the power and efficiency of the i2 ENGINE AND BOILER TRIALS. machinery, or a means of comparison with other apparatus of similar character and known excellence. A complete trial of engine and boiler involves the determi- nation of the quantity of energy stored in potential form in the fuel; the amount liberated by combustion in available form ; the proportion and the quantity taken up by the boiler; the amount stored in the steam, and in any water taken up by it, and transferred to the engine ; and the distribution at the engine into useful and lost work, and wasted heat. The methods of computation of these quantities will be given presently. The purposes and methods of such trials are thus the exact and unquestionable determination of one or several of the efficiencies of the engine—or the boiler—and these methods are usually intended to be such as will give scientifically accu- rate measures of the heat, the steam, the feed-water, and the energy supplied to the system ; the heat, steam, and energy reaching the engine ; the power developed ; the distribution, usefully and wastefully, of heat, energy, or power, or of all; the power and the thermodynamic and the actual efficiency of the engine considered as a heat-engine; and also the efficiency of the engine considered as a train of mechanism, i.e. as a machine. It is not always essential that all these determina- ' tions shall be made, or that such as are made shall be rigidly exact. Trials are often made which give partial results, and by methods which are only approximate and sometimes but roughly approximate, if judged from the standpoint of experi- mental science. As in all engineering work, the ultimate gauge of expediency, as judged from a financial standpoint and with an eye to a final summation of results, determines the extent to which the engineer is justified in giving his time and incurring expense in making steam-engine and boiler trials. On exten- sive contracts and important and costly work, all the resources of physical science and engineering practice are applied ; in minor matters, but little expense or labor is deemed justifiable. 2. Specifications of Performance, and, often, a guarantee, with forfeiture in case of non-fulfilment, should form a part ofSPECIFICATIONS OF PERFORMANCE. 3 "the contract; and those assurances of efficiency should be so exact and definite that no question can arise as to their mean- ing and fair interpretation, when the time arrives for their veri- fication. The customary forms of such specifications are now fairly well settled, and the usual methods of comparison and verification will be exhibited and exemplified. When no such .specification exists, it is assumed that the maker is bound to do reasonably good work and to assure to the buyers reasonably good economical performance. Obvious and unquestionable delinquency, as shown by test-trial, relieves the buyer of every responsibility not specifically and unqualifiedly assumed, and throws it upon the constructor and vendor. Engine Duty is commonly the technical measure of the effi- ciency of the engine as determined by the cost of the work done in fuel consumed. The “ horse-power/’ taken in British measure as 33,000 foot-pounds per minute or 1,980,000 per hour, demands the transformation of the equivalent amount of heat into work each minute or hour; which quantity should be supplied by one-fourth of a pound of good fuel, or less than 2\ pounds of steam, as worked in the perfect, ideal engine having an efficiency, unity. The actual consumption of energy derived from the boiler, as will be seen later, is rarely less than eight or ten times these amounts. Pumping-engines are commonly rated by the work done by the consumption of a specified weight of fuel, as one hundred pounds. A duty of 100,000,000 foot pounds, on this basis, would correspond to a consumption of 1.98 pounds of fuel per horse-power per hour. Mr. Sherman, assuming 90 per cent, as the efficiency of machine, including pumps as well as engine, obtains the figures in the following table (page 4).* Mr. Emery has compared steam-engines of various kinds on the assumption that the boiler is capable of absorbing 10,000 heat-units per pound of coal consumed. This corresponds to an evaporation of 8.99 pounds of water at 80 pounds; 9.03 pounds at 60 pounds; or, 9.08 pounds at 40 pounds gauge- * Trans. Am. Water-works Assoc., 1885.4 ENGINE AND BOILER TRIALS. DUTY OF PUMPING-ENGINES. One Million Gallons of Water in 24 Hours raised 200 Feet. Duty’ and Quality of Fuel per Hour per Horse-power. Duty. Lbs. coal per million gallons. Lbs. coal per hour per H. P. Duty. Lbs. coal per million gallons. | Lbs. coal per hour per H. P. Duty. Lbs. coal per million gallons. Lbs. coal per hour per H. P. Duty. Lbs. coal per million gallons. Lbs. coal per hour per H. P. 30 5560 5-94 51 3271 3-49 71 2349 2-5* 91 1833 1.96 31 5380 5-75 52 . 3208 3-43 72 2317 2.48 92 1813 1.94 32 5212 5-57 53 3H7 3-36 73 2285 2.44 93 *793 1.92 33 5054 5.40 54 3089 3-30 74 2254 2.41 94 1774 1.90- 34 4906 5 • 24 55 3°33 3-24 75 2224 2.38 95 1756 1.88 35 4766 5-°9 56 2979 3-18 76 2195 2-35 96 *738 1.86* 36 4634 4-95 57 2926 3-13 77 2166 2.31 97 1720 1.84 37 45°8 4.82 58 2876 3-07 78 2138 2.28 98 1702 1.82 38 4390 4 69 i 59 2827 3.02 79 2111 2 26 99 1685 1.80 39 4276 4-57 I 60 2780 2.97 80 K) 0 00 2 23 100 1668 1.78 40 4i7° 4-45 j 61 2734 2.92 81 2059 2.20 101 1651 1.76 4i 4068 4-35 62 2690 2.87 82 2034 2.17 102 1635 1 • 7> 42 3972 424 63 2648 2.83 83 2009 2.15 103 1619 1 • 73- 43 3880 4.14 ! 64 2606 2.78 84 1986 2.12 104 1604 1.71 44 3790 4°5 1 65 2566 2.74 85 1962 2.10 105 1589 J.70-. 45 3707 3-95 ! 66 2527 2.70 86 1940 2.07 106 1573 1.68 46 3626 3-87 i 67 2490 2.66 87 1917 2.05 107 x559 1.67" 47 3549 3-79 ! 68 2453 2.62 88 1895 2.02 108 *544 1.65 48 3475 3-71 J 69 2417 2.58 89 1874 2.00 109 153° 1.63. 49 3404 3-63 ! 70 2383 2-55 90 1853 1.98 IXO 1516 1.62 3336 3.56 j 1 pressure from a temperature of ioo° F. in each case. Ten thou- sand heat-units per pound of coal is equivalent to one million heat-units per 100 pounds of coal, and as the duty of pumping- engines is conventionally expressed in millions of foot-pounds per 100 pounds of coal, it follows on the basis presented that the number of foot-pounds per heat-unit represents also the num- ber of millions of foot-pounds duty per 100 pounds of coal. * The performance of all kinds of steam-engines may be readily com- pared on this basis. Ten thousand heat-units per pound of coal represent an efficiency of only (10,000 x 100 -r- 14,5°° —} 69 per cent, of the calorific value of pure carbon and of the best anthracite; so that ordinarily more than (100 — 69=) 31 per cent, of the heat in the fuel is carried up the chimney. The mechanical equivalent of one heat-unit is 772 foot-pounds, which, on the basis above, correspond to a duty of 772 millions of foot-pounds per 100 pounds of coal. The most economical * Centennial Report; Group XX; 1876.OBJECTS SOUGHT IN TEST-TRIALS. 5 steam-engines have been claimed to give as a maximum only about 130 millions, on the same basis, equivalent to an ultimate •efficiency of (130 x 100-f- 772 =) 16.84 per cent, of the heat in the steam, and but (16.84 x .69 =) 11.62 percent, of the calorific value of the fuel. If D z=z duty in foot-pounds per 100 pounds of coal, H — the height of lift per gauge, T = the initial and t the final temperatures, respectively, then D = 1 000000 T — t -f .0013//* The standard taken by British engineers in measuring duty is usually the number of pounds raised one foot either by 94 pounds of coal, or by one “ hundred-weight’’ (112 pounds). On this basis, the duty is computed from the ascertained weight of fuel per I. H. P. per hour, thus: D = duty in millions; F = weight of fuel per I. H. P. per hour; 186.12 D = —-p—, where the unit is 94 lbs.; 221.76 F where in cwts. 3. The Various Objects, in Detail, sought in test-trials are determined in part by the specific purpose of the trial; but, in nearly every case, they require the measurement of power obtained and of cost of obtaining it, expressed either in money or in fuel consumed ; and this means the exact weighing of fuel, the measurement of water used, the determination of the •qualityof the fuel and of the steam made, and its quantity, and the distribution of the stored energy, by the engine, in useful and in wasteful directions. Every quantity must be exactly Meas- ured which has importance in relation to the question at issue, and the data collected must be secured in such manner that their6 ENGINE AND BOILER TRIALS. magnitudes may be readily introduced into the computations* and may, if question arises, be readily checked and verified- The methods of determination and of record thus become matters of importance and careful study, and the application of the greatest possible ingenuity and skill are demanded in the effort to devise an acceptable and reliable system. In studying the efficiency of capital, it is first necessary to consider the ele- ments of cost of power. The Annual Cost of Steam-power consists: (1) Of certain expenses, which, in any given case, are usu- ally invariable, whether the work is done by a large engine with high ratio of expansion and small boilers, or with a smaller en- gine working at a low rate of expansion and with larger boilers- These are usually: rent of building or interest on cost, taxes,, repairs, etc., etc., of structure and location, the engineer’s salary and sometimes all or part of the fireman’s or stoker’s, also sundry minor expenses or a part of each of other expenses; which, as a whole, are variable. Both of the latter classes may usually be neglected in solving the problem here first considered- (2) The interest on first cost of engine in place, the cost of repairs, and a sum which measures the depreciation in value of the machine due to its natural wear, or to its decreasing value in presence of changes that finally compel the substitution for it of an improved engine. Oil, waste, and other engineer’s stores fall under this head. These items are variable with size and style of engine. (3) The expenses of supplying the engine with steam. These are : (a) The cost on fuel account of the steam supplied, and which includes, also, the cost of steam condensed en route to the engines and wasted by cylinder condensation and leakage, as well as that actually utilized. This total quantity of steam greatly exceeds that actually used in the production of power by simple transformation of heat-energy. This item varies with the efficiency of engine and size of boiler demanded. (T> dT Cw-JTt q ~ aJT„ (T- r, {T-tf Assume {T — f) — x, then =[—]:-[^ . A___i_______1 • ' aCw ~ Tt-t Tl — t~~ {T^ t){T% - t) * and the efficiency becomes E = Tt — t ~aCwKI' Then, since Tx — t _ S( Tx — t) -f- 1 _ 5( Tx — t) -|- aCw Tt— t~ aCw ~ aCw ’ ... ^ 16 ENGINE AND BOILER TRIALS. and (Tx — t) — (Tt 1 1 1 Tx-t 1 1 ** F_Tt-T, S(T, — t) T1 — t ~ S(Tt -t) + aCw If the total heat absorbed per hour be taken as H, H= Cw{ Tt — t) ; T, H * - Cw' and a simplified expression, E = S S + aC2w*’ -ir- is obtained, in which Cw may be taken as proportional to the weight of air supplied or of fuel burned, and H as proportional to the same quantity. Thus if F is the weight of fuel burned in the given time, on unity of grate-area, the efficiency may be expressed as F BS B S + AF~~ i + AR’ which is the formula sought. A and B are constants to be ob- tained by experiment for the special type of boiler to be con- sidered. When S and F represent respectively the number of square feet of heating-surface per square foot of grate in any boiler, and the number of pounds of fuel burned as the square foot of F grate per hour, and R = the values of A and B, as given bjr Rankine,* are as follows: * Steam-engine, p. 294.EFFICIENCY OF HE A TING-SURFACE. 17 Boiler Type. A. B. Class i. Best convection, chimney draught...... 0.5 1.00 “ 2. Ordinary “ “ “ 0.5 0.90 “ 3. Best “ forced “ ...... 0.3 1.00 “ 4. Ordinary “ “ “ 0.3 0.95 These constants are derived from experience with good fest-burning bituminous coals; for anthracites of good quality the Author has usually found the following values more in ac- cordance with good practice: Boiler Type. Class I..... “ 2....... “ 3..... " 4..... A. B. 0.5 O.90 0.5 O.80 0.3 O 90 0.3 O.85 When feed-water heaters are used, or superheaters are em- ployed, their surface should be included in the area S. The formula assumes no loss by excess of air-supply. Where such excess is noted or anticipated, it may be allowed for by increas- ing the value of A in proportion to the square of the total quantity of air supplied. The following table presents values of efficiency for a wide range of practice; EFFICIENCY OF BOILERS. B. Bituminous Coal. Class of Boiler. Anthracite Coal. Class of Boiler. I. n. hi. IV. I. II. III. IV. IO O.16 0.15 0.25 0.22 O.14 0.14 0.23 0.20 4 0*33 0.31 0.45 0.43 O.30 0.28 0.40 0-39 2 O.50 0.46 0.62 0.59 0-45 0.50 0.56 0-53 I 0.66 0.61 0.77 0.73 0.60 0-55 0.70 0.66 0.80 0 71 0.65 0.81 0.77 0.64 0.59 0-73 o.6q O.67 0-75 0.69 0.83 0.79 0.67 0.63 o.75 0.72 O.5O 0.80 0.73 0.87 0.83 O.72 0.65 0.78 0-75 O.4O 0.83 0.76 0.89 0.85 0-75 0.68 0.80 0.77 0-333 0.86 0.80 0.90 0.86 0.77 0.72 0.81 0.78 0.167 0-93 0.85 0.95 0.90 O. 84 0.77 0.86 0.81 O.III 0.95 0.87 0.97 0.92 0.86 0.78 0.88 0.83 These values have been found to agree well with practice up to rates of combustion exceeding 50 or 60 pounds peri8 ENGINE AND BOILER TRIALS. square foot of grate-surface per hour, beyond which point the efficiency falls off. But agreement can only be expected where the combustion and air-supply are in accordance with the assumptions on which the formula is based. The problem of the designer of steam-boilers often takes the form: Required to determine the area of heating-surface needed to secure a stated efficiency. • In this case the formula above given must be transformed thus: “i + AR~ F' ■+s 5- F • 0 B E~ 1 P 5 ■ F B ’ * * * E 1 from which expressions, the efficiency aimed at being given, the ratio of heating to grate-surface and the extent of heating- surface may be computed. As will be seen later, the question to what extent efficiency may be economically carried by ex- tending heating-surface is one of the problems arising in de- signing boilers. Mr. Emery finds that the results of extensive series of ex- periments on good forms of boiler may be represented by the empirical expression, for vertical tubular boilers, 46.045 c-j- 3.016 1.067; in which E is the ratio of weight of water evaporated into dry steam, “from and at the boiling-point,” under atmospheric pres- sure, to weight of fuel used ; and c is the weight of combustible consumed per square foot of heating surface per hour, in pounds.EFFECTIVE DEVELOPMENT, ETC., OF HEAT. x9 For horizontal boilers, E = 27.287 c —[- 2.04 0.824. The evaporation is here the maximum practicable with good anthracite coal. The maximum efficiency is given as in which e is the observed evaporation, reduced to the standard basis. These relations are shown in the table on p. 20. For badly designed or mismanaged boilers deduction must be made from the efficiencies and evaporations here given,‘to the extent of ten per cent or more, according to magnitude of the defect. In land boilers, it is customary to keep the rate of combus- tion per square foot of grate down to about eight pounds per hour, although it frequently rises to 10 and 12. In marine boilers this rate is increased to 12 and 16 pounds per square foot of grate per hour when anthracite coal is burned with nat- ural draught, and to 20 pounds and upward per hour for bituminous coal. In a locomotive, however, with forced draught, 75 and 100 pounds of coal are burned per square foot of grate. Apparently no losses result from such variations in the size of the grate, and, in fact, it appears indisputably that with a reduced grate and forced draught the air-dilution is re- duced and the evaporization therefore somewhat increased. It is reasonable to conclude, therefore, that when care is taken to insure perfect combustion by ordinary tests, the relative area of the grate upon which the coal is consumed does not affect the result, and economy depends under proper conditions upon the rate of combustion per unit of heating surface as stated. 12. Effective Development, Transfer, and Storage of Heat, in the best possible combination, is evidently what is de- manded in the operation of the steam-boiler. In securing complete combustion, an ample supply of air20 ENGINE AND BOILER TRIALS. PERFORMANCE OF BOILERS.*—Emery. I 2 3 4 5 6 c E cE E -*- 15 34.52 + 1.2 E 34.52 cE Combustible consumed per square foot of heat- ing surface. Water evaporated at atmos- pheric pressure from tempera- ture of 212°. Ultimate efficiency, Coal (with 1-6 refuse) per horsepower per nour. Heating sur- face per horse- power. Per pound of combustible. Per square foot of heating surface. On basis that one horse-power requires 30 pounds of water per hour, evaporated at 70 pounds pressure from temperature of ioo°, or 34.52 pounds at atmos- pheric pressure from tempera- ture of 212°. Pounds. Pounds. Pounds. Pounds. Square Feet. Minimum. 14.20 0.95' 0.1 13-71 i-37 0.91 3.02 25.18 0.2 13-25 2.65 0.88 3-13 13.03 0-3 12.82 3-85 0.85 3-23 8.98 0.4 12.41 4.96 0.83 3-34 6.95 0.5 12.03 6.02 0 80 3-44 5-74 0.6 11.68 7.01 0. 7S 3-55 4.92 0.7 11.32 7.92 0.75 3.66 4.36 0.8 11.00 8.80 0.73 3-77 3-92 0.9 10.69 9.62 0.71 3-87 3-59 1.0 10.39 10.39 0 69 3-99 3-32 1-5 9-13 13.70 0.61 4-54 2.52 2.0 S. 11 16.22 0-54 5-H 2.13 2-5 7.28 18.20 0.49 5-69 1.90 3-o 6-57 19.71 0.44 6.30 i-75 3-5 6.00 21.00 0.40 6.90 1.64 4.0 5-50 22.00 o.37 7-53 1-57 4-5 5.06 22.77 o-34 8.19 1.52 5-o 4.68 23.40 0.21 8.S5 1.48 and its thorough intermixture with the combustible elements of the fuel are essential; for the second, high temperature of fur- nace, it is necessary that the air-supply shall not be in excess of that absolutely needed to give complete combustion. The efficiency of a furnace burning fuel completely is measured by £-T-T" T-t ' * Set. Am. Supplement. No. 687, p. 10 972.EFFECTIVE DEVELOPMENT, ETC., OF HEAT. 21 in which £ represents the ratio of heat utilized to the whole calorific value of the fuel; T is the furnace-temperature; T', the temperature of the chimney; and /, that of the external air. Hence the higher the furnace temperature and the lower that of the chimney, the greater the proportion of available heat. It is further evident that, however perfect the combustion, no heat can be utilized if either the temperature of chimney ap- proximates to that of the furnace, or if the temperature of the furnace is reduced by dilution approximately to that of the chimney. Concentration of heat in the furnace is secured, in some cases, by special expedients; as by heating the entering air, or, as in the Siemens gas-furnace, heating both the combus- tible gases and the supporter of combustion. Detached fire- brick furnaces have an advantage over the “ fireboxes” of steam-boilers in their higher temperature; surrounding the fire with non-conducting and highly-heated surfaces is an effective method of securing more perfect combustion and high furnace- temperature. In arranging heating-surface, the effort should be to impede the draught as little as possible, and so to place them that the circulation of water within the boiler should be free and rapid at every part reached by the hot gases. The directions of circulation of water on the one side and of gas on the other side the sheet should, whenever possible, be opposite. The cold water should enter where the cooled gases leave, and the steam should be taken off farthest from that point. The temperature of chimney-gases has thus been re- duced by actual experiment to less than 300° Fahr., and an efficiency equal to 0.75 to 0.80 the theoretical is attainable. The extent of heating-surface simply, in all of the best forms of boiler, determines the efficiency, and the disposition of that surface in such boilers seldom affects it to any great ^extent. The area of heating-surface may also be varied within wide limits without greatly modifying efficiency. A ratio of 25 to 1 in flue and 30 to 1 in tubular boilers represents the relative area of heating and grate surfaces in the practice of the best-known builders. This proportion may be often settled by •exact calculation.22 ENGINE AND BO/LER 7'RIALS. The material of the boiler, as will be shown later, should be tough and ductile iron, or, better, a soft steel containing very little carbon and thoroughly homogeneous. The factor of safety is very often too low. The boiler should be built strong enough to bear a pressure at least six times the proposed working-pressure ; as the boiler grows weak with age, it should be occasionally tested to a pressure far above the working-pressure, which latter should be reduced gradually to keep within the bounds of safety. The factor of safety is seldom more than four in new boilers; and even this is reduced practically by the operation of the inspection laws. Effective development of heat is secured primarily by the selection of good fuel, by which is usually meant fuel which consists, to the greatest possible extent, of available combusti- ble material; but for the purposes of the engineer who designs the boiler, or of the owner for whom it is to be constructed, the real criterion of quality is the quantity of heat which the com- bustible, as burned in the furnace, will yield for any given sum of money expended in obtaining that heat. The cost of a fuel to the consumer consists, not simply of money paid for it to the dealer who supplies it, but also of cost of transportation and of placing in the grate, of removal of ash, of incidental ex- penses inseparable from its use, such as injury to boilers and other property, increased risks, and other such expenses, many if not most of which are very difficult of determination with any satisfactory decree of accuracy. Other things being equal, that fuel which gives the greatest quantity of available heat for the total money expenditure is that which permits most effec- tive development in the sense here taken. Effective heat-de- velopment from any selected fuel is secured, as already stated, by its complete combustion in such manner as to give the highest possible temperature. Effective transfer of heat is secured by such a form of steam-generator, and such extent and disposition of “ heating- surfaces,” as will most completely utilize the heat developed in the furnace and flues by causing it to flow, with the least pos- sible loss, into the water and steam contained within the boiler and this is effected by proper arrangement of surfaces absorb-EFFICIENT UTILIZA TION OF HE A T. 23 ing heat from the gases and yielding it to the liquid as already generally described. Effective storage of heat can be secured by providing large volumes of water and of steam, within which the heat transferred from the furnace and flues can be stored, and by carefully pro- tecting the whole heated system from waste by conduction or radiation to adjacent bodies. Where the demand is steady, and the supply from the fuel fairly steady also, the amount stored need not be great, as the use of the reservoir is simply that of a regulator between furnace and engine or other apparatus re- ceiving it; but where either supply or demand is variable, con- siderable storage capacity may be needed. 13. Efficient Utilization of Heat is as essential to the satis- factory working of any system of generation and application of heat as is efficient production, transfer, and storage. The mode of attaining maximum efficiency depends upon the nature of the demand and the method of expenditure ; and the considera- tion of this subject in detail would be here out of place. In general it may be said that where the heat and steam are re- quired for the impulsion of an engine, the higher the safe pres- sure and the practically attainable temperature at which the supply is effected, the more efficient the utilization of the heat. These limits of temperature and pressure are the higher as the actual working conditions are made the more closely to approxi- mate to the ideal conditions prescribed by pure science. Where heating simply, without transformation into work, is intended, the principal and only very important requisite, usually, is to provide such thorough protection for the system of transfer and use, that no wastes of importance can take place by radiation or conduction. The character of the steam made, as to humidity, is in this case comparatively unimportant; but in the preceding case it will be found essential that it should be always dry, and it is often much the better for being super- heated considerably above the boiling-point due to its pressure. The actual standing of the best steam-engine of the present time, as an efficient heat-engine, is really very high. The sources of loss are principally quite apart from the principles of design and construction, and even from the operation of the24 ENGINE AND BOILER TRIALS. machine; and it may be readily shown that, to secure any really important advance toward theoretical efficiency, a radical change of our methods must be adopted, and probably that we must throw aside the heat-engine in all its forms, and substitute for it some other apparatus by which we may utilize some mode of motion and of natural energy other than heat. The very best classes of modern steam-engines very seldom consume less than two pounds (0.9 kilog.) of coal per horse- power per hour, and it is a good engine that works regularly on three pounds (1.37 kilog.). The first-class steam-engine, therefore, yields less than 10 per cent of the work stored up in good fuel, and the average engine probably utilizes less than 5 per cent. A part of this loss is unavoidable, being due to natural conditions beyond the control of human power, while another portion is, to a consid- erable extent, controllable by the engineer or by the engine- driver. Scientific research has shown that the proportion of heat stored up in any fluid, which may be utilized by perfect mechanism, must be represented by a fraction, the numerator of which is the range of temperature of the fluid while doing useful work, and the denominator of which is the temperature of the fluid when entering the machine, measured from the “ absolute zero.” Thus, steam, at a temperature of 320° Fahr., being taken into a perfect steam-engine, and doing work there until it is thrown into the condenser at ioo° Fahr., would yield 320 — 100 ----;—= 0.28 4-, or rather more than one fourth of the 320 -f 4^1 work which it should have received from each pound of fuel. The proportion of work that a non-condensing but other- wise perfect engine, using steam of 75 pounds (5 atmos.) pres- sure, could utilize would be ?2° -2 *2 — o, 14 — 4; and, while 320 + 461 7 the perfect condensing engine would consume two thirds of a pound (0.3 kilog.) of good coal per hour, the perfect non-con- densing engine would use i£ pounds (0.6 kilog.) per hour for each horse-power developed, the steam being taken into the engine and exhausted at the temperatures assumed above.EFFICIENT UTILIZA TION OF HE A T. 25 Also, were it possible to work steam down to the absolute zero of temperature, the perfect engine would require but 0.19 pound (0.09 kilog.) of similar fuel. It may therefore be stated, with a close approximation to exactness, that, of all the heat derived from the fuel about seven tenths is lost through the existence of natural conditions over which man can probably never expect to obtain control, two tenths are lost through imperfections in our apparatus, and only one tenth is utilized in even good engines. Boiler and engine are intended to be included when writing of the steam- engine above. In this combination a waste of probably two tenths at least of the heat derived from the fuel takes place in the boiler and steam-pipes, on the average, in the best of prac- tice, and we are therefore only able to anticipate a possible saving of 0.2 X 0.75 = 0.15, about one sixth of the fuel now expended in our best class of engines, by improvements in the machine itself. The best steam-engine, apart from its boiler, therefore, has 0.85, about five sixths, of the efficiency of a perfect engine, and the remaining sixth is lost through waste of heat by radiation and conduction externally, by condensation within the cylinder, and by friction and other useless work done within itself. Tt is to improvement in these points that inventors must turn their attention if they would improve upon the best modern practice by changes in construction. To attain further economy, after having perfected the machine in these particulars, they must contrive to use a fluid which they may work through a wider range of temperature, as has been attempted in air-engines by raising the upper limit of temperature, and in binary vapor engines by reaching toward a lower limit, or by working a fluid from a higher temperature than is now done down to the lowest possible temperature. The upper limit is fixed by the -heat-resisting power of our materials of construction, and the lower by the mean tempera- ture of objects on the surface of earth, being much lower at some seasons than at others. In the boiler the endeavor must be made to take up all the heat of combustion, sending the gases into the chimney at as low a temperature as possible, and securing in the furnace perfect combustion without excess of air-supply.26 ENGINE AND BOILER TRIALS. Good furnace management, to secure maximum heat-supply from the unit weight of fuel, is evidently as essential to econ- omy and efficiency of steam production as choice of proper fuels. In the management of the furnace the effort should be made to secure the best conditions for economy, and as nearly as possible perfect uniformity of those conditions. The fuel should be spread over the grate very evenly, and the tendency to burn irregularly, and especially into holes or thin spots, should be met by skilful “ firing,” or “ stoking,” as it is also termed, at such intervals as may by experience be found best. The smaller the coal, where anthracite is used, the thinner should be the fire ; the stronger the draught, the thicker the bed of fuel, of whatever kind. With too thin a fire, the danger arises of excess of air-supply; with too heavy a fire, carbon monoxide (carbonic oxide) may be produced. In the former case combustion will be complete, but the heat generated will be distributed throughout the diluting excess of air, and thus rendered less available, and the efficiency of the furnace will be correspondingly reduced; while in the latter case a loss arises from incomplete combustion, and waste takes place by the passage of combustible gas up the chimney. The second is the less common cause of loss of the two, but both are liable to arise in almost any boiler, and we may even have both losses exhibited in the same boiler and at the same time. Successful working demands a very perfect mixture of the combustible with the supporter of combustion, and should this not be secured, serious waste will take place. The appearance of smoke at the chimney-top is not always indicative of serious loss, nor is its non-appearance always proof of complete combustion. With soft coals and other fuels con- taining the hydrocarbons sortie smoke usually accompanies the best practically attainable conditions; anthracites, charcoal, and coke never produce true smoke. Attempts to improve the efficiency of a heat-generating apparatus by ‘‘ burning the smoke” usually fail by introducing such an excess of air as to cause a loss exceeding that before experienced from the forma-TRIALS TO ASCERTAIN MAXIMUM CAPACITY. 2J tion of smoke. Thorough intermixture of a minimum air-supply with the gases distilled from the fuel is the only means of attaining high efficiency. In firing, or stoking, especial care should be taken to sec that the sides and corners of the grate are properly attended to. Regulation of the fire is best secured by the careful ad- justment of the damper. The manipulation of the furnace doors for this purpose is likely to cause waste. Liquid fuels are especially liable to waste by excessive air-supply, and gas eous fuel exhibits a peculiar liability to the opposite method of loss; both should be, if possible, even more carefully handled than any solid fuels. 14. Trials to Ascertain Power or Maximum Capacity to do useful work are often, perhaps usually, made under the same contract as are those to determine efficiency of engine. Steam machinery is commonly guaranteed, both as to economy and capacity. Such trials are sometimes made at the same time with efficiency-trials; but the maximum power of engines, and boilers is seldom, if ever, that at which best economy is obtainable. A single trial is made when the power guaranteed is that of normal working and that for which the guarantee of economy is made by the contract. A trial for capacity simply, is one in which the power only need be measured, and its cost, unless specifically demanded, is not determined. The methods employed, so far as they go, are the same as in the preceding and more complete kind of trial. The actual power of steam and of boilers evidently depends upon the efficiency of the method of application, end on the apparatus employed. The quantity of heat-energy supplied to the engine and yielded by the generator has been seen to be easily calculable by simply multiplying the quantity of heat given to the steam, by the fuel, by the mechanical equivalent of heat. The amount available as energy may be the total quantity so supplied, as when the steam is condensed in heating buildings or otherwise, and is returned as feed-water to the boilers; or it maybe any less amount, according as the method of utilization is more or less effective. The tables given in the28 ENGINE AND BOILER TRIALS. Appendix furnish the data for calculation in any case in which the efficiency of transfer and of transformation is known. Where no constant value can be assumed for the efficiency of the system employed, it is sometimes, nevertheless, found to be important to establish a standard conventionally. Thus, in the calculation of available stored energy, as given in the Appendix, it was assumed that the steam would be expanded to atmos- pheric pressure. Similarly, convention has established the unit horse-power of steam-boilers, in order to afford a standard of comparison in test-trials, and to give a means of rating boilers by the designer, the builder, or the purchaser and user. The operation of boilers occurs under a wide range of actual conditions—the steam-pressure, the temperature of feed-water, the rate of combustion and of evaporization, and, in fact, every other variable condition, differing in any two trials to such an extent that direct comparison of the totals obtained, as a matter of information regarding the relative value of the boilers, or of the fuel used, becomes out of the question. It has hence gradually come to be the custom to reduce all results to the common standard of weight of water evaporated by the unit- weight of fuel, the evaporation being considered to have taken place at mean atmospheric pressure, and at the temperature due that pressure, the feed-water, being also assumed to have been supplied at the same temperature. This, in technical lan- guage, is said to be the “ equivalent evaporation from and at the boiling-point” (212° F., ioo° Cent.). This standard has now become generally incorporated into the science and the practice of steam-engineering. The “ Unit of Evaporation” is one pound of water at the boiling-point, evaporated into steam of the same temperature. This is equivalent to the utilization of 966, nearly, British thermal units per pound of water so evaporated. The economy of the boiler may thus be expressed by the number of units of evaporation obtained per pound of combustible. Newcomen used steam of barely more than atmospheric pressure, and raised 105,000 pounds of water one foot high, with a pound of coal consumed. Smeaton raised the steam-pressure to eight pounds, and increased the duty to 120,000. WattQUANTITIES MEASURED AND RESULTS SOUGHT 29 started with a duty of double that of Newcomen, and raised it 320,000 foot-pounds per pound of coal, with steam at ten pounds. To-day, Cornish engines of the same general plan as those of Watt, but worked with forty to sixty pounds pressure, expanding three to six times, bring up the duty to 600,000 foot- pounds; while more modern compound engines have boilers carrying 150 pounds (ten atmospheres) above the normal air pressure, and the duty has been since raised to above 1,200,000 foot-pounds per pound of fuel used. 15. The Quantities Measured and Results sought to be secured are thus, in detail, as follows for any complete trial : When the trial includes, as is most frequently the case, a trial of the boiler, the combined efficiency of boiler and engine being the final determination, arrangements must be made in advance to ascertain exactly the weights of fuel, gross and net, coal and ash for example; the weight of water supplied as “ feed the weights, temperatures, and pressures of dry steam, and weight of entrained water; the temperatures of furnace, flues, and chimney; of superheating steam, if it be so heated; the power of the engine, gross and net; the friction of engine; the wastes by cylinder-condensation and otherwise; the steam- pressure in boiler and steam-chest; and the continually varying pressures in the working cylinder throughout the whole cycle, revolution by revolution, of the engine. Each of these quan- tities is measured at specified intervals, and a comparison of mean values of power usefully applied, and of expenditures made to produce it, gives the measure of the economy attained. At the same time that the gross power developed by the action of the steam in the cylinder, the indicated power, is measured, the diagrams taken furnish the means of ascertaining precisely how the pressures and volumes of the steam simul- taneously vary within the engine, and thus give a clue to, and usually a fairly exact determination of, the setting and motion of the valves and the extent to which the distribution of steam is such as will best conduce to economical working. These dia- grams also enable the engineer to compute with consider- able accuracy the volumes and weights of the steam at any30. ENGINE AND BOILER TRIALS. point, and at every point, in the stroke. A comparison of the quantities so calculated with the actual measures obtained at the boiler, or before the steam enters the cylinder, gives the measure of the quantity condensed in the cylinder, as the piston moves forward, and of the later re-evaporation. The cylinder- wastes are thus also determinable with a fair degree of accuracy. These “ cards” also exhibit the amount of back-pressure, and this measures the resistances in the exhaust passages and at the condenser, if there be one, and thus afford a means of criticism of the design and construction of the engine in this respect. Similarly, the difference between the steam-pressures in the cylinder and in the steam-chest and the exhaust-chest, is a measure of the losses in the steam passages. The usual rates of evaporation and the effect of varying the proportions of tubes has been well determined by the experi- ments of Isherwood and others. The proportions of flues and tubes vary somewhat in prac- tice ; but it will be found seldom advisable to make tubes more than 50 or 60 diameters in length. Where the heating-surface consists principally of tubes, the efficiency will be found to vary with their length nearly as follows : Length of tube (diameters)............. .... 60 50 40 30 20 Water per unit-weight of fuel............ 12 11 10 9 8 When the ratio of heating to grate area was 25 to 1, Isher- wood found the evaporation to vary thus: Fuel per hour......................... 8 10 12 16 20 24 Evaporation........................... 10.5 10.1 9.5 8.2 7.3 6.8 which series is represented by W — , nearly. VF Clark obtained with locomotives an equal evaporation with Fuel (coke)................ 15 25 38 56 76 98 125 153 Ratio of H. S. to G. S....30 40 50 60 70 80 90 100QUANTITIES MEASURED AND RESULTS SOUGHT. 31 the evaporation being constant at 9 of water to 1 of fuel, which may be expressed by S = 8 VF, nearly, being the ratio of the two areas and F the weight of coke burned on the unit of area of grate. In estimating area of heating-surfaces the whole surface exposed to the hot-furnace gusts is reckoned. The formula for efficiency already given illustrates the progressive variation of the evaporative power with change of proportions of boiler. The relation of size of boiler to quantity of steam de- manded is one that occasionally becomes worthy of considera- tion. Where the steam is required for driving steam-engines it is very important that it should be thoroughly dry, and it is an advantage to moderately superheat it. Maximum econ- omy cannot be attained where wet steam is used. A boiler attached to a steam-engine, and especially where fuel is costly and efficiency important, should have ample heating-surface, some superheating-surface if practicable, ample extent of water- surface area to permit free separation of steam and water, and large steam-space. Steam employed for heating purposes is not necessarily dry ; it may carry a large amount of water with it into the system of heating-coils or radiators, and yet give good results, if the latter are of large section. Where the pipes are of restricted area of section, however, wet steam flowing less freely than when dry or superheated, there may result such a retardation of flow and of circulation as may cause considerable increase of cost. This has been found sufficiently great, in some cases, to justify drying, and perhaps superheating, the exhaust-steam from engines where used for heating purposes. As a general rule, the boiler must be made a trifle larger to supply perfectly dry steam and do good work. In the use of steam for heating purposes, one square foot of boiler-surface will supply from 7 to 10 square feet of radiating surface. Small boilers should be larger proportionately than large boilers. Each horse-power of boiler will supply from 25032 ENGINE AND BOILER TRIALS. to 350 feet of i-in. steam-pipe, or 80 to 120 square feet of radiat- ing surface. Under ordinary conditions one horse-power will heat about— Brick dwellings, in blocks, as in cities. 15,000 to 20,000 cub. ft. “ stores “ 10,000 “ 15,000 “ “ “ dwellings exposed all around....... 10,000 “ 15,000 “ “ “ mills, shops, factories, etc........ 7,000 “ 10,000 “ “ Wooden dwellings, exposed................. 7,000 “ 10,000 0 “ Foundries and wooden shops................ 6,000 “ 10,000 “ Exhibition buildings, largely glass, etc.. 4,000 “ 15,000 “ “ The system of heating mills and manufactories by means of pipes placed overhead is recommended. The air required for ventilation is usually warmed by the “ indirect’' system of radiation, the current passing through boxes or chambers in which a sufficient amount of pipe is coiled to heat it well. From 5 to 15 cubic feet per individual per minute are allowed, the former in crowded halls, the latter in dwellings, and about one-tenth as much for each gas-burner or lamp. Small engines, according to Buel, demand steam, ordinarily, as below: Pressure of Steam in Pounds of Water per effective Horse- Pressure of Steam in Pounds of Water per effective Horse- Boiler, by Gauge. power per Hour. Boiler by Gauge. power per Hour. IO Il8 60 75 15 III 70 7i 20 105 80 68 25 IOO 90 65 30 93 IOO 63 40 84 120 61 50 79 150 58 Pressures lower than 60 pounds are not usually adopted for small engines. Good examples of such engines have been found by the Author to demand from 25 to 33 per cent less steam, or feed-water, than is above given. The table on the next page gives what are considered by the Author as fair estimates of water and steam consumption for the best classes of engines in common use, when of moder- ate size and in good order. It is considered usually advisable to assume a set of practi- cally attainable conditions in average good practice, and to takeGENERAL SCHEMES. 33 Non-condensing Engines. Steam Pressure. Pounds per H. P. per Hour.—Ratio of Expansion. Atmospheres. Lbs. per sq.in. 2 3 4 5 7 10 3 45 40 39 40 49 , 42 45 4 6o 35 34 36 36 38 40 5 75 30 28 27 26 30 32 6 go 28 27 26 25 27 29 7 105 26 25 24 23 25 27 8 120 25 24 23 22 22 21 IO 150 24 23 22 21 20 20 Condensing Engines. 4 30 30 28 28 30 35 40 5 45 28 27 27 26 28 32 4 60 27 26 25 24 25 27 5 75 26 25 25 23 22 24 6 90 26 24 24 22 21 20 8 120 25 23 23 22 21 20 10 150 25 23 22 21 20 19 the power so obtainable as the measure of the power of the boiler in commercial and engineering transactions. The unit generally assumed has been usually the weight of steam de- manded per horse-power per hour by a fairly good steam-en- gine. This magnitude has been gradually decreasing from the earliest period of the history of the steam-engine. In the time of Watt, one cubic foot of water per hour was thought fair; at the middle of the present century, ten pounds of coal was a usual figure, and five pounds, commonly equivalent to about forty pounds of feed-water evaporated, was allowed the best engines. After the introduction of the modern forms of en- gine this last figure was reduced twenty-five per cent, and the most recent improvements have still further lessened the con- sumption of fuel and of steam. By general consent, the unit has now become thirty pounds of dry steam per horse-power per hour, which represents the performance of good non-con- densing mill engines. 16. General Schemes of Trial or Tests of Engines are adopted by engineers which, while varying in detail, all closely34 ENGINE AND BOILER TRIALS. resemble each other in their main purposes, and are somewhat similar in methods. They commonly include boiler-trials as the only practicable and satisfactory means of ascertaining the quantity and quality of steam supplied, and the cost of power in steam, fuel, and money. They invariably involve the appli- cation of the indicator or the dynamometer, and, if complete, of both, for power measurements. When the question to be solved is simply the efficiency of engine, or of engine consid- ered dynamically, of the engine as a machine, a comparison of the indicated with the dynamometric power gives the solution ; but when the thermal efficiency and the efficiency in trans- formation of energy is to be measured, the measurement of the quantity of energy supplied in the form of heat, and hence a boiler-trial, must necessarily form a part of the operation. All general systems may therefore be said to involve the whole series of determinations of quantity already indicated ; but the details have not yet been authoritatively prescribed in such manner as to fix a standard system or standard methods. The experience of the most experienced and distinguished practition- ers is, however, gradually producing a tolerably well settled cus- tom in the more important of the several operations involved. Some such methods and some general plans of test-trials will be later described. 17. Steam-Boiler Trials, apart from the engine-test, and made for the purpose of ascertaining the quantity and quality of steam made, its cost in fuel and in combustible matter contained therein, and the efficiency of the boiler and of its heating-surface, are now very generally made by a fairly well recognized system. In the United States and in Germany, particularly, such methods are now made to follow very gen- erally the prescribed order of procedure devised and published by engineers of recognized standing. Such a standard system is that proposed by the committee of the American Society of Mechanical Engineers, and this standard will be that accepted in this work.* * Transactions American Society of Mechanical Engineers, vol. vii., 1884. A Manual of Steam-Boilers, by R. H. Thurston (N. Y. : J. Wiley & Sons, 1888), chap. xiv. pp. 484-537.BOILER-TRIALS, APART FROM THE ENGINE-TEST 35 In the operation of conducting any trial, we have, usually, a single, well-understood object to attain, and the engineer .should accustom himself to carefully define that object in his own mind, and to as carefully describe that object in his in- structions and regulations for the proposed trial. The whole operation can then be carried on with that point distinctly in view, and the proposed end can then be accomplished with maximum economy of time and labor, as well as with greatest exactness. The observations must be made by the engineer conducting the trial, or by his assistants, with this object clearly in mind, and each should have a well-defined part of the work assigned him, and should assume responsibility for that part, having a distinct understanding in regard to the ex- tent of his responsibility, and a good idea of the extent and nature of the work done by his colleagues, and the relations of each part to his own. No observations should be permitted to be made by unauthorized persons for entrance upon the log; and no duties should be permitted to be delegated by one assistant to another, without consultation and distinct under- standing with the engineer in charge. The aim of the observers is, in boiler trials, for example, to obtain an exact determina- tion of the weight of fuel used, its proportion of combustible matter effective in developing heat, the exact weight of water evaporated under the known conditions of the trial, into steam, the determination of the character of that steam, and often the nature of the combustion and the composition of the furnace- gases. Each of these distinct objects requires the determina- tion of certain well-defined quantities, and the observer to whom each set of observations is intrusted should, whenever possible, be made sufficiently well acquainted with the object to be attained, and the method to be pursued in reaching it, to be able to make his own readings with accuracy, and to work up the results correctly. It is only after he has acquired this knowledge that he can be expected to do his work without •direct supervision, and with satisfactory precision. The trial should, wherever possible, be so conducted that any error that may occur in the record may be detected, checked, or, if ad- visable, removed, by some process of mutual verification of36 ENGINE AND BOILER TRIALS. related observations. It is in this direction that the use of graphical methods of record and automatic instruments has greatest value. We should lose no opportunity to introduce both. 18. Engine Trials may or may not include determination of boiler performance and efficiency; but if they are to be sat- isfactorily complete, measurements of the quantity and quality of the steam supplied are as essential as any other determina- tions of quantity. In some cases, only a comparison of the work done with its cost in fuel is called for; but in this case the total efficiency so obtained cannot be analyzed into the two factors, engine efficiency and boiler efficiency, and it is impossible to say to what extent engine or boiler is responsible for the final results obtained. The complete investigation of the action and performance of the engine, as a heat-engine and prime motor, must always include some method of obtaining a measure of the amount of heat-energy supplied to the machine ; the proportion of that energy which reaches the engine in available form; the distribution and disposition of the available part; the extent to which it is converted into use- ful work and into wasted power; the amount in detail of the various wastes ; the method as well as extent of wastes; and the ameliorating or exaggerating effect of any observable acci- dental or purposely produced variations of condition and of operation upon the wastes, the economies, and the several efficiencies of the engine. It is thus important that ways should be found and methods practised, that will determine the quantity and quality—whether wet or dry—of the steam supplied ; the pressures and volumes of every stage of transfer and of transformation, and the quan- tities of heat stored, conveyed, and utilized or wasted. 19. Engine and Boiler Tests are thus necessarily com- monly conducted simultaneously in the settlement of important contracts, and essential data can only be thus secured. Where the quantities to be ascertained and measured are not likely to vary greatly with period of operation, a trial of a few hours’’ duration will answer all purposes. Gas-engines are often tested a single hour, and five hours is quite as long as is often de-APPARATUS OF STEAM-BOILER TRIALS. 37 sirable. Steam-engine and boiler trials are seldom les9 than ten hours in length, often occupy a full day of twenty-four hours, sometimes last a week, unintermittedly, night and day, and it is even sometimes prescribed that the more important data shall be recorded for several months or for a year at a time. Ordi- narily, a ten-hour trial is quite sufficient, if properly conducted. 20. The Apparatus of Steam-boiler Trials consists of tanks to receive and in which to weigh the feed-water; scales with which to effect these measurements and to weigh fuel and ashes; thermometers with which to determine the temperature of the water and steam, and pyrometers for the furnace-flue and chimney temperatures; and it is now usual to employ a calorimeter v/ith which to determine the condition of the steam, and to measure the proportion of entrained water. Before the systems of boiler trial usually adopted are employed, it will be necessary to understand the methods of use and of calibration and of standardizing these various kinds of apparatus, the sources from which they may be obtained, and the best methods of their application to the securing of the needed data. It is usually thought best to weigh all water, rather than measure its volume. If measured, it should be carefully noted that its variation of density with temperature is considerable, and suffi- cient to introduce observable errors if a constant density is assumed. The Apparatus of Engine-testing consists of steam-engine indicators, dynamometers, counters and gauges, and good tim- ing instruments. The use of these instruments and the methods of test and correction are simple; and, with the exception of the indicator, none demands very extended notice. The indi- cator, however, is an instrument which must be made with the utmost possible care and skill, and the study and interpreta- tion of its diagrams is a matter demanding some skill, knowl- edge, and experience. Considerable space will therefore be devoted to the description of this interesting and indispensable instrument, its uses and applications, to the study of the methods of interpretation of its record, and necessary measure- ment and computations.CHAPTER II. STEAM-BOILER TRIALS.* 21. The Object of a Trial of a Steam-boiler is to de- termine what is the quantity of steam that a boiler can supply under definitely prescribed conditions; what is the quality, as. to moisture or dryness, of that steam ; what is the amount of fuel demanded to produce that steam ; what the character of the combustion, and the actual conditions of operation of the boiler when at work. The conditions prescribed for one trial may differ greatly from those of another trial, and such differ- ences are often the essential matters to be studied. In any case it is assumed that the conditions under which the boiler is to be worked are to be definitely stated, and the engineer con- ducting the experiments is expected to ascertain all the facts which go to determine the performance of the boiler, and to state them with accuracy, conciseness, and completeness. In the attempt to ascertain those facts the engineer meets with some difficulties, and finds it necessary to exercise the utmost care and skill. In conducting a steam-boiler trial the weight of the water supplied to the boiler must be determined ; the weight of the fuel consumed must be obtained ; the state of the steam made must be determined ; and these quantities must all be noted at frequent intervals. It is also necessary to know whether the combustion is perfect or imperfect, and to what extent the conditions and facts noted are due to the boiler, and what to external conditions. It has now come to be considered that the determination of power and economy of a steam-boiler demands all the care, skill, and perfection of method and of apparatus of any purely scientific investigation. It is desirable that all work of this kind shall be done in substantially the same way, in order that com- parisons may be made. * Mainly from the Author’s “Manual of Steam Boilers,” New York; pub- lished by John Wiley & Sons. 38VALUE OF FUEL. 39 22. Tests of Value of Fuel are sometimes the sole object of a trial of a steam-boiler, the intent being to ascertain by actual experiment what quantity of water a fuel of unknown quality can evaporate in a boiler of which the general efficiency is fairiy well established. In such cases the fuel is employed in the usual manner and the results compared with those ob- tained with fuels of known excellence. Thus, in a good type of boiler, having a good proportion of area of heating-surface to weight of fuel burned per hour, it may be found that a fuel of established reputation for uniform excellence will evaporate ten times its own weight of water “ from and at ” the boiling-point. The trial of a fuel of unknown quality may prove that this boiler will, under precisely similar conditions, evaporate an equal amount of water into steam, and yet the market price of the fuel may be considerably less than that of the other. The immediate result would be the substitution of the second for the first, should no counterbalancing disadvantages exist. In such cases the method of conducting the experiment is precisely the same as where the efficiency of the boiler is de- termined ; but the object sought is quite a different one. This also commonly compels at least two trials, the one of the old and standard, the other of the new and uncertain fuel, and a comparison of boiler-efficiency as found in the two trials. 23. The Determination of the Value of a steam-boiler involves the measurement of its efficiency, independently of the nature of the fuel, and it is thus important that a standard system of measuring the effectiveness of the fuel should be settled upon, or that all variations of such effectiveness should be eliminated. The latter is commonly the course taken ; and the determination of the efficiency of the boiler is based upon the measurement of the evaporation of water, under stated standard conditions, per unit weight of the combustible and burned portion of the fuel supplied during the trial. But the power of the boiler is as important an element of its value as its efficiency, and a complete trial includes, usually, measurements of efficiency at both the rated and the maximum working power of the boiler as operated for its special purpose. 24. The Evaporative Power of Fuels depends upon40 ENGINE AND BOILER TRIALS. not only their chemical composition as fuels, but also to an important extent upon their structure and their physical con- dition in every aspect; on their greater or less purity, and the admixture of earths, moisture, or other foreign matters; the fitness of the furnace for their utilization; the air-supply; its quantity, temperature, and humidity; the proximity of chilling surfaces; the extent of the combustion-chamber in which the gases rising from the bed of coal or other combustible may be more or less completely consumed; and many other minor con- ditions, all of which tell, in a more or less important degree, upon their value and the efficiency of the system of heat- generation. 25. Analyses of Fuels are sometimes made, either as a check upon the results of the trial or in substitution for it. Should analysis show that a given fuel is rich in heat-producing elements, while trial fails to give the results that should have been obtained, and such as the use of other fuels in the same boilers indicates to be possible, it will at once appear that the fuel demands peculiar treatment, or some other arrangement of furnace. Should doubt exist which of a number of fuels of the same class is best, chemical analysis may give a quicker and cheaper answer to the question than a formal trial. It rarely happens, however, that any system is as satisfactory, in the end, as actual trial extending over so long a period as to eliminate uncertainties. Methods of analysis differ somewhat. The following is a standard method of general treatment as prescribed by the Union of Engineers of Germany:* In order to take a sample of the fuel, a shovelful from each barrow or wagon will be thrown into a box with a cover. The coal will be mixed up and spread in the form of a square upon a level floor, and then divided by two diagonals into four parts. Of these, two opposite parts will be taken away, the other two will be broken up small and mixed together. Another shovelful will then be thrown in, and the method continued until about 10 kilogrammes are in the box. This will then be * American Engineer, August, 1883.ANALYSES OF FUELS. 41 dosed and reserved for chemical analysis. For accurate ex- periments the halves which have been taken away should also be analyzed. To determine the moisture in the coal, about 10 grammes from the above-named sample is to be heated for two hours to 105° or no° C. The loss in weight shows the moisture in the coal. Coal which happens to have been wetted by rain or otherwise should not be used. The test should be applied to coal in the average state of moisture at which it is delivered from the pit mouth, and this state should, if necessary, be determined beforehand. The remainder of the sample, pow- dered and mixed thoroughly, serves to determine the ash, the carbon, the hydrogen, the nitrogen, and the sulphur. The heating-value of the coal is determined as follows: Suppose that it is found t-o contain c per cent of carbon, h per cent of hydrogen, s per cent of sulphur, o per cent of oxygen, and w per cent of water, then the theoretical heating-value is given by the formula of Dulong as follows: (a). Referred to Water at o° Cent. 81000 + 34320 +25005. ( rt JB bfi bfi 3 rt Q External Air. Boiler-room. Flue. Feed-water. Steam. Time. Pounds. Time. Pounds ore. ft. • INSTRUCTIONS AND RULES. 53 REPORTING THE TRIAL. XVII. The final results should be recorded upon a properly prepared blank, and should include as many of the following items as are adapted for the specific object for which the trial is made. The items marked with a * may be omitted for or- dinary trials, but are desirable for comparison with similar data from other sources. Results of the trials of a....................... Boiler at..,........ ,....................... .... To determine..................................... 1. 2. Date of trial____ Duration of trial hours. DIMENSIONS AND PROPORTIONS. Leave space for complete description. See Ap pendix XXIII. 3. Grate surface... .wide... .long... .Area---- 4. Water-heating surface....................... 5. Superheating-surface....................... 6. Ratio of water heating surface to grate-sur- face...................................... sq. ft. sq. ft. sq. ft. AVERAGE PRESSURES. 7. Steam-pressure in boiler, by gauge... *8. Absolute steam-pressure............ *9. Atmospheric pressure, per barometer. 10. Force of draught in inches of water.. AVERAGE TEMPERATURES. ■*n. Of external air.................... *12. Of fire-room....................... “*13. Of steam.......................... 14. Of escaping gases.................. 15. Of feed-water...................... lbs. lbs. in. in. deg. deg. deg. deg. deg. FUEL. 16. 17. 18. x9- *21. *22. Total amount of coal consumed f......... Moisture in coal........................ Dry coal consumed................. ..... Total refuse, dry....pounds =........... Total combustible (dry weight of coal, Item 18, less refuse, Item 19)............. Dry coal consumed per hour.............. Combustible consumed per hour........... lbs. per cent, lbs. per cent. lbs.. lbs. lbs. * See reference in paragraph preceding table. f Including equivalent of wood used in lighting fire. 1 pound of wood •equals 0.4 pound coal. Not including unburnt coal withdrawn from fire at end of test.54 ENGINE AND BOILER TRIALS. 23. 24. 25. 26. 27. 28. *29. 30. 3i. 32. 33. RESULTS OF CALORIMETRIC TESTS. Quality of steam, dry steam being taken as unity................................. Percentage of moisture in steam......... per cent. Number of degrees superheated........... deg. WATER. Total weight of water pumped into boiler and apparently evaporated *............. Water actually evaporated, corrected for quality of steam f....................... Equivalent water evaporated into dry steam from and at 2120 F.f..................... Equivalent total heat derived from fuel in British thermal units f................. Equivalent water evaporated into dry steam from and at 212° F. per hour.............. lbs. lbs. lbs. \ B. T. U. lbs. ECONOMIC EVAPORATION. Water actually evaporated per pound of dry coal, from actual pressure and tempera- ture f ................................... Equivalent water evaporated per pound of dry coal from and at 212° F.f........... Equivalent water evaporated per pound of combustible from and at 2120 F.f.......... lbs. lbs. lbs. * Corrected for inequality of water-level and of steam-pressure at beginning and end of test. f The following shows how some of the items in the above table are de- rived from others: Item 27 = Item 26 X Item 23. Item 28 = Item 27 X Factor of evaporation. H — h Factor of evaporation == ^ ^ , /if and h being respectively the total heat- units in steam of the average observed pressure and in water of the average observed temperature of feed, as obtained from tables of the properties of steam and water. Item 29 = Item 27 X (N— h). Item 31 = Item 27 -r- Item 18. Item 32 = Item 28 -7- Item 18 or = Item 31 X Factor of evaporation. Item 33 — Item 28 -4- Item 20 or = Item 32 -f- (per cent 100 — Item 19)* Items 36 to 38. First term = Item 20 X- Items 40 to 42. First term = Item 39 X 0.8698. - T Item 30 Item 43 = Item 29 X 0.00003 or =--------j2-. 34i , Difference of Items 43 and 44 Item 45 =-----------i---------—-----—. ^ Item 44.PRECAUTIONS TO BE TAKEN. 55 COMMERCIAL EVAPORATION. 34. Equivalent water evaporated per pound of dry coal with one sixth refuse, at 70 pounds gauge-pressure, from temperature of ioor F. =Item 33 multiplied by 0.7249............. RATE OF COMBUSTION. 35. Dry coal actually burned per square foot of grate-surface per hour.................. ~ Per sq. ft. of grate- Consumption of dry coal per hour. Coal assumed with one sixth refuse, f *36. *37. *38. surface Per sq. ft. of water- heating surface___ Per sq. ft. of least area for draught.. RATE OF EVAPORATION. 39- *40. *41. *42. Water evaporated from and at 2120 F. per square foot of heating-surface per hour... ( Water evaporated per hour from tem- perature of ioo° F. into steam of 70 I pounds gauge-pres- [sure.f Per sq. ft. of grate- surface ^ Per sq. ft. of water- y heating surface.. Per sq. ft. of least area for draught. COMMERCIAL HORSE-POWER. lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. 43. On basis of thirty pounds of water per hour evaporated from temperature of ioo° F. into steam of 70 pounds gauge pressure, (= 34^ lbs. from and at 2120) f........ 44. Horse-power, builders* rating, at..square feet per horse-power................... 45. Per cent developed above, or below, rat- ingt-.................................. H. P. H. p. Per cent. 34. Precautions are to be taken in every possible way to prevent and avoid irregularities in the conduct of the trial and errors of observation.* In preparing for and conducting trials of steam-boilers the specific object of the proposed trial should be clearly defined and steadily kept in view, and as suggested by Mr. Hoadley— (1) If it be to determine the efficiency of a given style of boiler or of boiler-setting under normal conditions, the boiler brickwork, grates, dampers, flues, pipes, in short, the whole ap- paratus, should be carefully examined and accurately described, * The appendix to the report above quoted should be read in this connection.ENGINE AND BOILER TRIALS\ 56 and any variation from a normal condition should be remedied, if possible, and if irremediable, clearly described and pointed out. (2) If it be to ascertain the condition of a given boiler or set of boilers with a view to the improvement of whatever may be faulty, the conditions actually existing should be accurately observed and clearly described. (3) If the object be to determine the relative value of two or more kinds of coal, or the actual value of any kind, exact equality of conditions should be maintained if possible, or, where that is not practicable, all variations should be duly al- lowed for. (4) Only one variable should be allowed to enter into the problem; or, since the entire exclusion of disturbing variations cannot usually be effected, they should be kept as closely as possible within narrow limits, and allowed for with all possible accuracy. Blanks should be provided in advance, in which to enter all data observed during the test. The preceding instructions contain the form used in presenting the general results. Rec- ords should be, as far as possible, made in a standard form, in order that all may be bomparable. The observations must be made by the engineer conduct- ing the trial, or by his assistants, with this object distinctly in mind; and each should have a well-defined part of the work assigned him, and should assume responsibility for that part, having a distinct understanding in regard to the extent of his responsibility, and a good idea of the extent and nature of the work done by his colleagues, and the relations of each part to his own. No observations should be permitted to be made by unauthorized persons for entrance upon the log; and no duties should be permitted to be delegated by one as- sistant to another, without consultation and distinct under- standing with the engineer in charge. The trial should, wher- ever possible, be so conducted that any error that may occur in the record may be detected, checked, or, if advisable, removed, by some process of mutual verification of related observations. It is in this direction that the use of graphical methods of rec- ord and automatic instruments have greatest value.PRECAUTIONS TO BE TAKEN. 57 Several methods of weighing fuel have been found very satis- factory, but it should be an essential, feature that the weights shall be made by one observer and checked by another, at as distant a point as is convenient. The weighing of the fuel by one observer at the point of storage, and the record at that point of times of delivery, as well as of weights of each lot, and the tallying of the number and record of the time of receipt at the furnace-door, will be usually found a safe system. The fail- ure to record anyone weight leads to similar error, and can only be certainly prevented by an effective method of double observation and check. The same remarks apply, to a considerable extent, to the weighing of the water fed to the boiler. A careful arrangement of weighing apparatus, a double set of observations, where pos- sible, and thus safe checks on the figures obtained, are essential to certainty of results. With good observers at the tank, and with small demand for water, a single tank can be used; but two are preferable in all cases, and three should be used if the work demands very large amounts of feed-water, as at trials of very large boilers, or of “ batteries.” The more uniform the water-supply, as well as the more steady the firing, the less the liability to mistake in making the record. The two blanks which follow were prepared by the Author for use in laboratory as well as professional work. Such blanks are always desirable, and are sometimes even more elaborate than those here illustrated.* For ordinary purposes, a less complete tabulation may be sufficient; while, for special purposes and for scientific investigations and the work of research, considerable more elaboration may be found desirable, or even necessary. Graphical methods of representation of the data and con- ditions and of the progress of the trial, as elsewhere illustrated, are also often found exceedingly useful and convenient. * Vide “ Stevens Indicator,” Nov. ’89.TABLE I. LOG OF TRIAL BY MECHANICAL LABORATORY, DEPARTMENT OF ENGINEERING. 58 ENGINE AND BOILER TRIALS. I 3 •5 8. I + 1 d o> •o a B H Remarks. Weights. Feed-water. Per Tank. Per Metre. Fuel. Temperatures. Steam. Feed- water. Fuel. Boiler- room. External Air. Pressures. JS • 23 Q Steam- gauge. Barom- eter. j Time. Remarks. Super- heating. •sjiun * -^H •S33X83Q * •Sairauj JO 9J8BJU30I9J X •jajarauofe^ ojui uni uiB9is aajB^v tnojj lean // - I - H EDB33S tUOJJ lBOfl[ n = yx At •J3J301U01B3 OJ «o Q t 2 X z 2 , s u o » •raBOis < K w w jeOh K ~ fc o « f •J3JBM. aJ | be > w K c^ * II $ 6$ a: W rt C' PS S td Ed H w H I- g "c 5 »—t o •J V ^ u t/3 tn H X be o 3 C '53 u £ C «k u •saanssaad -wvai§ w H oTABLE II. AVERAGE AND TOTAL RESULTS OF TRIAL, MECHANICAL LABORATORY, DEPARTMENT OF ENGINEERING. Trial made at____________._______________ Fuel __________________________________________ on--------------------------------------- Composition_________________ FORMS OF BOILER-ROOM LOG. S9 «? Ui X s Heat- quired i one Water. •ajnssajd-meats fentae te pue • j „ziz mojj tuajBAinbg sq. ft. W °^o S§ 0 0 *g 0ziz te pue mojj tuajeAinbg d* 1 V~ rt 0.0 4J,U « 2c§ .a l.l23 CA •aiaiisnawo^ 'ivaox 'ajnssajd -meats jemae tB pue jatBM-paaj jo ajnt -Biadmat lentDB rnojg ibjox uoit-iodojg ■J 0 8* H X i o§. 8# ajnssajd-meats IBntOB tB puB * J 0ziz mojj tua[BAinbg « < •[B50X i Per Square Fi Heating-surtac Hour. c* unoq jad aaejjns JA X •g 0ziz jb puB mojj tuafBAmbg CA o z O • -Suiteau io •}J'bs jag 0 5 K 'ajnssajd -meats jentDB tB puB jatBM-paaj jo ajnt -Bjadmat jentoe mojg CO H W £: s •jnoq O a. CA z o U idd 3tBJ0 jo tooj ajenbs jag lbs. ► j < a 3 •ajnssajd-meais ]BntDB IB pus ' J 0ziz mojj tuaiBAinbg 1 *l^oX & w Ji •g 0ziz tB pue mojj tua[eAinbg 1 -aline# -tqSnEJQ 3 3 a0jQ 0U si a 'ajnssajd -meats jentoe jb puB jatBM-paaj jo ajnt -Bjadmat lentDB mojg < g W (A > w *a#ne# -meats i £ Pm •jataraojeg CO £ 1 •ajnssajd-meats lentDB tB pue • j 0nz mojj tuaiBAinbg CO ja UajEAV Fahr. b . -paajl 0 «o •g ozlz ?b puB mojj tuajBAinbg i w *Xaumiq3 ot aoueitug *2* a 3 Average 4PERATUI fci 0 Oh ‘ajnssajd -meats lentDB te pue £ uiy leaiatxg u ■s PU jatBM-paaj jo ajnt -Bjadmat fentoB mojg w h ajnssajd-meats £ ■ H •tiiooj -aaijog hi ■9 0 a 0 g lentoe te pue 0ziz mojj tua[BAinbg b . >M V. •g #ziz te pue mojj tua[BAinbg •aDVJHHS « h. -t SfJ S.5F «.s h ftf £ -ONIXVHH Oi 3XVH0 ao OliVg 'ajnssajd -meats jentoe te pue oi JO •sanjg jo do itoas -SS0J3 tseaq d jatBM-paaj jo ajnt •Bjadmat jeniDB mojg s* O a 'ajnssajd-meats 1 •aDBjans -JSaiteaq -jadns d § X 0 u lentoe te pue * j 0ziz mojj tuapjAtnbg < H ST 0 cu hi . 0 jy •g 0ziz te pue mojj tuafBAmbg CA X < •aDBjjns -•Suiteajj d > w 73 3 C3 3 CA £ ST h 2 O 3 -ajnssajd •3tBJO sq. ft. « « £ a. u £ -meats p?ntDB te pue jatBM-paaj jo ajnt -ejadmat |entDB mojg CO £ < 'ajnssajd-meats •qviHx ao HiONaq e a 0 u 3 ft, jentoe te pue * j 0ziz mojj tuaiBAinbg £ hrt hU 'o •g 0ziz te pue mojj tuaieAinbg CA •tvie i jo sxvrr •a c £ 3 j£ 'ajnssajd 'iviax jo aaawnj^ 1 •Cft‘ gsr . 05 JQ IIs < 3 3 «°u 3 < g « H H — O < 5 e . flj o < 75 2 "2 5 > CJ^ « £fp 21* > aJ o 'll 5 w| *- o — rt U rt *2 3 £ JjS g y 2 g a 8 rt rt 5 Ju S aJ'O rt 2* gg-B-aS fr. E'h C g* ** « C«Si oi M w cd « w •jBnjoy o 0. w « o K *P3^H V =S cq ni #■ cmv y jo samv^ ^ •pajuransg 'IBjuaiDijadra > u w u •pajBunjsg s y E 13-73 8.94 I 13,550 13,263 8,636 1 63 835,569 18 Loco. f ^OKe 6.76 IO.OI 13,550 6.530 9,669 ! 71 463,630 19 Loco. ) 7-39 11.2 ; I3,55° 7,138 10,819 I 77 549.626 20 Torpedo 12.54 8-37 | 14.727 12,113 8,085 ! 54 654,102 21 Torpedo 14.86 7.78 i 14,727 14,354 7-523 1 51 732,054 22 Torpedo 17.90 7-49 j 14.727 17,291 7-235 ! 49 847.259 23 Torpedo 20.74 7;°4 14,727 20,034 6,800 46 921,564 24 a b c d e ! / 1 £ The “ locomotive” boiler is found to be more efficient as a part of the engine and on the track than when mounted* as a stationary boiler, an unexpected result. 41. The Quality of Steam made in any boiler, or as sup- plied to an engine, is hardly less important than the quantity. When the steam is required for heating purposes simply, or even when all the heat issuing as waste, necessary or other, from the exhaust-ports of a non-condensing engine cylinder can be utilized for useful and paying purposes, this is a matter of no importance; but when it is essential that loss in the engine shall be made a minimum, and that the engine shall have maximum efficiency, the quality of the steam becomes exceedingly important. Dry steam is very much more efficient as a working substance in the steam-engine than wet; since, where the latter is supplied from the boiler, the waste by cylinder-condensation is greatly increased—and so greatly that the more obvious direct loss by the passing of heat through the engine in unavailable form, hot water acting as its vehicle, becomes comparatively small. The determination of the qualityQUALITY OF STEAM MADE. 85 of steam by any boiler is thus as important as the measure of its apparent evaporation. The difference between the apparent and the actual evapo- ration is often very great. A good boiler properly managed will usually “ prime” less than five per cent, even though having no superheating-surface, and less than two per cent may usually be hoped for. Steam is often made practically dry. But a hard-worked boiler, or one having defective circu- lation, will often prime ten or twenty per cent; and cases have been found in the experience of the Author in which the quan tity of water carried out of the boiler by the current of steam ex- ceeded the weight of the steam itself. It has thus happened that, where no measure of this defect has been made, the apparent evaporation only being reported, the quantity of water said to have been evaporated has equalled, and sometimes has even greatly exceeded, the theoretically possible evaporation of an absolutely perfect boiler. It is thus essential that, when the apparent evaporation has been determined by trial, the quantity of water entrained with the steam be measured and deducted, and then real evaporation thus ascertained and reduced for the standard conditions. Under ordinarily good conditions, a real evaporation of ten or eleven times the weight of the fuel, cor- responding to an efficiency of 0.75 to 0.80, represents the best practice, and a real evaporation of twelve of water by one of combustible, from and at the boiling-point, or an efficiency of eighty per cent, is rarely observed under the usually best con- ditions of steam-boiler practice. Where more than the efficiency here given as probable is reported, the work should be very care- fully revised, and errors sought until absolute certainty is secured. Trials not including calorimetric measurement of the water entrained with the steam are comparatively valueless, and should be rejected in any important case. Reports of extra- ordinary economy are often based on this kind of error. The experiments of M. Hirn at Mulhouse showed an average of about 5 per cent priming ; Zeuner makes it approximately from to 15 per cent; while the experiments of the Author at the American Institute in 1871 give from 3 to 6.9 per cent.86 ENGINE AND BOILER TRIALS. A recently devised method of measuring the amount of moisture in the steam is to introduce into the boiler with the feed-water sulphate of soda, and at intervals to draw from the lower gauge-cock a small amount of water, and also from the steam, condensing either by a coil of pipe in water or a small pipe in air. A chemical analysis gives the proportion of sul- phate of soda in each portion, and the quotient of the propor- tion of sulphate of soda in the portion from the steam by the proportion in that from the water gives the ratio of water entrained, as steam does not carry sulphate of soda, which is only brought over by the hot water entrained. This method was used by Professor Stahlschmidt at the Diisseldorf Exhibi- tion Trials. 42. The Calorimeters used in determining the quantity of moisture in steam have several forms, widely differing in construction, and to some extent in value. They nearly all embody the same principles, however. The objects sought to be attained in their construction are: The exact measure- ment of the weight of steam received by them from the boiler,, and of its temperature and pressure at the boiler; the determi- nation of the weight of water used in its condensation and the range of temperature through which it is raised in the operation; the reduction of wastes of heat in the calorimeter to a minimum, and the exact measurement of that waste if it is sensibly or practically noticeable. The Barrel or Tank Calorimeter as employed by the Author, is the simplest form of this instrument which has been produced. It consists of a strong barrel or tank, of hard wood, absorbing little of either water or heat, and having a movable cover. This tank is mounted on platform-scales capable of accurate adjustment and having as fine readings as possible. It is filled with water to within about one fourth its height from the top, and the steam is led into it through a rubber tube or hose of sufficient capacity to supply the steam to the amount of one eighth or one tenth the weight of the water in three or five minutes. A steam-gauge of known accuracy gives the boiler-pressure, and the corresponding temperature and totaL heat of the steam are ascertained from the steam-tables.CALORIMETERS. 8 7 In using this apparatus the steam is rapidly passed into the mass of water contained in the tank, until the scales show that the desired quantity has been added. The steam is so directed by varying the position of the end of the tube, and by inserting it so deeply in the water that the whole mass is very thoroughly stirred, and a very perfect mixture secured of condensing water with the water of condensation ; and so that the temperatures indicated by the inserted thermometer shall be the real mean temperature of the mass. The weights and temperatures are then inserted in the log of the trial, as below, and the proportion of water brought over with the steam is thence easily calculable. The thermometers employed usually read to tenths of a degree Fahrenheit, or to twentieths of a centigrade degree, accordingly as the one or the other scale is employed. Readings must be made with the greatest pos- sible accuracy, and in sufficient number to insure a satis- factorily exact mean. With good thermometers and scales, a reliable gauge, and care in operation, good results can be obtained by averaging a series of trials.* The Him Calorimeter is substantially the same as the above, with the addition of an apparatus for stirring the water Fig. i.—The Calorimeter. Report on Boiler Trial, Trans. A. S. M. E. 1884, vol. vi.88 ENGINE AND BOILER TRIALS. in the tank to insure thorough mixture and readings of tem- perature of condensing water exactly representative of the true mean temperature of the mass after the introduction of the steam. This is not an essential feature of the apparatus, if the Author may judge by his own experience, provided the jet of entering steam is so directed as to cause rapid circulation. No stirring apparatus could operate more efficiently than the force of the steam itself, properly directed. Hirn was probably the first (1868) to attempt the determination of the quality of steam as delivered from steam-boilers.* A similar apparatus was used at the trials of the Centennial International Exhibition, Philadelphia, i8/6.f 43. The Theory of the Calorimeter is as follows:% Each pound of saturated steam transferred to the condens- ing water the quantity of heat which had been required to raise it from the temperature of the water of condensation to that due to the pressure at which it left the boiler, plus the heat required to evaporate it at that temperature. Each pound of water gives up only the quantity of heat required to raise it from the temperature of the water of condensation to that of the steam, with which it is mingled. The total amount of heat is made up of two quantities, therefore, and a very simple algebraic equation may be constructed, which shall express the conditions of the problem: Let, as in § 258, H = heat-units transferred per pound of steam ; h = heat-units transferred per pound of water; U = total quantity of heat transferred to condenser; W = total weight of steam and water, or of feed-water; x — total weight of steam ; W — x = total weight of water primed. * Bulletin de la Societe Industrielle de Mulhouse, 1868-9. f Reports of Judges, vol. vi. % First published by the Author, who had not then become aware of the work done by M. Hirn, in Trans. Am. Inst. Report on Boiler Trial, 1871. See also Vienna Reports, vol. iii. p. 123.THEORY OF THE CALORIMETER. 89 Then Hx +h (IV- x) =U; or * =■ A ~W U-Wh ~H -H-h ' T“‘ Substituting the proper values in this equation, we deter- mine the absolute weights and percentages of steam and water delivered by the boiler. Or, let Q = quality of the steam, dry saturated steam being unity ; Hr = total heat of steam at observed pressure; T = “ “ “ water “ “ h! = “ “ “ condensing water, original; hx = u u u “ final. And we have the equivalent expression, as written by Mr. Kent, The value of the quantity U is obtained by multiplying the weight of water in the calorimeter originally by the range of temperature caused by the introduction of the steam from the boiler. Mr. Emery employs another form, as below, in which Q is the quality of steam as before ; W the weight of con- densing water ; w the weight added from the boiler; T the temperature due the steam-pressure in the boiler; t the initial and tx the final temperature of the calorimeter; / the latent heat of evaporation of the boiler-steam; and the weight of steam corresponding to L Thus, Q- H' -T W(tx — f) — w {T — tt) l and Q = x_ _ W(t, - Iw w90 ENGINE AND BOILER TRIALS. The following expressions give the quality of steam as com- puted from metric data supplied by the calorimeter, and Boss- cha’s corrections being introduced for specific heat of water at varying temperatures: * wx = weight of condensing water; px = absolute pressure of steam; /, — the initial temperature of condensing water; /3 = the final temperature of the water; t% — the temperature of steam in boiler; w2 = cold-water weight; w% = weight of steam condensed; xf = percentage of steam in the mixture from the boiler, uncorrected for specific heat of water; x — same as xf, but with Bosscha’s correction; , _ —ti)w* — (t*— (606.5—0.695*,)w, ’ X _ 0.00011[(*/-*,a)w,-(*3a-*, X (606.5 — 0.695*3)^, Mr. Nystrom has employed the Hirn calorimeter, substi- tuting ice for cold water as a condensing medium.f In this case, adopting his notation, w = pounds of cold water put into the barrel; h = units of heat per pound of w when cold and above 320; / = pounds of ice put into the barrel; W = pounds of heated water in the barrel after the comple- tion of the experiment; that is, including the weight of the condensed steam ; k' = units of heat per pound of Wabove 320; f — pounds of foam or water carried over with the steam into the barrel; 5 = pounds of saturated steam blown into the barrel; * Proc. Brit. Inst. C. E., 1888, No. 2306. f Pocket-book; Humidity of Steam, p. 572.THEORY OF THE CALORIMETER. 9* H = units of heat per pound of the steam S; Hf = units of heat per pound of the foam f; p = pounds of steam and foam carried over from the boiler into the barrel; P = units of heat passed over with the steam and foam into- the barrel; The weight p must then be equal to the sum of the weights of the steam 5 and foam f, which is evidently the same as the difference between the weights W and w. That is, p = S-\- f — W — w. The total units of heat P passed over with the steam 5 and foam f must then be : P = HS + H'f= Wh! — wk. By solving this formula for the steam S, we have: P-HJ ~~ H jy—w—f. S = p-f-. f(H-H') = Hp — P. From this formula we have the weight of foam carried over with the steam from the boiler into the barrel; namely, . Hp-P 7 ~~ H — H'‘ But P = Whf — wk, which, inserted in the formula, gives: Pounds of foam, / = Hp + wh — Wh’ H~^~H92 ENGINE AND BOILER TRIALS. The percentage of humidity of the steam will then be: The Formula (8) is ready for use of the data obtained by the calorimeter when p — W — w, and when no ice is used. For the melting of i pound of ice requires 142.65 units of heat, according to Regnault’s delicate experiments, but for the caloric experiments on humidity of steam 142.6 units of steam will be more correct. Then the units of heat required to melt the ice to water of 320 by the steam in the barrel will be 142.6/, and the heat required to raise the temperature of that water; from 320 to that of W when the experiment is completed will be Ih'. But the weight of ice melted to water is included in the weight W; the heat passed with the steam from the boiler into the ice and cold water will be, P = Wti — wh -f- 142.6/. This formula, inserted for P in Formula (7), will give the weight of foam passed with the steam from the boiler into the ice and cold water. Hp + wh — (Wh! + 142.6/) H—H' When no cold water is used, but the humid steam is blown into only ice in the barrel, then the weight of foam will be: Hp-(Wkf + 142.61) f ~~ H-H The percentage of humidity will be in either case For humid steam, Hp > P. For saturated steam, Hp = P. For superheated steam, Hp < P.THEORY OF THE CALORIMETER. 93 When the steam is superheated, the formulas give a nega- tive value of f. The following data and results are given in illustration of this method by its author: Example.—Steam-pressure by gauge, 98 pounds. H — 1184.6 and H' = 308.7. Weight of empty barrel with top,...........64.25 lbs. I — 80.5 pounds of ice,................... 144-75 “ w — 287.25 pounds of water at 710 h = 39.015, 432.00 “ W= 404 pounds of mixture at 136° h — 104.2, 468.25 “ p = 36.25 pounds of steam and foam. Formula 11. 1 i84-6x 36.25+287-25 X 39-pi 5 -(404 X 104.24-142.6x 80.5) 1184.6 — 308.7 = 0.653 lbs. 100 x 0.6?3 Humidity of the steam, c/0 =---D0 = 1.8 per cent. In the use of the calorimeter it may be reasonably expected that errors may be made, by careful work, something less than one per cent. The results of good work should agree within less than one-half per cent. Thermometers should read within one-tenth of a degree; steam-gauges should be correct within less than one or two pounds, and weights within one per cent or less. The latter are the most trying quantities to measure with satisfactory accuracy. Generally the lower the initial tem- perature of the calorimeter the better the results, and it is often thought advisable to cool the condensing water, by the use of ice, down to the melting point. The amount of steam intro- duced should be as great as is possible without causing so high a final temperature as to cause the production of troublesome quantities of vapor in the calorimeter.94 ENGINE AND BOILER TRIALS. If Q exceeds unity, the steam is superheated by the amount 02-iy 048 = 2.0833/(0-/);* and if less than unity, the priming is, in per cent, 100 (1 — Q). 44. Records of calorimetric tests should be even more carefully and more frequently made than in any other part of the work of a boiler-trial. The following, from work conducted by the Author, illustrates the method. The symbols relate to the first of the above formulas. PRIMING TESTS. Calorimeter. Heat-units fis.K r-ouiso tn tj B la B 0 ^ £ w Weights. Tempera- ture. from Boiler. c 0 S -■gs § a el| «.£ c 6 cn o> u 3 u 52 rt > s|| B y s B 2 ~ £ w c3 g'C 2o< V CU 02 7 1209.19 19775. 1082.49 181.37 18.231 7.82 7 2.25 60. | 250. 18.2 44.2 122.3 78-1 309.88 1207.61 19525. 1085.31 187.58 17.946 7-74 8 3.10 6 x.5'250. 16.92 44.6 121.7,77.1 311.27 1208.02 19275. 1086.32 189.57 17.917 7.68 9 3-55 65. : 250. 17.1 47-3 121.4 74.1 3*4-44 1208.96 18525. 1087.56 193.04 17.0x9 7-30 20 4-3° 6l. 250. 17.1 '46.6 i 120.6174.0 310.81 1 1 1207.88 18500. 1087.28 190.21 16.996 7.29 The boiler was a water-tubular boiler, which was not so handled as to give as dry steam as was desired; and one object of the trial, of which the above is a part of the record, was to ascertain how seriously was the quality of the steam affected. It is seen that the priming amounted to seven or eight per cent, with fairly uniform figures through the period of test. The steam should have entrained less than one half this proportion, had the boiler been all that was expected of it. Errors of small magnitude, absolutely, may greatly affect the results of calculation, as is well illustrated by the following example presented by Mr. Kent: * Centennial Report, pp. 138-9.RECORDS OF CALORIMETRIC TESTS,. 95 Assume the values of the quantities to be, as read, column I: Observed Reading. True Reading. Amount of Error. Weight of condensing water, corrected for equivalent of apparatus,* IV 200.5 lbs. 9.9 “ 78. “ 44° *5 “ ioo°.5 “ 200 lbs. £ pound. 2 pounds, degree. "Weight of condensed steam, w 10.0 “ Pressure of steam by gauge, P 80 “ Original temperature of condensing water, t.... Final temperature of condensing water, 1! 45° “ IOO° “ Then let it be assumed that errors of instruments or of ob- servation have led to the recording of slightly different figures from the true quantities, as given in column 2: Substituting in the formula the “ true Moisture per cent. Error per cent. readings,” we have for the value of Q = 0.9874 = 1.26 = O. All readings true except W- 200.5, Q = .9906 = O.94 = 0.32 w = 9*9> Q = 1.0000 = 0.00 = 1.26 t i ti ft tt P - 78.0, Q— .9880=1.20 = 0.06 «t if (( tt t — 44-5, Q = .9989 = 0.11 = 1.15 it it ft ft t' — 100.5, Q = .9994 = 0.06 = 1.20 “ “ incorrect... Q = 1.0272 = (minus) = 3.98 . The last case is equivalent to 50.2 degrees superheating. Errors of 0.1 or even 0.25 per cent in weights and of tem- perature of equal amount not infrequently occur, probably, where ordinary instruments are employed. The errors due to false weight in measurement of the condensed steam are liable to be very serious, and it is only by making a consider- able number of observations and obtaining the mean that re- sults can be secured, ordinarily, of real value. 45. The “ Coil Calorimeter,, has been devised to secure more exact results in the weighing of the water of condensation than can be obtained when it is weighed as part of the larger mass. In this instrument a coil of pipe is introduced into the tank and serves as a surface-condenser in which the boiler-steam is received and condensed, and from which it is transferred to another vessel in which it is weighed by itself with scales con- structed to weigh such small weights with accuracy; or the coil is removed and weighed with the contained water. In the * Correction made only for . coil calorimeter-to be described.96 ENGINE AND BOILER TRIALS former case, drops of water may adhere to the internal surfaces of the coil and escape measurement; in the latter, the weight to be determined is increased by the known weight of the coil, and less delicacy of weighing becomes possible. The following is Kent’s description of his calorimeter, which is of this class, and has been found to give good results: * A surface-condenser is made of light-weight copper tubing f,f in diameter and about 50' in length, coiled into two coils, one inside of the other, the outer coil 14" and the inner 10" in diameter, both coils being 15" high. The lower ends of the coils are connected by means of a brazed T-coupling to a shorter coil, about 5' long, of 2" copper tubing, which is placed at the bottom of the smaller coil and acts as a receiver to contain the condensed water. The larger coil is brazed to a £" pipe, which passes upward alongside of the outer coil to just above the level of the top of the coil and ends in a globe-valve, and a short elbow-pipe which points outward from the coil. The upper ends of the two f" coils are brazed together into a T, and con- nected thereby to a £" vertical pipe provided with a globe-valve, immediately above which is placed a three-way cock, and above that a brass union ground steam-tight. The upper portion of the union is connected to the steam-hose, which latter is thoroughly felted down to the union. The three-way cock has a piece of pipe a few inches long attached to its middle outlet and pointing outward from the coil. A water-barrel, large enough to receive the coil and with some space to spare, is lined with a cylindrical vessel of galva- nized iron. The space between the iron and the wood of the barrel is filled with hair-felt. The iron lining is made to return over the edge of the barrel, and is nailed down to the outer edge so as to keep the felt always dry. The barrel is furnished also with a small propeller, the shaft of which runs inside of the inner coil when the latter is placed in the barrel. The barrel is hung on trunnions by a bail by which it may be raised for weighing on a steelyard supported on a tripod and lifting lever. The steelyard for weighing the barrel is graduated * Trans. Am. Soc. M. E. 1884.THE “COIL” CALORIMETER. 97 to tenths of a pound, and a smaller steelyard is used for weigh- ing the coil, which is graduated to hundredths of a pound. In operation, the coil, thoroughly dry inside and out, is carefully weighed on the small steelyard. It is then placed in the barrel, which is filled with cold water up to the level of the top of the globe-valves of the coil and just below the level of the three-way cock, the propeller being inserted and its handle con- nected. The barrel and its contents are carefully weighed on the large steelyard ; the steam-hose is connected by means of its union to the coil, and the three-way cock turned so as to let the steam flow through it into the outer air, by which means the hose is thoroughly heated ; but no steam is allowed to go into the coil. The water in the barrel is now rapidly stirred in reverse directions by the propeller and its temperature taken. The three-way cock is then quickly turned, so as to stop the steam escaping into the air and to turn it into the coil; the thermometer is held in the barrel, and the water stirred until the thermometer indicates from five to ten degrees less than the maximum temperature desired. The globe-valve leading to the coil is then rapidly and tightly closed, the three-way cock turned to let the steam in the hose escape into the air, and the steam entering the hose shut off. During this time the water is being stirred, and the observer carefully notes the thermometer until the maximum temperature is reached, which is recorded as the final temperature of the condensing water. The union is then disconnected and the barrel and coil weighed together on the large steelyard; the coil is then withdrawn from the barrel and hung up to dry thoroughly on the outside. When dry it is weighed on the small scales. If the temperature of the water in the barrel is raised to no° or 1200 the coil will dry to con- stant weight in a few minutes. After the weight is taken, both globe-valves to the coil are opened, the steam-hose connected, and all of the condensed water blown out of the coil, and steam allowed to blow through the coil freely for a few seconds at full pressure. When the coil cools it may be weighed again, and is then ready for another test. If both steelyards were perfectly accurate, and there were no losses by leakage or evaporation, the difference between the98 ENGINE AND BOILER TRIALS. original and final weights of the barrel and contents should be exactly the same as the difference between the original and final weights of the coil. In practice this is rarely found to be the case, since there is a slight possible error in each weighing, which is larger in the weighing on the large steelyard. In making calculations the weights of the coil on the small steel- yard should be used, the weight on the large steelyard being used merely as a check against large errors. The late Mr. J. C. Hoadley constructed exceedingly accu- rate apparatus of the “ coil ” type and obtained excellent re- sults. It is evident that this calorimeter may be used continuously, if desired, instead of intermittently. In this case a continuous flow of condensing water into and out of the barrel must be established, and the temperature of inflow and outflow and of the condensed steam read at short intervals of time. 46. The Continuous Calorimeter is an instrument in which the operations of transfer of steam to the instrument and its examination are not intermitted, as is necessarily the case in the more commonly employed forms of the apparatus. The instrument being thus kept in use continuously, every variation in the quality of steam can be observed and the num- ber of observations can be increased to any desired extent, and, the apparatus being accurate, any degree of exactness of mean results can be attained. One of the earliest forms of this instrument was devised by Mr. John D. Van Buren, of the U. S. N. Engineers, and In- structor in Engineering at the Naval Academy, about 1867. This instrument, as constructed by Mr. T. Skeel, and used by a committee of judges* at the exhibition of the American In- stitute, 1874-5, of which the Author was chairman, was made as follows : Steam was drawn from the steam-drum, near the safety- valve, through a felted pipe i£ inches (3.8 cm.) diameter, into a rectangular spiral or coil consisting of 80 feet (24.4 m.) of pipe of similar size. Condensing water from the street-main was led into the tank surrounding the coil or “ worm,” and * Trans. Am. Inst. 1875; Van Nostrand’s Mag. 1875.THE CONTINUOUS CALORIMETER. 99 issued at the bottom through a “ standard orifice,” the rate of -discharge from which had been determined and the law of its variation with change of head ascertained. The quantity of condensing water thus became known by observing the head •of water within the tank. The water of condensation from the coil was caught in a convenient vessel, and weighed on scales provided for that purpose. The temperature of the condensing water at entrance and exit was shown by fixed thermometers, and that of the water of condensation at its issue from the coil was similarly shown, while the steam-gauge placed on the boiler gave the other needed data. The calculations are evidently precisely the same as with the preceding type of calorimeter. The Barrus Calorimeter * (Fig. 2) is essentially of a small surface-condenser. The steam enters by the pipe j. The con- Fig. 2.-The Continuous Calorimeter. to the bottom by means of the tube k, and overflows at the pipe, c> after passing through the mixing chambers, m. The amount of water admitted is regu- lated so as to secure a temperature at the overflow of 750 or 8o° Fahr., or the approximate temperature of the surrounding atmosphere. The thermometers, / and g, which are read to densing-surface, a, is a continua- tion and enlargement of the supply-pipe, a i-inch (2.54 cm.) iron pipe with a length of 12 inches (30.4 cm.) of exposed sur- face. This pipe is under the full pressure of steam. The con- densed water collects in the lower parts of the apparatus, where its level is shown in the glass, e> and is drawn off by means of the valve, d. The injection-water, cooled to a temperature of 40° Fahr., or less, enters the wooden vessel, o, through the valve, b, and circulates around the con- densing pipe, carried downward Trans. Am. Soc. M. E. 1884.IOO ENGINE AND BOILER TRIALS. tenths of a degree, show the temperature of injection and over- flow water, and the thermometer, /*, shows that of the com densed water. The overflow water and the condensed water are collected in a system of weighing tanks. The steam-pipe down to the surface of the water, and the pipes in the lower part of the apparatus, are covered with felt. There is no wire-drawing of the steam, and no allowance to be made for specific heat of the apparatus. The only correct tion to be made of material amount is for radiation from the pipes covered with felt, and this can be accurately determined by an independent radiation experiment, made when the con- denser vessel is empty. Another form of instrument devised by the same engineer is arranged in such manner as to permit the steam from the boiler to be dried and the quantity of heat so employed meas- ured as a gauge of the amount of water contained in the steam. This form of this apparatus is found very satisfactory.* The pipe conveying the steam to be tested is usually a half-inch (1.27 cm.) iron pipe. A long thread is cut on this pipe, and it is screwed into the main steam supply-pipe of the boiler in such a manner as to extend diametrically across to the opposite side. The inclosed part is perforated with from 40 to 50 small holes, and the open end of the pipe sealed. If the pipe is screwed into the under side the perforations begin at a distance of one inch (2.54 cm.) from the bottom. The connection is made as short as possible, and covered with felt. Where the calorimeter can be attached to the under side of the main, the distance to the top valve need not exceed six inches (15 cm.). In this position it is self-supporting. The steam for the superheater is also supplied by a half-inch iron pipe, but this may be at- tached to the main at any convenient point. Steam to be tested enters by the pipe, which has a jacket. On passing out the thermometer gives its tem- perature, and it is discharged through a small orifice £ inch (0.32 cm.) in diameter. Steam to be superheated enters and is superheated by a gas-lamp, passes the thermometer, * Trans. Am. Soc. Mech. Engrs., vol. vii. p. 178.THE CONTINUOUS CALORIMETER. IOI and issues through an opening like that for the steam. The thermometers are immersed in oil-wells surrounded by the current of steam to be tested, or of that used in drying the boiler-steam. In the operation of this calorimeter steam at full pressure enters the apparatus, and the jacket-steam is heated until a perceptible rise of temperature above that due the pres- sure indicates that its moisture has been evaporated. The working having become steady, the difference between the temperatures is noted and corrected by deducting the ex- cess above that of moist steam at the observed pressure, and the number of degrees of superheating thus determined, as the rate of flow is the same from both orifices. Here the evaporation of one per cent of moisture from steam at 80 pounds pressure (5.6 kilogs. per sq. cm.) reduces the tempera- ture of superheated steam about i8°.7 Fahr. (io°.4 Cent.), and the percentage of moisture is obtained by dividing the range of superheat, as above, by this number, or generally by the quotient of the latent heat at the observed pressure by 47.5. The following are data and results obtained by the use of this apparatus: Data and Results in Full of Calorimeter Tests. Number for Reference. Date. Gauge- pressure. Number of degrees in- let steam was super- heated. Number of degrees outlet steam was superheated. Number of degrees wet steam was super- heated. Number of degrees lost by superheated steam due to radi- ation from calorime- ter. Number of degrees representing radia- tion from supply- pipe. Amount of Moisture in the Wet Steam. Expressed in degrees of superheat. Expressed in j percentage.* I Apr. 13 89. 99. 54-5 8. 8. 9*5 19. 1.02 2 “ 14 89. 75- 37* 5-5 8. 9-5 16. 0.86 3 “ 15 86. 74- 37- 7- 10.5 9-5 IO. 0-54 4 “ 16 86. 74. 39* 9-5 7- 9-5 9- 0 49 5 “ 30 85. 72. 38. 10.5 8. 9-5 6. 0.32 6 May 4 80. 77.5 4i-5 9-5 • 8. 9-5 9- 0.49 7 “ 5 84. 68. 36.5 6.5 7.5 9-5 8. 0.43 Note.—The duration of each of these tests was about one hour. * Obtained by dividing tfce preceding column by 18.6, the number of degrees corresponding to 1 per cent of moisture.102 ENGINE AND BOILER TRIALS. An exceedingly simple form of calorimeter, practically avail- able when the steam is fairly dry, is that devised by Professor Peabody, which depends on the fact that dry steam is super- heated by wire-drawing.* A piece of pipe six inches in diameter and ten inches long- was capped at each end. Into the upper end was fitted a half- inch pipe bringing the steam to be tested, a thermometer cup, and a steam-gauge. From the lower cap an inch pipe led away- the exhaust steam. Near the calorimeter was a T which formed a pocket, with a drip at the lower opening, and a branch from the side opening leading to an angle valve in the upper cap of the condenser. The pipe further was well wrapped with hair felt, and the calorimeter was wrapped in asbestos board and hair felt, and covered with russia iron. Two other calorimeters differ from the first only in size.. One is made of a piece of two-inch pipe eight inches long, and the other of a piece of four-inch pipe of the same length. The smaller are more sensitive. To make an experiment, the valve in the supply-pipe is partly opened, and a valve in the exhaust-pipe is regulated to give the desired pressure in the calorimeter. After the gauge and thermometer attached become steady, their readings are taken, and the reading of the boiler-gauge. If px is the boiler-pressure, / is the heat of vaporization, and h the heat of the liquid corresponding, x may represent the dry steam in one pound of the mixture from the steam-pipe; i — x is the water or priming. The heat in one pound of the mix- ture is xl -f- h. Let /2 be the pressure in the calorimeter, and hx the total heat, and the temperature corresponding. Let /2 be the tem- perature of the superheated steam by the thermometer. Then the heat in one pound of steam in the calorimeter is K + CU* — A)> * Trans. Am. Soc. M. E.. 188S, vol. x.THE CONTINUOUS CALORIMETER. 103 in which cP is the specific heat of the superheated steam at con- stant pressure (0.4808). Assuming that no heat is lost, xl + h = hx + cp{t% — tx) ; . _ K + ~~ A) r * ‘x— / and the priming is 1 — ;r. The following experiments were made: Gauge Pressures. Temperature in the calo- rimeter F. Priming. Boiler. Calorimeter. 71.2 38.5 286.7 O.OII 60.3 26.8 271.8 O.OI2 63.0 17-5 264.9 O.O13 60.6 7.0 258.8 O.OII 69.0 3-7 258.I 1 0.012 The other calorimeters gave substantially the same results. This type of calorimeter can be used only when the prim- ing is not excessive; otherwise the wire-drawing will fail to superheat the steam. To find this limit for any pressure, we may assume that the steam is just dry and saturated at that limit in the calorimeter The limit is higher for higher pressures, but the calorimeter can be applied only where the priming is moderate, thus: Pressure. Priming. Absolute. Gauge. 300 285.3 O.077 250 235-3 O.070 200 185.3 O.061 175 160.3 0.058 150 135-3 O.052 125 HO.3 0.046 IOO 85.3 0.040 75 60.3 O.032 50 35-3 O.023104 ENGINE AND BOILER TRIALS. The limit may be extended by connecting the exhaust to a condenser. The limit at ioo pounds absolute, with 3 pounds absolute in the calorimeter, thus becomes 0.064, instead of 0.046. The thermometer should be absolutely reliable. A consid- erable error in the temperature would produce an inconsider- able effect on the result in other cases. Thus, at 100 pounds absolute with atmospheric pressure in the calorimeter, io° F. of superheating indicates 0.035 priming, and 150 F. indicates 0.032 priming. A slight error in the gauge-reading has little effect. If reading be apparently 100.5 pounds absolute instead of 100, with io° of superheating, the priming appears to be 0.033 instead of 0.032. In the Barrus calorimeter, as has been seen, the steam to be tested is dried and superheated by a stream of highly super- heated steam. The following table has been calculated on the assumption that the superheated steam has an initial tempera- ture of 500°, and a final temperature of io° above the tempera- ture of saturated steam of the given pressure, while the moist steam is supposed to be dried and superheated 50. The limit under these conditions is widest for lowest pressures, and also is narrower at high, pressures than that of the new type: Pressure. Priming. Absolute. Gauge. 50 35-3 O.170 75 60.3 O.O95 IOO 185.3 0.086 125 no.3 0.078 150 135.3 O.071 175 160.3 0.065 200 185-3 O.059 250 235.3 O.049 300 285.3 O.040 One or another of these instruments may thus be best, ac- cording to pressure of steam carried.ANALYSIS OF GASES. 105 Many other forms of calorimeter have been devised, but space will not permit their description. 47. The Analysis of Gases* issuing from the furnace and passing up the chimney is sometimes an important detail of the work of testing a steam-boiler. Such an investigation involves only an operation of great simplicity which can easily be performed by any engineer. If it is not found convenient to make the analysis in the office of the engineer, he can have the work done, at little expense, by a chemist of known skill and reliability. It is only by a knowledge of the proportions of constituents of the flue-gases that it can be determined whether the combustion is complete, whether the products of combustion are diluted with excess of air, and whether the fuel used has been so burned as to give its best effect. Such analyses also enable the engineer to ascertain the best method of burn- ing the fuel. In sampling the gases, a matter in regard to which some precaution is advisable, the method of Mr. Hoadly is found very satisfactory.*!* Very great diversities in composition often exist in the same flue at the same time. To obtain a sample, allow one orifice to draw off gases through for each 25 sq. inches (161 sq. cm.) of cross-section of flue. The pipes must be of equal diameter and of equal length. These should be secured in a box of galvanized sheet-iron, equal in thickness to one course of brick, so that the ends may be evenly distributed over the flue A (Fig. 3), and their other open ends inclosed in the r Fig. 3.—Flue-gas Sampling. * Consult Handbook of Gas Analysis, by C. Winkler. London : J. Van Voorst. 1885. f Trans. Am. Spc. M. E., vol. vi.io6 ENGINE AND BOILER TRIALS. receiver B. If the flue gases be drawn off from the receiver B by four tubes C C', into a mixing box D, beneath, a good mixture can be obtained. The sampling of the gas should be carried out at intervals of io to 15 minutes throughout the trial. The gas should be received in an air-tight pipe or jar. The composition of the gases should be determined as far as regards carbonic acid, car- bonic oxide, and oxygen. The tube should be of porcelain or glass for very hot flues, since iron tubes at such temperatures are oxidized. Supposing an analysis of the gas give K per cent of carbonic acid, 0 per cent of oxygen, and A* per cent of nitrogen, then the proportion of air actually used to the theoretical quantity required is 1 to x. Where N x = or * 21 N— — 0 2i-79~ 21 /yN unity of weight of this coal will then give, at a temperature of O0 and a pressure of one atmosphere, ----C = carbonic acid : 10 KO —- = oxygen ; KN — nitrogen. A The quantity of moisture in the escaping gases may be cal- culated from the moisture in the coal, from that formed by burning the hydrogen, and from that contained in the air ad- mitted to the furnace where the latter has been determined. Any serious break in the setting can be detected by filling the grate with smoky coal and then closing the damper. The following sketch shows the apparatus employed by Mr. Wilson* * Journal Society of Arts, Feb. 1SS9.ANALYSIS OF GASES. 107 A. Apparatus employed for the gas analyses. The whole apparatus being filled with mercury, the gas is introduced into the eudiometer a and its volume measured. The stopcock b and the three-way cock c are then opened, and the gas passes over into the laboratory vessel dy followed by some mercury to drive all the gas out of the capillary tube. The reagent is then poured into the cup e, and admitted to the laboratory vessel by the three-way cock. When the absorption is complete, the mercury bottle is placed on the upper shelf and the cocks being opened the gas passes back into the eudiometer. When the reagent rises to c the three-way cock is turned to communicate with the cup so that the reagent passes into it. Some mercury is then driven over into the eudiometer to clear the gas from the capillary tube, and the volume is again read. The two ends of the capillary tubes at f are made funnel-shaped, and connected by a thick india- rubber tube. By lowering the eudi- ometer a little when the gas is pass- ed from a to dy and raising it for the passage in the opposite direction, the whole of the gas is driven out of the tube. Fig. 4.—Apparatus for Gas Analysis. B. One of the tubes used for taking samples of gas. The sampler, completely filled with mercury, is connected with the gas to be taken by means of an india-rubber tube (previously, aspirated if necessary). The vessel is then inclined so as to allow mercury to flow out of the opposite tube until only enough remains to seal up the sample. The apparatus designed by Professor Elliott, and employed in work carried on under the direction of the Author, consists.io8 ENGINE AND BOILER TRIALS. 1K Li \ w cyll llo B* * yL t* gz: a Fig. .5.—Apparatus for Gas Analysis. as shown in Fig. 5, of two vertical glass tubes, AB, A'B', joined by rubber-tubing, E, at their upper ends. The large tube, AB, is the treating, the smaller, A'B', the measuring tube; the latter is suitably graduated to cubic centi- metres. Water-bottles, K, L, are connected with the lower ends of the tubes by tubing, NO, N'O', and are used in effecting transfer of I the gas from tube to tube. M is a funnel I through which the reagents used may be in- troduced. G, Fy and / are cocks of suitable _ size and construction. In filling the apparatus it is set up conveniently near the flue, and the line of tubing from the collector, within the latter, is connected with the tube AB. The receiver L being de- tached the lower end of AB is connected with an aspirator or equivalent apparatus, such, for example, as might be improvised by the use of an air-tight tank or a barrel; and the flow thus produced, when the aspirator is emptied of its water, fills the tube AB with gas drawn from the flue. It is retained by clos- ing the valves F and I, which had been open during the opera- tion of filling. The tube is then disconnected from the aspi- rator, and the receiver, or bottle, L, connected as shown, and in such manner that no air can reach the tube AB. Removing the apparatus to the laboratory or other con- venient location, the analysis is made as follows: Pass into A'B' a convenient volume, as too c.c. of the gas, and discharge the remainder through the valve and funnel F and M\ filling the tube AB with water from L. Transfer the measured gas back to AB, through E, and add a solution from M, which will absorb some one constituent. Return the gas to A'B', and again read its volumes. The difference is the quan- tity of gas absorbed. Repeat this process, using next an ab- sorbent which will take up a second constituent of the gas, and thus obtain a second measure of volume; and thus continue until all the desired determinations are made. All readings should be made at the same temperature, or practically so. The tubeANALYSIS OF GASES. IOg AB should be well washed at each operation, in order that no reagent should be affected by traces of that previously used. The absorbeilts employed are best taken in the following order: 1. Caustic potash—to absorb carbonic acid. 2. Potassium pyrogallate—to absorb free oxygen. 3. Cuprous chloride in concentrated hydrochloric-acid solu- tion—to absorb carbonic oxide. After their use nitrogen will remain, and will be measured as a balance which, added to the sum of the measured volumes of gases absorbed, should give the original total. Where weights are to be determined, the volumetric measures ob- tained as above are to be reduced by the usual process. The atomic weights of the principal constituents being, oxygen, 16; nitrogen, 14; carbon monoxide, 28; carbon dioxide, 44, we shall have by percentages, where the symbols represent per cent in volumes, for each, when the total is M = i4iV+ 16O + 28CO + 44C02, 14N 160 2 8CO • 44^2 . . Hf’ ~M’ ' M ’ resPectlvely- 16 \ 32 Since the total per cent of oxygen is measured by — COQ -f-' 44 12, + free oxygen, and the total per cent of carbon is —6Y7. 12 '+ -gC#, we shall have for the percentage of each, 32 X 44 X COq 16 X 2S X CO 160 U “ 44^ + 28M ^ M ; 12 X 44 X CO3 12 X 28 X CO 44 M + 28 M ;I IO ENGINE AND BOILER TRIALS. or, u — 32 M ' ID w ’ M „ ' CO, . CO C ~ 12 M +12 M' The total oxygen is that which entered the furnace as the supporter of combustion, and is a measure of the air supplied. The ratio of free to combined oxygen is a measure of the ratio of the air acting as a diluent simply to that supporting com- bustion. Thus these measurements exhibit the efficiency of combus- tion, the quantity of air employed, and the magnitude of the wastes of heat at the chimney, occurring through imperfect combustion or excess of air-supply. It is evident, however, that where moisture or steam accompanies the gases, it escapes measurement; this, however, introduces no important error in ordinary work. Efficiency of combustion is indicated by the analysis of the flue-gases with very great certainty. The appearance of carbon monoxide at the chimney proves the combustion to be imperfect in proportion as it is more or less abundant. The presence of unconsumed oxygen, on the other hand, in the ab- sence of carbon monoxide, proves an excess of air-supply. Both gases appearing is a proof of incomplete intermixture of air and combustible, or of so low a temperature of furnace as to check combustion. This analysis being compared with that of the fuel reveals the character and the perfection of combus- tion, and permits a very exact determination to be made of the specific heat of the gases, and is thus a check on calculations of wasted heat. 48. Draught-gauges are made for the purpose of deter- mining the head-producing draught and the intensity of the draught, which are of many forms, but which usually depend upon the measurement of the head of water which balances that head at the chimney. A very compact and accurate formDR A UGHT-GA UGES. Ill of draught-gauge, used by the Author with very satisfactory results, is that of Mr. J. M. Allen (Fig. 6). A and A' are glass tubes, mounted as shown, communicating with each other by a passage through the base, which may be closed by means of the stop-cock shown. Surrounding the glass tubes are two brass rings, B and B'. These rings are attached to blocks which slide in dovetailed grooves in the Fig. 6.—Draught-gauge. body of the instrument, and may be moved up and down by screws at FF. The scales are divided into fortieths of an inch, and read to thousandths of an inch by the verniers e and er> which are attached to the sliding rings B B'. If the two short rings are set at different heights, the difference in readings will give the difference of level. The thermometer is for the purpose of noting the temperature of the external air. The method of using the instrument is as follows :* At a con- * The Locomotive, May, 1884, p. 67.112 ENGINE AND BOILER TRIALS. venient point near the base of the chimney a hole is made large enough to insert. a thermometer. The height from this opening to the top of chimney, and also of grates, should be noted. The chimney-gauge is attached to some convenient wall. The tubes are filled about half full of water, when the verniers afford an easy means of setting it perpendicular. One end of a flexible rubber tube is then inserted into the upper end of one of the glass tubes, and the other end of the tube is in the chimney-flue. The tubes B B' are adjusted until their upper ends are just tangent to the surface of the water in the two tubes. The reading of the two scales is then taken, and their difference. At the same time the temperature of the flue is noted, as well as that of the external atmosphere. Com- parison may then be made with the following table, computed for use in this connection for a chimney ioo feet high, with various temperatures outside and inside of the flue, and on the supposition that the temperature of the chimney is uniform from top to bottom—an inaccurate though usual' assumption, however. For other heights than ioo feet, the theoretical height is found by simple proportion, thus: Suppose the exter- nal temperature is 6o°, temperature of flue 380°, height of chimney 137 feet, then under 6o° at the top of the table, and opposite to 380° interpolated in the left-hand margin, we find .52". Then 100 : 137 :: •52// : .71", which is the required height for a 137-foot chimney, and similarly for any other height. HEIGHT OF WATER COLUMN DUE TO UNBALANCED PRESSURE IN CHIMNEY IOO FEET HIGH. Temperature Temperature (Fahr.) of the External Air—Barometer, 14.7. Chimney. Fahr. 20° if* © O 60° 80° 100° 220 .419 •355 .298 .244 . 192 250 .468 • 405 •347 .294 .242 300 •541 .478 .420 •367 • 315 350 .607 •543 .486 •432 ,380 400 .662 • 598 •541 .488 .436 450 .714 .651 •593 .540 .488 500 .760 .697 •639 .586 .534DRA UGHT-GA UGES. 113 The most common form of gauge-testing apparatus is shown in the accompanying engraving. The standard gauge, which is known by comparison with a mercury column or by other test to be right, is mounted as shown. The instrument to be tested is attached to one of the other cocks, and, both being subjected to the same pressures, a comparison of their readings will exhibit the errors of the second gauge. 49- A Sample Trial is described in the following report, which will illustrate well the methods and results of a carefully made test of a boiler in which a complete trial was attempted, under the direction of the Author.* * Sci. Am. Supplement, No. 641, p. 10234.ENGINE AND BOILER TRIALS. 114 Trial of a Water-tube Boiler, This boiler was used to supply steam to one or more en- gines, as needed, or to heat the buildings of the college. The principal dimensions are as follows: Length of drum, ..............13 ft. Diameter, .......................... 2 ft. 6 in. Number of water-tubes, . ....................40 Outside diameter of tubes,...................... . 4 in. Length, . . . .............................13 ft. 8 in. Width of furnace,...............................3 ft. 3^ in. Length of furnace,........................ . . . 6 ft. I in. Length of grate-bars, ......................... . 3 ft. Width of grate-bars, . . . . ... . . . f in. Width of air-spaces, . . . f in. Number of grate-bars, . . .................54 Area of chimney,................................ 3.65 sq. ft. Height of chimney,..............................60.25 ft. Area of grate-surface, . ....................20 sq. ft. Area of heating-surface,........................682.57 sq. ft. Area for draught between tubes,................. 4.75 “ Ratio of grate to heating-surface, . . . . . 1:34.1 Ratio of draught area to grate,.................0.25 Ratio of grate-surface to cross-section of chim- ney, . . . ............................... 5.48 Ratio of area of grate to area of air-spaces, . . 2.24 Whole area of damper opening, . . . ... 3 sq. ft. The main steam-pipe after passing horizontally to the rear of the “setting” descends vertically a distance of 4 ft. and passes out of the boiler-room to the chimney. Draught is pro- duced by a chimney which rises directly at the back end of the boiler, the first 9^ ft. being brick and the remainder a sheet- iron cylindrical stack. A vertical sliding damper is placed in the opening leading to the chimney. Two partitions of fire-SAMPLE TRIAL OF A WATER-TUBE BOILER. IIS brick supported by irpn plates are placed transversely across the nest of water-tubes. The first is 7 ft. 1 in. from the front end of the tubes, and the second 3 ft. 7 in. from the first. These partitions cause the gases to pass among the tubes three times, then across the rising tubes into the back connection, and from there to the chimney. The object of the trial was: 1. To determine the evaporative efficiency of the boiler. 2. To estimate the horse-power devel- oped under ordinary working conditions, a horse-power being taken as equivalent to 30 lbs. of feed-water supplied per hour at a temperature of ioo° F., and evaporated under 70 lbs. gauge-pressure. Previous to the test all cracks and holes in the setting and around the doors leading to the flues were carefully stopped with fire- clay and mortar. The blow-off and return ^ “drip” pipes were disconnected and caps If j placed on the exposed ends. An =*a= caps on the exposed ends. An injector nJ ? T feed-pipe connected with the boiler was left fig. 8.—Gas sampler. in place, as its disconnection would be attended with some difficulty. The overflow-pipe was, however, left open, in order to detect any leak which might occur. The feed-pipe was dis- connected from the “mains,” and a suction-pipe from it placed in a barrel into which the feed-water was run after having been weighed. A pipe leading to the outside of the boiler-house was connected with the main steam-pipe, so that all steam made by the boiler, over and above that required to run the engine and heat the buildings, could be discharged into the air. At 7 A.M. April 28, the fire, which had been banked on the preceding evening, was started, and the steam pressure brought to 80 lbs. by the large gauge. The fire was then quickly drawn and the contents of the ash-pit removed. A new fire was started immediately with a weighed quantity of hemlock wood and brought to the normal condition with coal. The amount of water shown by the water-glass was noted. At 8 A.M. the en- gine was started, and the trial commenced. Both ash-pit doors 4-ii6 ENGINE AND BOILER TRIALS. were left open at first and the damper wide open. The damper was lowered 3 in. at 9.30 A.M., and at 12.50 a further amount of 3 in. At 11.17 A.M. one of the ash-pit doors was closed and this arrangement of damper and draught door was observed in the higher temperature of the flue gases at the base of the chimney. “ grate coal.” An average sample of this coal was weighedy working up the results of the trial, this figure was taken to repre- sent the percentage of moisture in the coal. The coal was weighed by the barrow load in uniform charges of 200 lbs. each,, and dumped before the door as needed. The stoking or firing was performed regularly every half hour and fire cleaned every third time. During the period of stoking, the back damper was closed to avoid loss of heat by the current of cold air which otherwise would rush through the heated flues. The feed-water^ was drawn from the mains into a barrel placed on a platform scale, where it was carefully, weighed. It was then drawn off into another barrel, from which it was . pumped into the boiler by a steam-pump of the ordinary type. It was the endeavor to deliver the water to the boiler as continuously as possible. The temperature of the feed-water was noted at each weighing. The observations which were called for, and the results of which were finally recorded as the log of the trial, were such as would ordinarily be demanded in any usual case of engineering practice of this character, and were sufficient to enable the observers to make all essential computations ; while none were made which were not either of importance in that respect, or of real interest to the engineer concerned in the questions proposed to be settled by the trial as conducted. so remained during the remainder of the trial. The effect of The fuel used was anthracite coal, known in the market as Fig. 9.—Pyrometer. pulverized, and placed in an evaPorating oven to dry. After seven hours it was found to have lost 3.81 per cent, in weight. InSAMPLE TRIAL OF A WATER-TUBE BOILER. Il/ The method of conduct of the trial, in tolerably full detail, is described in the succeeding pages. The observations made are indicated ; the processes involved in their reduction, com- putation, and tabulation are exhibited and illustrated; and the final deductions and conclusions are stated at length. The following observations were made every half-hour: 1. Temperature of flue gases at the base of chimney. 2. Temperature of boiler-room. 3. Temperature of outside air. 4. Reading of draught pressure-gauge. 5. Readings of the several steam-gauges. 6. The pyrometer used in measuring the temperature of the flue gases had previously been compared with a mercury ther- mometer between temperatures of 2130 F. and 3220 F. This was accomplished by means of a simple apparatus .shown in Fig. 9. The stem of the pyrometer was inclosed in a steam- pipe which has communication to the boiler through a smaller pipe fitted with a stop-valve. The thermometer used in the comparison was also screwed into the larger pipe. As steam was admitted the mercury rose, and soon registered a tempera- ture corresponding to the steam-pressure, which was kept con- stant for several minutes until the pyrometer reading no longer changed. Both readings were noted, and more steam admitted, giving a higher temperature. The several readings were “ plotted,” and the law of varia- tion of the pyrometer from the thermometer reading was found to be approximately a straight line, continually falling below and diverging from the line representing the temperature as read from the thermometer. The pyrometer was corrected from this line, and is believed to be approximately correct. The draught pressure-gauge, which was attached to the stack near the base, was made for the Sibley College laboratories by the Hartford Steam Boiler Insurance Co. It consisted of a U-tube partially filled with water and provided with a movable vernier and scale for measuring the difference in level of the water in the two arms.118 ; ENGINE AND BOILER TRIALS. A recording steam-gauge and a mercury-gauge were attached to the boiler in addition to the large gauge ordinarily used. The * mercury-gauge was taken as the standard, and the others corrected by it. Experiments were made every hour to determine the quality of the steam. A well-made barrel which had been thoroughly shellacked inside was placed on a very sensitive standardized platform scale, made for this work, the beam of which was graduated to of a pound and provided with a sliding poise. The steam was taken from the main steam-pipe, i ft. from its connection with the boiler, and was conducted to the calo- rimeter through a ^-in. pipe, 9 ft. long, to the end of which was attached a piece of rubber hose 7 ft. long. The pipe was cov- ered with hair-felt to prevent radiation of heat. Before placing the end of the hose in the calorimeter, steam was allowed to blow through until all the water of condensation had been dis- charged and the pipe and hose were thoroughly warmed up. The end of the hose was given an inclination downward toward the bottom of the barrel by means of a light strip of wood fast- ened to it. The steam passing .into the condensing water at an angle produced a strong agitation, and thus a thorough mixture of the water was effected.* A standard Centigrade thermometer, graduated to tenths of one degree, was used with the calorimeter, and the readings were afterward reduced to the Fahrenheit scale. During the trial five samples of flue gas were taken for analysis. The tabulated results of the analysis are as follows: PER CENT. BY VOLUME. No. Time. CO,, Observed. Free O, Observed. CO, Calculated. N, Calculated. I 8.30 A.Mi 12 5-2 4.6 78.13 2 10.20 A.M. 12 6.7 2.16 79-13 3 12.20 P.M. II. I 7.9 1.6 79-3 4 2.20 P.M. 11.7 6.8 2.5 79 5 4.20 P.M. 11.5 7 2-5 79 * Probably, on the whole, as good an arrangement as any plan involving the use of stirring apparatus. See Manual of the Steam Boiler.SAMPLE TRIAL OF A WATER-TUBE BOILER. 119 BY WEIGHT. No. . Time. CO«j, Calculated. Free O, Calculated. CO, Calculated. N, Calculated. I 8.30 A.M. 17-56 5-5 4.33 72.62 2 10.20 A.M. 17.52 7.07 2 73.40 3 12.20 P.M. 16.27 8.39 1‘95 73.86 4 2.20 P.M. 17.II 7-19 2.32 73.38 5 4.20 P.M. 16.83 7.41 2.32 73-44 No. Time. Per Cent by Weight, Total O. Per Cent by Weight, Total C. Air Supplied, Per lb. C. Free O Combined O I 8.30 A.M. 20.74 6.65 14 O.36 2 10.20 A.M. 20.96 5-64 16.7 O.51 3 12.20 P.M. 21.31 5-27 18 0.64 4 2.20 P.M. 20.95 5*66 16.6 O.52 5 4.20 P.M. 20.97 5.58 • 16.9 O.54 Professor Elliott’s apparatus, Fig. 10, was used for the analysis. For the absorption of COQ a solution of potassic hydrate (1 to 20) was used, and for oxygen absorption, potassic pyrogallate; this latter being prepared by adding 5 per cent of pyrogallic acid to a solution of potassic hydrate (1 to 8). Num- bers 1 and 2 were tested for CO with cuprous chloride, but as none was absorbed, and it was evidently present, the amount was calculated as follows: For No. 1 we have 12 per cent C02, whose volume is equal to the volume of the O which combined to form it, and 52 per cent of free O. The volume of O in these two is, therefore, = 12 —(— 5.2 '= 17.2 per cent. Assuming that the atmospheric air is composed of 4 parts of N and 1 part of O, by volume, to correspond to this 17.2 per cent of O we should have 17.2 X4 = 68.8 per cent N; but after absorbing the 17.2 per cent of C02 and O, there remains 100 — 17.2 = 82.8 per cent. Taking 68.8 per cent from 82.8 per cent, we have 14 per cent, which must be composed of N and CO. Since the volume of CO is equal to twice the volume of the combined O, we shall CO have the volume of O —-, and since there is four times as 2 '120 ENGINE AND BOILER TRIALS. much N as O, the N === 2CO. Therefore of this 14 2 per cent. I part is CO and 2 parts are N ; CO = — = 4.6 -f-> and N = 4.6X2 = 9.3-f, which being added to the 68.8 per cent. N, which corresponds to the free O, and that of the C02 = 78.13 per cent. To reduce per cent, by volume to per cent, by weight, we use the following constants: Weight of 1 liter of C02, 1.9774 grams. “ “ 1 “ “ O, 1.43 “ 1 “ “ CO, 1.254 “ “ 1 “ “ N, 1.256SAMPLE TRIAL OF A WATER-TUBE BOILER. 121 Multiplying the per cent, by the volume of each gas by the weight of a liter of that gas, we get certain values, a> a\ a'\ etc. Taking the sum of these = s, then the per cent, of weight would be—, —, —, etc. s s s To get the total O and the total C : The atomic weight of O 2 X 16 = 16 and of C = 12; .\ the amount of O in COa= 12 g — and the amount of C = - , . 11 12 + (2 X 16) In the same manner the amount of O in CO = 12+ (2 X 16) I2__ _3_ 44 11' 16 _4 12 -|— 16 _ 7’ and C = A. 7 Hence the total O = — COa 4- - CO 4- O, and the total C ii 7 = — COa + — CO. II 7 To get the ratio of air for dilution to thaj for combustion, Free O O we have Combined O — CO, + i CO ii 7 To get a measure of the air supplied per pound of carbon, we take the per cent, by weight of total O + per cent, by weight of N, and -4- by the per cent, by weight of C. At the time of taking the samples of gas the conditions were as follows: No. 1. Fire had not completely burned clear from first fir- ing. Back damper was wide open, as were the draught doors. No. 2. Fire burning clear. Back damper dropped 3 inches. Draught doors wide open. No. 3. Fire clear. Back damper 3 inches down. One draught door closed.122 ENGINE AND BOILER TRIALS. No. 4. Fires clear. Back damper 6 inches down. One draught door closed. No. 5. Same as No. 4. From these figures the following results are obtained : FLUE' GASES. Average free O, by weight, 7.108 per cent. “ “ COa, “ “ 17.059 “ “ CO, “ “ 2.584 “ “ “ N, “ “ 73.34 “ The average ratio of the amount of air for dilution of the gaseous products of combustion to that necessary for combus- tion is as 0.514 to 1, i.e.y 16.44 lb. of air per pound of combusti- ble, or 1.37 times the theoretical amount. The ratio of amount of air reqired for the dilution of the gaseous products of com- bustion to that necessary for combustion is variously estimated by different authors, but is generally taken as £: 1. It will be seen that a very small per cent, of CO passed up the chimney, the average being 2.67 per cent, by volume, showing the com- bustion to be nearly complete. The waste by air in the chimney is calculated by the fol- lowing formula: Let W = the number of pounds of air for combustion and dilution; t = temperature of chimney ; = temperature of external air; 5 = specific heat of air. Then H= W(t-t')S, where If is the number of heat-units carried off by the escap- ing gases.SAMPLE TRIAL OF A WATER-TUBE BOILER. 12$ We have W= 16.44; t = 435-7° Fahr.; t' = 60.39° “ S = 0.238. Hence H = 16.44 (435.7 — 60.39) 0.238 = 1468.48 units. Assuming that a pound of coal will evaporate 15 pounds of water from and at 212° Fahr., or equal to 14,491 heat-units, the loss by chimney is 0.101. The height of chimney required under the above conditions is found from Rankine’s formulae as follows: Let W = weight of fuel burned in the furnace, per second ; V0 = the volume at 320 F. of air supplied per lb. of fuel; T = the absolute temperature of gas discharged by the chimney; A = sectional area of damper opening. Then the velocity of the current in the chimney in feet per second is Hence 0.06869 (12.386 X 16.45) 896.9 2.222 X 493 = 11.449 ft. per sec., and A, the head required to produce this draught, is124 ENGINE AND BOILER TRIALS. where l = the whole length of chimney and flue leading to it in feet; m — its hydraulic mean radius ; f = coefficient of friction ; (estimated by Pectet at 0.012;) G. = a factor of resistance for the passage of air through grate and fuel; (given by Pectet as 12.) Hence r (11.440)* ( . 0.012 X 93\ o h — v—f 13-I-----------CL22) = 30.7138 ft. 2X32.2^ 534 ' Then /r= a-5-(0.96^- -1), where H is the height of chimney: H = 30.7138 -f- (0.961) = 47-25 ft. The actual height as measured was 60.25 ft. The difference between this and the calculated height, or the throttling effect of the damper, being 60.25 —47.25 = 13 ft. The following data were taken during the trial: Total coal,..........................2963.2 lbs. Total ash and waste,.................342 “ Per cent, ash and waste,............. 11.5 “ The wood used was considered as equal to 0.4 the same weight of coal. At 6 P.M. the fire was hauled and the unconsumed coal and the contents of the ash-pit were weighed up dry. The height of water in the gauge-glass was brought to the same positionSAMPLE TRIAL OF A WATER-TUBE BOILER. 125 as at the start, and all conditions made as near those at the beginning of the trial as possible. The following are the records: Total weight of water, ... 23, 912.5 lbs. Average temperature, ... 46.125 Fahr. Mercury-gauge,......................85.78 lbs. Edson gauge, by record chart, corrected, 85.4 “ Barometer readings were taken from the report of the Uni- versity Signal Service. Let x = weight of dry steam run into calorimeter; y' — weight of water in the steam; y — percentage of priming; W — weight of condensing water; w = weight of condensed steam; tn = the initial temperature; = the final temperature; T = heat-units per lb. of steam ; t = heat-units per lb. of water. AVERAGE PRESSURES. Then Range of temperature, . . . R = t' — t"; Heat transferred to calorimeter, U = WxR; Heat from steam, per lb., . . H ~ T — tr; Heat from water, per lb., . . k = t — x -\-yf = w, Hx + hy'= U. (o (2) From 1 and 2, x(H — k) = U — wh, U — wh126 ENGINE AND BOILER TRIALS. Percentage of priming, 7 = IOO w — X w The ten calorimeter experiments gave the following average results: Steam-pressure,...............................100.522 lbs. Weight of condensing water,....................382.985 “ Weight of steam condensed,............... . 24.335 “ Initial temperature,........................... 47-979 Fahr. Final temperature,............................117.430 “ Range of temperature,.........................6945 “ Dry steam run into the calorimeter, .... 24.2853 lbs. Per cent, of priming,............................0.189 DATA AND RESULTS. Date of test,............................... . April 28, 1887 Weight of wood used in lighting fires, .... 245.5 lbs. Equivalent value of wood referred to fuel, . . 98.2 “ Weight of anthracite coal used,.................3265 “ Total weight of fuel,.........................3363.2 “ Weight of unconsumed coal left on the grates, . 400 “ Total weight of fuel consumed,................2963.2 “ Weight of ashes and clinkers,....................342 “ Percentage of ash and clinkers to fuel consumed, 11.5 Percentage of moisture in coal,............... 3.81 Weight of fuel, less moisture,................2752.11 “ Weight of combustible used,...................2410.11 “ Total weight of feed-water supplied and evapo- rated, ........................................23912.5 “ Average steam-pressure,....................... 85.4 “ Average temperature feed-water,............... 46.71 Fr. Average temperature of escaping gases, . . . 435-7 “ Average force of draught in inches of water, . 0.275 in. Water evaporated per lb. of fuel, observed con- ditions, .................................... 8.68 lbs.SAMPLE TRIAL OF A WATER-TUBE BOILER. 127 Equivalent evaporation, per lb. of fuel, from and at 212° Fahr.,......................... Water evaporated per lb. of combustible, . . . Equivalent from and at 212°,................... Average temperature of boiler-room, . • . . Average temperature of outside air,............ Average height of barometer,................... Horse-power developed on a basis of 30 lbs. of feed-water supplied at ioo° Fahr. and evap- orated at 70 lbs.,............................. Rated horse-power,............................. Per cent above rated capacity, . .............. 10.486 lbs. 9.92 “ 11.984 “ 80.06 Fr. 60.39 “ 28.702 in. 83.75 61 37 Fig. 11.—Autographic record of steam-pressure during the trial, from Edson ga«ge. Mean pressure as shown on the diagram, 78.4 lbs. per sq. in. Mean pressure, corrected,.............85.4 “ “ “CHAPTER IV. THE STEAM-ENGINE INDICATOR. 50. The Indicator and the Dynamometer are the instru- ments employed in the engine-test proper. The purpose of their use is the measurement by the one of all fluctuations of pressure and of volume of the steam within the working cylinder, and of the work done and power developed by its action on the piston, the gross work performed by the trans- formation of heat-energy, and by the other the net work of the engine, the work done and power available at the engine-shaft for useful application. The difference between these two quantities is the measure of the lost energy and the wasted power, due to the resistances of the machine itself, the sum of the friction-resistances and the back pressure on the exhaust side of the piston, if the gross indicated power is measured to the line of external atmospheric or condenser pressure, or to friction alone if the power is taken as exclusive of back-pres- sure work. The indicator is sometimes a “ continuous indicator,” giv- ing a running, continuous, record of power developed. The most usual form, however, is that which gives a graphical rep- resentation of the whole cycle on one side of the piston, and thus permits a study to be made of all the variations of pres- sure throughout the stroke, and thus a deduction of the condi- tions of valve adjustment or setting, and of its action in dis- tributing steam. The dynamometer is sometimes of the trans- mitting form, stationed between the engine and its work or any introduced resistance; but it is most usually of the type known as the Prony brake or the absorbing dynamometer, and takes up the whole external power of the engine, converting 128PRINCIPLES OF THE INDICATOR. I29 all that energy into heat; which heat it wastes by conduction and radiation to surrounding objects or to a stream of water kept flowing over it, or through the rim of the brake-wheel. 51. The Principles of the Indicator of the usual construc- . tion and type, those which govern its action and determine its value, are as follows: (1) It must exhibit with precision the pressure of the steam within the working cylinder at every instant throughout the stroke. (2) Simultaneous measures must be given of the position of the piston corresponding to the given pressure, each instant. (3) The diagram produced must be so made, automati- cally, as to have its ordinates exactly proportional to the steam- pressures and its abscissas as accurately proportional to the motions of the piston, each point in the curve, by its coordi- nates, giving a measure, simultaneously, of these two quantities. (4) The diagram must be unaffected either by the forces acting on the engine, other than that which it is constructed to measure, or those brought into existence by its own motions, and whether they are active or passive, whether of inertia or of friction. The ideal indicator would be an instrument pos- sessing the above qualities, and would trace a conveniently large diagram with absolute exactness. It would be free from inertia and perfectly inflexible in every part. As these ideal conditions are approximated, differences among the best makes of indicators become less and less, and should finally disap- pear. As they are now sometimes made, however, unless care- fully selected and as carefully tested and standardized, it is perfectly possible for differences of very considerable import- ance to be observed. The Author has sometimes noted results from indicators, simultaneously used, varying from ten to fif- teen per cent. 52. The Essentials of a Good Indicator are: (1) Such form and construction as will insure its meeting the prescribed general conditions—accuracy of representation of the variations of steam-pressure and the simultaneous move- ment of the piston at all times.130 ENGINE AND BOILER TRIALS, (2) Such simplicity of form as will make it free from liabil- ity to accident and failure in operation. (3) Such lightness of parts, and such rigidity as a whole, as will prevent any inaccuracy of indications arising from its in- ertia. (4) It should be easily, conveniently, and safely attachable and removable, and readily and handily manipulated. Stiffness, lightness, and exactness of standardization are the prime essentials. The springs should be exactly standard ; the moving parts as light as is consistent with proper strength and stiffness; the stationary parts should be carefully proportioned and rigid ; the whole instrument should be portable, and yet the scale of its diagram as large as practicable, and consistent with exactness in its production. 53. The Forms of the Indicator, as commonly con- structed, are usually very similar, the more important differences being found in the recording system. The original indicator employed from about 1814* by Watt, Fig. 12, consisted of a small steam-cylinder, AA, traversed by a piston, K, the latter held by a spring, F, which was compressed or extend- ed proportionally to the pressure, the cylinder being placed in communica- tion with the interior of the working cylinder by a pipe, B> of sufficient size and fitted with a cock, H, by means of which the steam could be cut off from the instrument at any instant. So long* as this cock was open, the indicator, if properly mounted, and the main steam piston were affected by precisely the same intensity of pressure, and the Fig. 12.—the wattInd^ator. movement q£ former was a measure' of the pressure on the latter. A pencil, was attached to * See Tredgold on the Steam-engine. London, 1827.FORMS OF THE INDICATOR. 131 the indicator-piston, and its point recorded all such variations of- steam-pressure on a movable slate, D, which was so con- nected, through SE, with the mechanism of the engine as to move in exact coincidence with the main piston, and precisely at right angles to the line of motion of the pencil. Thus, the abscisses of the curve produced were proportional to the motions of the piston, and the ordinates of the same point? in the curve gave the simultaneous pressures. In the later instruments of McNaught and Hopkinson, metal cylinders revolving on vertical axes were substituted for the sliding panel of Watt’s arrangement, and a much more com- pact instrument was thus made. McNaught’s indicator, which was in general use until about i860, when the first of the more modern forms, that of Rich- ards, was introduced, had the form seen in the sketch, as de- scribed by Rankine, about the above date.* AB is the barrel. Its lower end, A, contains a small cylin- der, fitted with a piston, which cylinder, by means of the screwed nozzle at A, can be fixed in any convenient position on either end of the cylinder. The communication between the en- gine cylinder and the indicator cylinder is made by means of the cock, K. The upper end, B, of the cylindrical case contains a coiled spring, one end of which is attached to the piston, and the other to the top of the casing. The piston is pressed from below by steam, and from above by the atmos- phere. When the pressure of the steam ex- ceeds that of the amosphere, the piston is driven upward, and the spring compressed; FiG. i3.—McNaught’s when the pressure of the steam is less, the Indicator. piston is driven downwards, and the spring extended. A short arm C, a pointer Z>, which shows the pressure on a, scale whose zero denotes the pressure of the atmosphere, and which is graduated upwards and downwards from that zero. * Steam-engine, p. 47 et seq.132 M-NGINE,AND BOILER TRIALS. At the other side, the short arm has a longer arm, carrying a pencil i?. A is a brass paper-drum, which rotates backward and forward about a vertical axis, and which, when used, carries a piece of paper called a “card.” The cord H is to be con- nected with the engine in any manner which shall insure that the velocity of rotation of the drum shall bear a constant ratio to that of the engine piston. . ' The later devices have been introduced with a view to se- curing lightness of parts and reduced motion of piston. Fig. 14 is a sketch, partly in section* of the first of the later type of instrument, the Richards indicator, invented by Professor C. B. Richards about i860. A A is the cylinder; B is the piston, connected by a properly made spring, CD, withFORMS OF THE INDICATOR. 133 the cap, E, of the barrel. The head of the piston-rod, F, is attached by a link, Gy to the lever, HI, by means of which a comparatively large motion of the pencil, Ky is obtained without much movement of the piston and its attached parts, and con- sequently with but little inertia-effect. A parallel motion of the Watt type, HI, KLM, guides the pencil-holder, Ky in a right line parallel to this path of the piston of the indicator. The paper is wrapped about the cylinder, <9, and secured at its ends by the clamps, PQ. The paper-cylinder is turned on its axis by a cord on the pulley, RSy which cord is attached to some form of “ reducing motion” which causes it to move with the engine-piston. Communication with the engine-cylinder is established by a steam passage through the cock, and the instrument is se- cured in place-by the clamp U. When in action, this cock is opened; the indicator-piston rises and falls with the varying pressure in that end of the engine-cylinder, and the paper- barrel rotates backward and forward as the engine-piston moves. When all is ready, the in- strument being heated up and .working smoothly, the pencil is pushed lightly against the paper, and a diagram is drawn, repre- senting all changes of pressure and volume of the working fluid during the period of contact. This modification of the indicator was found to give satisfactory results up to a comparatively high speed, and its limit of efficiency was de- termined by the degree to which the lightening of its parts could be safely carried. A still later form (1875) is that of Mr. J. W. Thompson, Fig. 15. In this indicator the same general style is retained, but the parallel motion is modified. The134 ENGINE AND BOILER TRIALS. cylinder, AA, contains a piston, By connected by a spring, as before, to the cap, DE ; while the head, Fy of the rod actuates a pencil-arm, HK, and a parallel motion is obtained by linking on LI from the standard, LM, and G from the swivelling support MN, which also carries L. The action of the instrument when in use is precisely as before ; its decreased weights of moving parts, however, enabled it to be confidently relied upon at speeds far above those of even the Richards instrument. The old Mc- Naught indicator became unsatisfactory at about 60 revolutions per minute ; the Richards carried this limit well up toward and sometimes above 200 revolutions; while the Thompson indicator was found capable of doing good work on even the fast engines of the most modern type at the date of its invention. The most recent and a still lighter style of this instrument is shown in Fig. 16. The later improvements consist in lightening the moving parts, substituting steel screws in place of :aper pins, using a light steel link instead of a brass one, reducing the weight at the pencil-lever and elsewhere, shortening the length and reducing Fig. 16.—The Thompson Indicator.STANDARDIZA TION OF INDICA TOR. 135 the weight of the paper-cylinder one-half, and reducing friction to a minimum. The paper-cylinder is so constructed that the tension of the coiled drum-spring within it can be varied for different speeds. As little or as much of the spring can be taken up or let out as desired, thus providing for fine adjustments. Sufficient tension should be given to keep the cord taut at all points. When exceptionally accurate work is desired, the length of the diagram may be carefully measured, and compared with the length of a line traced on the paper when the engine is moved slowly. If the diagram is found to differ in length from this line, vary the tension of the spring till they agree. All these indicators are provided with a piston 0.798 inch diameter, -|-inch area, and with springs for indicating pressures up to 250 pounds. When higher pressure is to be indicated, an extra piston 0.564 inch diameter, J-inch area, is used, which, when substituted for the other piston, doubles the capacity of each spring, thereby adapting the indicator for indicating pressures up to 500 lbs. The Tabor Indicator, Fig. 17, the invention of Mr. H. Tabor (1879), illustrates another ingenious attempt to evade all those difficulties incident to high speed of engines which have elim- Pig. 17.—'The Tabor Indicator.136 ENGINE AND BOILER TRIALS. inated all the old forms of the indicator from the field. In this instrument the number of parts is still further reduced and the weight of such as remain is made as small as is thought safe. In the Tabor Indicator a stationary plate containing a curved slot is firmly secured in an upright position to the cover of the steam-cylinder. This slot serves as a guide and controls the motion of the pencil-bar. The side of the pencil-bar carries a roller which turns on a pin, and this is fitted so as to roll freely from end to end of the slot, with little lost motion. The curve of the slot is so adjusted and the pin attached to such a point that the end of the pencil-bar, which carries the pencil, moves up and down in a straight line, when the roller is moved from one end of the slot to the other. The curve of the slot just compensates the tendency of the pencil point to move in a cir- cular arc, and a straight-line motion results. The outside of the curve is nearly a true circle with a radius of one inch.* The steam-cyclinder and the base of the paper-drum are made in one casting. Inside the steam-cyclinder is a movable lining cylinder, within which the piston of the indicator works. This cylinder is attached by means of a screw-thread at the bottom, and openings at the opposite sides at the top are provided for the introduction of a tool for screwing it in or out. Openings through the sides of the outer cylinder are provided to allow the steam which leaks by the piston to escape. The pencil mechanism is carried by the cover of the outside cyclinder. The cover proper is stationary, but a nicely fitted swivel-plate which extends over nearly the whole of the cover, is provided, and to this plate the direct attachment of the pencil mechan- ism is made. By means of the swivel-plate, the pencil mechan- ism may be turned so .as to bring the pencil into contact with the paper-drum, as is done in the act of taking a diagram. The pencil mechanism is attached to the swivel by means of the vertical plate containing the slot, which has been re- ferred to, and a small standard placed on the opposite side of the swivel for connecting the back link. The connection be- tween the piston and the pencil mechanism is made by means * “The Tabor Indicator;” G. H. Barrus, N. Y., 1S88.STAND iRDIZA TION OF INDICA TOR. 137 of a steel piston-rod. At the upper end where it passes through the cover, it is hollow and has an outside diameter measuring Ts¥ of an inch. At the lower end it is solid and its diameter is reduced. It connects with the piston through a ball-and-socket joint. A number of shallow grooves are cut upon the outside of the piston to serve as a so-called water- packing. . Fig. 18.—The Tabor Indicator, The springs used in the Tabor Indicator are of the duplex type, being made of two spiral coils of wire with fittings, as shown in the cut. The springs are so mounted that the points of connection of the two coils lie on opposite sides of the fitting. The Crosby Indicator, Fig. 19, is still another successful recent type of the instrument (1879), one which also illus- trates that remarkable combination of lightness and accuracy which characterizes all good indicators. In this case, a still dif- ferent form of parallel motion, light, stiff, and carefully ad- justed, guides a very light pencil-holder carried at the end of a correspondingly light steel arm. The general arrangement of the indicator barrel and the paper-cylinder, with their attach- ments, is quite similar to those observed in the Richards and its successors. If the conditions under which the spring acts be considered,138 ENGINE AND BOILER TRIALS. it is readily seen that, when the cord has the maximum other resistances to overcome, the drum-spring should offer minimum resistance. At the beginning of the stroke, when the spring is overcoming the inertia and friction of the drum, its resistance should be a maximum, and should gradually decrease. Here, a short spiral drum-spring is adopted, giving at the beginning of the stroke a comparatively slight resistance, which gradually Fig, 19.—The Crosby Indicator. increases until it reaches the maximum at the end of the stroke. In the other direction the recoil is strongest at the beginning of the stroke, and decreases to the end. Duprez, Hirn, and Webb employ a screw, by means of which the steam is prevented from lifting the piston until the pres- sure exceeds a certain amount. Until this instant the indicator- diagram is a horizontal line; it then becomes curved. WhenSTANDARDIZATION OF INDICATOR. 139 the screw is turned, the piston is again prevented frorri moving until the pressure exceeds a certain other limit, so that a series of corners is obtained, which are points on the real indicator- diagram, and may be joined by hand. When vibrations of the spring are in this way destroyed, exactly the same indication may often be obtained during four or five successive strokes.* Mon. Hirn would prefer, where practicable, a directly com nected spring, of considerable amplitude of range, stretching and compressing it by means of the screw just described, and allowing the attainment of the pressure registered at any in- stant to be indicated by the slight vibration or jump permitted by, the lost motion in the grip on the spring as the steam-pres- sure passes that point. In these indicators it is evident that -the __________70 lb. Pressure Line (Boiler)__________ diagram produced is then a “ composite” of a number of succes- sive indications, taken in as many successive revolutions of the engine. At the high speeds for which only such instruments are designed this is probably no disadvantage; but the instru- ment cannot show what occurs throughout any one revolution- The screw is usually so attached, however, that it may be read- ily removed at any moment, and the indicator thus quickly converted into the common form. * Perry, The Steam-Engine, 1874; Bulletin de la Soc. Ind. de Mulhouse, 1876; London Engineering, Dec. 14, 1888, p. 576.140 ENGINE AND BOILER TRIALS.. The indicator of Professor Webb is intended for u$e on fast-running engines where the inertia of the parts of the standard type of instruments is embarrassing. Fig. 20 is a diagram taken at 400 revolutions per minute. The series of zigzag lines is the blank diagram. Each line is made by one stroke of the engine, and at 400 revolutions it would be about three seconds before the diagram is finished. If the indicator cock is open, the pencil will make the diagram. Instead, at the start, of following the 55-lb. line, it jumps up until the pressure on the cylinder falls again to 55 lbs., when it will come back to the line and finish it. The pencil will then return to the left side on the diagonal line, and the pro- cess will be repeated until the card is complete. In Fig. 21 an indicator is shown with this device attached.* The frame of the instrument is extended up to e, and a hole is made through it in which the screw b slides freely. This screw has a. nut, which moves the slide, C, receives its motion from a crank not shown. The swinging leaf, F> holds the paper on which the diagram is to be taken. The indicator is clamped to the plate, and the drum-cord connected with the spring. The crank is Fig. 23.—Drum- testing Apparatus. * Mr. Wallace finds the yield of a good ordinary stretched indicator-cord to be from 0.008 to 0.0125 Per f°ot Per pound ; and of wire No. 36 B. W. G. 0.003.STANDARDIZA TIQAT OF INDICA TOR. H7 made to move at the speed desired. The paper is then raised to the pencil, and the diagram taken. If the strain on the cord is constant, the forward and return strokes will be paral- lel ; but if the strain is not constant, the pencil will rise and fall as the strain varies. The line below the diagram is the line of no stress, drawn when the cord has been detached from the indicator. The diagrams are shown two thirds their original size. Indicator. 250 revolutions Indicator. 250 revolutions Oscillations of the pencil about its proper position, and the consequent production of wavy lines in the diagram, cause the most serious defects in diagrams taken at high speeds of engine. Such deformations of the diagram are due to the inertia of the pencil and its holder and connections, and become greater as speeds increase, until, with every instrument, a speed is finally reached at which the diagram becomes unintelligible, as in the figure on page 148, which represents the card obtained by using an old style of indicator, with a light spring, at 300 revo- lutions per minute. With the best modern indicators it is easy to secure a perfectly smooth diagram at this speed. These vibrations are the more serious as the proportion of the weight of the moving parts of the indicator are the heavier and as the spring is lighter. Their effect is not only to disguise the true form of the diagram, but also to enlarge it and thus to give too great values of power developed. Professor Reynolds gives the following as speeds at which this variation becomes one per cent, in an indicator having a piston-area of one-half14B ENGINE AND BOILER TRIALS. square inch and a weight of moving parts equivalent to 0.33 pound at the piston : * Spring used, lbs. per sq. in. 20 No. revolutions per minute, 166 40 60 80 100 237 288 332 371 This error varies directly as the weight of the moving parts. In modern indicators of the best forms, it is probably inap- Fig. 25.—Indicator Vibrations. preciable at all familiar engine speeds, the maximum being taken at about 300 revolutions per minute, five per second; and it may be assumed by the engineer that if his indicator is of good make, if he finds its parts correctly made, and if he keeps them in good order, he may rely, in all ordinary cases, on obtaining diagrams correct to within the limits'of his nicest measurement, if the instrument is properly attached to the engine and skilfully handled.f For higher speeds than are now obtained, indicators of the class illustrated by that of Duprez must be employed. * Proceedings Inst. C. E., vol. lxxxiii., 1885. f Barrus on Modern Indicators, and Discussion thereon: Trans. Am. Soc./ M. E., vol. v. pp. 310-339. 1884.STANDARDIZA TION OF INDICA TOR. 149 The following is a description of Professor Reynolds' device for checking the movement of the drum, and to ascertain what distortion is caused by its irregular fling and friction : * A Grove battery of five cells, in conjunction with a Ruhm- korff coil, is used. The wire from one pole was connected with one of the binding-screws (H) of the coil as usual, but the wire from the other pole of the battery was connected with the engine. A wire from the other binding-screw (G) was attached to the contact-breaker (B), a smooth piece of wood, into which pieces of wire were inserted at equal distances, the distance between the first and last wire being the length of the stroke of the engine. This was fixed on the lower slide, so that a pointer (A), secured to the cross-head, should slide on it. One wire of the secondary coil was connected with the drum (E), and the other to a cup of mercury, into which the metallic pencil (F) dipped, thus completing the circuit when the pencil touched the paper. In the following diagrams the relative positions of the circles show which parts of the diagrams are lengthened, and which are shortened. The effect is not merely to shorten the ends and lengthen the middle of the diagrams, but also to dis- tort them, i.e., to cause corresponding points hot to lie in the same vertical line. The amount of this distortion is shown by the distance between corresponding points on the atmospheric line. (Fig. 27.) It is evident that the pencil may be made barely to touch Fig. 26.—Distortion by Stretch of Indicator-cord. Proc. Brit. Inst. C. E., 1885, No. 2070.ENGINE AND BOILER TRIALS. 150 the paper without marking it and the diagram made by the sparks alone. Front-end pricked diagram taken with wire at 107 revolutions. Front-end pricked diagram taken with string at 107 revolutions. qi : go 0 ■ ro ■■ -co -oo o —cP co "'-Q' < Front-end pricked diagram taken with wire at 127 revolutions. Front-end pricked diagram taken with string at 127 revolutions. Fig. 27.—Electric Diagrams. Comparisons of indicators will often eliminate uncertainty as to their reliability. If an indicator is known to be right, the diagrams produced by it should be, under similar conditions, duplicated by an instrument the accuracy of which is doubted. Where three or more instruments are compared, the presump- tion is usually a fair one that, if one differs in any important degree where the others agree, it is defective. Where several are to be compared, it is sometimes practicable to take dia- grams from them all simultaneously by fitting up properly. In such cases, all should be equidistant from the steam-cylinder and should have equally straight and large connecting pipes. One large pipe and cock, taking steam from the cylinder, ter- minated by the several pipes leading radially from its top to the several instruments, will usually answer the purpose. In comparing the details of construction, it is to be remem- bered that the points to be studied are the exactness and per-STANDARDIZATION OF INDICATOR, 151 fection of dimensions and workmanship, and the weight of parts and their action as affected by inertia. The latter point has been seen to be peculiarly important when the instrument is to be used on engines at speeds exceeding about a hundred revolutions per minute. Comparing, in this particular, the action of the paper-cylin- ders, or -drums, we find the time of a vibration, the forces freely acting, to be in which d is the angular displacement, here to be reckoned from the position of mid-throw, and a the angular velocity. and the couple acting to start the drum into harmonic motion is That instrument, therefore, which has the least value of I the moment of inertia of the drum, is least liable to inaccuracy from this source of stress. The best adjustment should be sought in each case, and the comparison effected after this adjustment has been made. Since the effort of the drum-spring is usually directly proportional to the angle of motion, and since the force due acceleration is zero at mid-throw, if the dif- ference of tension on the cord at the beginning and end of the motion is twice the effort required to overcome the inertia- resistance of the drum at starting, the action on the cord will be uniform when at speed, and the diagram entirely free from distortion from this cause. Other things being equal, that is Then and 1 length diagram . I 2 radius of drum ”” rI52 ENGINE AND BOILER TRIALS. the best instrument in which this adjustment is secured. In some cases they are arranged for such adjustment at several usual speeds, or so as to permit the tension of the spring to be altered as desired—increasing it at high speeds, diminishing it at lower speeds* The acceleration for a 4^-inch card is 0.11523 r • 1 , 0.7703 , , ---^----, or for a 3-inch card —; and, for the power, a pound acting at the circumference of a drum 2 inches in diam- eter will give the following speeds:* maximum resistance at the stated Revs, per min. R. Revs, per min. R. 120 0-5 360 4.2 180 1.0 480 7-4 24O 1.8 600 11.5 300 2.9 IOOO 32.0 These stresses evidently become serious at high velocities, in- creasing, as they do, as the square of the speed; and the higher the speed the greater the difference in favor of that instrument having lightest drum. The stretch of the cord used (if sensible) should be observed ; as this is an element which determines also the amount of dis- tortion of the diagram due to the inertia of the drum and the action of its spring. In all cases we have the moment of the pull, P, on the cord, Pr = ^ + Rr + Fr-, (Pot in which the angular acceleration is and Rr and Fr are the spring and the friction moments. The first quantity has been seen to.be zero at mid-throw, its value increasing each way; the friction moment may be taken constant and unimportant, and the spring-resistance variable with its flexure, as already seen. The stronger and the less elastrc the cord, and the better the adjustment of the spring-action to the inertia-effect, the * Wallace on the Indicator : Trans. Inst. Scotland, 1S88, p. 3.STANDARDIZATION OF INDICATOR. 153 more accurate the diagram. In good examples these effects are unimportant. Comparing the indicators as to the effect of surges and oscillations, it is found that both these actions may become serious at high speed and with heavy pencils, springs, and pis- tons. The surge of the moving parts due to their rise or fall through the height of the diagram tends to increase the area of the curve. If indicators give similar and correct results at moderate speeds, this increase at higher speeds may be com- pared to determine their relative merits. It should never equal 1 per cent. This limit is found by Professor Reynolds, for the Richards indicator, at the speeds already given. It is seen that the maximum speeds of rotation in revolutions per minute is about where s is the scale of the spring in pounds to the square inch; and this disturbance varies directly as the weights. This com- parison may therefore be effected by weighing the moving parts. The vibratory disturbance of the pencil is due to the elas- ticity of the spring, and its time is where wR is the effect of the moving parts reduced to the work- ing-point ; py my and g are the total load on the piston, the ratio of pencil and piston motion, and the acceleration of gravity. These disturbances are not serious as affecting the area of the diagram, but they are sometimes important as obscuring its meaning. A comparison of indicators in this regard would be made by taking diagrams at continually increasing speeds and noting the point at which the outlines of the figure become wavy and when they interfere with its legibility. It is seen that this defect increases as the square root of weight of moving parts, and is the more serious as the weights are nearer the R = 40 Vs , t — 271 12 pmg* wr154 ENGINE AND BOILER TRIALS. pencil and subject to rapid movements and quick changes of direction of motion. These irregularities may be partially con- trolled by the pressure and friction of the pencil, but only at the sacrifice of accuracy. The value of t should always be as small as practicable. If too large, the diagram may be seriously distorted. Any number of oscillations in the tracing of the card exceeding 25 or 30 may be permitted ; less than 20 or 25 is objectionable. Comparing springs, it will be often found that considerable differences are observable in their indications, both cold and hot. They should be examined to see that they take no per- manent set, that they yield in exact proportion to the pressure, and that their attachment to the instrument is such as not to produce lateral strain or friction. Springs which have been already repeatedly given their full set by the makers are best. They should always be tested and compared hot.* The best indicator, as is now evident, is that which, by such comparison and examination as has been described, is found to give the most exact and reliable diagram, and to be least af- fected by inertia-forces and the action of its own parts at high speed ; it is that, in detail, which has proportionally the largest and lightest piston, the stiffest and lightest springs, the least friction of moving parts, the most perfect pencil mechanism, the most accurate and constant scale of pressures, the most perfect adjustment of drum spring, and the lightest moving parts generally. The following is the method of comparing indicators adopt- ed by the Navy Department: f A -horizontal pipe, 2 inches diameter and 24 inches long, fitted with suitable pipes and valves for the admission and dis- charge of steam and provided with three nipples, two for the attachment of indicator and one for a steam-gauge, was used in the tests. * See the valuable papers of Dr. Berndt on this subject in the Sachsische Ingenieur und Architecten Verein, 1882-85 meetings ; and Lond. Engineering, 1877-8. f Report of Chief of Bureau of Steam Engineering, 1888.STANDARDIZATION OF INDICATOR. 155 The steam-gauge having been secured in place, steam was blown through the test-pipe and indicator-nipples several times to free the pipe of water and dirt. The indicators, after being well oiled, were secured in posi- tion and steam admitted, the pressure being allowed to rise until the limit for which the springs were designed was reached, in order to bring the instruments to their working tempera- ture. After trying the instruments to see that their movements were free, steam was discharged from the test-pipe and the in- dicator-cocks closed. The piston of each instrument was then pressed down slightly by hand and allowed to return to its nor- mal position, with the friction of the moving parts opposed to the movement of the spring. When this had been done, the atmospheric line was drawn across the card. Steam was then admitted to the instruments and so regulated that the hand of the steam-gauge would rise slowly to the interval of pressure to be noted; and when it reached that point, at the word “ mark,” an operator stationed at each instrument drew the re- quired line of its scale. All lines of the scales were drawn in the same manner, the top steam-line of the first test of each series being extended across the card. Before beginning the down scales, the steam was allowed to rise a pound or two above the pressure to be first noted, in order to oppose the friction of the instrument to the movement of the spring. At the end of the down scale, the steam was shut off and discharged from the pipe and the indicator-cock closed before drawing the atmospheric line. To determine the comparative indications of identically the same power by the two instruments, the following method was used : The indicator-pipe at the outer end of the engine was fitted with a T and two right-angle branch pipes of equal diameters and lengths terminating in nipples. To the latter, the indica- tors were attached, after clearing the pipes of water and dirt and lubricating the cylinders. The springs of the paper-drums were adjusted to approximately the same tension. The cords156 ENGINE AND BOILER TRIALS. around these drums were tied to each other and to a single cord connecting with the indicator motion. This arrangement gave coincident motion to both drums without sensibly affect- ing the lead of the cords, as the angle between the latter was small. One operator could readily take cards from both indicators at the same time. Ten cards having been taken from each indicator, the latter were interchanged and then ten more cards taken from each. This change was make in order to eliminate any errors due to possible differences in the bore and lead of the branch pipes. The test to determine the pencil movement was made as follows: The spring of each indicator having been removed, a microm- eter gauge was fitted to the cylinder and the weight of the piston and attachments taken on the end of the micrometer screw, the zero of the wheel coinciding with that of the vernier. A line was then drawn with the pencil of the instrument and formed the first one of the scale. The micrometer screw was then turned one revolution and a second line drawn ; this was repeated until the scale was complete for the movement of the piston. A test to determine the line of motion of the pencil in each instrument was made as follows : The spring having been removed, the piston was pushed up its entire stroke, the pencil at the same time drawing a line on the card, while the paper-drum was securely held by the detent attachment. Ten such lines were drawn on the card with each instrument. All moving parts of both instruments were carefully weighed and their weights in Troy grains found. At the conclusion of the foregoing tests, the steam-gauges used in the work were carefully compared with the mercury column. The test of indicators, taking simultaneous diagrams from the same end of the 'engine, is liable to give misleading results unless great care is taken to have both equally well fitted andSTANDARDIZATION OF INDICATOR. 157 similarly situated. To insure perfect fairness, they should be transposed and again compared. The following is the result of a comparison so made. The results can of course only be taken as gauging the work of the individual indicators so com- pared : Tests of Indicators. Simultaneous cards taken from engine with A and B indicators fitted with 20-pound springs. Number of Cards. Mean pressure. Indicated horse- power. Mean pressure. I Indicated horse- I power. A B Difference. A B Difference, j A B Difference. A B Difference. z 13-30 12.65 •65 26.797 25.487 1 • 3TO 14.6c 14-3° •30 29.842 29.229 .613 2 13.80 13.20 .60 27.803 26.595 1.208 14.80 T4.00 .80 30251 , 28.6l6 1 • 635 3 13-65 12.85 .80 27.502 25.890 1.612 13.90 13.20 .70 28.412 26.981 1-431 4 13-45 12.65 .80 27.099 25487 1.612 13-5° 12.75 •75 27-594 26.o6l 1-533 5 I3-3° 12.55 •75 26.797 25.286 1 • 511 14.60 14-35 •25 29.643 ; 29.122 •521 6 13-47 12.60 •8 7 26.942 25.203 1 • 739 13.00 12.45 •55 26.572 25.448 1.124 7 13 62 12.58 1.04 27-243 25.163 2.080 12.15 11.85 •30 24-835 ! 24.221 .614 8 14.20 13-25 •95 28.403 26.503 1.900 12.52 12.50 .02 25.S91 ; 25-550 .041 9 13.90 12.85 1.05 27.803 25.702 2.101 12.70 12.20 •50 26.144 25115 1.019 10 14.30 J3 3° 1.00 28.603 26.603 2.000 12.50 12.00 •50 25-55°! 24.528 1.022 1 16.95 16.16 •79 33•161 31-615 1.546 15-7° 15 10 .60 33-oo8 31-746 1.262 2 15.80 14.60 1.20 31-372 28.990 2.382 14.00 12.75 1-25 29.025 26.433 2 - 592 3 i5-5o 14.28 1.22 30.664 28.250 2.414 14-35 14.00 •35 28.886 28.207 .679 4 15 45 14.10 1 -35 30.677 27.997 2.680 17.00 16.43 •57 33-259 32.144 1 • 115 5 17.00 15-65 i-35 34-003 31-303 2.700 14-75 14.60 •15 29.718 29.416 .302 6 15-25 13.90 1 -35 30.503 27.803 2.700 18.40 17-25 115 36.535! 34-252 2.283 7 14.20 13.00 1.20 28.403 26.003 2.400 17.20 16.50 •70 35-1571 ■33 726 1-431 8 16.20 14.70 1.50 32•403 29.403 3.000 16.20 15-70 •50 33-113 32.091 1.022 9 15-20 13.80 1.40 3°•4°3 27.603 2.800 15-50 15.00 ■50 31.682 30.660 i .022 10 12.65 12.35 •30 25-303 24.702 .601 14.85 14.50 •35 30.353 29.638 •7i5 Means 14-5595 I3-55IO 1.0085 29.0942 27.0794 2.0148; 14.6110 14.0715 •5395 29./585 28.6592 1.0993 Simultaneous cards taken from engine with A and B indicators fitted with 40- pound springs. Power measured by A 7.4403 per cent, greater than measured by B. Power measured by A 3.8358 per cent, greater than measured by B. Note.—First series: A on left-hand pipe. Second series; A on right-hand pipe. This comparison has no value or meaning unless one instru- ment is known to be accurate and standard. To test the friction of the working parts of the indicator, if a means can be secured of obtaining a manageable and variable steam-pressure, try the instrument at various pressures, as shown by a reliable steam-gauge, and compare the gauge-read- ings with those obtained by measurement of the diagram, as exhibited in the figures on page 158.i5» ENGINE AND BOILER TRIALS,L In A, Fig. 28, the diagram is that given by an instrument fitted with a “ 30-lb. spring,” and having considerable friction of pencil movement; in By the diagram is that of an indicator of little friction, and fitted with a “ 20-lb. spring.” How far such tests and comparisons may be taken as quan- titatively gauging the value or accurracy of the instrument is Up. Down. B Up. Down. Fig. 28.—Indicator Test. uncertain. Probably the less the friction—as a rule, though not always—the better the indicator; but the action of move- ment in use, and the effect of inertia of parts, so modify final results, the former by lessening, the latter by exaggerating, the effect of friction, that it is quite impossible, so far as is to-day known, to predicate definite quantitative deductions re- lating to the accuracy of the instrument. . We can only say that the lighter the parts, the less the friction, and the more accurate the spring-tensions and the pencil-movements, the better the indicator, and that the best now made, under the usual working conditions of the best engines, may be expected to give sensibly correct diagrams. This fact does not make it any the less imperative that every indicator to be used in any important work should be fully and carefully tested.ATTACHMENT OF INDICATOR. 159 The standardization of the indicator is the more important from the fact that there is no available means of checking its work. The work of the engine, as otherwise customarily measured, is rarely known with accuracy, and the Author has known several indicators, used under similar conditions, to differ among themselves 10 and 15 per cent., with no means at hand of determining which of them were wrong, or the extent of their errors. Where a dynamometric brake is used, the check is more satisfactory, as the friction of the engine is commonly known, or ascertainable within a comparatively small limit of error. The best makers of indicators are, however, usually prepared to guarantee, to standardize, and to give variation-tables of their instruments; and the errors are now reduced in such cases to probably very small amounts. 55. The Attachment of the Indicator should always be so effected that its piston may receive precisely the pressure simultaneously acting on the engine-piston, and so that the motion of the paper shall exactly reproduce, as to time and in its proper proportion, the movement of the piston. This means that the steam-connection should be amply large and free from bends and angles, and that the cord and reducing motion giv- ing movement to the paper-cylinder, or -drum, should be so arranged as to lead right, and to be perfectly free from lost motion or stretch. In attaching the instrument, it is usual to drill a half-inch hole in each end of the steam-cylinder, and to make connec- tions with half-inch pipe to the indicator-cock as directly as possible. In many cases it will be found that the drilling has already been done by the builder of the engine. The opening into the cylinder is commonly in the clearance space back of the piston. Care should be taken that it is not covered by the piston at the end of stroke, and that the in-rush of steam from the steam-port is not likely to produce any sensible effect by blowing across the hole. Especial care should be taken to prevent chips from the drill falling into the cylinder and lodg- ing where they can do injury. The work should, if practicable, be done with the heads removed ; if this is not practicable, ai6o ENGINE AND BOILER TRIALS. little steam should be turned on and the chips blown out before starting. If the indicator-cock can be screwed directly into* the cylinder, it is an advantage. The indicator should, if possible, stand in the vertical position when in use, and one should be placed at each end of the cylinder, and diagrams taken as nearly simultaneously as possible. The cock between the indicator and the cylinder should be of the full size of the pipe, and should be so made that steam may be at any time either turned on the instrument or blown out into the air to clear the passages, and to see that all is right. The Reducing Motion is made in many ways, and is often, by the ingenious engineer, improvised for the occasion. It must reduce the motion of the piston so as to give a correct throw at the drum and exactly proportionally at every part of the move- ment. One of the simplest and best devices is the “ Brumbo Pul- ley,” Fig. 29. It consists of a sector, A, vibrating about an axis, By and actuated by an arm, C, and a link, D; the latter connected as directly as possible with the cross-head. This may Fig. 29.—The Brumbo Pulley.ATTACHMENT OF INDICATOR. 161 often be accomplished by attaching its free end to a set-screw on the latter. The sector is usually of wood ; but if to be per- manently set, is sometimes a light frame of brass. The arm and link are usually of light iron or steel, secured together with nicely fitted pins. The longer the arm in proportion to the stroke of engine-piston, the truer the action ; the proportion of two to one should be obtained if it can be done. . The accompanying sketch illustrates a neat device for secur- ing a correct adjustment of the indicator-cord when taking mo- tion from a simple suspended lever. The pin to which the cord is attached is set in a right-angled piece of wood with lines marked upon it parallel to its lower edge and indi- cating the proper direction of the cord. This is secured on the pendent lever in proper position, when the latter hangs verti- cally, the engine at mid-stroke, and is then fastened securely by small screws. A modification of the Brumbo arrange- ment which the Author has found to work excellently well on high-speed engines is illustrated in the next sketch, as designed originallyby Mr. Sweet. When used under the direction of the Author in work done at the Sibley College of Cornell University, it was constructed as follows: Fig. 30.—Cord Attach- ment.ENGINE AND BOILER TRIALS. 162 The reducing mechanism used in connecting the indicator- barrel to the cross-head of the engine was fitted with a very firm connecting arrangement, and with an ingenious detaching device. A sector was constructed which was pivoted above the cross-head and hung in the vertical plane above the latter, the engine being horizontal. The arc of the sector carried a pair of steel ribbons, one attached to each end, each carried around the arc and secured, at its opposite end, to the end of a bar fas- tened on the cross-head, in such manner that, the two ends of the ribbons at the cross-head bar being well secured and tight- ly drawn up by means of screws placed conveniently for the purpose, all back-lash was prevented, and an absolutely exact synchronism of movement of indicator-line and cross-head was obtained. A smaller sector at the upper part of the larger one was the carrier of the cord, and the combination was thus a per- fect means of reproducing the motion of the engine on the smaller scale required in working the paper-barrel of the indi- cator. The “ cord” was piano-wire, a material much less liable to cause difficulty by stretching than any other that was avail- able. Its free part was kept taut by a “ spiral ” (helical) spring, attached beyond the point of connection with the paper-cylin- der. The cord may either be taken around a groove in the rim of the sector or led from a properly set pin on its side. The lat- ter is the more accurate, pro- vided the cord at half-stroke is led off at right angles to a radius of the pulley passing through the centre of the pin. A “ pantagraph motion/’ if well made, nicely adjusted, and properly attached, makes an excellent reducing ar- Fig. 32.—THE pantagraph. rangement. This is seen in Fig. 32.* It consists of a system of levers of wood ; those marked B are single strips, and American Machinist, Dec. 27, 1879.ATTACHMENT OF INDICATOR. 163 those marked A double strips. The pivot-holes should be bushed. The strip G should be arranged so that it may be shifted in the holes E, and bring a hitch-pole, in a line passing through pivots C, D. The end pivots C and D should have a projection below, with the end somewhat pointed. The engine cross-head must have a vertical hole in it somewhere, so that pivot C can be dropped into it. A stake must be set in’the floor near the guides, having a socket for the pivot D in its top. Its socket must be level with the cross-head socket, and must be directly opposite the former when the latter is at mid-stroke. The indicator-cord is hooked to the centre peg A, and the cord should lead off parallel with the guides. Fig. 33.—The Pant.agraph in Place. The next illustration shows the apparatus in place, and the indicator attached. Various modifications of this device are in use, all of which embody the same principles.. Fig. 34 shows another form of pantagraph. The working end, Ay takes motion from the cross-head, and B is attached to the floor. The pin, D, is fixed in line between the pivot and the working end, and the pulleys, E, guide the cords.* * Barrus on the Indicator.164 ENGINE AND BOILER TRIALS. Avoid the use of long cords. If the motion must be car- ried a . long distance, strips of wood may often be arranged in their place and operated with direct connections. Braided Fig. 34.—The Pantagraph. linen cord, a little over one-sixteenth of an inch in diameter,, is a suitable material. The next two engravings exhibit Mr. Thompson’s usual methods of attachment for engines of his own design: A is the lever, B the connecting bar, C a strip of board attached to the cross-head, D a firm support, and E the indicator-cord, which is shown horizontal. This horizontal direction allows the pivot ay the cord pin b, and the pivot c to be in line, and when no pipe fittings are used to connect the instrument, and it consequently* is shifted from end to end of the cylinder, it is correct for both positions. Fig. 36 shows a device that will give a movement perfectly*ATTACHMENT OF INDICATOR. l6$ free from distortion. The cord is attached to the end of a short bar,which slides freely in a bearing in the carrying-post. This bar is connected to the lever CD by a link AB. The lever is con- nected to the cross-head at E by a bar,DE. The pivots C, B, E are in line at all times; and the distortions of the movement of the lever due to the .vibration of DE, will be corrected by the equal vibration of the link AB; since, CD : DE :: CA : AB. This, to be correct, must be proportioned for the engine. The cord should be nearly level. The cord employed should be as short as possible. If un- avoidably long, a fine wire of steel, of iron piano wire, or of hard-drawn brass should be used. Braided cord is usually sup- plied by makers of indicators which has been made especially for the purpose and well stretched. A hook on the end of the cord attached to the drum and a loop, Fig. 37, on the adjacent Fig. 37.—The Loop. end of the cord from the reducing motion afford means of ready connection and disconnection. The loop is adjusted, be- fore hooking on, to just the right length so as to avoid liability of accident by maladjustment when starting. The spring chosen should usually be rated at above one-half the maximum gauge reading ; in other words, so that the maximum rise of the pencil may not be above two inches. The minor details of op-i66 ENGINE AND BOILER TRIALS. eration are always fully described in the instructions supplied ’ by the maker of the indicator. Mr. Lyne’s method of attachment of the indicator to the locomotive is shown in the accompanying engraving.* Fig. 38.—“Indicating” Locomotives. In making connections, a hole is drilled close to the flange at each end and tapped to fit a f-inch nipple (wrought-iron pipe). These holes should be so drilled that the piston may not cover the holes at the ends of the stroke. After the holes have been drilled and tapped (which may be done without removing the cylinder casing or back cover), two nipples hav- ing |-inch malleable-iron elbows upon the ends are screwed in place. These should be tightly screwed up, and set looking towards each other. Two long nipples, having brass collars brazed upon one end, are then cut of a proper length to fill the space between the elbows and cock. Brass should be used for the collars, as solder will not run through the threads if the * Am. Machinist, Apr. 1, 1882, p. 1.ATTACHMENT OF INDICATOR. 167 collars are of iron. The end of one of these nipples is to be cut in the usual way and tightly screwed in place, while upon the other nipple the die is run up inch for the application of a lock-nut. It is then screwed into the elbow, the three-way cock is put in place, the joints being made with washers of annealed sheet copper. Rubber and all other fibrous material should be avoided in making these joints. The nipple having the lock-nut is screwed out from the elbow until the joints are firmly made upon the cock, then the lock-nut is to be set up against the face of the elbow, a few strands of lamp-wick hav- ing previously been wound between the two surfaces to avoid any possibility of leaks. The ends of all the pipes shopld be carefully rounded inside with a file, and nothing but clean oil should be used in making the joints. If red lead is used, the operator, in taking the diagrams, will have the annoyance of seeing his instrument stick, and will be obliged to remove the piston frequently and pick the lead and dirt out of the instrument. The three-way cock, shown in the sketch, is of a heavy pattern. The brass centre of the handle has a wooden cover- ing, which protects the hands from being burned. The pas- sages are of quite easy curvature and of large diameter— T9^- inch in this case. The details of this construction are seen in the sketches herewith given. In applying these devices to a locomotive, place the cross- head at half-stroke, attach the frame to the guides, and set the lever at right angles to the guides and screw up all the nuts, being careful to spread the blocks so that the cross-head will not strike them. Adjust the lever vertically, in the following manner: With a pair of trammels set to the length of the lever, describe an arc, and draw a straight line with the ends touching the arc. Measure from the centre of the line to the arc, and set the centre, of the lower pin in the lever half this distance below the centre of the cross-head, then tighten the nut on the upper pin. This will equalize the vibration. This should all be done beforehand, and the distances put168 ENGINE AND BOILER TRIALS. f 2 of this. ^ \ Rough. TJttL - . +. Yd.'. lL_ 2 Of this. Rough. Fig. 39.—Details of Indicator-motion. down in a book for reference. To prevent the cord from getting out of the groove, a wire loop should be used, as shown. This arrangement can be applied and adjusted with-ATTACHMENT OF INDICATOR. 169 out movingthe engine. The indicator-cord is short, and the lever quite long. The cord is best braided linen line, well stretched and lightly waxed. The box bottom is 9 inches below the beam by a f-inch bolt through it and the flag-stand; the back is supported by an iron bracket attached to the stud in the centre of the cylinder-head. The counter is attached to a board bolted to the front brace, as shown. In applying an indicator to the steam-chest, drill a hole in the centre horizontally and vertically; then screw in a half-inch nipple and elbow, and set up the indicator in line with the grooved arc. The cord connection will be very short. Holes should be drilled in every cylinder while the engine is in the shop, and brass plugs, with hexagon heads, screwed into them. The cross-heads should be drilled and tapped, so that upon an hour’s notice the indicator may be attached without the necessity of doing any work. In cold weather it is desirable to erect a screen to protect the operator from the wind. The method of attachment found, on the whole, most convenient, in the work of the Author on vertical marine engines, is that shown in Figs. 40 and 41.* This apparatus was designed for the Author by Mr. Lyne, and used on the steam-yacht “ Namouna,” while preparing to make some improvements. The engines are of the compound “ tandem” type, their cranks at right angles. The high-pressure cylinders are 22 inches in diameter and placed above the low-pressure cylinders, which are 42 inches in diameter with a stroke of 28 inches. The propeller has four blades and a pitch of 18 feet; the boiler-pressure is 80 or 85 pounds per square inch; the en- gines make from 80 to 85 revolutions per minute. At A is the high-presssure cylinder; the low-pressure at B; while C is the frame, E the guides, D one of the columns supporting the engine. A wrought-iron arm, G> is bolted to the pin on the cross- head F. This arm had a rectangular end for the slide K. The arm G was at right angles to the guides, and, by the aid of a steel steady pin, can be readily removed and replaced, the * Am. Machinist, Aug. 19, 1882, p. 3.I/O ENGINE AND BOILER TRIALS. hole for the pin being reamed tapering and the body of the bolt filling the hole. The prin- cipal object in making this arm so long was to use a lever, Hy 40 inches long. Errors are less with a long lever than with a short one. The lever was at- tached to a thimble, P, and a pin or feather inserted to avoid possibility of the lever chang- ing its position. A collar, /, was fitted to the column D by being bored with a piece of iron 3V inch thick in the joint, so that, after the collar was finished and this iron re- moved, the collar would grip the column. A segment, y, was bored to fit upon the thimble P in plan, and to the cross-head; T is the slide, Q the collar at- tached to the column, and P the thimble with grooved seg- ment. N, 0 are the positions in plan of the two indicators Z, M. The pipes were all of brass,, and neatly finished. The cords run directly to the indi- cators, and no guide-pulleys are used. The grooved seg- ment has a radius to give a diagram 5 inches long. The advantages are as fol- lows : It may be run constantlyATTACHMENT OF INDICATOR. 171 with but little wear, as the wearing surfaces are all large, and it is always ready for use. It is simple and easily made, and diagrams may be taken in a heavy sea with as great accuracy as in smooth water, as there are no guide-pulleys attached to the woodwork of the vessel. Two cords for working the indicators are attached to the grooved segment J9 by passing the end of each through a hole at each side of the groove, as shown at a a a in plan, and knot- ting the ends. The steam-pipes to the indicators are f inch in diameter. The experience of the Author with this arrangement was thoroughly satisfactory. It is somewhat costly, in compari- son with less , perfect* devices ; but its operation is so effective as to fully compensate that disadvantage where, as in this case, it is intended t6 be a permanent attachment, and kept ready for daily use. The working drawings of the details of this attachment are presented in the next figure. A is the lever, B the composition sleeve, upon which is fitted the segment C. The bearing D is turned down in the middle to form an oil-chamber. The bearing is screwed into the collar K. The screws for holding this collar together are oper- ated by a screw-driver. The slide F is made of composition, having a gib to take up the lost motion. No set-screw is used, as it is safer to insert a liner on top of the gib. The piny is attached to the slide F\ and forms a journal for the lever. The thimble I is fitted to the pin J’. GH shows the arm bolted to the cross-head. The following are the details of proportioning several simple indicator-motions devised and described by Mr. Nystrom.* Fig. 42 represents one of these indicator-motions; though not absolutely correct, the error is insensible. It consists of a horizontal lever, L, with its fulcrum at C, and the other end attached to the pendulum P> the lower end of which is attached to the cross-head. The fulcrum C should, as advised by its designer, be placed near the indicator /, so as to make the Mechanics, June 1883.\J2 ENGINE AND BOILER TRIALS. lever L of nearly the same length as that of the cord connect- ing the indicator with the pendulum. The error on the card will then be the difference of the versed-sines of half the angles formed by the motions of the lever and cord. All linear dimensions in the following analysis are to be expressed in inches. L ' = length of the lever ; l = length of the cord from the indicator to the vertical position of the pendulum; P = length of the pendulum ; s =’ half the stroke of the steam-piston; 0 = angle moved by the lever L;ATTACHMENT OF INDICATOR. m 01 = angle moved by the cord; d = differential v = half the angle of the pendulum motion ; e = vertical motion of the joint of the pendulum and lever. e=P- VP* - Example —The pendulum P = 36, and j = 12 inches. Re- quired the motion of the joint. e = 36 — V362 — 128 = 2.0588 inches. Half of this motion will then be 1.0294 inches. Assume the lever L = 48 inches, and half the angle

The versed-sine for this angle is 0.00023 X 48 = 0.011 of an inch.. h = 35.5 inches vertical mean height of the cord above the direction of the stroke s; then the versed-sine will be reduced h 0.011 X 31*5 * , . , to -p, or-------------= 0.009025 of an inch. The vertical motion of the cord at the pendulum will be 2.0588X31.5 . , -------------= 1.80145 inches, of which one-half = 0.900725. Half the angle of the cord will then be O 00072 c sin -J0' = -L-^— =0.00187765 = sin i° 4' 30". / = 54 inches. The versed-sine for this angle is 0.00017 X 54 = 0.00918 of174 ENGINE AND BOILER TRIALS. an inch. The error on the card caused by this indicator-motion will then be 0.009625 — 0.00918 = 0.000445 of an inch. This error is too small for detection on the indicator-card, but it can be removed entirely by placing the fulcrum C at C/ on the other side of the indicator. Fig. 42 can therefore be considered a reliable indicator-motion. The letters ^Pand B represent the position of the pendulum when the piston is at the front or back of the cylinder. Fig. 43 represents another of these indicator-motions for the locomotive. It is similar to that of Fig. 42, except that the lever L is placed at the other side of the pendulum, as a matter of convenience. There were two cylinders to be indicated simulta- neously, for which purpose horns, ab> Fig. 44, were fixed on the pendulum from which cords were led. The pendulum was of steel, 2 Fig. 43.—Indicator-motion. inches wide by f inch thick, and the pivot-holes were % inch. The ends of the pendulum were made 3 inches in diameter for the purpose of making it firm against uneven action on the horns, which were f inch in diameter at the pendulum and tapering to J inch at the eyes. This made a very rigid system, which worked well. The fulcrum C for the lever L was fixed on the foot-board of the locomotive. The pendulum was 36 inches, lever 24 inches; and stroke of steam-piston 24 inches, stroke of card 3 inches. The calcula- tion for error is the same as that for Fig. 42, except that the versed-sine of the cord must be added to that of the lever L. The error so obtained was 0.018, which, divided at each end Fig 44._horns on Of the Card, makes it O.OO9. This error exists Indicator-motion. at •§• from each end of the card, positive at one end and nega- oATTACHMENT OF INDICATOR. 175 tive on the other; but when cards are taken from both ends of the cylinder the errors compensate. The angle v of the pendulum at the ends of the stroke is The indicator-motion, as represented by Figs. 45, 46, and 47, is a defective indicator-motion. Fig. 45 exhibits the characteristics of link indicator-motions. The cross-head moves in the direction of the dotted line FB ; the linkZ is made very short in proportion to the length of the pendulum P, for the purpose of better illustrating the motion. The different positions of the link and pendulum are num- bered 1, 2, 3, etc., of which in the first position the link and the pendulum are in a straight line; the cross-head is stationary while the pendulum moves. The line Cc is the vertical posi- tion of the pendulum. The point on the vertical Cc, where the direction of the link crosses, shows the motions of the cross- head and of the pendulum; the motion of cross-head is to pendulum as Ca is to Cc. In the fifth position the link sin v — C B Fig. 45.—Link Indicator-motion.176 ENGINE AND BOILER TRIALS. crosses the vertical at c\ the motions of the pendulum and cross-head are alike. In the eighth position the line of the link crosses the vertical at i; the motion of cross-head is to pendulum as Ci is to Cc. On the right side of the vertical the pendulum moves faster than the cross-head, and on the left side the cross-head moves the faster. When the link is less than half the length of the pendulum, the latter should move over a much smaller angle on the link side than on the other side of the vertical. The motion of the pendulum transmitted to the indicator by a circle-sector, A, n, k, will make the cord move too fast at the ends of the stroke. A sector should not be circular, but of the form e, n, d, for the proportion of link and pendulum shown in Fig. 45 ; then, . CL) . Cy Cy dy : Cy 1ly == Cy by ! Cy Cy (s y C y . dy — C y CLy . C y b * The indicator-cord fixed on the pendulum, without a sector, will mgve too fast on the link side and too slow on the other side at the end of stroke. The cord should be fixed at of on, the link side of the vertical, and so that Cy fy : Cy fly — Cy ay \ Cy Cy Cy gy • Cy fly -- Cy by . Cy Cy Cy /, : Cy gy ^ Cy ay : Cy b. When the cord is attached to the sector hy ny ky or to the pen- dulum at fly the pendulum should make a smaller angle on the link side and a greater angle on the other side, but it will not make a true card in any case. Fig. 46 represents a motion very much used. The direc- tion of motion from the cross-head bisects the versed-sine of the angle made by the pendulum, and the angles v are alike on both sides of the vertical.ATTACHMENT OF INDICATOR. 177 Here, P = 18 inches; L = 8 inches; ^ = finches; h — 17J inches ; v = 26° 23'; 5= 16 inches; C# = 15.05 inches. From these data we find that the indicator will move 14 per^c, cent, faster at the back than at-----:2s==^jfes the front end of stroke. Fig. 46.—Indicator-motion. Lengthening the link, correct the defect in part, and the motion would make a tolerably correct card. Fig. 47 represents a motion in which P = 48t3f inches, length of pendulum ; L = 34yi inches, length of link ; h = 38 inches, height of fulcrum; v = 30°, half angle of motion ; S = 48 inches, stroke of piston; Ca = 44^ inches; Cb = 39 inches. C The indicator would move nearly 14 per cent, faster at the front than at the back end of stroke. The link should be178 ENGINE AND BOILER TRIALS made 29 inches long, to make 'the angle of motion greater on the link than on the other side the vertical. The motion would then pro- duce a better card. Slot motions for indicators have been tried, and abandoned. Fig. 48 represents a motion in which the cord is moved by a circle- sector. The slot-pin is fixed in the cross- head of the engine, and the problem is to find the relative motion of pin Fig. 48. Slot Indicator-motion. to slot on the arc ab. The height R of the fulcrum is constant. P = distance from the fulcrum to any position of the slot- pin; 5 = half the stroke of the steam-piston; a = half the length of the arc ab. R sin v tan v =----------. cos v Differentiate this formula, and we have cos 8 sin — sin 8 cos 8 tan = 8 tan = 8 tan = cos (sin3 -f- cos3*) 8a cos 8a cos and 8 a = cos2 8 tan. The differential of the tangent is the differential motion of the pin, which we may take as unit, 8a = cos2. The motion of pin is to arc motion as 1 : cos3. If radius R = 36 inches, and s = 15 inches, v will be tan v — = 0.41666 = tan 320 37'.PRECA UT 10NS. 179 The cosine for this angle is 0.923.1. The square 0.923.1*'=-0.8521, and when the motion of the pin is i, near the end of the stroke, that in the arc at a will be 0.85, 15 per cent, too slow. The error may be corrected by converting the sector into a triangle, as shown by the dotted line. Fig. 49 represents a motion in which the cord is fixed without a sector. In this case d sin must be inserted for da; then 6 sin =cos da. d sin da =------. cos Insert this for day and we have d sin cos cos2, or d sin = cos8. The motion of pin is to cord as 1 : cos3. Let R = 36, s = 15, v = 22° 37' and cos v = O.9231; 0.9231s = 0.7865. When the motion of the pin is 1, near the end of the stroke, that of the cord will be then 21 percent too slow. Slot motions distort the card at the ends of stroke, where greatest accuracy is required for exhibiting the method of distribution of steam. 56. Precautions essential to the successful employment of the indicator have been already detailed at some length; briefly summarized, they are: (1) Make sure of accuracy of construc- tion of the instrument in its dimensions and fitting; (2) Secure exactness in scale of’ the spring employed, not when cold, but when hot and in use; (3) Demand the utmost lightness and stiffness of moving parts; (4) See the spring in the paper-drum correctly adjusted to the speed of the engine; (5) See that the instrument is well lubricated, and with the best of light oils, and that it works freely and without friction; (6) Make the steam- connections short, straight, and large; (7) Use a short cord, and substitute wire where any considerable length is necessary; (8) See that the reducing motion is perfectly accurate, freei8o ENGINE AND BOILER TRIALS, from lost motion, and both strong and light; (9) In taking the diagrams, see the steam-cock opened full, the indicator well heated up, the steam condensed in the connections completely blown out, and the touch of the pencil on the paper as light as is consistent with making perfectly legible diagrams. Every maker gives detailed instructions for care of the in- strument and for its dissection and assemblage. The principal points are the following, details varying with the style of the indicator: Before using any indicator, take it apart, clean, and oil it. Try each part separately. See if it works smoothly; if so, put it together without the spring. Lift the pencil lever, and let it fall; if perfectly free, put in the spring, and connect. Give it steam, but do not attempt to take a card until it blows dry steam through the relief openings. If the oil from the en- gine gums the indicator, take it off and clean it. Never use red or white lead in connecting, as it is liable to get into the instrument. Attach the indicator to the cock by coupling the differential threads of the indicator shank and cock. The lighter the spring used, the higher will be the dia- gram produced, and the more accurate the measurements ob- tained ; in selecting a spring, choose one to give diagram about two inches high. After the desired number of diagrams have been taken, re- move the piston, spring, etc., from the indicator, while it is still upon the cylinder; allow the steam to blow for a moment through the indicator cylinder ; then examine piston, spring, and all movable parts, which must be thoroughly wiped, oiled, and cleaned. Particular attention should be paid to the springs,, as their accuracy will be impaired if they are allowed to rust; and great care should be exercised that no gritty substance be introduced, to cut the cylinder or the piston. The springs should not be left in the indicator. The pencils can be best sharpened with a fine file. Each blank indicator-card usually has printed on its back a set of data to be filled out, such, for example, as the following. The number and character of these items differ in the practiceINDICATOR RECORDS. 181 of different engineers; but the more important are never omitted. % Diafrram from Engine Rnd. No.. Diameter of Cylinder and Area. Built by H. P. Factor.... Initial Pressure I. H. P Length of Stroke Brake H. P Clearance and Barometer reads Revolutions per Minute T hermometer Piston Speed Pressure of Steam, in lbs., in Boiler Point of Cut-off Position of Throttle-valve Observer Vacuum per Gauge, in inches Remarks. Temperature of Hot-well “ “ Injection Scale of Spring M. E. P Inside Diameter of Feed-pipe “ “ “ Exhaust-pipe The Author has used the next form many years. It is am- ply complete for most cases; indeed is rarely entirely filled out. Time Date R. H. THURSTON, Consulting Engineer. Diam. of Cylinder Length of Stroke Revolution per min Owner 0/ Engine : Speed of Piston Diam. Piston-rod Area Steam-port Kind 0/ Work Driven by Engine : “ Exhaust-port Piston Clearance Port “ Boiler Pressure Remarks : Initial “ M. E. Pressure Barometer Builder of Eng. j Kind of Valve Motion..... “ “ Steam-valves... . . “ “ Exhaust-valves..... “ “ Condenser ......... “ “ Heater............. “ “ Boiler............. “ Fuel .................. Temperature of Feed-water, “ “ Hot-well___ Water per hour........... Coal “ “ ..........CHAPTER V. INDICATOR-DIAGRAMS INTERPRETED. 57. Indicator-diagrams taken under proper conditions and with good instruments are diagrams of energy on which the ordinates measure the varying pressures in the cylinder, corresponding to the positions of the piston as measured off by the simultaneous abscissas of the diagram ; while the area represents the work done by the steam on the piston of the engine. The forms and relations of the several lines of which the diagram is composed reveal the method of action of the valves and the effectiveness of the pipes and passages as con- duits for the entering and the exhausted steam. The correct interpretation of the diagram thus becomes an exceedingly important matter. 58. The Typical Diagram and its Nomenclature, as- suming the indicator applied to the steam-engine, are as be- low. The curves described on the indicator-cards of engines present many differences as to the mode in which pressure and volume vary, and their figures cannot be expressed by any mathematical formulae; since it is impossible to separate those irregularities which arise from fluctuations in the pressure of the steam from those which arise from the friction and inertia of the moving parts of the indicator, and also because the law of such changes as actually take place in the cylinder of the engine is not precisely known. An approximate form of diagram is therefore taken in theoretical treatment, which diagram is approached more and more closely as the machine is improved. Fig. 50 is such a diagram. AB represents the volume of the mass of steam 182INDICA TOR-DIAGRAMS. 183 when admitted into the cylinder. The first assumption is that the pressure of the steam remains constant during admission, so that AB is a line parallel to OX, and the pressure is repre- sented by OA = GB. The second * t Y assumption consists in assigning to the curve BC one or other of two definite A--------- forms: to expand without receiving or giving J-----------g---------- but heat; so that BC is an adiabatic Fig. so.-Idbal diagram. curve. (II) When there is a steam-jacket, it is assumed that the heat communicated by means of that jacket is just sufficient to prevent any appreciable part of the steam from becoming liquid; so that BC is a curve of pressures and volumes of satu- rated steam. The real diagram of the ordinary engine is of somewhat different form. The next figure illustrates these differences. The accepted nomenclature is as follows: The admission line AB is produced by steam on admis- sion. Its normal direction is vertical, or nearly so, as it is traced while the crank is passing its dead-centres. Leaning outward indicates lead. With no lead it would lean inwards, as sometimes with condensing engines. The steam line BC is traced after the piston has commenced its stroke. Its proper direction is horizontal at a pressure nearly equal to that in the boiler ; but this can only be ap- proximated with such openings that the maximum velocity of flow will not exceed about 100 feet per second. But with throttling-engine diagrams the steam line inclines downwards. The point of cut-off C is the point where the entering steam is cut off. It is usually anticipated by a fall of pressure, which is less as the valve closes more promptly. With some engines, having multiported gridiron valves with detachable valve-gear, this fall of pressure is not appreciable, and the point of cut-off is well defined. (I) When the cylinder has no D steam-jacket, the steam is assumed F C £184 ENGINE AND BOILER TRIALS. When the instrument has been in good working order, the cut-off may be located at the point of contrary flexure. The expansion line CD begins at cut-off and terminates at exhaust. The point of exhaust D is where exhaust begins ; the ex- pansion curve there ends and the pressure begins to fall rapidly. The exhaust line DE is traced while the steam is escap- ing. When it occupies a considerable part of the return stroke, or nearly all, it indicates a cramped exhaust opening. The back-pressure line EF represents the pressure in the cylinder during the return stroke. With non-condensing en- gines the position of this line is somewhat above atmospheric pressure. With condensing engines it indicates a pressure somewhat in excess of that in the condenser. The point of exhaust closure F is anticipated by a rise of pressure ; the eye may locate it very exactly. The compression curve FA exhibits the method and ex- tent of variation of pressure after the exhaust-valve closes. The atmospheric line GG locates the position of equilib- rium of the piston of the indicator before steam is introduced. The vacuum line HH is drawn parallel with the atmos- pheric line at such a distance below it as will measure the pressure of the atmosphere. It is generally placed 14.7 lbs. below the atmospheric line. When a barometer can be con-INDICA TOR-DIA GRA MS. 18 5 suited, its reading in inches, divided by 2, will give approxi- mately the atmospheric pressure. The next figure illustrates the form of the diagram obtained from an explosive gas-engine of the Otto type. The three lines, ABC, are the result of three successive explosions with varying rates of combustion, A indicating rapid, and C show- F ing slow, combustion; neither representing a true explosion, which would have given an initial line above A> and vertical. Here the mixture of gases with air enters on the induction- stroke IH; compression occurs on the return of the piston, HK; explosion follows and a second out-stroke, KFG; ex- haust takes place at G; and expulsion of the charge of non- consumed gases takes place on the second return-stroke, HIENGINE AND BOILER TRIALS. 186 The indicator-diagram, although generally assumed to repre- sent the variation of the effort on the piston of the engine at each half-revolution, really exhibits only one part of that action at any given instant. The line ABCFy Fig. 53, exhibits the effort of the steam during the forward stroke ; but that effort is partly equilibrated by the back-pressure and the compression on the opposite side. If these are represented by the line DCE, it is evident that the real variations of net effort are exhibited by the space ABCD and by CEF\ the former being positive, the latter negative. It is thus necessary to combine parts of two opposite simultaneous diagrams to ascertain the real pressures transmitted from the piston. 59. The Causes of Modified Forms of Diagram are usually simple and easily traced. The actual form of the dia- gram differs from the ideal form, as just described, in con- sequence of the occurrence of a number of conditions which are usually more or less objectionable. These conditions are classed thus: Causes which affect the power of the engine, as well as the figure of the diagram : (1) Wire-drawing in taking steam and at cut-off. (2) Clearance in the cylinder and passages. (3) Compression, or cushioning. (4) Pre-release. (5) Conduction of heat by the metal of the cylinder. (6) Liquid water present in the cylinder. Causes which affect the figure of the diagram only: (7) Undulations in the motion of the pencil. (8) Friction of the indicator. (9) Position of the indicator. In the accompanying sketch, in which the ideal and a modi- fied form are compared, it is easy to trace some of the causes of difference. At A the pressure of steam is usually a maximum. Should the induction occur at the right time and in the right way, the cylinder will be full of steam at the instant of forward move- ment of the piston; should the valve open late, A will be foundMODIFIED DIAGRAMS, 187 nearer B, and the line KA will be inclined toward the right; early opening of the induction-port will produce a line starting nearer My and terminating at A as at first. If the pressure is not well sustained, AB will fall toward B; and if the cut-off does not take place promptly, the comer at B will be rounded off, as from H to G. At the end C, of the expansion-line, similarly, early opening of exhaust will give QRS or PI; late opening may give CMy and the exhaust-line and back- pressure line may become confounded. Early closing of the exhaust-valve may produce a compression-line, MA. In all well-designed and properly adjusted steam-engines, this com- pression, as well as the expansion, will be so arranged as to utilize to best advantage the available heat-energy of the fluid. Some of these modifications of the ideal diagram are, there- fore, due to practical conditions which dictate them. Thus, as the steam-ports are now made, in high-speed engines partic- ularly, it is impossible to secure instantaneously, on opening them, the full pressure of steam in the cylinder; they are therefore given “lead”—opened in advance. The same cause usually retards the inflow of the steam up to the point of cut- off, and thus produces a fall of pressure along the steam-line. Similarly, to meet the disadvantages inherent in the inertia of the fluid, as well as that of practically limited port-area, pre- release of the exhaust-steam is customary. The slower the action of the expansion-valves and of the exhaust-valves, the more are the sharp corners of the ideal diagram rounded off ini88 ENGINE AND BOILER TRIALS. the real indicator-card. This action is called “ wire-drawing” the steam. Where the corner at cut-off is obscured in this way, the real point of cut-off may be approximately determined by carrying out the lines AH and PG to their intersection at By which is taken at the point required. This has been called the point of virtual, or effective, cut-off.* Wavy lines indicate a defect in the indicator, or its inappli- cability at such speeds of engine. They do not always give rise, however, to inaccurate computations. Broken and irregular lines indicate the presence of grit in the instrument. The accompanying fac-similes of cards taken from a “ high- speed ” engine well illustrate the method of variation of the diagram, with loads varying from overload to simple friction of engine. The data relating to this case are as follow: Diameter of cylinder ... =8" Stroke of pistqn.............= io" Scale, 60 lbs. to i inch. Revolutions..................= 340 per minute. * Rankme; Steam-engine, p. 418.INTERPRETATION OF DIAGRAM. 189 Weight of reciprocating parts Connecting-rod length . . . Maximum valve travel . . . “ lead................ “ port-opening . . Clearance, each end, . . . = 152 lbs. = 6 cranks = 2*" = r = *" = n% Maximum, crank end, “ front “ “ mean, j M. E. P. = 61.80 lbs. (H.P. = 5376 ( M. E. P. = 69 lbs. ( H. P. = 60.03 ( M. E. P. = 65.40 lbs. ( H. P. = 56.89 Average initial pressures . . =80 lbs. 60. The Interpretation of Diagrams is usually easily effected, and by means of this “ engineer’s stethoscope” it be- comes possible to ascertain the nature and cause of almost every defect in the distribution of pressures and volumes of the work- ing fluid, as in the adjustment of the valve-motion, and the size or proportions of steam-passages, or of the connecting pipes. The power exerted by the steam is easily measurable. These several points may be summarized thus: (1) Gross power exerted by the steam. (2) Net power of the steam, and equivalent net power of the engine. (3) Resistance of unloaded engine. (4) Net power of the engine. (5) Details of various wastes of power, as by wire-drawing, back-pressure, etc. (6) Valve-adjustments. (7) Effectiveness of valve-gearing. (8) Adequacy of sizes of port. (9) Quantity of steam present at any point in the stroke. (10) Feed-water demanded, exclusive of that wasted by cylinder condensation. (u) With a boiler-trial, the actual expenditure of steam, fuel, and money, for a given amount of power; and wastes by leakage and condensation.8 ENGINE AND BOILER TRIALS. 190 Of these, the principal are only determined by careful com- putation, employing as data the quantities graphically meas- ured on the indicator-diagram ; others are at once seen by the practised eye, demanding only an inspection of the figures shown on the card. An engine well adapted to its purpose, a perfect engine in the engineer’s sense, will usually exhibit an early induction; wide port-opening; an admission-line closely approaching boiler-pressure, and nearly or quite horizontal; Revs. LH.P. B.H.P. F.H.P. 443 Revs. 7.751.H.P. 7.41 B.H.P. .34 F.H.P. Fig. 56.—Effect of Speed. a sharp cut-off; an expansion-line closely approaching the com- mon, or equilateral, hyperbola in form ; a somewhat early and a prompt release or exhaust; a low and uniform back-pressure; and a compression carried up well toward initial pressure. These effects are obtained by giving some steam and exhaust lead—greater as speeds and pressures are higher—having good area of ports, securing quick action of the expansion-valve, and a well-adjusted closure of the exhaust-valve. Any depar-INTERPRETATION OF DIAGRAM. igi lure from these conditions is ordinarily to be taken as evidence of defective construction or adjustment. The reduced copies on the opposite page show how the ideal diagram is departed from in the operation of engines, especially at high speeds (Fig. 56). * All these cards were taken with the same indicators and from the same engine. All exhibit similar departures from the ideal form of diagram, and all illustrate well the two kinds of effect already described—those due to practical conditions of construction and operation of the engine, and those produced by the inertia and friction of the indicator. As an illustration of the interpretation of the diagram, we may take the following example (Fig. 57): f In this case the eccentric sheave had been given, instead of the usual angular advance, a reversed position 43 degrees be- hind its proper location on the shaft. The admission commences only when the piston has trav- elled one-sixteenth of the stroke. The release is late by an * Variable Load, etc., R. H. Thurston ; Trans. Am. Soc. M. E., 1888. f Barrus on the Indicator, p. 19.ENGINE AND BOILER TRIALS. I92 average similar amount. The pressure before cut-off is low, the back-pressure high, and there is no compression. Waste of power is here evidently produced ; the expansion is too early terminated and the exhaust is deferred, wasting steam in even higher degree than power of engine. The suc- ceeding figure represents as close an approach to the ideal form as is often seen, and probably has too high a ratio of expansion to give best results. The accompanying diagram, taken by Mr. King* from the condensing engines of the “ Powhatan,” and the dotted varia- tions from the actual line, exhibit again the various principal deductions to be made. Fig. 59 is what would be termed a good diagram. Steam......... 10 “ Powhatan” stb. cylinder, bottom. Vacuum........ 27 Nov. 7, 1855, 10 a.M, Hot-well...... 106 Fahr. One engine and one wheel in Revolutions... 9.5 operation. Throttle...... 8. Smooth sea. It appears, however, that the piston of the indicator worked tightly, which occasioned it to stick in places, as is evidenced by the steps in the expansion-line, and also at ab in the vacuum- line. Should Fig. 59, instead of as shown, have the lower right- hand corner cut off as at cd, the exhaust-valve closed too soon, —at c instead of —occasioning cushioning. * Practical Notes, p. 46.INTERPRETATION OF DIAGRAM. 193 Had the upper right-hand corner been as shown by the line fgy the steam-valve must have opened too late. Had the ex- haust corner been cut-off, as shown by hi, the exhaust-valve would have opened too soon; but had it been at kl, it would have opened too late, and would move too slowly, preventing free escape of steam ; or the exhaust-passages would have been too small, which would produce a similar effect. Had the steam- line fallen as at mn, it would have shown that the throttle was partially closed, or the steam-passages too small. Should there be excessive lead to the steam-valve, the line dm will have the top inclined to the right as L from to m. Late opening would produce an inclination in the opposite direction. Top of cylinder Steam side. Bottom of cylinder Steam side. Fig. 60.—Unsymmetrical Valve-setting. This figure is a double diagram taken from one of the pad- dle engines of the “ Great Eastern,” when on her trial-trip in the British Channel. It will be observed that the valves were unevenly set. The diagram from the top of the cylinder shows that the pressure on the piston was 20 pounds, cut-off at one-third the length of the stroke, and expanded down to atmospheric pressure at the termination. The diagram from the bottom of the cylinder shows that the steam was at 22 pounds, cut-off at half-stroke, and expanding to 4 pounds above the atmosphere at the ter- mination ; in both cases the vacuum being 12 pounds or about 24 inches. The number of strokes was uf, and the speed of the piston 331 feet per minute. The exhaust closed when the piston had travelled five-sixths of the length of the cylinder,194 ENGINE AND BOILER TRIALS. checking the progress of the piston when about two feet from the end of the cylinder. Whenever the adjustment of valves is proposed, guided by the indicator, it should be carefully noted whether parts affected by such adjustment are liable to injury by the change. Slide-valves, for example, which have been long at work, some- times wear their seats to a shoulder when they are not ter- minated by a depression which is overrun by the valve. If this shoulder is not first removed, the change may cause leak- age, or even accident. 61. Compound-engine Diagrams, as produced by the steam-engine indicator, often differ even more than with the simple engine, from that ideal “ card ” which would be given were the expansion precisely as intended, and the engine free from defect, as in clearance-spaces and port-resistances. The best compound engines show considerable loss, as has been seen, in these ways, and also in that drop of pressure between highl- and low-pressure cylinders which often constitutes a very sen- sible source of waste of heat, steam, and fuel. Where the Wolff system is adopted, however, if the load be constant and the machine well proportioned to its work, and if the “ dead-spaces’" can be made small, the approximation of the actual to the ideal card may be very close, as is illustrated by the accom- panying pair of diagrams from a pumping-engine of this character. The action of the steam and its variations of pressure are here seen throughout the cycle to be precisely similar to that in a simple engine. Large steam-ports and a good expansion- gear bring the steam-line close up to that of boiler-pressure; a well-jacketed cylinder allows the expansion-line to follow closely that laid down for the ideal engine, short and free ports between the two cylinders give an exhaust from the high-pressure and a supply to the low-pressure cylinder which are nearly coincident; and the two cards would, if reduced to a single diagram, exhibit a very close approximation to that which would have been constructed as the ideal diagram of this class of engine. Such satisfactory results are rare; and in mostCOMPOUND-ENGINE DIAGRAMS. 195 cases the differences between the actual and the ideal case are very marked, and are serious in their effect upon efficiency. Fig. 6i.—Action of Steam; Wolff Engine. The next diagrams represent the pair of cards taken from a well-known single-acting compound engine of small size. The action is precisely as before, except that heavy compression is introduced to fill the comparatively large clearance-spaces.196 ENGINE AND BOILER TRIALS. This distribution is peculiarly well adapted to high-speed practice, such as it actually illustrates. The small loss of pres- sure between the two cylinders well exhibits this special advan- tage of well-proportioned engines of the Wolff type. The Construction of Diagrams exhibiting the method of action of steam in the cylinders of the compound engine, as a preliminary to the settlement of the details of the design, is usually as below; these ideal or theoretical indicator-cards indicating the ideal action of the type of engine proposed, as modified by such conditions of operation as the designer can with more or less exactness define and represent. The separate diagrams appertaining to the two cylinders, high- and low- pressure, of an ideal compound engine, are to be combined in a manner indicated as follows,—to obtain a single diagram representing the complete cycle of changes of pressure and volume of the steam from the moment of entrance up to that of its discharge,—the Wolff type of engine being chosen for illustration: The steam being admitted into the smaller cylin- der until it fills a volume, represented by BC in Fig. 64, the absolute pressure is represented by BO above zero on POQ~ The steam is then cut off, and it expands with a pressure gradually di- minishing, as shown by the curve CD. DN being perpendicular to OQy UN represents the space swept through by the piston of the small cylinder. Next, a communication is opened between the small and the large cylinder ; and the forward stroke of the large piston takes place at the same time with the return stroke of the small cylinder. Thus the steam is driven before the piston of the small cylin- der, and drives that of the larger cylinder, and it exerts more energy on the latter than it receives from the former, as the piston of the large cylinder sweeps through greater space ; the difference between those quantities of energy is added to the energy exerted on the piston of the small cylinder. This O N Fig. 64.—Combined Diagrams.CONSTRUCTION OF DIAGRAMS. 197 action is represented by DA and EF\ the ordinates of DA representing the backward pressures in the small cylinder, and EF the forward pressures in the large cylinder. During return stroke of the larger cylinder the steam is expelled, exerting a back-pressure along FA ; while steam is admitted again into the small cylinder, and expanded during a new stroke of that cylinder. Thus are obtained the diagrams BCDAB for the small cyl- inder and EFAF for the large, and the sum of their areas rep- resents the energy exerted by the quantity of steam expended. When the diagrams are to be used for the purpose of study- ing the relations between heat expended and work performed, it is best to combine them into one diagram, thus: Draw a line KGH parallel to POQ, intersecting both dia- grams, and layoff upon it HL — KG\ and GL — GH-\-KG represents the total volume in both of the steam-cylinders, when its pressure is OG; while L is a point which would have been reached had the action taken place in the large cylinder alone. By drawing a number of lines, as KL, any number of points may be found to complete the combined diagram BCDLMAB, whose length OQ = OP represents the volume of the large cylinder; and this diagram may be discussed as if it represented the action of the steam in the large cylinder only. Thus, as observed by Rankine,* the energy exerted by a given portion of a fluid during a given series of changes of pres- sure and volume depends on that series of changes, and not on the number and arrangement of the cylinders in which those changes are undergone. When the diagrams taken from the two cylinders of the simplest form of compound engine are placed together, having the same length, they form a whole such as is illustrated in Figs. 61, 62, and 63. Since, however, the diagram should be constructed so as to make the horizontal scale one of volumes, the pair cannot be compared with the card taken from a simple engine, and they must be reduced to a common scale of vol- * Steam-engine, § 261, p. 336.ENGINE AND BOILER TRIALS. I98 umes by either reconstructing the smaller on the volume scale of the larger, or vice versa. The latter is the usual course, as is illustrated in the succeeding examples of compound-engine diagrams. In thus combining these diagrams, it must be re- membered that the work represented is that of the engine for one stroke or is that of a single charge of steam, just as in the single cylinder. The base-line measures the stroke, or the volume swept through by the piston in one forward movement. To make a combined diagram, each abscissa of the low-pres- sure diagram must be increased in such a proportion as to cause it to become proportional to the total volume assumed by the steam at the instant of the production of that line. The ratio of the enlargement is that of the effective capacities of the two cylinders. If the diagrams have both been taken with the same indicator-spring, the two diagrams may now be adjusted to make a single one which exhibits, at all periods of its cycle, the actual relations of pressure and volume of the steam. Were the engine perfect in its proportions and its operation, the two figures would produce a combined diagram precisely like that which might be obtained from a single engine working the same weight and pressure of steam with the same expansion-ratio. At any point in the simultaneous motion of the two pis- tons the volume of the steam will evidently be the sum of the volumes, vx traversed by the large, and Vx still to be moved throifgh by the small, piston; and if the part of the vol- ume traversed in each cylinder is x, this total volume, as to x, is v— x-\- — x = vx+ Vx; V and the pressure at this point is measured by the ratio of the volumes; so that . -s- ri _ P*v _________________P,v________ vx + Vx r,(vx + Vx) rp -f (r — r,)x.CONSTRUCTION OF DIAGRAMS. 199 This value is somewhat modified by the presence of the in- termediate passages between the cylinders, a drop occurring in the pressure at the instant of opening the exhaust from the small cylinder; but this drop is less as those passages are larger; and if forming an intermediate reservoir, as is sometimes the case where “ reheating” between the cylinders is practised, this loss and the corresponding reduction in the mean pressure ob- tained, in work done, and in the actual total ratio of expan- sion, is sometimes quite unimportant compared with the gain by that process. A common value for the reduction of total expansion is not far from twenty per cent., rising to one-third with small reservoirs and falling to a lower figure with larger spaces. The loss of work may usually be neglected. The receiver type of engine with equidistant cranks and in- termediate reservoirs is less seriously affected by intermediate spaces. The reduction of pressure and the loss of total expan- sion is but about ten per cent., where the receiver-space is equal to the volume of the smaller cylinder, and falls to less than five, in usual cases, when the receiver is as large as the larger cylinder ; losses which may be easily approximately estimated and allowed for in any case.* In the next illustration from Mr. Porter’s report, the nat- ural form of the expansion-line, in the single cylinder, having the capacity here observed in the low-pressure engine, would be that shown by one or other of the two dotted lines, accord- ingly as the expansion approached more or less closely the hy- perbolic form. The initial volume is AB, and the pressure as shown on the vertical scale ; while the gradual loss of pres- sure with increase of volume is shown by the two scales as the line progresses toward the right to its terminal point at I. The deviation from the dotted line of the actual expansion-line between B and C illustrates the gain of weight and pressure due to the progressing re-evaporation of steam originally con- densed in the cylinder at the opening of the steam-valve, and to the admission of the fluid into the colder cylinder. Here * For exact expressions, see Sennett, Appendix ; and Clarke’s Manual, pp. 849 et seq.200 ENGINE AND BOILER TRIALS. expansion occurs from the initial pressure and volume at B down to the terminal point C in the high-pressure, and from C or H to / in the low-pressure, cylinder. The indicator-dia- grams actually obtained are ABCD and JSFGy the latter being the equivalent in the low-pressure cylinder of the card HIJy ° ' 2 J 4 5 6 78 9 "> II I! 13 14 15 16 I? 18 19 » 21 22 23 24 25 26 27 2$ 29 30 Fig. 65.—Compound-engine Diagrams. which would have been produced had the high-pressure cylin- der been given sufficient length to permit the completion of the expansion in that cylinder. The variation of the full line, representing the real diagram, from the ideal dotted expan- sion-line is indicative of the fluctuations of pressure produced by the condensation and re-evaporations taking place as expan- sion progresses in the metallic chamber serving as working cyl- inder. The succeeding figure illustrates the visible differences be- tween the diagrams actually taken from the two cylinders of a compound engine—in this case a “ Reynolds-Corliss”—and the ideal combined card. This next diagram, from an engine of similar class with theCONSTRUCTION OF DIAGRAMS. 201 preceding and published by its designer, exhibits at once the method of reducing the actual indicator-diagrams to the com- bined form, and the variations from the ideal expansion-line due to imperfections of the engine as a work of human art. Pressures are measured in pounds on the square inch and vol- umes in cubic feet, actual capacities of cylinder being given. As shown on the diagram, about 3^ cubic feet of steam enter the high-pressure cylinder, each stroke, at a pressure of 110 pounds per square inch above vacuum ; it expands nearly adiabatically to cubic feet, is then transferred to the low- pressure, dropping from the terminal pressure, 40 pounds in the high-pressure cylinder to 20 in the low-pressure, and then expanding in the latter down to about 12 pounds when it passes into the condenser, the back-pressure thus becoming not far from an average of 6 pounds. The two indicator-diagrams202 ENGINE AND BOILER TRIALS. are shown by the “hatched ” spaces; the ideal diagram incloses both, its outline being the dotted lines. The very considerable space measuring the difference of the two areas is a gauge of the imperfection of the cycle. The departure of the actual line from the two ideal expansion curves, and the fact that the former lies within both the latter, indicate that the jacket does not supply heat enough to compensate the condensation of the expanding fluid; far less enough to retain its temperature con- stant or to continuously superheat it. The discordant fluctuations of similar lines in the two in- dicator-diagrams exhibit the effect of non-synchronous motion of the two cylinders. The accompanying illustration exhibits the proportions of the diagrams taken from a triple-expansion engine, drawn to common volume and pressure scales, and placed under the Mariotte line. The engine has cylinders having the ratios i: 2.25 : 2.42, and the total ratio of expansion is 8, the cut-off in the several cylinders being set at 1.47, 1.3, 1.3. An advan- tage of this type of receiver engine, with its cranks making equal angles, is that the drop in pressure may be reduced to anSPECIAL APPLICATIONS. 20J unimportant amount. Here steam-pressure is carried at 125 pounds by gauge; the efficiency 0.18, and the coal used 1.5 pounds per I. H. P. per hour. 62. Special Applications of the indicator are of peculiar interest to the engineer. Valve-adjustment is often performed, and should always be checked, by the aid of this instrument. The application of the indicator to the steam-chest, and the com- parison of its readings with those of the ordinary diagrams and of the steam-gauge at the boiler, will often reveal defects in the steam-passages or valve-action otherwise difficult of detection ; its use on the air-pumps of condensing engines and on the main pumps of pumping-engines similarly reveals anything objection- able in their construction and operation ; and the motion being derived from the eccentric or the valve-mechanism when at- tached to the engine in the usual manner will permit a more minute examination of those phases of operation which are not easily studied on the common form of card. In some cases a continuous motion, derived from the crank-shaft, is adopted for this purpose. In valve-adjustment, an inspection of the diagram shows the operation of the valve-mechanism as set. The necessity of adding lead or the reverse, of resetting the valves and eccentrics, is seen, and they are readjusted and diagrams again taken, these operations being repeated until the form of diagram desired is approximated as closely as is practicable. In illustration of the forms of diagram obtained from the steam-chest and their interpretation, Mr. Porter gives those exhibited in the illustration.* In these figures the steam-pressure fluctuates in the valve- chest with the draught upon it by the engine, rising to boiler- pressure after cut-off takes place, and falling below it more or less as the steam enters the valve-ports more or less rapidly. The extremities of the diagram correspond to the end of stroke of engine-piston ; the points c to the points of cut-off at each stroke. The lower line shows the pressure in the chest during the interval up to the moment of action of the expansion-valve. *The Richards Steam-engine Indicator, pp. 177-S,204 ENGINE AND BOILER TRIALS. Immediately afterward the pressure rises to boiler-pressure and there remains until the point is reached at which a drop of the upper line shows that the opposite end of the cylinder has be- gun to take steam. In A and B the pressure, when at its maximum, actually exceeds boiler-pressure, the surge of the mass in the steam-pipes and chest, when suddenly checked, causing a wave of abnormally high pressure. These were taken from Mr. Porter’s engine at the Paris Exposition of 1867, when making 200 revolutions per minute. In C, evidence is found of insufficient area of steam-pipe, A c Fig. 68.—Valve-chest Diagrams. resulting in the observed considerable fall of pressure when the engine takes steam at either extremity and the correspondingly large rise at the cut-off, c. The pipe having been enlarged, the card D was obtained; the sudden drop and continuous fall of pressure while the engine takes steam and the considerable loss of pressure, of power, and of efficiency indicated in C are in D all absent. 63. Pump Diagrams obtained by application of the instru- ment to the air-pump of a condensing engine are seen illus- trated in the two succeeding figures, given by Mr. King, asPUMP DIAGRAMS, 205 taken by him from the air-pumps of the U. S. S. “ Powhatan,” a paddle steamer of old type, having jet-condensers.* With the first of the pair the engine was working as usual; in the second case the pump was taking in a large excess of air through the bilge-injection. The pump, in the first ex- ample, draws the mingled air, vapor, and water from the condenser at a pressure about 4 pounds above a vacuum, throughout the induction-stroke, and on the return or educ- tion-stroke they are compressed under a regularly increasing pressure to the point at which, the delivery-valve opening about 5 pounds above atmospheric pressure, the whole mass is dis- charged with fluctuations of the line due to rise and fall of the * Practical Notes, pp. 56-60.206 ENGINE AND BOILER TRIALS. valve and irregular expulsion of air and vapor. The pressure then falls to about 2 pounds, and the end of the stroke is reached. Excess above the last observed pressure is due to friction in the discharge-passages and delivery-pipes. These diagrams are seen to be characteristically different from those obtained from the engine. Pumps raising water, or any other incompressible fluid, should give a diagram like that here shown, as taken from the remarkable pumping-engine built by Mr. Corliss for the town of Pawtucket, R. I. This diagram is seen to be perfectly rectangular, the water entering from beginning to end of stroke A By the pressure about five pounds below that of the atmos- phere ; the change to the delivery pressure, BC, a little above ioo pounds per square inch, taking place instantly on reversal, and the discharge, CD, occurring at uniform pressure. The slight disturbance at one corner, C, is due to a jar of the spring of the instrument. Air-compression Diagrams exhibit this effect, as in the adjacent figures, showing a steam-engine and an air-compressor card taken from the Allen “ positive valve-motion"’ compressor at the same time The engine drives the compressor, and the work shown on the engine-card exceeds that of the compressor by the lost work of the apparatus. The engine is seen to have early admission, incomplete expansion, early release, and cush- ioning, all of which are practically to some extent required forAIR- COMP RE SSION DIAGRAMS. 20 7 best effect; but the compressor takes in its charge throughout the induction-stroke, compresses steadily from the minimum to the maximum pressure, and has no observable variations from the ideal diagram such as are exhibited in the case of the steam-engine. This machine was running at 144 revolutions per minute when . “ indicated// and this speed caused those fluctuations of the curve due to inertia in the instrument. Diagrams taken with the motion of the paper derived from the main shaft are of the form seen in the next figure. From A to B is the exhaust and vacuum line; from B to C, the cushioning; C to D, receiving-line ; D to E, steam-line ; E to A, expansion ; FF are supposed to be the ends of the stroke. Fig. 74 is the same diagram extended more nearly to its original length, the ends joined and then folded at FF so as to represent more nearly the usual diagram, but still preserving the peculiar length and proportion of lines. Diagrams taken in this manner expose more perfectly defective arrangements of valves; and a studious comparison of them in connection with208 ENGINE AND BOILER TRIALS. the usual form may often be useful in detecting defective sizes and proportions of valves, steam-passages, etc., and show very correctly the proportion of time occupied in each different operation during the revolution of the engine.* Attaching the line to the eccentric motion will give simi- larly useful diagrams. 64. Peculiar Forms of diagram are often met with, each invariably exemplifying some singular or abnormal arrange- ment of the engine. Steam in boilers.... 9 lbs. ** Powhatan,” Feb. 13, 1854. Revolutions.. 5 Stb. cylinder bottom, working by hand. Hot-well..... ioo° Throttle..... 4 10 9 8 765432 1_ 6. 4 2 0 2 6 8 10 12 14.<7 r j A / / L \ / \ —Jh s' s a Fig. 75.—Working by Hand. Fig. 75, from King, is a diagram showing the operation of the valves while working by hand. This valve exhibits large * Stillman on the Indicator, p. 31.PECULIAR FORMS OF DIAGRAMS. 209 cushioning and steam lead, the exhaust-valve closing at a, and the steam-valve opening at b, so that the engine passed the centre against a pressure of 6J pounds above the atmosphere. Fig. 76 is obtained from the same source as the last. In this case the engine was working as a non-condensing engine with a B very low pressure of steam. The exhaust closes at A causing the pent-up steam to be compressed to B, where the steam- valve opens, and the pressure in the cylinder, being greater than that in the boiler, immediately falls to C. The hook at C is occasioned by the momentum of the indicator-piston. At D the cut-off closes, causing the steam to be expanded to E, below the atmosphere. At E the exhaust-valve opens and the pressure rises up -equal to the back-pressure, causing the loop on that corner of the diagram. Fig. 77 is a diagram from a non-condensing engine. The pressure rises from b to c; but supposing the exhaust to open at b, there could be no reason why the pressure should rise beyond d, the amount of back-pressure on the opposite side of the piston ; such a diagram could only be formed from a slide- valve engine, in this manner: Steam being admitted until the210 ENGINE AND BOILER TRIALS, piston arrived at ay the independent slide-valve cut off the steam ; it was then expanded to the point b; at b—the steam- valve having deficient lap and lead, and thus being open—the cut-off valve opened, admitting fresh steam, which caused the line be to be traced. At c the steam is shut off by the steam- valve itself and the exhaust opened ; the pressure then falls to d, and the exhaust-line is traced. Fig. 78 is an Otto gas-engine diagram, taken purposely, by Messrs. Brooks and Stewart, with a light spring, in order to exhibit better the action of the machine at the more obscure points.* The induction-stroke begins at 1 ; the mixed gases are taken in throughout the stroke to 2; compression occurs from 2y the pressure rising again to atmospheric at 3 and reaching the * The Otto Gas-engine, Van Nostrand’s Magazine, 1883.PECULIAR FORMS OF DIAGRAMS. 211 limit of the spring at the line 4, 5, 6. The mixture is fired on the succeeding stroke, the pressure continuing above the limit of the spring to 7; then the exhaust-valve opens and the expul- sion occurs, producing the line 7, 8, 9, 10, 1. The depressed part 9-10 may be due to inertia. In the next example a steam-engine moving very slowly gives an expansion BA, which differs remarkably from the curve BA' cf Marriotte, usually closely followed by good engines. The cause is now well known to be what is called internal or cylinder condensation, and re-evaporation—a phe- nomenon discussed fully elsewhere.CHAPTER VI. MEASUREMENT OF DIAGRAMS; COMPUTATIONS; APPA- RATUS AND METHODS. 65. The Apparatus and Methods of measurement of the power of the engine by means of indicator-diagrams are nec- essarily somewhat different with differences of purpose and of data desired. They include such as aid in the direct measure- ment of the diagrams, and also instruments employed to measure the speed of the engine and its fluctuations. Among the former is the planimeter ; among the latter, speed-indicators, counters, and chronographs of various kinds. The methods of their use and of computations based on their work should al- ways be such as will yield results of the greatest practicable exactness. 66. The Measurements taken in working of indicator- diagrams demand great care and accuracy. The figure to be measured is small; its bounding-lines often obscure and gener- ally irregular; and the determination of its exact area, which is the usual problem, requires nice manipulations. An indicator- diagram represents the pressures, volumes, and work of the steam, or other fluid, at every instant throughout a single rev- olution of the engine, on one side of the piston. A pair of cards exhibits these quantities on both sides during one revo- lution. A series of such pairs exhibits the varying pressures and work of the engine at the several single revolutions to which they severally appertain. The average of the pressures shown on one card is the mean pressure for a single revolution on one side the piston ; the average obtained from a series of diagrams gives a mean of the pressures, for the period covered, with a degree of approximation dependent upon the number of diagrams and the uniformity of action of the engine. By taking diagrams with sufficient frequency, any desired accuracy may be attained. In practice, they are often taken as seldom 212MEASUREMENT OF DIAGRAMS. 213 as once an hour, and, on trials of importance, sometimes as often as every fifteen minutes. At sea, it is customary on na- val vessels to take a set of diagrams once a day to be preserved in the log-book. Since the diagram only gives the pressures, the other fac- tors of work and of power must be determined otherwise. The indicated work of the engine at each stroke is the prod- uct of the net intensity of pressure on its piston by the vol- ume traversed. The power is the work done by the engine in the unit of time; in British measures, H.P. = 2 Ilan : 33000 where p is the average net effective pressure of the steam as shown by the indicator; / is the length of stroke; a is the ef- fective area of piston ; n is the number of revolutions per min- ute. Pressures are here, as usual, measured in pounds on the square inch, areas of piston in square inches, the stroke in feet, and work in foot-pounds per minute. Of these quantities, all but p are obtained by direct measurement and by observation. The pressure p is the one quantity obtained by the use of the indicator. The method of determination is to measure the area of the diagram, divide by its total length, and thus obtain in the quotient its mean altitude. This being multiplied by the scale of the spring and of the ordinates gives the mean pressure. The mean total pressure is this quantity measured to the vacuum line of the card. The mean effective pressure is the mean pressure measured from the indicator-card, and that which represents the net pressure acting in the production of the indicated work. It is this pressure, usually, which is sought in making computations. The area of the diagram may be obtained in either of several ways. The best method is by the use of the planimeter, which, with careful handling, should give the area to hundredths of a square inch. Divide the area by the length, and the result will be the height of a rectangle having equal area, and the av- erage height of the actual diagram. Or:214 ENGINE AND BOILER TRIALS. Draw ten, or any other equidistant number, of lines, as in Fig. 80, perpendicular to the atmospheric line. The first and last half of the intermediate distance from the ends, and the height of each, represent the approximate height of the space which it marks. Measure the length of each ordinate, and divide the sum by the number of ordinates. Multiply the av- erage length thus found by the scale of the spring, and the re- sult is the mean effective pressure. In case there is a loop, as in Fig. 81, caused by expanding below the back-pressure line, the engine being non-condensing, the ordinates below are negative, and must be subtracted from the lengths of the ordinates above. Then, using the pressure so obtained, multiply the net area of the piston by the mean effective pressure (M. E. P.). Multiply this product by the distance through which the piston travels per minute, divide by 33,000, and then, as already seen, _ Net area of piston X M. E. P. X revs, per minute X 2 X stroke. 33000.MEASUREMENT OF DIAGRAMS. 215 When there are a number of diagrams from the same en- gine, the calculations may be simplified by multiplying the area of the piston by twice the length of the stroke, and di- viding the result by 33,000, thus grouping the constants, and thus obtain the “ constant for the engine/’ the power developed at one revolution per minute with one pound mean effective pressure. If we multiply this constant by the number of revo- lutions and the mean effective pressure, the product will be the I. H. P. If the number of revolutions is constant, multiply the “ constant for the engine ’ by the revolutions per minute. This gives “ horse-power constant,” or power developed per pound of effective pressure. Multiply this constant by the M. E. P., and the result will be the indicated horse-power. A quick method of measurement of ordinates is to use a strip of paper, and mark, one after another, the lengths of ordinate on its edge, thus making the addition, and with a single final meas- urement. Lay the edge of the paper on the first line, mark off the distance, starting from the end of the paper; transfer the edge of the paper to the last line, add its length to the first measurement, and continue the addition for the intermediate divisions. Finally, measure, with the scale of the spring, the total length, and divide the result by ten. A small adjustable set of parallel rods is often supplied by the makers with each pair of indicators, which may be used, as in the illustration, to lay off and describe the ten ordinates usually adopted in measuring the dia- gram. Or a scale dividing off ten parts in a space a trifle longer than the paper may be laid on the diagram diagonally, in such man- ner that its extremities will coin- cide with the ends of the diagram and the location of ten ordinates pointed off on the paper, between which the vertical measurements fig. 82.-Parallel Rods. should be made. The use of a scale prepared like that seen in2l6 ENGINE AND BOILER TRIALS. the accompanying sketch, and which can be easily adjusted to any ordinary length of diagram, is still more convenient. Here the ordinates are correctly set, so as to give a half-space at each end to admit the measurement being made on the lines. A very rapid approximation to a correct volume of the mean pressure can be obtained by the expedient illustrated in Fig. 84. Fig. 84.—Mean Pressure.MEASUREMENT OF DIAGRAMS. 217 Ox being the back-pressure line, draw ab in such manner as to make the areas c and d between that line and the upper border of the card as nearly equal as possible. This can be quite closely judged by the eye. Then the ordinate, ef \ drawn at the middle of the diagram gives the mean effective pressure. The following, from Rankine, illustrates a good method of record and computation.* Ten ordinates are measured and the results for both cylinders of a compound engine are given. Compound-engine Diagrams. Ordinates. First Cylinder. Second Cylinder. Top. Bottom. T op. Bottom. to 27 1 36 16.O 12.4 t\o 13 12 2.0 3-8 Sum 40 48 18.0 l6.2 Half sum 20 24 9.0 8.1 tx 83 97 10.5 10.8 91 96 8-5 9.0 91 84 7-5 8.0 64 64 7.0 7.1 to 57 57 6.6 6.7 bo 53 46 6.2 6.0 t- 42 40 6.0 5-6 35 32 5-1 54 22 22 4.5 5-o Sum 558 562 70.9 7i-7 Sum -4- 10 = M. E. P 55-8 56.2 1 7.09 7.17 v s Mean, top and bottom , T l 56.0 j 1 7 •13 X area of piston, sq. ins 345 1 1380 Mean effort, in lbs 19320 9839.4 X stroke, in feet, X revol* l 262 utions per minute, 52^ X 2 = J • 5 262.5 Ft.-lbs. per minute 5071500 2582842.5 Total Y 7654342.5 «+• 33000 — 232 I. H. P. * Steam-engine, p. 51.218 ENGINE AND BOILER TRIALS. These mean pressures are found by a process which may be algebraically represented as follows: Divide the length of the diagram into any convenient num- ber, n, of equal parts, and measure the ordinates at the two ends and the n — I points of division; so that ordinates are measured from n -f- I equidistant points. Let /0 be the first, pn the last, and px, , etc., the inter- mediate ordinates of the upper curve; let // be the first, // the last, and //, //, etc., the intermediate ordinates of the lower curve; let pm denote the mean forward pressure, pj the mean back pressure, and pm — pj the mean effective pressure. Then A. = ^(~~+A H‘A + etc j +A+A+etc---'^±^i The mean effective pressure may be computed at once by measuring a series of equidistant breadths of the diagram the mean of which breadths represents the mean effective pressure. That is, let b0 be the first, bn the last, and bl9 b3, etc., the inter- mediate breadths. Then Pm Pm = - ( * + K + K +> etc-)- The effective energy exerted by the steam on the piston during each revolution is twice the product of the mean effective pressure, the area of the piston, and the length of stroke, or 2(pm — pmf)As; and if N be the number of double^ strokes in a minute, the in- dicated power in foot-pounds per minute is 2(Pm — pm ) A Ns;PLANIMETERS. 219 from which the indicated horse-power is found by dividing by 33,000. The presence of the piston-rod or of a “ half-trunk” on one side the piston produces a difference of areas which, in the lat- ter case, is of considerable magnitude. Where measured sepa- rately, if Ax and A2 are the two areas, the power is I H p — (A^i +A^a)^ 33000 ’ / and n being the length of strokes of piston and the number per minute. 67. Planimeters, plane-area measuring instruments, me- chanical integrators, as they are variously called, furnish the best known means of measuring the area of the indicator-dia- gram. By their use the work can be done by an expert hand' with great rapidity and with marvellous accuracy. Liability to error is exceedingly small, and the magnitude of the prob- able error is quite inappreciable in the ordinary work of the engineer * * * §—sometimes as little as one part in above ten thou- sand. Errors exceeding one tenth of one per cent are usually due to inexperience of the operator. The best known instru- ment is that of Amsler; that of Coradi,f of similarly general application, and that of Coffin,;{; designed especially for the measurement of indicator-diagrams, are also in common use, the two former mainly in Europe, the latter in the United States. They commonly operate by the combined sliding and rolling motion of a small measuring wheel which has a total rotation proportional to the area enclosed by the figure the periphery of which it traverses. § The integrating wheel, or roller, is best made of steel. A vernier on the instrument en- * “ Ueber die Genauigkeit der Planimeter Professor Lorber ; Oesterreiche Zeitschrift ftir Berg- und Htittenwesen ; vol. xxxi; p. 22. f Ueber das Roll Planimeter von Coradi; Franz Lorber, Zeitschrift des . Oesterr. Ing. & Arch. Verein ; vol. xxxvi; p. 135. % Barrus on the Indicator, p. 6i^ § Bramwell on the Amsler Planimeter. Report Brit. Association, 1872, p. 404. Shaw on Mechanical Integrators; Proc. Brit. Inst. C. E., 1884-5, No. 2063.220 ENGINE AND BOILER TRIALS, ables the readings of the motion of the roller to be taken with great accuracy, and repeated measurements may be made to eliminate errors less in amount than the finest readings given. A very simple modification of the Amsler Planimeter, designed by Mr. J. W. See, is made especially for indicator work. The following are the maker’s instructions, in detail, for using the most recent form of Amsler planimeter: i. Adjust the screw-centres upon which the index-roller D revolves, so that the roller works freely, and does not touch the vernier. The same care must also be taken with the centre- pin C. Oil the screw-centres now and then. Care should be taken to prevent the tube B, the tracer Ef and the point E from being bent, and also to see that the barrel D is kept uninjured. 2. To find the area of any figure, set the roller D and the ■counting-wheel G to zero ; the square rod A must be pushed into the tube B, and the line on A marked I sq. dem., or o.i •sq. ft., etc., must come even with the small line on the bevelled part of the tube B; when this is done, place the instrument on the paper, and see that the roller D, the tracing-point Et and the needle-point E touch the paper. Press the point E slightly into the paper, and put the small weight on the hole over the point; the instrument is then ready for work. 3. Take any point P on the outline of the figure about to be measured, set the tracing-point F to that point, and when it is marked, read off the index-roller D and counting-wheel G. For example, suppose the counting-wheel shows 2, the roller 91, and the vernier 5, the number will be 291.5. Follow thePLANIME TERS. 221 outline of the figure with the point F as accurately as possible to the right, until you come to the starting-point. Straight lines can be followed along a ruler; then read off the numbers on wheel and roller; say it is the second time 476.7. 4. When these two numbers are obtained, there are two cases to be observed: 1st. If the point E is outside the figure, subtract the first reading 291.5 from the second 476.7, the remainder is 185.2, which shows that the area contains 185.2 units. Of course the units depend entirely on the regulation of the bar A, if they are 0.1 sq. ft. we have 185.2 X 0.1 = 18.52 sq. feet, as the area of the figure measured on the paper. The rule therefore is, when the point E is outside, multiply the difference of the two readings by the number on the bar to the right of the corresponding division. 2d. When the point E is inside the figure, before making the subtraction, the number engraved on the top of bar Ay above the corresponding line of division, must be added to the second reading. In this instance, suppose the number on top of bar A is 20.985, the second reading is 4.767, the calculation would be as under: Second reading................= 4.767 Number over 0.1 sq. ft.......= 20.985 25.752 Deduct first reading...........= 2.915 Remainder.................. 22.837 The area is therefore 22.837 units or 22.837 X 0.1 = 2.2837 square feet. It is of no consequence whether the roller is inside or outside the figure, provided it is on the same level. In using the Coffin planimeter, the diagram is set with the atmospheric line parallel with the lower edge of the clamp C, and the end even with the perpendicular edge. The clamp K is moved up to the other end. The block Q being introduced into the groove /, the tracer is set upon the point D, where the edge of the clamp L touches the figure. The wheel is222 ENGINE AND BOILER TRIALS. turned so as to bring the reading to zero, and the tracer is then moved over the line of the diagram in the direction of the motion of the hands of a watch. The tracer is then moved along the edge of the clamp till the reading is again made to zero. The distance of A from D, now measured on the scale of the spring, is the mean effective pressure. The reading on the wheel is the area of the diagram in square inches. From this area the mean effective pressure may be also computed,.SPEED-INDICA TORS. 223 by multiplying it by the quotient obtained by dividing the number of the spring by the length of the diagram in inches.* This measurement may be made and computations com- puted on forty or fifty diagrams per hour by an expert com- puter using this instrument, obtaining the value of the mean effective pressure, inserting it in the formula already given, and computing the indicated horse-power. Mr. Lea has made an interesting modificator of the ordinary indicator by the substitution of a planimeter for the pencil- motion,—either permanently or temporarily, as may be desired, —thus at once getting a measure and registry of the work done.f 68. Tachometers, Speed-indicators, Chronographs, and Counters are instruments of various kinds and classes used by the engineer in determining the speed of the engine, the second of the essential factors obtained by observation in measuring its power. Of these instruments, the counters and many speed-indicators give the exact and positive measures of the engine-speed required by the observer as data. They mechanically register the revolutions of the machine one by one, and give either the totals or the differences for selected intervals; or, more usually, they work continuously, and these totals or differences are read off at regular intervals by the observer and recorded in the log, thus giving the means of obtaining the average speed of engine throughout the trial. When indicator-diagrams are taken, the speed of rotation of the engine is taken as nearly simultaneously as possible. This measurement is commonly taken with one of the small hand speed-indicators, the spindle of which is applied to the centre in the end of the main shaft and there held a quarter or half minute, a full minute, or more, as less or greater accuracy is desired and as the speed of the engine is greater or less. Very exact measurement is usually demanded for purposes of com- putation* The “ tachometers” are a class of instruments which exhibit * Barrus, p. 63. f Mechanics; Jan. 20, 1883; p. 39.224 ENGINE AND BOILER TRIALS. on a dial the speed of rotation of the shafts by which they are driven. They are not generally relied upon to give exact read- ings ; but their closely approximate indications check the hand- counter record at any moment, as the hourly or daily readings of the mechanically registering counters permanently attached to the engine check the averages of that record. The tachom- eters, Fig. 87, are actuated by pulleys or gearing, and are designed to indicate the number of revolu- tions performed per minute by shafting, by a pointer travelling over a graduated dial. In the cylindrical case rotate two suspended weights or pendulums, connected together by a strong flat coiled spring. The purpose of this spring is ^counterbalance the'cen- trifugal force of the pendulums. The devia- tions of the pendulums are communicated by a rod to clockwork in the case behind the dial, and produce corresponding deflections of the pointer. These instruments possess the advantages of exhibiting to the eye the momentary fluctuations of speed which cannot be thus shown by the revolution- counters. In some cases, by the addition of a recording mechanism and a roll of paper to receive the record, the tachometer is converted into a “tachograph,” and it is in this form often attached to engines or other machines to supply a constant and permanent record of their operations. For experimental purposes the paper is driven at comparatively high speed, as high as an inch (2.5 cm.) per minute, the more common speed being one half or one quarter that velocity. When used on the locomotive engine, it is customary to mark the dial in miles per hour as well as revolutions per minute. Various forms of the instrument are made for the various pur- poses of engineering, and are applicable to all speeds—from that of the slowest engine to that of the fastest electric machinery. The Edson speed-recording instrument, and the Mosscrop and other familiar apparatus, are of this class. Fig. 87.—Tachometer.THE SPEED-RECORDER. 225 The modern Speed-recorder is an instrument, Fig. 88, which registers the fluctuations of speed of the engine, or of other machinery, on a travelling strip of paper actuated by a clock. The variations of velocity are produced by the movement of a revolving pendulum, like the Watt governor, which moves a pencil across the line of motion. The curve thus traced is a record of the whole history of the time of observation. A widely serrated line shows great irregularity of speed; the less and the closer the ser- rations, the better the speed; the rise of the line above the mean indicates a steady ac- celeration ; a fall means re- tardation ; a wide, even, band of oscillations shows a light wheel; a narrow band U&S along the correct mean indi-fiS ="] cates a good balance-wheel a gradual fall may indicateg change of steam-pressure,®! and sudden variation of® location of the record line or band usually indicates Fig. 88.—The Mosscrop Recorder. fluctuation of the load, and its extent of fluctuation the effective- ness of the system of regulation. The kinds of unsteadiness due to changing load and pressure and to inefficiency of regu- lation are easily distinguished, and the various causes of varia- tion of speed may usually be easily traced out and remedied. Chronographs, such as are employed by the physicist, may be used when it is desired to determine the method and extent of variation of speed during any single revolution of the engine,226 ENGINE AND BOILER TRI4LS. or part of the stroke, as in investigating the effect of the vary- ing pressure on the piston and the torsional moment at the shaft: conditions which can only be studied experimentally by the use of apparatus of extraordinary delicacy and quickness of action and record. The chronograph was first applied to measure the variations of velocity of the steam-engine by a committee of the British Association in 1843-4, in their determinations of the speeds of piston of the Cornish engine.* It has been applied by Mr. Woodbury, as early as 1873, to pumping-engines, determining the fluctuations of velocity of fly-wheel, and, later, by Mr. Eckart in observing similar fluctuations of pump-rod speed, at great depths in the Comstock lode in Nevada.*}* The latter found it practicable to use the instrument at speeds of from 80 feet per minute up to 1400 feet. Messrs. Dix and Mack, under the supervision of the Author, applied the same instru- ment, still later, to the “ high-speed ” engine, making 250 revolutions per minute. The following are Mr. Woodbury’s records from three engines: $ Portion of Revolution. Lowell Pumping- engine. Lynn Pumping-engine. Horizontal Engine. 13-26 Revolutions 18.61 per Minute. 13.90 19-39 Velocity in Feet per Second. .00 6.42 9.80 7-13 IO.16 .04 6.46 9.82 > 7.27 10.62 .08 6.54 9.92 7-53 IO.84 .12 6.68 IO.08 7.72 10.96 .16 6.84 IO.14 7-75 IO.90 .20 6.96 IO.16 7.70 IO.72 .24 7.06 IO. IO 7-53 IO.42 .28 7.10 9.96 7-33 IO.04 .32 7.06 9.70 7.02 9-58 •36 7.02 9-43 6.60 9-25 .40 6.92 9.23 6.20 9.14 .44 6.82 9.08 5-87 9.27 .4S 6.77 9.00 5-73 9.66 .50 6.75 8.97 5-71 9.92 * Trans. B. A. A. S., 1844. \ Trans. Am. Soc. M. E.; Vol. HI.; 1882. \ Ibid.CHRONOGRAPHS,. 227 The curves here shown represent the motion of the fly- wheel of the Lynn engine. By the use of the ordinary form of physicist’s chronograph, or a slightly modified instrument, the speed of engine, and its variations, are measured, not only stroke by stroke, but even from point to point in the single revolutioii of the engine. This is a matter of importance in the application of engines, and especially if at low speed, to the driving of dynamo-electric machinery, where variations of speed, however limited as to time, are seriously objectionable. The frontispiece exhibits the method of attachment of the instrument to a “ high-speed,” direct-acting, horizontal engine of common type. A is the steam-cylinder; B, the engine-frame; C, the end of the main shaft; D, the balance-wheel; E, the brake-pulley, with strap F, and scale weighing the turning effort at G. On the extremity of the shaft, a coupling, H, is attached which drives the chron- ograph, /, through a slender rod seen connecting them. The revolving cylinder, on which the paper is smoothly stretched, to receive the record, is seen at J, and the stylus or pen is at KThe whole is mounted on a firm support as Z. When in operation, the cylinder is turned by the engine, Peet per Second228 ENGINE AND BOILER TRIALS. instead of its usual motor apparatus, and the pen, slowly traversing the cylinder, produces a closely compressed helix. At regular intervals, a circuit is made and broken by the standard clock or other timing instrument, and the line is given a V-shaped jog which marks the time-interval on the cylinder. The adjustment should be such that, at normal speed, these breaks should occur at precisely the same points in the circum- ference of the chronograph cylinder at each of its revolutions or at each tenth or other fraction of a revolution, as may be determined upon. Any acceleration or retardation will then be exhibited by the production of the break in advance of, or behind, its normal position. In the first case all such breaks fall into straight lines along the cylinder, parallel to the axis; in the latter case they will fall into regular helical, or curvi- linear, or irregular, lines, accordingly as the acceleration or retardation is uniform, smoothly variable, or irregular. The inclination of the lines, or of the tangents to the curves so pro- duced, to the axis is thus a measure of the change of speed. Thus, if C = the circumference of the record cylinder; d — distance traversed by the pen per revolution; n — number of revolutions of engine per minute ; n' = revolutions of the chronograph ; n c = n 6 == angle made by the line produced as above with the axis,— then we have Cn C ± d tan 0 . * $oc( d \ 60c 2n n \ C / using the positive and negative signs for acceleration and for retardation, respectively. When d = o,CHRONOGRAPHS. 229 For a case of actual work, C = 21.84; d = 0.0833 + > r = 285 ; n = 30; and « = 285 (1 ± ~ tan ej ; and, making a variation of i°, the angular deviation would become tan-1 6f = 420 36'; since nd n — 285 = tan ff — 1, and tan 0' = -^ = tan-1 0' = 420 36'. nd 21.84 It often requires very nice adjustment to secure sufficiently perfect arrangement of speeds to give a good line for the normal operation of the engine; especially as the sensitiveness of the instrument increases with decreasing values of the angle 6. The following is a set of data thus obtained in the course of a trial of a good type of engine, cohsiderably out of adjust- ment : Observation. 0 *i“*a "2 D.H.P. I + 75° 5i' 80" + 4-35 289.35 O 2 - 720 14' 17" - 3-55 281.45 4.22 3 -78° 32' 58" — 454 280.46 7.01 4 ~ 79° 48' 46" — 6.05 278.95 977 5 - 8o° 43' 54" - 6.63 278.37 12-53 6 ~85° 18' 45" — 13.2b 271.74 14.95 7 -85° 58' 47" — 15.47 268.53 17.45 The next engraving exhibits the chronograph as used by Mr. Eckart. The reference-letters are as follow: CC—Cast-iron base-plate, covered with sheet-brass, upon which the mechanism is secured. B—Metal frame containing gearing /or driving drum A and escapement-wheel b; motion commu^cated by means of adjustable weights D. AA—Light brass drum, accurately balanced, revolving on fric- tion-rollers 8, 8, at both ends.230 ENGINE And boiler trials. ff—Parallel guide-bars upon which the tracing-point h{„ and its carriage travel back and forth, receiving motion in one direction from the engine or other moving parts through the cord Pt passing through the bars f and attached to the tracing carriage; the return motion is. derived from a coiled spring in the spring drum C. ee—Small electro-magnets on tracing carriage for raising the* tracing-point h{„ off the paper and replacing it at any desired point to be especially observed. ^—Electro-magnets on separate carriage kk9 adjustable on parallel bars /, operating the steel tracing-point g, at- tached to the armature of d^forthe purpose of record- ing seconds on the margin of the paper or at other parts of same as required. i—Chronoscope or watch supported on frames, the second- hand of which swings the light platinum wire J, break- ing contact with the insulated wire k, thereby breaking circuit %ith d and recording seconds through the tracing-point g on the paper. q—Adjusting screw for the wire J. a—Steel spring of escapement. This spring is securelyTHE HAND SPEED-INDICATOR. 231 clamped in F, its flexibility being controlled to a cer- tain extent by means of the thumb-screws 0 and p. •This instrument was found to give with great exactness the fluctuations of piston-speed in a pumping engine at 80 feet per minute, and for a hoisting engine at 1400 feet. It is thus peculiarly well adapted for pit-work. Instead of, as is usual, employing a clock pendulum to mark time and give the velocity-curve of the engine, a portable time- keeper is here used. This is the common form of “ timer/’ de- signed especially for timing in trials of speed of vessels, or on the race-course. The hand of the instrument, revolving once per second, breaks the circuit, and the stylus or pen g is caused to mark the interval. The stylus or tracing-point barely touches the lamp-black, being counterbalanced in such- manner as to remove the coating without bearing perceptibly upon the paper, producing a fine white line on the black surface. In fitting the paper, it is cut slightly longer than the circumference which it is to cover, and lapping the edges and gluing them together, the lap is carefully sandpapered to as nearly as possible uniform thickness at the joint and elsewhere. The surface is then smoked, and is ready for use. The Hand Speed-indicator is made in various forms. One which the Author has found very satisfactory is shown in the illustration. It answers equally well in whichever direction the engine may turn, is convenient in use, and gives reliable results. The Author has often found a different shape of point more certain to hold, and has often flattened the point and given it a semicircular sharp-edged termination, to obtain a more secure hold on the centre of the shaft. The usual method of counting the revolutions of the engine, by means of the hand speed-indicator or the registering “counter” attached to .the machine, gives the mean speed for a certain time—as for a minute—for which the count is taken. The use of the chronograph in the manner just indicated gives a meas- ure of the rate ox speed for the instant, for each revolution. To ascertain the rate during successive portions of the revolu- tion, the method of Woodbury or of Eckart may be adopted.232 ENGINE AND BOILER TRIALS. These processes may all be used—properly fitting up the chronograph for the purpose; but a much less costly, more Fig. 91.—Double Pocket Speed-indicator. convenient, and simpler method may be employed, the measur- ing instrument being the ordinary tuning-fork or “timing-fork.” The Timing-fork used in timing engines, and in measur- ing speeds and speed-variations during a single revolution of the engine, may be of any convenient size, but preferably one of slow vibration and low note. The fastest engines ordinarily make about one revolution in the fifth of a second ; but very small engines, and especially those used in electrical and high- speed torpedo-boat work, sometimes make a revolution in the tenth of a second. A standard C fork making 256 vibrations per second would thus space off Ihe engine-cycle into from 25 to 50 parts with the fastest of small engines, or into 256 parts if the engine makes 60 revolutions per minute. The normal fork, for concert pitch, at the Conservatoire de Musique, Paris, makes 870 vibrations for standard a, treble staff, corresponding to 261 vibrations for C. This would similarly measure speeds at intervals of 87 or 174 parts for the fastest engines, or 870 parts ’ at 60 revolutions. The usual method of application is that of Mons. Duhamel, who covers an accurately turned cylinder with a sheet of paper having a smooth and firm surface, uniformly covered with lamp-black, and permits a fork mounted on a firm stationary sup- port to record its motions in a sinuous curve on the paper, as the cylinder is regularly turned beneath the point of a light stylus fixed on the end of the fork. The rate of the fork beingTHE TIMING-FORK. 233 known, and the number of sinuosities of the line being counted for any specified period, the time becomes known. If the line be marked at each revolution or specified part of a revolution of the engine, by any convenient automatic system, the veloci- ties become known for each of those periods. The cylinder carrying the paper should be caused to traverse longitudinally by the action of a screw of conveniently chosen pitch, as is illustrated by the recording mechanism of the Scott phonauto- graph.* The record on the smoked paper being made, it may be saved and rendered permanent by dipping it* in an alcoholic solution of shellac, or of sandarack or other gum. In engine-testing the following method has been found to be very satisfactory : A toothed wheel or disk is 'mounted on the end of the main shaft, the number of teeth being deter- mined by the degree of accuracy sought, as 36 to give measures for each ten degrees in the revolution of the crank and shaft, or 72 for five-degree intervals. These teeth consti- tuted the circuit-breaking apparatus for a small battery, the current from which was the primary for a small induction-coil, the induced current being caused to pass through the stylus and to the paper-cylinder, each spark breaking through the smoked surface and leaving its mark, and the space and time between successive points thus made giving a measure of the speed of the engine in that ten-degree interval. Some care is necessary to get a good form of sty- lus for this work. The sketch shows that adopted by Messrs. Dix and Mack £ for their investigation of this subject. A light metal frame, AA, carries the very fine and light needle, or stylus, B, of which the point P is smoothly rounded so as not to tear the paper, and which is guided by an opening, C> and held up to a gentle contact by the Stylus for Timing-fork. spring of D. A small screw, S, holds the whole firmly in place on the end F of the fork. * See Ganot’s Physics, § 246.234 ENGINE AND BOILER TRIALS. The next figure shows an improvised and simple, but effec- tive, method of moving the fork. B is the engine-frame ; C is Fig. 93.—Mounting the Timing-fork. the crank-shaft; F the fork, mounted on a platform, GG, in such manner that it may be smoothly and steadily traversed Fig 94.—Variation of Rotation.THE TIMING-FORK. 235 before the smoked cylindrical surface H by sliding its base- piece, /, between the guides. Below are the data thus secured by test of an engine making about 285 revolutions per minute : Angle. Vibrations. Variation. Per Cent. Angle. Vibrations. Variation. Per Cent. o°~30° 3.7 -2.3 i8o°-2IO° 8.8 “3-4 30 -60 8.6 — 1.2 210-240 8.75 “2-9 60 -90 8.75 -2.9 240 -270 8.8 “3-4 90 -120 8.75 -2.9 270 -300 8.7 “2-3 120 -150 8.7 -2.3 300 -330 . 8.75 -2.9 150 -180 8.9 -4.6 330 -360' 8-5 0 = .normal. Plotting these data, the accompanying figure is obtained, and a comparison of the curve with that representing the varying accelerating moments acting on the engineTshaft; the two are found to accord—as should be expected. Radii here measure velocities. The connecting-rod was here six cranks in length, the ratio of expansion about four. The accompanying illustration exhibits the mounting of the Fig. 95.—Timing-fork. timing-fork as devised by Mr. Ransom.* The timing-fork* kept in motion by an electric current, is mounted on a rest driven by a screw, parallel to the axis of the paper-cylinder. * Journal of the Society of Arts, Feb. 15, 1889, p. 243.236 ENGINE AND BOILER TRIALS. The operation of the instrument is the same as in the cases already described. The record obtained is similar, and maybe illustrated by that given, full size, in the next figure, which represents a mean speed of 141 revolutions per minute. Fig. 96.—Speed Record. Good regulation is usually considered to imply: (1) Uniform rotation; meaning minimun variation of angu- lar motion during the revolution of the crank-shaft. This variation depends, for its amount, upon the simulta- neous variations of effort and resistance, and upon the magni- tude of the regulating mass, the fly-wheel. (2) The speed of engine, revolution by revolution, should be very nearly constant. This variation should not usually be allowed to exceed two, and is often less than one, per cent. (3) The mean engine-speed should remain constant over the whole period of its operation. (4) The mean speed of the engine should be precisely that at which it is intended to be operated, irrespective of variation of load or of steam-pressure. The Computation of Pozver, or of the work of the steam on the piston, is possible whenever, the dimensions of the engine being known, the mean pressure on the piston and its mean velocity have been measured for the required period. The mean effective pressure can only be obtained by the use of the indicator and from its diagram. The mean speed of piston is readily computed when, by counting the revolutions of the engine by the eye, watch in hand, or by the use of any convenient and reliable form of counter, the average number is obtained for the unit of time. The mean effective pressureSTEAM OR WATER CONSUMPTION. 237 in pounds per square inch and the velocity of the piston in feet per minute being thus ascertained, the product of these factors into the net area of piston in square inches—the area of the rod being deducted on that side—gives the work, 2pmLANf in foot-pounds per minute ; and the indicated horse-power, I. H. P. = 2pJLAN 33000 ’ is at once given. If working up many diagrams from the same engine, the first step should be the computation of the “ constant of the engine,” a figure which expresses- the horse power of the engine, under its regular conditions of operation, for each pound mean pressure on the piston. Thus, 2pmLAN _ 2pm VA 33000 33000"' and when pm =1, this becomes 2LAN _ 2 VA 30000 _ 33000’ where the symbols are those customarily used. Each diagram is then measured up and its mean pressure obtained, and the multiplication of this quantity by the constant thus computed gives the horse-power for that diagram. 69. The Steam or Water Consumption of the engine cannot be exactly ascertained by the use of the indicator, since a portion of the steam entering the engine is always instantly condensed by contact with the cooler walls of the cylinder, and another portion, sometimes considerable in amount, may escape past the piston, or through the valves, by leakage. The indicator does exhibit, however, the pressure and volume of steam actually present at each instant in the steam-cylinder, and it thus becomes easy to compute its weight and to obtain a measure of the quantity thus shown by the indicator, for comparison with the total quantity supplied by the boiler, and233 ENGINE AND BOILER TRIALS. thus to ascertain the losses, by condensation and leakage, of power, heat, and steam. The pressure being shown on the diagram at every point in the stroke, the “ steam-tables” give the corresponding specific weights, the weights per unit of volume; and the space traversed by the piston up to the given point, plus the clearance-space, measures the actual volume; the latter quantity, multiplied by the specific weight, is the weight of uncondensed steam present in the cylinder at the specified point. The mean weight per stroke, multiplied by the number of strokes, being compared with the total weight supplied by the boiler in the same time, as shown by the log of the boiler-trial, the difference is the waste by internal con- densation and leakage. The real measure of the efficiency of any engine is the quantity of steam used by it to develop unity of power, and that efficiency is the greater the smaller its legitimate demand for steam, and the less its waste in these directions. Should it be impracticable to conduct a boiler-trial to determine the amount of steam drawn off to supply the engine, it may be possible to secure a fairly approximate measure—when it is known that the boiler gives dry steam—by observing the rate of fall of the water-level with the feed shut off and computing the volume and weight evaporated from the known dimensions of the volume thus traversed by the subsiding water-surface. Care must be taken not to allow its fall to go so far as to become a source of risk. It is usually easy to measure the volume corre- sponding to a fall nearly equal to the length of the gauge-glass. In many cases the quantity of steam shown by the indicator, at the point of cut-off, may be determined from the diagram, and a known or probably fair allowance may be added for unin- dicated wastes, to obtain an approximate measure of the quan- tity of water demanded per horse-power and per hour. This waste has been seen to be rarely as little as ten per cent., and often as much as thirty per cent, and upward. The volume added by the clearance and port passages varies greatly with the type and build of the engine. In the single-valve and in the older forms of poppet-valve engines itSTEAM OR WATER CONSUMPTION. 239 is rarely less than six, and is often ten, per cent, and more; in the best of modern engines it is often as low as two per cent. It may be easily measured, either from the drawings of the engine or by filling these spaces with water from a quan- tity previously weighed. The weight required to fill the clear- ances and ports gives the means of computing their volume from the known density of the liquid. Where, as is usual in recent and well-designed engines, considerable compression is employed, the saving of steam thus effected is to be carefully allowed for in all determinations of steam accounted for by the indicator. The loss by leakage should be inappreciable in any good engine, and this being ascertained by test, giving steam at one end and observing the escape of steam, if any occurs, by opening the indicator-cock on the other end, the whole waste shown will be due to cylinder condensation, the amount of which, as a percentage of the steam accounted for by the indicator, and as the quantity to be added to the latter for engines of fair size and good construction, may be taken as, approximately, from about 0.15 Vr in the best cases of com- pound engines, to 0.2 Vr in ordinary good unjacketed engines, and above the latter figure for engines of older type and slower speeds of rotation ; r being the ratio of expansion for a single cylinder only, in the case of the compound engine, and that cylinder being taken which has the highest value of r. When the problem to be solved is, as usual, the determina- tion of the efficiency of any actual engine, as distinguished from the simple thermodynamic efficiency of the ideal engine, the indicator aids the engineer in its solution by showing the precise quantity of steam present at every instant during the stroke, and, hence, the quantity of water present at the same time; the sum of these two weights being always, if the piston and valves are tight, equal to the weight of feed- water passing through the boiler and entering the engine as a mixed working fluid. The volume and pressure of the steam are shown by the indicator, and the weight is easily computed from its known density at the given pressure. The portion of stroke traversed at any instant, added to the clearance-space,240 ENGINE AND BOILER TRIALS. measured in equivalent cylinder length, gives the volume of steam present. The quantity of steam supplied is equal to the measured quantity at the point of cut-off, less that retained by compression. The difference between the weight of steam thus measured at any point in the stroke, and the total weight of feed-water supplied, or steam entering the engine, per stroke,, is the weight of water present. Also, the total weight of mixed steam and water present from the point of cut-off to the opening of the exhaust-port is the sum of the quantity coming from the boiler and that com- pressed into the clearance-spaces. The variation of this quantity is well shown by the following data obtained by Mr. Spangler Weight of steam per I. H. P. per hour, . . . lbs. 28.15 u “ priming “ “ 9 per cent., . . << 2,78 ll “ feed-water “ u U 30.93 il “ steam at 0.9 stroke, U 20.06 u “ water “ “ “ 33 per cent., nearly, u 10.87 u “ steam “ 0.7 u a 19.23 it “ water “ “ “ 38 .per cent., nearly, a u.70 u “ steam “ 0.5 a 18.27 u “ water “ “ “ 40 per cent., nearly, (( 12.66 u “ steam “ 0.3 u 17-31 u “ water “ “ “ 58 per cent., nearly, u 13.62 These figures, as will be seen by comparison with other similar data, are indicative of a greater waste than usually occurs in large engines, due to the small size of that here referred to. It is evident that all variations from the proportions of the mixture entering the engine must be due to the transfer of heat to and from the metal of the cylinder and piston. The above figures show a gradual increase of the proportion of steam present produced by re-evaporation of that condensed ini- tially, on entrance, from the point of cutoff up to the end of the stroke. The weight of steam in the cylinder at any point of the * Journal Franklin Institute, Feb. 1886.STEAM OR WATER CONSUMPTION. 241 stroke, in pounds per indicated horse-power per hour, is always equal to W _ 60 X 2lanw' % pmlan______13750W I.H.P. 144 33000 = w, or w pm LVr Vj J in which = mean effective pressure; £ and cf = the volume of clearance-space and of steam at the point of closing of the exhaust-valve and beginning of compression ; c cf - and — = their ratios to total cylinder volume ; ^2 ^2 r = ratio of the given travel to full stroke of piston ; w, wf, and w" = weight of steam per indicated horse-power per hour, the specific weight at the pressure found at the given point, and the specific weight at the beginning of compression ; a — when the piston area is measured, as above, in square inches and the stroke in feet, 1980000 144 = I375°* This computation is commonly made for the points of cut- off and of release. At the former the “ initial condensation” is obtained, and probably the best measure of the waste by con- densation ; at the latter a measure is secured of the state of the mixture exhausted from the engine. The following example, from a diagram taken by Barrus,* employing Clarke’s tables,f illustrates these computations: Taking — = 0.308 at cut-off, and i = 0.901 at release, c = o.02^a; * On the Tabor Indicator, p. 48. f Manual for Mechanical Engineers.242 ENGINE AND BOILER TRIALS. c' = 0.071^; pm — 38.45; wr — 0.1844 at cut-off and 0.0705 at release ; w" — 0.0457. Then, at cut-off, w = (*375° -5- 38-45)[(o-3o8 + 0.02)0.1844 — (0.071 + 0.02)0.0457] = 20.13 lbs.; and, at release, w = (13750 -f- 38.45)[(o.9i + 0.02)0.0705 — (0.071 +0.02)0.0457] = 21.95 lbs. Here, the indicator, in the instance from which these figures are derived, shows a difference in computed weights of steam per horse-power and per hour at the points of cut-off and release amounting to nearly two pounds—about ten per cent., which difference is the measure of the re-evaporation taking place dur- ing expansion. To the figures above obtained must be added the allowances for total wastes. We have in many instances so little compression that it may be neglected. In such cases the following very simple process may be adopted: Assuming the working fluid to be water instead of steam, the quantity demanded would be, per horse-power per hour, 1980000 X 62.4 = —--------------- = 857900 144 pounds at one pound pressure per square inch; and, at any other pressure, /, 857900. wb — ——— » P while if steam be employed the weight would be less in propor- tion to its greater, its specific, volume, v\ and the weight actu- ally needed would be 857900 . wc = > nearly; PmV which may be corrected for clearance and compression.STEAM OR WATER CONSUMPTION. 243 The detailed method of computation from this indicator-dia- gram is illustrated fully, later (§ 71). The following is a convenient form of this expression for steam and water consumption: Let px = initial pressure, absolute; /8 = back-pressure, absolute; r = true expansion-ratio ; c = clearance fraction ; D = density of steam in lbs. per cu. ft.; w = weight of steam per horse-power per hour; The constant has been seen to have the value, in British meas- ures, a = 13750. Compression is here neglected. This ex- pression assumes a minimum value, for the ideal case, as is elsewhere seen, where This value is, in the real engine, found to be greatly reduced by the occurrence of internal wastes, by cylinder condensation or leakage. The following table, prepared by Mr. Thompson, gives the factors employed in computing the indicated consumption of water.* The method is illustrated in Fig. 97. The mean effec- tive pressure must be known, but the horse-power or the size of the cylinder need not be known. Draw a vertical at each end of the diagram, and continue the expansion-curve to /. From t draw tC. Measure the absolute pressure at t, and find in the table, page 244. the corresponding number. Numbers * Hemenway’s Indicator Practice ; N. Y., 1SS6 ; J. Wiley & Sons. Amer- ican Machinist. I “\~ C . r — .—!---------, nearly.Water-Computation Table. 244 ENGINE AND BOILER TRIALS. os O cjO omo O OO O' CO rs O O O O tO WOO rt O rtcO CM n co rs §00 - O'O O m o O'00 ^ nnW a m^ c? & 3 00 m o q-'O rt Is O' CM ■'to O'*-! 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P. represent the terminal pressure in pounds, and the figures, 1, 2, 3, etc., tenths of a pound. Divide this number by the mean effective pressure; the quotient will be the steam accounted for per horse-power per hour, uncorrected for compression. To make this correction multiply by tE and divide by tC. When the maximum compression is not as high as the ter- minal pressure, the compression-curve must be extended, as er and E will be outside the diagram. In illustration of the computation of the economical per- formance of engines by determining their expenditure of heat, measured in British thermal units, may be given the following,, as computed by Mr. Barrus,* using Clark’s tables.f Assume a non-condensing engine to use 27 lbs. of feed- water per horse-power per hour, supplied at 212° F.; a con- densing engine 18 lbs., at 130°; and a compound engine 14 lbs., at 170°. The pressure in the first two cases is 80 lbs. and in the last case 120. In the first two cases the steam contains £ per cent moisture, and in the last case it is superheated 20°. The total heat of saturated steam of 80 lbs. pressure [94.7 lbs. absolute] is 1212.2 B. T'. U. Deduct the heat corresponding to 0.05 moisture, 0.05 X 885.9 = 4-4 [885.9 being the latent heat], and there remain 1207.8 units, the total heat of steam * The Tabor Indicator, f Manual for Mechanical Engineers.STEAM OR WATER CONSUMPTION. 24 7 containing \ of one per cent of.moisture, measured above zero. Deduct the heat corresponding to a feed-water temperature of 2120, 212.9 thermal units, and there remain 994.9 units, the total heat of one pound of steam, containing J of one per cent moisture, above the temperature of feed-water. Multiply this by 27, and the product, 26,862.3 units, is the heat expended per horse-power per hour. A similar computation gives 19,400.4 thermal units per horse-power per hour for the second case. In the third case, the total heat of saturated steam of 120 lbs. pressure [134.7 lbs. above zero] is 1220.1 B. T. U. The heat corresponding to 20° superheating is 20 X 0.475 = 9-5, which gives 1229.6 units for the total heat of superheated steam. Deduct 170.4 thermal units, the heat corresponding to a feed-water temperature of 170°, and multiply by 14, and we have for a product 14,828.8 units, the heat expended per horse-power per. hour. These results are tabulated below : Kind of Engine. Non- Condensing. A. Condensing. B. Compound. C. Boiler-pressure 80 80 120 Av. temp, of feed-water 212 130 170 Feed-water per H. P. per hour 27 18 14 Percentage moisture in steam .... % 0.5 0.5 20° superh. Total heat of saturated steam th. un. 1212.2 1212.2 1220.1 Total heat corrected for moisture and super- heating th. un. .1207.8 1207.8 1229.6 Heat of feed-water “ 212.9 130 170.4 Heat expended per pound “ 994.9 1077.8 1059.2 Heat expended per H. P. per hour... 26,862.3 19,400.4 14,828.8 A comparison of the heat thus computed, as expended, with the heat-equivalent of the useful work performed, determines the efficiency. As each horse-power is the thermal equivalent of 42.75 heat-units per minute or 2565 units per hour, we have for the three cases, E: A. 2565 26862 0.096; B. 2565 19400 = 0.137; c. 2565 14829 = O.16 ;248 ENGINE AND BOILER TRIALS. or efficiencies of 9.6, 13.7, and 16 per cent., as compared with an engine of efficiency unity, perfectly utilizing all the heat- energy supplied to it. This is the method first adopted by Rankine, except that thermal, rather than mechanical, units are employed. 70. Constructing Hyperbolic Curves, such as are com- monly taken to represent the variations of pressure and volume in the ideal diagram, enables the engineer to obtain some idea of the method and extent of variation of the actual quantities in real engines from those of the ideal case. There are several methods of constructing these curves, of which the simplest are, perhaps, the following, as applied to produce the equilateral hyperbola, the curve of Mariotte, to which the expansion-line, in the best classes of engine, very closely approximates, and which is commonly taken as the standard. Let XX, YY be given asymptotes (i.e., the clearance and true vacuum lines of the indicator-card) and x any given point, and let xx, xy be its co-ordinates. Extend YO until OY' = YO and draw APy making YfP equal to x Y and parallel to XX. Divide YO and OY' into similar divisions.CONSTRUCTING HYPERBOLIC CUR FES. 249 Assume an ordinate Om of a point to be found, and draw mx" parallel to XX. At Y erect Y'n = Om, and draw Pnx" ; the point x" of intersection with x"n is the required point. For in the triangles ny'P, nmx" we shall have n Y/ : Y'P :: mn : x"m = = x"\ y i.e.,y": x :: y : x". Q. E. D. When the expansion-line is true to the hyperbolic curve, it becomes possible to obtain a fairly approximate measure from the diagram of the clearance-space; or, the latter being known, to determine the real locus of the hyperbolic expansion-curve, as follows: Let S', E, Ef, F, 5 represent an indicator-card ; let OX be the line of perfect vacuum ; OY the line at end of cylinder plus the clearance; then, OX and OY will be asymptotes of the hyper- bola E, A, A', E', the curve of expansion. Take two points on the curve A A', and AK> AC, A'B, and A 'H will be their co-ordinates. Draw AA\ and from C, the line CB parallel to AA'; the point B, where it intersects A'B, will be a point in the line OY. Or, draw HK parallel to AA', and K, the intersection with AK, will be such a point.250 ENGINE AND BOILER TRIALS. For by Mariotte’s law and from the properties of the hyperbola xy — m ; x'y' = m ; . *. xy = ;r'y. . *. : y :: y' : y; x' — x : x :: y — y': y'; or, :: : DC. And, from similar triangles (by construction), A'D :BD :: AD: DC. Q. E. D. Conversely, having given the clearance and the scale of the indicator, with point of cut-off, to find the expansiondine. In proportion y — y' : y' :: x' — x : x, assume xr and find values of y* by constructing the triangle KPH, similar to ADA\ Taking the point of release as a point in the hyperbolic curve, and laying down that curve on the diagram, it will be found, not only that the curve and the expansion-line of the diagram do not coincide, but that the latter falls above the former throughout its length, in nearly all cases, indicating, usually, initial condensation and later re-evaporation, but some- times indicating some leakage as well. If the weight of steam actually drawn from the boiler be taken as the basis of a dia- gram, using its volume as the initial ordinate of the hyperbolic curve, it becomes easy to trace the variations of the whole actual diagram from the ideal indicator-card, as here shown. In any case in which the curve represented by the expan- sion-line is of the class of which the equation is pvn = pxz\n =P*vtn, the co-ordinates sought, any one point, pxvx or /2^2 being given, may be found, and any new point in the ideal curve determined by computation, thus: From the above expression, n log v + log p — n log vx -f- log px; and if px and vx are known, for any assumed volume v, the log- arithm of the corresponding new pressure must be log / = n log vx -f- log px — n log v; which expression being used to determine several points, the curve may be drawn through them.CONSTRUCTING HYPERBOLIC CUR YES. 251 The values of n have been seen to be as follow: Equilateral hyberbola, . . . . 1 Curve of steam ; saturation or 1.0646 Adiabatic curve, steam, .... 1.035 “ “ gas,...........1.408 Isothermal “ “.............1.0 The variation of the actual ratios of expansion from their apparent values, in engines having large clearance-spaces, is very considerable at high ratios of expansion and in short- stroke engines. The following table (p. 252), published by Mr. Grimshaw, is sufficiently extensive for ordinary purposes, and well exhibits those differences.* The close approximation of the three principal steam-ex- Fig. 100.—The Three Expansion-curves. pansion lines is well shown by the accompanying diagram, a set of curves shown in various publications, but probably first laid down in this form by Mr. Porter.f AB exhibits the initial volume, as does also CD; AD and BC represent the initial pressure; EF is an ordinate, taken at convenience ; and the terminal ordinates are GH, /J/, and LK. OR is taken at half-stroke; while CN is the axis of the equilateral hyper- * Am. Machinist, Jan. 20, 1883, p. 5. f Steam-engine Indicator, p. 123.252 ENGINE AND BOILER TRIALS.CYLINDER CONDENSATION AND LEAKAGE. 253 bola, AOG, the upper curve, of which CB and CH are asymptotes. Ordinates measure absolute pressures in pounds per square inch ; abscissas represent volumes of unity of weight (i lb.). Thus BA is the volume (4.73 cu. ft.) of one pound of steam at a total pressure of 90 pounds per square inch ; A BCD is the external work done in its production. It is this curve which is commonly assumed to be that of the expansion of steam. The curve A 01 is the curve of dry and saturated steam, its co-ordinates representing the simultaneous pressure and volume of the fluid when in contact with the mass of water from which it is produced. The expansion is less, and the rate of fall of pressure greater, than if it were to follow the law of Mariotte. It is this curve which is assumed to be described when steam expands in well-jacketed engines. The lower line, AOLy is the adiabatic curve, assumed to be obtainable in engines with non-conducting cylinders and approximately in “ high-speed engines/’ The area under this, as under the other curves, represents the work done as the steam expands, and exhibits the gain obtainable by expansion, in each case. In all real engines, however, the expansion-line falls at first more rapidly, and finally more slowly, than either of these curves. As elsewhere seen, this variation from the ideal curve is often very observable. 71. Cylinder Condensation and Leakage produce varia- tions in the diagram, as obtained, which differently affect the different parts of the curve. Leakage can usually be elimi- nated, and always should be before the engine is set at work regularly. The first-named waste is usually irremediable. When the exact measure of the quantity of steam expended is obtained by a boiler-trial, it is easy to trace these variations, as in the diagram here given, as taken from the engine and worked up by the late Professor C. A. Smith, in which illustra- tion the diagram which should have been produced by the same steam, had there been no initial condensation, is shown with the real diagram.* * Steam-making, p. 91.254 ENGINE AND BOILER TRIALS. This indicator-diagram is an unusually good sample, as to form, and was taken from the St. Louis high-service pumping- engine, a machine of 705 I. H. P., 85 inches diameter of cylin- der, and 10 feet stroke of piston, making 11J revolutions per minute. Taking measures of the abscissas of the two dia- grams, it is seen that the condensation amounts to from about 30 per cent, as a minimum to 50 per cent, as a maximum, so far as measurable, the actual card illustrating the expansion in a metallic cylinder of the steam, which would have given the larger diagram in an ideal engine with its non-conducting cylinder. The complete ideal diagram would extend propor- tionally farther toward the right and beyond the limits of the actual figure. When the two lines continue so far separated, it is an indication of large initial condensation, and correspond- ingly great re-evaporation after the exhaust-valve opens; as the initial condensation is due to, and is proportional to, the re- evaporation. In most cases, however, the engineer, unable to determine these data, assumes the point of release, or the point of intersection of the expansion-line prolonged with the ordinate at the extreme end of the diagram, as that of coinci- dence of the ideal and the real curve, and draws the hyperbolic curve backward from that as a given point, in the manner already described. A comparison of the ideal diagram thus formed with the actual indicator-card will give a means of judging of the character of the engine studied as a thermo-CYLINDER CONDENSATION AND LEAKAGE. 255 dynamic apparatus, and of comparing different engines. An oxact coincidence of the two diagrams, in any given case, would not prove, or even give a presumption of freedom from such waste; nor would the equality, in this respect, of dia- grams from any two engines prove more than a probable general similarity in their performance, thermodynamically. Such comparisons are, nevertheless, both interesting and in- structive, as is seen in the following examples. They also give some indications of the probable consumption of water and steam, the real gauge of the efficiency of engines. The clear- ance may be determined by measurement of the engine, by the graphical method described in the preceding article, or by the following simple methods of construction.* In case 1 let p and d, p' and d’, be co-ordinates of the two given points, and x = the clearance ; then (•* + d)P = O + d')/> and * = y _ p ’ • Or we may determine the clearance geometrically by the fol- lowing construction (see case 2). Assume two points A and B in the compression-curve ; connect them by a right line, AB, continuing this line until it cuts FE at E. Draw AD and BC perpendicular to FEy and make FD = CE. Then F is the end of the ideal diagram including clearance, and the distance of F from the end of the indicator-diagram is the clearance. To lay out the theoretical diagram : Draw a line represent- ing the boiler-pressure and also a line of perfect vacuum, at 14.7 pounds below the atmospheric line, unless the true baro- * First published by Mr. G. H. Babcock ; Journal Franklin Institute, Sept. 1869.256 ENGINE AND BOILER TRIALS. metric reading is given. Next divide the length of the dia- gram, including clearance, into any number of equal parts, as ten. Measure the pressure at the point of release, and find the terminal pressure by any convenient method as that shown in case 3, in which AB is the length of the diagram, including clearance, and D is the point of release. Draw DE parallel to AB and join AE, cutting DC at F. Draw EG parallel to ABr and BG will represent the terminal pressure, the tension at which a quantity of steam equal to the whole capacity of the Fig. 103.—Ideal and Real Diagrams. cylinder and clearance would be discharged at the termination of the stroke. The pressure at any other point of the stroke is easily found by the usual methods. With ten divisions, the several ordi- nates of the expansion-curve may be obtained by multiplying the terminal pressure by the following factors: 1, 1.11, 1.25, 1.429, 1.667, 2, 2.5, 3.333, 5, 10. Having found the ideal pressure at each division, we trace a curve through these points and determine the ideal point of cut-off, giving the same ter- minal pressure as is observed in the actual case.CYLINDER CONDENSATION AND LEAKAGE. 257 If the exhaust-valve closes before the end of the return stroke, so much of the cylinder full of steam as is thus impris- oned must be allowed for in the ideal diagram. Draw a hy- perbolic curve tangent to the actual compression-line, and extending to the line of boiler-pressure, and thus find the boundary of the ideal diagram. The group of four diagrams, Fig. 103, is given by Mr. Bab- cock in illustration of this method. The upper pair show a .remarkable approximation of the actual to the standard figure, each giving, from the measured steam, 90 per cent, of the power which an engine having a non-conducting cylinder should give. One is a condensing, the other a non-condensing, mill engine; both designed by Mr. Babcock. The other pair are similar in their wastefulness, each giving but about one half the maximum, ideal, amount of work. One is from an old naval condensing engine, the other from a non-condensing stationary engine. The next figure is a facsimile of a pair of diagrams from an engine designed by Mr. J. W. Thompson, as studied by Mr. Hill, who gives the following analysis, using the curve of dry and saturated steam, having the equation pv^ = constant as the standard. The engine was 22 inches diameter of cylinder, and 44 inches stroke of piston, making 70 revolutions per minute. The clearance is stated at .0175 piston-displacement. The diagrams were measured with an “Amsler planimeter,” and read as follows:258 ENGINE AND BOILER TRIALS. Mean effective pressure above atmos- phere (both diagrams)..............19.9765 lbs. Mean effective pressure below atmos- phere (both diagrams)..............10.143 lbs. Together......................30.119 lbs. per sq. inch. Power independent of vacuum, “ constant ’ ” X A*, 5.9101 X 19*9765 = 118.063 H. P. Power due vacuum, 5.9101 X 10.143 = 59-946 H. P. Combined power, 178.009 H. P. Ratio of power below atmosphere to power above atmos- phere, 59.946 X 100 _ per Centum. 118.063 D 7/ r The total diagram including cushion reads 31.134 lbs.*, and the efficiency of cylinder becomes 3I£3J_-30-ii9^ 6; 3I-I34 and 1—.0326X 100 = 96.74 per centum of total capacity utilized. The expenditure of steam to produce the power according to the diagram is estimated as follows : 380.13 X 44 X 70 X 2 X 60 144 X 12 = 81305.532 cu. ft. total piston-displacement per hour. The release by the diagrams (both ends of cylinder) appears to occur at 43.175 inches from beginning of stroke, hence 81305.532 X 43-175 = 79781.05 cu. ft. to release. 44CYLINDER CONDENSATION AND LEAKAGE. 259 The exhaust closes (both ends of the cylinder) at 4.1712 inches from end of stroke (return); hence 8I3oS.S32 X 4-.7I? = 770; 7&4 c„. (t 44 Clearance-volume 81305.532 X -0175 = 1422.846 cu. ft. The volume of steam accounted for to release becomes 79781.05 + 1422.846 = 81203.896 cu. ft., and the volume of steam retained in the cylinder by closure of exhaust becomes 7707.764+ 1422.846 = 9130.61 cu. ft. The terminal pressure is - —= 12.125 lbs., and the weight of a cubic foot of steam at this pressure is ob- tained by Tate's formula, thus: 12.125 lbs. =f= 24.7 inches mercury; and a cubic foot of water at maximum density weighs, according to Berzelius, 62.388 lbs.; hence 62.388 25.62 + 49513 / + 72 = .0316 lbs., and 81203.896 X .0316 = 2566.043 lbs. steam. The steam retained by cushioning is as follows: The pres- sure in front of piston at time exhaust closes (both ends of cylinder) is 3.75 lbs., and the weight per cubic foot of steam at this pressure is 62.388 25.62 -} 49513 7.639+.72 = .01048 lbs.; hence, 9130.61 X .01048 = 95.688 lbs. steam retained by cush- ioning. Net steam consumed per hour, 2566.043 — 95.688 = 2470.355 lbs.;z6o ENGINE AND BOILER TRIALS. and steam (water) per indicated horse-power per hour by the diagrams,— 13.878 lbs. The effective vacuum was 20.66 inches, and the losses by leakage and extra condensation were estimated as probably 15 per centum, hence = 16.327 lbs., estimating an evaporative efficiency of connected boilers of 9 to 1 of coal; the cost of coal per I. H. P. per .hour becomes 1.814 lbs. This is probably too low an estimate of this waste. Taking it, however, as even double this amount, 30 per cent., the coal and water consumption would be, respectively, but 2.2 and 19.826 lbs. per I. H. P. per hour; low figures, both. The next illustration, a diagram published by Mr. Porter, as taken from a high-service pumping-engine at Providence, R. I.,, when making but one revolution per minute, exhibits the enormous extent to which initial condensation and later re-evap- oration can occur, most remarkably. The hyperbolic line is at AB, and the magnitude of the terminal ordinate of the diagram, as compared with the ordinate of the hyperbola, measures the proportion of re-evaporation. It is seen that more than three times as much steam must have been condensed at entrance as remained, to produce the dia- gram, this proportion, at least, being later re-evaporated. The following are the quantities of steam found at variousCYLINDER CONDENSATION AND LEAKAGE. 261 parts of the stroke of a compound Corliss engine, as reported by Mr. Hoadley: * Steam, lbs. H. P. Cut-off. Present. Condensed. O.178 9-97 6.80 .625 11.32 5.18 .750 n-35 5-i5 I.OOO n-35 5-i5 P. Cyl., end. 10.57 5-93 The condensation in cylinder and jackets was about one- half throughout. The next diagram, Fig. 106, illustrates the action of the air-compressor. The isothermal lines, which are here hyperbo- lic, are drawn from the atmospheric line as its starting-point. Two diagrams are shown superposed—the one of a common and somewhat inefficient compressor, the other of a more per- fect form. The former gives a diagram having an efficiency but 74 per cent, of the ideal, and the latter 93 per cent. Here the actual diagrams exceed the ideal in area, the heat of compres- sion carrying its compression-line above the isothermal, and the defects of construction and operation of the induction and eduction valves throwing the delivery-line above the limit of pressures in the receiving reservoir. * Steam-engine Practice in the U. S., 1884.• CHAPTER VII. ENGINE-FRICTION ; DYNAMOMETERS. 72. Engine-friction is an important element of waste in all engines. The resistance of the engine due to internal friction and the effort demanded for its impulsion are measured, accord- ing to size, type, and condition, by from about one pound on the square inch of piston in the best large and well-designed engines, to three or four pounds, and even more, in small and inefficient machines. An efficiency of machine exceeding 90 per cent, is rare, and is considered high. The efficiency of mechanism, the ratio of work done by the engine to the work performed by the steam on its piston, is in rare cases 95 per cent., in usual good practice about 85 or 90, and in fairly good work 85 per cent., or less. If the figure falls under 0.80, it is regarded as decidedly low. Before and during a trial, especially, the lubrication should be seen to be thoroughly efficient. A good lubricant should be chosen, and it should be properly applied and freely used. 73. Indicated Work less Engine-friction constitutes the net useful work of the machine. The power of the engine measured, not in its working cylinder, but as delivered from its crank-shaft, is that with which its proprietor and the engineer are most concerned. A complete engine-trial, therefore, includes a careful and exact measurement of the friction of the engine, and the so-called dynamometric power of the machine, as well as the indicated power recorded in the diagram. The friction of engine is sometimes allowed for when its direct measure- ment is impracticable, by assuming a certain pressure as suf- 262INDICATED WORK LESS ENGINE-FRICTION. 263 ficient to overcome its resistance, which pressure ranges from one or two pounds per square inch in large engines, to three or four in smaller sizes, the experience and judgment of the observer being taken as guides. It has been found that engine-friction may usually be taken as constant at all loads. In his various papers on this subject, the Author first called attention to the fact that the variation of load in steam-engines is not productive either of the method or of the amount of engine-friction that has been commonly assumed by earlier authorities on that subject.* It was shown that the formula of De Pambour, which makes the internal friction of the engine proportional to the load on its piston, is not usually correct, and probably is never so, with any familiar form of engine, or under any conditions often met with in practice. It was further shown that, under the conditions of usual practice, and at all ordinary speeds and pressures of steam, the resistance of the engine itself, its internal friction, remains sensibly constant, and that the so-called friction-card of the machine represents prac- tically the friction of the engine when fully loaded, the indicated power without load being sensibly the measure of the wasted work of the engine when in operation under load of whatever amount. Even the compound engine, contrary to the expecta- tion of the Author, exhibited substantially the same internal friction at all loads up to its full rated power, and with no load at all. He has shown the engine-friction to be independent of the load, but to be a function of the characteristics of the engine itself, of the speed of piston and rotation, of the steam- pressure, and of the method of steam-distribution, the two last- named conditions having slight effect, the others being most important. The weight and design, and the character of the workmanship of the engine, primarily determine the amount of its internal friction; the resistance is also a direct function of its speed, and it is slightly and observably affected, within * Friction of Non-condensing Engines. Trans. Am. S. M. E., Vol. VlII, No. CCXXVIII, and Vol. IX, No. CCLXV.264 ENGINE AND BOILER TRIALS. limits, by the steam-pressure variations, and by the character of valve-gear and of steam distribution and of regulation of engine. The speed and weight of the running parts of the engine may, so far as can now be ascertained, be taken as the elements controlling friction of the machine. This leads to the conclusion that the friction coefficient of the rubbing sur- faces decreases with the load on the engine and with increase of pressure on them, a result confirmed by numberless experi- ments of the Author and others, independently. With good lubrication, the coefficient of friction rapidly decreases with intensifying pressures, and to such an extent as to make the actual resistance to movement often very nearly constant. 74. Measurements of Gross and Net Power are com- monly made by means of the indicator and either the absorb- ing or the transmitting dynamometer, the former giving the gross or indicated power, the latter showing the amount of power applied by the engine to a brake or to its special pur- poses, and capable of doing useful work. It is only when such measurements of actually applied, net, power are made, that the real value of the engine as a motor can be ascertained. The efficiency of the engine as a machine, also, is thus determinable, and is measured by the ratio of the dynamometric to the indi- cated power; this ratio is usually about 80 per cent., but some- times exceeds 90. Transmitting Dynamometers are of various types and forms, but all consist of a set of pulleys so arranged that they may be placed between the prime motor and the machinery to be driven by it, while the effort is measured by, usually, a set of springs interposed between the receiving and the delivering pulleys. The magnitude of this effort is often, perhaps generally, auto- matically recorded on a travelling ribbon or strip of paper, and the speed of the machine is observed. The product of the effort into the velocity of the point at which it is measured is the measure of the work done in the unit of time and of the power expended. There are many forms of this instru- ment, but the class most generally known is probably that ofMEASUREMENTS OF GROSS AND NET POWER. 265 General Morin, as built in the Sibley College shops, Fig. 107, in which A is a pulley fast on the shaft, and C is a loose pulley on the same shaft, the motion being transmitted from the prime mover to one or other, according as it is desired to drive the shaft or not. A pulley, B, on the same shaft, carries the belt which trans- mits motion to the driven machine. This pulley is loose on the shaft, so that it is capable of moving backwards and forwards through a small arc, to admit of the deflection of a spring by which the effort is transmitted from the shaft to the pulley. One end of that spring is fixed so that the blade projects like an arm, and rotates with it. The other end is connected with By so that the spring undergoes deflection proportional to the effort exerted by the shaft on the pulley. A frame, rotating along with it, carries an apparatus for making a band of paper move radially with a velocity proportional to the speed with which it rotates. A pencil carried by this frame traces a zero line, and another pencil carried by the spring traces a line whose ordinates represent the forces exerted. The mechanism for moving the paper is driven by a toothed ring surrounding the shaft, and kept at rest while the shaft rotates by means of a catch. When that catch is drawn back, the toothed ring rotates with the machine, and the paper is thus stopped when desired. The Batchelder or Francis dynamometer, as designed by266 ENGINE AND BOILER TRIALS. Mr. Webber, is of the form shown in the following illustration. The principle of this machine’was originally invented by a Mr. Samuel White, in England, in 1780-90; and was brought over to this country by Mr. Samuel Batchelder in 1836. It is said that one of these machines has been used fifteen years, weigh- ing over one hundred and fifty thousand horse-power in small amounts, and the totals, in some cases aggregating two hundred and fifty horse-power, have sub- stantially agreed with the results obtained from indicator-cards taken from the engine driving Fig. 108.—Webber’s Dynamometer. the Same machinery. A transmitting dynamometer, another of many forms now obtainable, is shown in the next figure. This form is often em- ployed for light work, as in determining in detail the power con- sumed by each of the several machines driven by the prime motor; and this has also been used by the Author with satis- factory results. As here seen, the pulley A is loose on the shaft, and receives the power. Its connection with the shaft is made by means of the spider/, which is keyed or screwed firmly to the shaft in close contiguity with the receiving pulley, its hub, in fact, forming one of the guides to the position of the pulley on the shaft. To connect this spider with the loose receiving pulley A, a bell-crank lever is pivoted into projecting ears on the rim of the wheel A> on opposite sides, the long arm of which connects with an annular slotted collar on the shaft by means of short bars B, B. The short arms of the bell-crank levers connect on the inside of the fixed wheel with two radial bars, one parallel to the outer arm of the bell-crank, and the other at right angles to it, receiving near its upper end a pivot passing through a swivel hung to the arm of the spider wheel, and having its extreme end pivoted to a stud fixed on the inner side of theCALIBRATION. 267 rim of the receiving pulley. It will be seen that the strain of the power received through the belt on the pulley will neces- sarily react on the levers, and through them on the spider, which may be considered nothing more nor less than a support to these levers in sustaining them in position to connect the looseNreceiving pulley with the shaft* It will be seen that the levers are connected by pivots with the sliding collar BC, in Fig. 109.—The Emerson Dynamometer. the annular groove of which is seated a strap, with which is connected a forked lever, CH’ To the end of the long arm of this lever a rod, Fy with a short section of machine-chain is attached. This chain runs over the cylindrical head D of a pendulum weight, having a pointer, E, that traverses a fixed • quadrant, F, properly divided by a scale to denote the relative pressure exerted through the medium of the receiving pulley on the shaft; the motions are absolute, there being no chance for “ backlash.” 75. Calibration of a transmitting dynamometer, as an ex- ample, one of the Morin type, is illustrated in the following * Distribution of Internal Friction of Engines; R. H. Thurston; Trans. Am. Soc. M. E., Oct. 188S.268 ENGINE AND BOILER TRIALS. Fig. jio. The best result in this work was given by such a dynamom- eter built in the Sibley College shops, at Cornell University. Its action is like that above described and is shown clearly by Fig. iio. A pul- ley, of which the rim, B, is shown, is fitted loose on the shaft, 5. Four flat springs are securely bolted to the shaft, 5, and to the rim, B. Now, if force be applied by a belt around .5 to turn the pulley, and if resistance to its turning be produced by a fixed pulley on the shaft, 5, from which some machine is driven by the belting, the springs, will be deflected into new positions, c\ an amount proportional to the force, and the fixed pulley will then revolve, thus driving the machine. To show the amount of power transmitted, and any variation that may occur in that power, a pencil is attached to the rim of the pulley, or to a post having an equivalent motion, and a recording apparatus, consisting of a series of gear wheels actuated by a spiral thread on a sleeve on the axis, causes a band of paper to move radially under the pencil. The record- ing apparatus can be stopped or started at will, without inter- fering with the motion of the machinery, by causing the loose sleeve to engage with a lug on the shaft. The diagrams ob- tained from the dynamometer consisted of a series of waving lines (Fig. hi) of varying elevation and with different average ordinates.. The updulations were produced by changes of speeds probably caused by the inequalities of belt-lacings, etc. The dynamometer was calibrated'in three ways: First, by attaching a brake to the same shaft, and comparing the dia- grams with the brake-readings; secondly, by direct pull with a spring-balance against the springs of the dynamometer, and thus obtaining the ordinate for a given belt-pull; thirdly, on the same principle as the first, but a spring-balance was used, to measure the brake-weights, instead of scales. The object Fig.THE PRO NY BRAKE, 269 of these calibrations was to obtain the ordinate corresponding to any given belt-pull. The following results were obtained, in the last case, by direct pull against the springs of the dyna- mometer, which method being employed, gave uniform and satisfactory results. Pull on Dynam. Pulley. Pounds. Ordinate. Inches. Pull on Dynam. Pulley. Pounds. Ordinate. Inches. 0 0.40 35 I.80 5 0.65 40 2.08 10 0.80 45 2.32 15 1.02 50 2.58 25 1-33 60 3.08 30 i-55 70 3.52 The mean of three results corresponds very closely to the last, and, when plotted, gives a straight line, whose equation is Y = 0.046X 0.20, V being expressed in inches and X in pounds. According to General Morin, a good dynamometer should have (1) sensibility properly proportioned to the efforts to be measured; (2) the indications should be placed beyond the influence of the observer and given by the instrument; (3) the observer should be able to measure the effect at every point of the curve produced by the machine; (4) the apparatus should be constructed to give the total amount of work. 76. The Prony Brake, the Absorbing Dynamometer, or the Dynamometric Brake, has many forms.—A simple form of dynamometric brake for small powers is illustrated in Fig. 112. A is the shaft of the motor of which the power is to be deter- mined ; B is the pulley or drum on which the brake-blocks are changed by the bolts, C, C. The lugs, D, D, limit the move- ment of the be.am, E> which is counterbalanced by a fixed poise at Ff and the weights equilibrating the effort of the motor are applied at G. Basswood and poplar are excellent woods for use in the rubbing parts of the dynamometric brake; but any wood will work well if properly handled. The soft are usually found better than the hard woods, but white ash and maple are good. End-grain is often preferred .for rubbing surfaces. The wood270 ENGINE AND BOILER TRIALS. may be secured either to the pulley or to the strap of the brake. Where to be much or continuously used under heavy wear, it is perhaps better to put the blocks on the wheel. The dynamometric power may be ascertained by means of a rope-brake upon the fly-wheel of the engine. Two ropes are used for each wheel, kept at proper distances apart on the wheel by means of transverse wooden distance-pieces. The dead- load is usually applied by means of weights, and the back ten- sions necessary by means of a spring-balance. The spring- balance tension is deducted from' the dead-load applied. This brake is found to work perfectly satisfactorily. If any metal be used for attaching the wooden cross-pieces to the ropes, it must not rub against the rim of the wheel; if this happens, the metal becomes hot, and is liable to burn the rope. If it is assumed that L = length (effective) of the arm of the dynamometer in feet, W — weight (unbalanced) suspended on the arm in pounds, N = number of revolutions per minute, the horse-power will be T\ TT 27tWLN TXT T AT D. H. P. =-----—:—- = o.oooiqoaWLN. 33000 It is not unusual to make the effective value of r equal to —; so that, the circumference described being 33 feet, the 2 7t power is at once completed by multiplying the weight and number of revolutions of the shaft, W and N> together, and di- viding by 1000 to get the horse-power.THE PEONY BRAKE. 2JI A form of this brake which the Author has most frequently employed, and with satisfaction, is constructed as follows:* Like nearly all dynamometers of this class, it includes a brake-wheel, or pulley, which is keyed on the engine-shaft, and is sufficiently strong to sustain safely the maximum load an- ticipated. The rim of this pulley is turned flat and smooth, and fitted with a flexible brake-strap of wrought-iron, or other suitable material, which may be adjusted to such a tension as will enable it to control the engine at maximum power. In this case, the rim is trough-shaped in section, flanges extend- ing inward toward the shaft to a sufficient depth to permit the retention in the circular trough so formed of a stream of water which is used to keep the pulley cool, and to carry away the heat produced by transformation of mechanical energy. The two ends of the brake-strap are united by a right- and left-hand screw, in such manner that they may be drawn together and the strap set up to any desired degree of tension. The brake- arms consist of two beams of wood, forming a < frame, and secured to the strap at the upper and lower sides, and at their junction supported by a strut resting on a platform-scale of nice construction and great accuracy. As the engine-shaft re- volves, the tendency of the brake-arms to turn is resisted by the scale ; and the effort so measured, multiplied by the relative velocity of the engine-shaft and the supported point on the arm, gives a measure of the power expended. Water is sup- plied to the pulley-rim, by means of a hose, from any conven- ient source, and the excess is taken away in a similar manner. The centrifugal action of the rotating mass keeps the fluid in place in the pulley-rim, and the eduction-pipe receives the wa- ter carried away by it as the tender of a locomotive scoops wa- ter from between the tracks, when at high speed. This sys- tem permits efficient lubrication, without admixture of grease with the water, and secures a perfection of smoothness and uniformity of rubbing-surfaces unattainable with older forms of brake. * Construction of a Prony Brake ; R. H. Thurston ; Journal Franklin In- stitute, April 1886.272 ENGINE AND BOILER TRIALS. 77. Designing a Brake.—The following is an account of the design of a brake, which worked well under higher en- gine loads than the Author had ever before known to be con- trolled by this means.* It also illustrates fully its theory. The brake was designed for the maximum power of the en- gine, t.e. taking steam at full stroke, the engine running at 100 pounds pressure, and at 100 revolutions per minute. The di- ameter of the cylinder was 18 inches and the stroke 42 inches* and we have for the maximum power developed H. P. 254.47 X IOQ X 42 X 2 X TOO 33000 = 540 + The brake was accordingly designed to control the engine when exerting this power, and to be used upon a pulley of 5 feet diameter and 24-inch face. The size of the pulley was chosen of this diameter, simply because it compelled less re- moval of floor and railings about the engine, and would also cost less than a larger one. The calculations for the remaining parts of the controlling apparatus is as follows : Assumed diameter, 5 feet; assumed maximum speed of engine, 100 revolutions; circumference, 15.708 feet. This would give for the greatest linear velocity of the pulley per minute, 1570.8 feet. Dividing the number of foot-pounds de- veloped by the engine at its maximum speed and pressure, by the linear velocity, gives the resistance at the rim of the pul- ley 540 X 33000 „ , ------------= 11345 pounds; 15708 ^ which figure is the total friction, in pounds, on the face of the pulley. The brake-blocks were 2\ inches thick, 5 inches wide, and 24 inches long, of unseasoned white* oak, and were placed 7 inches from centre to centre, leaving a space of 2 inches, be- tween adjacent blocks, for diffusion of the heat and for lubri- cation. The blocks were attached to the flexible brake-straps *The designers were Messrs. Gately and Kletsch.273 THE PHONY BRAKE. I by means of wrought-iron lag-screws. The three blocks at the top and those at the bottom of the pulley were fastened to the arms of the brake. The straps, two in number, were calculated thus: Let Tx and 7"2 represent the tensions at the ends of the band which embraces the pulley, and let Tx be the maximum ten- sion. Then 7Y exceeds the tension 7^ by an amount equal to the friction between the blocks and the pulley; i.e., R = Ti- 7y= H345. Let c denote the ratio which the arc of contact bears to the circumference of the pulley,/' the coefficient of friction be- tween the blocks and the pulley; then the ratio Tx: 7!, is the number whose common logarithm is 2.7288cf; or, II = io2-7288* = N. c, the arc of contact of the bands, == 1, and/, the coefficient of friction between wood and cast-iron (well lubricated), was taken at 0.2; then or, j\r= iqwWc— io2*7288 x -2 x 1 ; T2 jo0, 54576 ==' - Having found R = 11345 pounds, we have for the greatest tension on the band Tt= R N N- 1 and substituting the values of R and N in this equation, we have Tt = 11345 = 15883 pounds.274 ENGINE AND BOILER TRIALS. Hence, for the combined tension on rthe band, and using two ^straps, we have for’the tension on one ^ j p0unds. Taking the tensile strength of such wrought-iron as safe at 40,000 pounds per square inch, and allowing for a sixfold factor of safety, we obtain for the section of the band 7941.5 X 6 40000 1.19 square inches. The nearest band-iron of this section was -|X3 inches, and, after careful testing, it was found to be of sufficient strength; giving, at the same time, that flexibility which is of vital im- portance in the operation of brakes. At each end of the bands it was found necessary to weld on round bar-iron of equal sec- tion, to admit of threads being cut for the purpose of tighten- ing and loosening the brake. , The arms were two in number, of 6x6 inches well-seasoned spruce. The length was made 10 feet 6.1 inches from centre of the bearing-surface on the pulley to centre of bearing-sur- face on the scale, as it brought the scale beyond the rim of the. fly-wheel, and also greatly facilitated calculations of the horse- power developed—the circumference of a circle, whose radius is 10 feet 6.1 inches, being 66 feet. Thus instead of multiply- ing by 66 feet, and then dividing by 33,000 to obtain the horse- power, it is only 'necessary to divide the product of the net scale-pressure and the revolutions per miniite by 550, the quo- tient being the horse-power developed, i.e., p _ W X Rev. X 66 _ W X Rev. ’ ~ - 33000 500 The stand through which the pressure was transmitted to the scale was composed of two uprights, 6x6 inches, of white pine, surmounting a pedestal covering the greater part of theTHE PEONY BEANE. 275 :3cale platform. Upon these uprights was placed a steel plate of |-inch thickness, which received the pressure of the bolts. The scale was carefully balanced, and was capable of accurately weighing 3000 pounds. All weights used were carefully weighed on a standard balance, and none were used that were found not to be absolutely correct. As the common segmental arm would give but a very nar- row bearing for the rim, the Author advised an arm of 1-sec- tion, which was found to answer the purpose. The calculations for the parts of the pulley were made ac- cording to Unwin,* giving for the thickness of rim t = 0.7$ + 0.005D = 0.65 inch; where D — diameter in inches = 60 inches; and d = thickness of belt taken at 0.5 inches. The number of arms was assumed at 6; and similarly, for the thickness at the nave, h = 0.1781 8.54 inches; P being the driving effort, 11345 pounds ; D = diameter = 60 inches; and n = number of arms == 6; h v hi = breadth of arms .= — = 4.27 inches. For h at the rim, we take f the diameter of the nave. For the thickness of the nave, $ — 0.18 + i == 2*1 Inches; where B is the face = 24 inches; D is the diameter = 60 inches. * Machine Design.276 ENGINE AND BOILER TRIALS. The diameter of the main shaft being 9.12 inches, the cal- culated thickness of the nave was judged rather small, and 2.5 was used instead. The. rim was also made inch heavier at the centre than the calculated dimension used for the edges of the rim. For the moment of inertia of this section of arm, "B---------- I - XV(2&/3); and, considering the arm as fixed at one end and loaded at the other, where P = load; / = length of arm ; /= moment of inertia; R= modulus of rupture; d=iD. Load on 1 arm — -J of 15600 = 2600 = P. I = 39 — 7i = 22.5 inches. I — tV(4 X 83) ~ yV(2 X X 5s) = 40*6. Allowing a factor of safety of 8, we have R = 17290, and the above sections and dimensions are ample. The standardization of this type of absorbing dynamometer consists simply of the careful determination of its exact dimen- sions, and of the accuracy of the scales employed. In the original device of Prony, the efforts on the brake were obtained by loading a scale-pan, a far less manageable system than that which is above described. Many modifica- tions of this instrument have been made by various ingenious engineers, some of which may be here briefly referred to.* In all cases and in all applications of the brake, the essential con- ditions are, mainly, accuracy of measurement and readings, and,. * See Beaumont on Friction-Brake Dynamometers; Proceed. Brit. Inst. C. E., 1888, for a very full account of these instruments.THE PEONY BRAKE. m above all else, uniform friction-resistance, such as can only be insured by good methods of lubrication. All conditions of the trial should be as constant as possible. For small powers, the arm may be omitted and the restraining effort exerted directly upon the strap, and this strap is sometimes merely a leather band or a rope, either with or without blocks. In all cases the work in actual horse-power with the load Pin pounds at the dis- tance R in feet from the centre of the wheel, making N revo- lutions in time t in minutes, will be H p _ (R X 2) X n X P X N 33000 X t •or taking c = circumference of circle of radius R, and V — ve- locity in feet per minute of circumference, then V — cN, and H.P.= P = cNP 330bot 33000 H. P. ~dST ' c = 33000 H. P. ' NP _ VP ~ 33000*’ _ 33000 H. P. ~ V ’ „ 33000HJP. cP In many forms of brake, it is sought to secure a self-adjust- ment of the grasp of the strap, as, for example, the dynamom- eter of Messrs. Amos and Appold, Fig. 113. It is provided with a compensating lever, K, by means of which the rise or fall of the load P is attended with a decrease or increase in tension on the brake-strap. With a given tension in the belt, and with the load P set with its point of suspension ZT opposite the point the lever takes a vertical posi- tion ; but as soon as the load Pis lifted the lever pivoted at X moves with and virtually increases the length of the belt, and thus slack- ens it, allowing the load again to descend. If the total friction de- creases, the descent of the load carries the compensating lever Fig. 113.—Compensating Brake.278 ENGINE AND BOILER TRIALS. to a new position, thus tightening the belt and increasing the friction. In ‘a form of Compensating brake designed by Mr. Balk, Fig. 114, the compensating lever is outside the Circumference of the strap. It is connected at B and at C to the strap, and a fixed pin, Fy passes through a slot at the outer end, where is suspended a weight, /, sufficient to keep the lever free. This Fig. 114.—Compensated Dynamometer. weight must be varied with change of condition of the brake- blocks, the lubricant and the temperature of the wheel, and as it must be taken as acting at the radius OF in favor of the weight Py these variations become troublesome by virtually making P a variant.* The form of pulley which has been described is illustrated in the next figure, which shows the proportions adopted by Mr. Halpin, who was probably the first to use it. Mr. Beaumont has proposed the following expression as a convenient means of comparing the relative capacity of brakes, judging by the amount of Work fbr which they have been designed, or to which they have been put. The coefficient WV' HP may be employed, W being the width of the wheel * See paper by Professor Btauer; Zeits. der Ver. Deutschen Irtg., Band xxxii; Seite 56.THE PRONY BRAKE. 279 in* inches, and V' — the velocity of the periphery of the wheel in feet per minute. This gives for the Royal Agricultural Society’s single brake K = 824 Compared in this same manner the Prpny br$k$ described by the Author, as devised for measuring a maximum of 549 Hv. P., the wheel being 5 feet in diameter and 2 feet wide, and $ ==? IOQ, gives K *= only 75. This brake was freely lubricated with beef tallow, plumbago, and lard oil, and although designed for a maximum of 540 H, P., it was not worked above 200 H. P., and at this power K =? 188. The more effective the brake the lower the coefficient. K = 400 may be taken as a good figure; the coefficient is less, apparently, on the water-cpoled hollow rim. Other things equal, the highest coefficients correspond to largest areas of rubbing-surface on the rim* Mr* Beaumont makes the following approximate estimate of the maximum pressure p per square foot of block. Wf being the width of the wheel in feet, p may be obtained thus: treble “ K = 495 Garrett’s water-cooled brake Ransomes, Balk’s brake K = 740 K — 1020 T+ T = Dp W', or T = ~j and T-\- T P ~ DWr ’28o ENGINE AND BOILER TRIALS. The greatest pressure per square foot of surface of the Author’s example of a Prony brake, if it had been used as pro- posed for 540 H. P., would have been, at f= 0.2, .At 200 H. P. / = 1180 lbs. The greatest pressure per square foot on the blocks of the Royal Agricultural Society’s brake at Newcastle was / = 312 lbs. with the blocks covering 0.8 of the surface of the,wheel. This is a rough approximation to the greatest pressure per square foot, but it affords a fair means of comparison of the pressure with the different brakes. A good method of fitting the dynamometric brake to a portable engine is shown in the illustration.* .A is the beam of the brake; B is the point of attachment of a strut which transmits the pressure due the turning effort to the platform- scale, seen below \ C is a counterbalance. In handling a brake cooled by water, it is advisable to use as small a quantity of the liquid as possible, and it will often be found perfectly practicable to even permit its complete evaporation, keeping the metal at 212° F., thus reducing the * On the Distribution of Internal Friction of Engines; R. H. Thurston; Trans. Am. Soc. M. E., 1888. ‘—®r— B B Fig. 116.—Dynamometric Brake.THE PRONY BRAHE. 28l quantity demanded to a small fraction of that often used, and largely doing away with the difficulties incident to its supply and wholly with those of discharge. In the Brauer dynamometric brake,* Fig. 117, instead of wooden jaws hugging the rims of the pulley, an iron band is used for flat-rim pulleys, and wire-ropes for grooved pulleys. The apparatus is composed of the following parts: 1st. The iron band or wire-rope. 2d. The clutch-producing arrangement and the regulation of the tension of the clutch-producing bands or ropes. The iron band applied to an ordinary flat-rim pulley is pro- vided with four double guides k (Fig. 117) to retain the band in position, fixed up by means of a stirrup bolt and link and a safety cord /72, so as to allow the band to have a play of 100 millimetres. These safety measures can be modified according to circumstances. The frictional parts are actuated in the following manner: The wire band is attached at its ends to the point of the application of resistance a, and to the point of rotation b by a lever abc. The point c of this lever is attached at d by means of a winding tackle ee^ and a spring f, to the upper end of the wire band. The cord of the winding tackle after leaving e is passed round the friction-roller g. The operator, by pulling the cord, produces the tightening action in such a way that the weight p is lifted and equilibrium established. In order that this condition may not be affected by the tension of the part of the cord from e3 to g, it is only necessary to fix the friction-roller in such a way as to be in line with the axis of the pulley or drum. The moment of this tension will then be nil. The friction-roller is not indispensable, but its application permits the operator to control the action of the brake at some distance. Automatic regulation is effected, according to the variations of the friction, by the combined action of the spring f and the cord h. It will be seen that if, owing to excessive friction, the weight p is lifted above its mean position, the cord * “Bulletin de la Soci6t6 Industrielle de Madhouse,” 1884, p. 485. Proc. Inst. C. E., No. 2079.282 ENGINE AND BOILER TRIALS. k will be stretched, augmenting the tension, and elongating the spring /. The result is a diminution of the clutching action, and the weight p will be lowered. The weight 4 which obviates the necessity of attaching the cord h to the floor-boards, should be equal the strain liable to be brought upon- the cord h. The lifting-tackle should always be . suspended in such a way as to reduce the traction upon the eord h to a minimum, and so that the influence of this factor upon the condition of equilibrium in general need not be taken into consideration. Lubrication may be effected in any convenient manner. The rim is usually sufficiently cool under light load without water. 78. Data obtained by the use of the transmitting dyna- mometer are often of great value as a check on other methods of test. Mr. Emerson gives the following as illustrating this fact: Testing woollen-mill machinery, running ten “sets,” eleven hours per day, with the boiler-pressure kept at 70 pounds, the driving-pulley on engine, 9 feet diameter, with 30-inch double belt, drove a 5-feet pulley upon the main line. Throwing on and off machinery caused a variation of four revolutions of the pulley on the engine, or from 12Q down to 116 per minute, 3J per cent.THE PRO NY BRAKE. 283 The results obtained were as follows: Average net effort for 11 hours, . 1163 lbs. Coal burned in 11 hours,- ...... 0 • . 4955 lbs. Average power in 11 hours, ........ 82.9 H. P. 4955 -5- 11 — 450.4 82.9 = 5.43 lbs. coal per horse-power per hour. The St. Joseph Milling Co., Mishawaka, Ind., 100-barrel mill, required 3.81 horse-power per bushel. The Ripple Mill, Mishawaka, Ind., 130-barrel mill, required 3.91’ horse-power of water per bushel ground, Mishawaka Mill, Mishawaka, Ind., 175-barrel mill, required 4.72 horse-power of water per bushel. Sage Brothers' Flouring Mill, Elkhart, Ind., roller-mill, 280- barrel capacity, required 3.18 horse-power of water per bushel ground. Tests on Spinning Frames, Speeders, etc. No. of Test. Time. I No. of Spin- 1 dies. . d w > 'o £ 9 & Condition. No. of Turns per Minute of Spindles. No. of Test. Heav- iest. Light est. Varia tion. Aver- age. 1 2.00 till 5.36 192 28s 6 Bobbins from £ full till doffed. 7343*5 7556.0 212.5 7449.2 1 “ “ 1‘* 3 Bobbins from doft till £ full. 7392:0 7343*5 9*3 74*9*3 “ t« “ “ ** 9 Total of above, 7343*5 7343*5 0 7434-4 44 2 8.00 till 10.00 192 28? i Bobbins full till 4 full aga n. 7228.5 7362.8 134*3 7287.2 2 3 10.30 till n.30 192 28* 6 Bobbin's l full till full’. 7355*4 7246.8 108.6 7324.2 3 1 H Horses-powEr to a Frame. Spindles per Horse-power. (i w H u* 0 d £ Heaviest. Lightest. Variation Average. Heaviest. Lightest. Variation. Average. 0 6 1 1.7000 1.6150 .0850 x.6660 113.0 119.0 6.0 i*5-3 1 “ 1.5050 1.3820 • *230 1.4420 127.7 138.0 9*3 . 132.4 “ “ 1.7000 X.3820 .3x80 *•59*5 113.0 138.0 25.0 120.7 “ 2 1.3504 i;25oo .1004 1.3106 142.2 . 153*6 li.4 146.5 2 3 1.6180 1.4205 .*975 1.5094 118.6 *35*o 16.4 127.2 3 Mr. S. Webber finds the friction of this class of dynamom- eters to be sensibly constant.CHAPTER VIII. STANDARD METHODS OF ENGINE TRIAL. 79. Standard Methods of Engine Trial have been pro- posed by various writers and practitioners, with the double purpose of securing all needed data, at least cost in time and money, and of making all results strictly comparable. In the absence of agreement in regard to method, a great variety of practice is liable to spring up, and as great a variety of methods of securing, tabulating, and computing results from the data obtained. It is therefore considered advisable that all such experimental work, whether for directly practical purposes or with a scientific object, should be made by that carefully planned and precisely stated system, which should be best adapted to the ready determination of all needed data, with least liability to error, and a most convenient means of check- ing all figures. Both engine and boiler trials should be made in accordance with such a system as is generally recognized as well adapted to its purposes, and accepted and indorsed by those whose learning and professional standing and experience best fit them to judge it. Standard engine and boiler trials are not yet as widely adopted as is desirable ; but they are gradually taking definite form and are steadily coming into general use. The results of any engine trial, if complete and accurate, should enable the engineer to answer several questions: (1) What is the real efficiency and the economical perform- ance of the system tested ? (2) How does it compare with standard apparatus of a sim- ilar character? and in what is it superior or inferior? What are its excellencies and its defects ? 285286 ENGINE AND BOILER TRIALS. (3) How are commercial and financial conditions affected by its operation? These questions being solved, the proprietor will know to what extent his expenditures and his methods of operation are wise and productive ; the builder will learn how successful he has been in his work, where it is defective, and what remedy is available; the engineer secures data which enable him to de- sign intelligently later and better constructions, and it may furnish a standard for still other comparisons. The duty-measurement should always be expressed in per- fectly definite terms. The usual expression may be interpreted to assume any one of several different units. If the efficiency of the system, engines and boilers included, is to be measured only, it is sufficient to ascertain the relation between the work performed and the cost of its performance as measured at the boilers; but even this may be a very uncertain measure unless the quality of the fuel is prescribed. The kind of fuel should be stated in all such cases; but a system of measurement which determines the heat produced in the furnace, in thermal units, or other equally definite terms, and the quantity of useful work which it yields, is the only satisfactory one. The only correct and exact method of gauging the perform- ance of any steam-engine is to determine the weight of steam or, better, the number of thermal units demanded by it per horse-power per hour. The proper measure of the boiler effi- ciency is the proportion of the heat of combustion of the fuel which is absorbed and stored as available energy in the steam which it produces. To rate th$ engine by the quantity of fuel burned at its boiler is wholly incorrect; to rate the boiler by the ratio of steam made to coal burned is hardly less indefinite. It is only by the habitual use of a known fuel of uniform com- position and physical character that comparisons of value may be effected at all. Even where the steam-unit is adopted, it must be taken at a standard temperature and pressure. In all heat-engines the proper measure of heat-energy is the heat- unit. There is, therefore, reason in the adoption of, for an exam-ENGINE AND BOILER TRIALS. 287 pie, 1000000 B. T. U., a figure sometimes so taken, as a stand- ard quantity in duty-trials of engines.* 80. Engine and Boiler Trials are so generally conducted together, and the former so commonly depend for their essen- tial data upon the latter, that the presentation of illustrations of standard methods tor both is considered advisable and will be given later. Of the two, the latter is usually much the more laborious and troublesome, and also more expensive in time and money. The boiler-trial also admits of a greater variety of methods than the engine-trial, and is correspond- ingly more liable to yield results of varying accuracy. For this case the best practice is better settled than for the other, and standard methods of steam-boiler trial are fairly well estab- lished on both sides the Atlantic. A good boiler should have an efficiency of not less than 75 per cent., giving thus 10875 B. T. U. per pound of carbon sup- plied as fuel, and, deducting ash, for good coal, about 10000 B. T. U. per pound of fuel, the equivalent of 0.25 pound of coal per horse-power and per hour, if all converted into work. The real efficiency of any engine is measured by the quotient of this quantity for the actual consumption. Thus, an engine using 2.5 pounds of good coal has an efficiency of heat ■n 0.25 E = —- = 10 per cent. 2.50 This is considered a good result. Ninety per cent, of all heat supplied is here wasted. An engine using 1.25 pound of best fuel, a result sometimes claimed, but certainly seldom reached, has an efficiency of E = = 20 per cent. 1.25 A consumption of 40 pounds of steam would give E = — — 6 per cent. 40 * This corresponds to 100 lbs. coal evaporating 11.25 lbs. water from and at 2120 F.288 ENGINE AND BOILER TRIALS. As an example of a systematic scheme of engine-trial, illus- trating the general characteristics of a standard method, we may take the following outline abstract from a plan for a pumping-engine duty-trial proposed by Mr. Barrus : * (1) It is presumed at the outset that the engine is in thorough order in every part, having been in operation a suf- ficient length of time, since its erection, to secure easy and proper working. If this has not been done, and especially if the plunger has been recently packed or its packing newly re- adjusted, the engine is worked for a run of at least twelve hours’ continuous service in preparation for the test. (2) The plant is subjected to a preliminary run, under the conditions determined upon for the test, for a period of at least three hours, so as to find the temperature of the feed-water (or the several temperatures, if there is more than one supply), for use in the calculation of the duty. During this run the obser- vations are made every fifteen minutes, and the results aver- aged. (3) The engine is now stopped for a time, in order, first, to connect up the measuring apparatus for determining the weight of the feed-water consumed, or of the various supplies of water if there are more than one ; and, second, to test the leakage of the plungers. The quantity of water which leaks by the plungers is most satisfactorily determined by removing the cylinder-heads. A wide board or plank is temporarily bolted to the lower part of the end of the cylinder, so as to hold back the water, in the manner of a dam, and an opening is made in the temporary head, thus provided, for the reception of an overflow pipe. The plunger is blocked at some intermediate point in the stroke (or if this position is not practicable, at the end of the stroke), and the water from the force-main is admitted at full pressure behind it. The leakage escapes through the overflow pipe, and it is collected in barrels and measured. The test need not continue over fifteen minutes, or, if carefully made, a less time, the desired object being to get a satisfactory deter- * London Engineering, Mch. 1, 1889, p. 217.ENGINE AND BOILER TRIALS1 289 mination of simply the rate of leakage. If no means exists for putting the back side of the plunger under water-pressure, a suitable pipe can readily be provided for the purpose. Should the escape of water in the engine-room be objectionable, a spout may be constructed to carry it out of the building. Where the leakage is too great to be readily measured in bar- rels, or where other objections arise, resort may be had to weir or orifice measurement, the weir or orifice taking the place of the overflow pipe in the temporary w^ooden head. The ap- paratus may be constructed in a somewhat rude manner, and be sufficiently accurate for practical requirements. In the case of a pump from which it is difficult to remove the cylinder-head, it may be desirable to take the leakage from one of the openings which are provided for the inspec- tion of the suction-valves, the head being allowed to remain in place. If the test is made without removing the head, leakage of the discharge-valves may be confounded with leakage of the plunger. Examination for such leakage should be made first of all, and if it occurs and it is found to be due to disordered valves, it should be remedied before making the plunger-test. The discharge-valves on the back end of the pump should like- wise be examined, as also the suction valves on both ends, and the disordered valves removed. Leakage of the discharge- valves will be shown by water passing down into the empty cylinder at either end when they are under pressure. Leak- age of the suction-valves will be shown by the disappearance of water which covers them. The leakage-test being completed, no change is allowed in the adjustment of the packing of the plunger (supposing this to be of a form capable of adjustment), the head is imme- diately replaced and preparations made for at once beginning the main duty-trial. (4) The duty-trial is here assumed to apply to a complete plant, embracing a test of the performance of the boiler, as well as that of the engine. The test of the two will go on simul- taneously after both are started, although the boiler-test will begin a short time previous to the commencement of the en-290 ENGINE AND BOILER TRIALS. gine-test, and continue after the engine-test is finished. The mode of procedure is as follows : While the preparations are being made to start the engine, after the completion of the leakage-trial, steam is raised in the boiler to the working pressure. The fire is then hauled, the furnace and ash-pit cleaned, and the test of the boiler is com- menced. This test is made in accordance with the rules for a standard method recommended by the Committee on Boiler- Tests of the American Society of Mechanical Engineers.* This method, briefly described, consists in starting the test with a new fire lighted with wood, the boiler being previously heated to its normal working degree ; operating the boiler in accord- ance with the conditions determined upon, weighing coal, ashes, and feed-water ; observing the draught, temperatures of feed-water and escaping gases, and such other data as may be incidentally desired ; determining the quantity of moisture in the coal and in the steam : and at the close of the test hauling the fire and deducting from the weight of coal fired whatever unburned coal is contained in the refuse withdrawn from the furnace, the quantity of water in the boiler and the steam-pres- sure being the same as at the time of lighting the fire at the beginning of the test. The temperature of the feed-water is observed at the point where the water leaves the engine-heater if this be used, or at the point where it enters the flue-heater if this apparatus is employed. In either case, where an in- jector is used for supplying the water, a deduction is to be made for the increased temperature of the water due to this method of feeding. As soon after the beginning of the boiler-test as practi- cable, the engine is started and preparations are made for the beginning of the engine-test. The formal commencement of this test is delayed till the plant is in normal working condition, which should be not over one hour after the time of lighting the fire. When the time for commencement arrives, the feed- water is momentarily shut off, and the water in the lower tank See this report as given in Chapter II of the present work.ENGINE AND BOILER TRIALS. 29I is brought to a mark. Observations are then made of the number of tanks of water thus far supplied, the height of water in the gauge-glass, and the indication of the counter on the engine, after which the supply of feed-water is started and the regular observations of the test commenced. The test is to continue at least ten hours. At its expiration the feed- pump is again momentarily stopped, care having been taken to have the water slightly higher than at the start, and the water in the lower tank is brought to the mark. When the water in the gauge-glass has settled to the point which it occupied at the beginning, the time of day and the indication of the counter observed, together with the number of tanks of water thus far supplied, the engine-test is held to be finished. The engine continues to run after this time till the fire reaches a condition for hauling and completing the boiler-test. It is then stopped, and the final observations relating to the boiler-test are taken. The observations to be made and data obtained for the pur- poses of the engine-test embrace the weight of feed-water sup- plied by the main feeding apparatus, that of the water drained from the jackets, and any other water which is ordinarily sup- plied to the boiler, determined in the manner already pointed out. They also embrace the number of hours’ duration and number of strokes of the pump during the test, as noted, to- gether with the length of the stroke (in direct-acting engines), the indication of the gauge attached to the force-main, and in- dicator-diagrams from the pump. It is desirable that indicator- diagrams be obtained also from the steam-cylinders. Observations of the length of the stroke should be made every five minutes ; observations of the water-pressure gauges every fifteen minutes ; observations of the remaining instru- ments—such as steam-gauge, vacuum-gauge, thermometer in pump-well, thermometer in feed-pipe, thermometers showing temperature of engine-room, boiler-room, and outside air, ther- mometer in flue, thermometer in steam-pipe if the boiler has steam-heating surface, barometer and other instruments which may be used—every half-hour ; indicator-diagrams should be292 ENGINE AND BOILER TRIALS. taken every half-hour, both from the steam and from the water cylinders. Should the diagrams from the pump be rectangular* they may be taken, if desired, with less frequency. When the duty-trial embraces simply a test of the engine apart from the boiler, the course of procedure will be the same as that described, excepting that the fires will not be hauled and the special observations relating to the performance of the boiler will not be taken. (5) In making preparation for the test, attention should be given to the following provisions in the arrangement of the ap- paratus : The gauge attached to the force-main is liable to a consid- erable amount of fluctuation unless the gauge-cock is nearly closed. The practice of choking the cock is objectionable. The difficulty may be satisfactorily overcome and a nearly steady indication secured, with cock wide open, if a small reservoir having an air-chamber is interposed between the gauge and the force-main. By means of a gauge-glass on the side of the chamber and an air-valve, the average water-level may be adjusted to the height of the centre of the gauge, and correction for this element of variation avoided. To determine the length of stroke in the case of direct-act- ing engines, a scale should be securely fastened to the frame which connects the steam and water cylinders, in a position parallel to the piston-rod, and a pointer attached to the rod so as to move back and forth over the graduations on the scale. The marks on the scale, which the pointer reaches at the two ends of the stroke, are thus readily observed and the distance moved over computed. If the length of the stroke can be determined by the use of some form of registering apparatus, this method of measurement is preferred. The personal errors in observing the exact scale-marks, which are liable to creep in, may thereby be avoided. The form of calorimeter to be used for testing the quality of the steam is left to the decision of the person who conducts the trial. It is preferred that some form of continuous calorim- eter be used which acts directly on the moisture tested. IfENGINE AND BOILER TRIALS. 293 either the superheating calorimeter or the wire-drawing instru- ment be employed, the steam which it discharges is to be meas- ured either by numerous short trials, made by condensing it in a barrel of water previously weighed, thereby obtaining the rate by which it is discharged, or by passing it through a sur- face-condenser of some simple construction, and measuring the whole quantity consumed. When neither of these instruments is at hand, and dependence must be placed upon the barrel calorimeter, scales should be used which are sensitive to a change in weight of a small fraction of a pound, and thermom- eters which may be read to tenths of a degree. The pipe which supplies the calorimeter should be thoroughly warmed and drained just previous to each test. In making the calcula- tions, the specific heat of the material of the barrel should be taken into account, whether this be of metal or of wood. If the steam is superheated, or if the boiler is provided with steam-heating surface, the temperature of the steam is to be taken by means of a high-grade thermometer resting in a cup holding oil or mercury, which is screwed into the steam-pipe so as to be surrounded by the current of steam. The tempera- ture of the feed-water is preferably taken by means of a cup screwed into the feed-pipe in the same manner. Indicator-pipes and connections used for the water-cylin- ders should be of ample size, and so far as possible free from bends; f-in. pipes are preferred, and the indicators should be attached one at each end of the cylinder. It should be remem- bered that indicator-springs which are correct under steam heat are erroneous when used for cold water. When steam springs are used, the amount of error should be determined if calcula- tions are made of the indicated work done in the water-cylin- ders. To avoid errors in conducting the test due to leakage of stop-valves either on the steam-pipes, feed-water pipes, or blow- off pipes, all these pipes not concerned in the operation of the plant under test should be disconnected. (6) The engine is to be worked on the duty-trial, unless otherwise stipulated, at its rated capacity of discharge.294 ENGINE AND BOILER TRIALS. (7) In review of the method thus pointed out, the various steps may be summed up as follows: a. Preliminary run to determine the temperature of the feed-water; b. Erection of weighing apparatus, examination of pump, and test of plunger leakage ; c. Commencement of boiler-test; d. “ “ engine-test; e. Boiler and engine test go on simultaneously ; f. Close of engine-test; g. u “ boiler-test. (8) It is desirable that the report of a duty-trial should be sufficiently full to show the performance of the engine and its various members in all other respects than the simple expres- sion of the amount of duty performed. For this reason the horse-power developed by the steam-cylinders, the feed-water consumption per horse-power per hour, the steam accounted for by the indicator, and other information relating to the work of the engine in the capacity of a steam-engine, should be de- termined and given. The efficiency of the mechanism of the engine should also be determined and stated, that is, the proportion which the work done upon the water bears to the work done in the steam- cylinders. This efficiency may be expressed by any formula in which the numerator is the duty and the denominator is the work done during the trial, measured from the indicator-cards taken from the steam-cylinders. This efficiency measures a quantity which is of primary importance in the operation of the engine and should always be carefully and exactly de- termined. 81. Fitting of the Engine for a Test, whether of effi- ciency or of capacity, is best done in advance of the trial, and ample time should be taken to see that not only all apparatus,, but the engine itself, is in readiness; though, if the intention is, as is sometimes the case, simply to ascertain the condi- tion of the engine as found, no other preparations are per- missible than those customary before starting up. A goodFITTING GF AN ENGINE FOR A TEST. 295 example of the fitting up of a small high-speed engine is illustrated in Fig. 118, and, in plan, in Fig. 119, in which AA is the engine, BB its shaft, CC the indicators, D the indicator reducing-gear, driven from the crosshead; EE is the Prony Brake, receiving its cooling water at F and dis- charging it at G, and attached to the platform-scale arranged at H; the screw tightening its strap is at /. The speed- indicators were, in this case, of several kinds. Hand in- struments of various kinds were used to check the records of the automatic instruments. A “ tachometer/’^, was attached and belted at K to the engine-shaft, and afforded a very con- venient means of watching the momentary fluctuations due to variations of load, of steam-pressure, and of accidental disturb- ances. A chronograph at L was also attached, connected with a standard clock to beat seconds, and a current was derived from the battery at O. A commutator, M, was placed on the engine-shaft, making contact at each revolution, and a key, JV9 near the engine, for the purpose of breaking contact. A Brown296 ENGINE AND BOILER TRIALS. mercury speed-indicator served excellently well for a constant speed-indicator. The chronograph was set in operation when the indicator-cards were taken, and thus gave the exact speed of the engine at that instant. Great care must be taken to keep the instruments, and the engine as well, in good order and well lubricated throughout the series of experiments. 82. TWo Methods of Trial are available in testing steam- engines, both of which are found to be capable of giving exact results: (1) Measuring the energy supplied by the boiler in the form of heat transferred to the engine by the steam, and comparing the mechanical equivalent of this heat-energy with the quantity of mechanical energy obtained from the engine. (2) Determining the amount of energy rejected, as measured in the heat carried away by the exhaust, and similarly corrtpar- ing this with the work done. In the first case, the quotient of the useful energy gained by the total energy expended is a measure of the efficiency of the system; in the second case, the same measure is obtained by dividing the work done by the sum of that quantity and the rejected energy. Of these two systems of trial, the first is that customarily employed by engineers for many years past; the second is that comparatively recently introduced by Messrs. Farey and Donkin. Both are fully described elsewhere. The first system being adopted, the quantity of heat-energy expended is measured by determining the weight of steam pro- duced and its physical condition, and the quantity of heat brought to the boiler by the feed water. The total heat com- municated to the steam, less the heat received with the feed, is the net expenditure. It is usual to take a standard tempera- ture at o° F., 320 F., or o° C., as that to which all temperature measurements are referred. In such case, assuming the standard point on the scale to be o°, the total heat supplied by the boiler is ascertained by weighing the feed-water for a specified time, and thus determining the weight of steam, wet or dry, passing to the engine; next ascertaining what proportion of the fluid is still liquid, or what is the amount of superheating; comput- ing the heat stored in the fluid; then, finally, deducting the* METHODS OF TRIAL. 2$7 heat stored in the feed-water, both measured from o°, thus ob- taining the net quantity which comes from the fuel. The second system being employed, the quantity of rejected heat is determined by measuring that received in the condenser and wasted in other ways. The total rejected heat consists of the following parts: (i) Heat carried away by air and vapor from the hot-well and by the water of condensation, measured from o° or the standard point on the thermometer. (2) Heat received and carried away by the condensing water, the meas- urement being made between the limits of reception and re- jection of that water. (3) Heat wasted by conduction and radiation from the exterior of the heated parts of the machine. In illustration of such distribution of energy we find the fol- lowing, as deduced by Prof. Ewing,* from data supplied by Mr. Main: f Data. Steam-pressure, absolute, lbs. per sq. in............ 76 Time occupied by trial, hours........................ 6 I. H. P..........................................., . . 127.4 Feed-water, lbs. per revolution (24 per min.)|....... 1.394 Air-pump discharge, lbs. per revolution.............. 51.1 Water drained from jackets, lbs. per revolution...... 0.186 Per cent, priming.................................... 4 Temperatures: feed, injection, and discharge... 590, 50°, 73°-4 Results. Quality of steam........................................ 0.96 Quantity of steam supplied per revolution, lbs.......... 1.028 “ “ injection-water “ “ “.......... 49.9 Latent heat of steam, B. T. U........................... 898 Heat in water of boiler, “ (from 320 F.)............ 278° “ “ “ “ feed, “ ......................... 27 “ “ “ “ injection, B. T. U................... 18 “ “ “ “ discharge, “ .................... 41.4 * Encyclopaedia Britannica, 9th ed.; art. Steam-engine, f Minutes Proc. Inst. C. E., vol. Ixx.298 ENGINE AND BOILER TRIALS. Heat from boiler to engine, per revolution........... 1377 “ “ “ jackets, “ “ ........... 212 “ “ “ total B. T. U. per revolution......... 1589 “ returned to boiler, “ “ “ ..... 38 “ ^/supply “ “ “ 1551 “ converted into work “ “ “ ...... 227 “ total rejected “ “ “ 1324 The loss by conduction and radiation, externally, was about 6 per cent. The actual efficiency of the engine was £ = —- = 0.146, 1551 or not quite 15 per cent., while the thermodynamic efficiency was 0.335, more than twice as great. This latter method is known as that of Messrs. Farey and Donkin. In duty-trials of pumping-engines, the best system yet pro- posed is probably that already mentioned, which bases the efficiency determination upon the measured amount of work done by the system on a consumption of 1000000 B. T. U. supplied in the boiler-furnace, or used in the engine, as the case may be. The heat consumed should be taken to be all supplied by the fuel, or all received by the engine, including that wasted by all its accessories. The useful work should be, wherever practicable, measured by the product of weight of water pumped, as ascertained by the use of a weir, into the head against which it is pumped, as measured by a pressure-gauge, or otherwise, at the pump- delivery. Losses by leakage, lost action, etc., are thus detected. Internal friction thus properly tells against the engine; ex- ternal friction—in mains, etc.—is as properly ignored. 83. The Farey and Donkin System of trial of engines is one in which the quantity of heat supplied by the boiler and received by the engine is not directly determined, but is ascertained by observation of the quantities of heat rejected by the engine and carried away in the condensing water. ThisTHE FAREY AND DONKIN SYSTEM. 299 method only applies to condensing-engines and to those which can be temporarily converted into condensing-engines for the purposes of the test. A boiler-trial is always a troublesome and disagreeable operation, and usually involves considerable expense both in preparation and in its conduct. Where it is only the engine that is to be tried and judged, the avoidance of a boiler-trial is a decided advantage. The ability to test an engine by itself is very often an important desideratum, and especially as permitting more frequent determinations of the condition of the machine and a more complete knowledge of its action at all times. It has been seen that the heat supplied to any engine is disposed of in three directions : by conduction and radiation to surrounding objects; by conversion into mechanical work, and by rejection in the exhaust steam and the water accompanying it. Of these quantities the first is comparatively small, and is often entirely ignored as unimportant; the second ranges in good engines between, perhaps, 10 and 15 per cent., rarely exceeding the latter figure; while the last item includes, as a rule, above 85 per cent., and generally 90 per cent., of the total quantity sent over from the boilers. In the condensing-engine all this heat may be found and measured up in the water pass- ing out at the delivery-pipe from the hot-well. It is obvious that the sum of the heat-equivalent of the indicated power of the engine, plus the heat so rejected, and the small quantity added to represent losses by radiation and conduction, will be the measure of the heat-supply from the boiler. To determine this total, therefore, we have but to measure the indicated power of the engine and the heat discharged from the con- denser. The first of these processes is already understood. To secure the second measurement, it is only necessary to measure the flow of the heated water by a weir and notch, at the same time measuring its temperature by accurate ther- mometers. A high value for the quantity of heat discharged, per horse-power and per hour, indicates an inefficient engine; a low value is the proof of good economy. The apparatus employed by Messrs. Farey and Donkin con-300 ENGINE AND BOILER TRIALS. sists, Fig. 120, of a simple measuring-box, A A, of convenient size, six or eight feet long usually, three to five feet wide and two to four feet deep, fitted with a notch, D, which is com- monly about 6 inches wide. On the engraving this box is of iron, but it is perhaps oftenest of wood.* It is fitted with transverse partitions BB, while at D a thin brass or copper plate has formed in it the notch producing the tumbling-bay. The notch in end of the box is larger than the notch in the plate, so that the approach of the water may not be interfered with. The box also is so placed that the water has a clear fall of 12 or 18 inches. The water from the hot-well is delivered into the box at one end, and flows over, under, and through the partitions, as shown, so as to be thor- oughly mixed and the current steadied. The box is provided at C with a standard fixed to the bottom, having a hole in it which receives the stem on which the float e moves loosely. At the top is a scale of inches capable of being adjusted by screws, while the float carries a pointer f which moves up and down this scale with the float. Fig. i2o.—Farey and Donkin’s Apparatus. To fix the zero-point, a straight-edge a is provided, and another, b, forming an extension of the bottom edge of a; a is then placed with one end resting on the notch, while b is be- neath the gauge d, this gauge being free to move vertically in its holder; a is then adjusted until the spirit-levelcshows it to be level when the gauge d is fixed by its clamping-screw. The straight-edge and spirit-level are then removed. A scale can * London Engineering, Feb. 5, 1875.THE FAREY AND DONKIN SYSTEM. 301 now be fixed so that its zero agrees with a mark on the gauge stem. If a float is to be employed, the gauge is only used to determine the zero of the float-scale. The float having been put in place, water is admitted into the box until the surface is found just to touch the point of the point-gauge, and the scale is adjusted so that the zero-point agrees with the index of the float. The depth of water in the notch being measured by the gauge or the float, and the width of the notch being exactly known, the quantity of water flowing is at once readily com- puted by use of the standard formulas for flow, through a notch or over a weir. The temperatures of the water being taken at the same time, before the water enters and as it leaves the condenser, the product of the mean weight of water flowing per hour by the mean range of temperature measures the heat- units discharged. This quantity, divided by the mean indicator horse-power for the same period, gives the desired figures per indicator horse-power per hour, or ur__ VxDxSx(T1^Ti)t ~ I.H.P. 1 when Hr = heat-units as above ; V = volume of water flowing per hour ; D = density of water at the observed temperature ; 5 = specific heat, usually taken as unity; T = observed temperature ; /. H. P. = indicated horse-power; The quantity H' is often called the constant for the engine. Since each horse-power demands 1980000 ~ 772 = 2564.5, or 33000 772 42-75, heat-units per hour or per minute, the quantity of steam sup- plying the heat converted into work per hour is 2564.5 = w,302 ENGINE AND BOILER TRIALS. when h and t are the total heat of the steam and the tempera- ture of the condenser, ranging from 2\ to 2\ pounds, accord- ing to circumstances. The heat discharged, H\ being given, the weight’ of steam supplying it is varying from about 15 pounds upward per /. H. P., the total of both items thus measuring the demand on the boiler, amounting to w + w' = 17 or more pounds per horse-power and per hour in good engines. If the boiler “ foams” or “ primes,” this ex- penditure of feed-water is correspondingly increased. This relation being established, any variation in it or in the “ con- stant” for the engine, as shown at the “ tumbling-bay” or weir- notch, indicates some change in the working of the engine, and will call for attention. Mr. Donkin gives the following table for use in making trials by the Farey and Donkin method : WEIGHT OF WATER THAT WILL FLOW OVER A TUMBLING-BAY SIX INCHES WIDE. Inches over Bay. Pounds of Water per Minute. Inches over Bay. Pounds of Water per Minute. Inches over Bay. Pounds of Water per Minute. Inches over Bay. Pounds of Water per Minute. if 274 2f 547 3i 874 4i 1250 1A 292 2rs‘ 568 3tV 900 4A 1279 if 310 2f 589 3t 926 4i 1306 iH 327 2* 612 3tV 951 4 h 1336 if 345 2f 634 3i 977 4f 1365 ill 365 657 3t96 1003 4A 1394 if 383 2f 680 3i 1030 4i 1424 iff 402 2ff 704 3tt 1056 4A 1454 2 421 2f 727 3f 1083 4f 1483 2TV 442 2ff 751 3ff 1112 4if 1514 462 3 775 3f 1139 44 1544 2* 483 3tV 800 3 if 1166 4if 1575 2* 503 3f 825 4 1193 4f 1605 2* 525 3 A 850 4tV 1221 4if 1635 N.B.—10 pounds of water is taken equal to one gallon.TRIALS OF GAS-ENGINES. 303 84. Trials of Gas-Engines usually involve the determina- tion not only of the indicated and dynamometric power, and the quantity of gas consumed as working fluid and in ignition, but also, if satisfactorily complete, the extent and the method of the several wastes, as by the water-jacket, by conduction and radiation within the working cylinder, and by the exhaust-pipe. The volume of water flowing through the jacket and its varia- tion of temperature readily determine the waste by the jacket, but the measurement of the loss at the exhaust is less easy. This involves the measurement of the volume and density of the gases entering and leaving the engine, and their alteration of temperature. It has been found that, to determine this quantity of fluid, it is necessary to use a meter on both the air and the gas entering the working cylinder of the engine. It is not certain, in any case, that the total volume can be ascer- tained by the measurement of the cylinder ; although, in ordi- nary work, it maybe so taken with a fair degree of approxima- tion to accuracy. The quality of the gas should also be careful- ly ascertained by analysis. A good engine, using good gas, in sizes exceeding ten actual horse-power, should not consume ^above 20 cubic feet (566 litres) per indicated horse-power per hour, or 30 feet (850 litres) per dynamometric H. P.; but illu- minating gas often may give a result less satisfactory by ten per cent, or more. Many gas-engines of less perfect construc- tion demand double this quantity and upward. A cubic foot of good gas should supply about 620 B. T. U. of heat; a cubic metre should yield about 56O0 calories. The theoretical mixture will be usually found to be not far from seven vol- umes of air to one of gas; but it is better to use a slight excess of air. As has been already seen, the complete indicator-card is, in the compression type of engine, only obtained after four revo- lutions, and the observer should be careful to see that he has the diagram of the complete cycle before removing the pencil from the paper. The data are complete when they permit the computer to show precisely how much gas, how much heat, and how much304 ENGINE AND BOILER TRIALS. energy are supplied to the engine ; how much is applied useful- ly ; how much is wasted and what are the measures in detail of all wastes ; securing results in such manner, that it is made pos- sible to construct an account that shall exactly or approximate- ly exhibit on its balance-sheet all receipts and expenditures, and an exact balance. 85. Simple and Binary Vapor-engine Trials involve no peculiar methods or operations. In these, as in all other cases, the problem of the engineer is the determination of the heat- energy developed and applied in the engine and of the nature and magnitudes of all wastes. In vapor-engines, as in the am- monia or the naphtha-vapor engine, the only differences in its working, when compared with the steam-engine, are due to pecu- liarities of physical properties, and involve no essential modifica- tion of the method of heat or power measurement. The pur- pose of the trial is commonly to obtain a comparison of effici- ency with that obtainable under similar circumstances, with a steam-engine of equally good design and construction, or of standard make and operating in the customary manner. A common practice, on the part of promoters of new schemes in this direction, is to exhibit a comparison with a comparatively wasteful and badly constructed steam-engine. The engineer making such trials should be especially careful in this matter. The Binary Vapor-engine is commonly a complex machine, • composed of a steam-engine and a simple vapor-engine utiliz- ing the heat of the rejected steam. This combination is tested with the steam-engine of fairly comparable design and construc- tion. As a rule, the comparison lies between the combined motor and a condensing steam-engine. The trial determines the efficiency of the steam-engine and the vapor-engine, separate- ly and combined, and should give complete data relating to quan- tities of heat transferred and transformed, of fuel, and of fluids employed, and of work, useful and lost, as well as of the power developed by each. When testing other vapors than steam, it is often important that their essential chemical and physical characteristics should be redetermined for the occasion ; as they sometimes vary somewhat, as in the case of the petroleumGAS AND VAPOR ENGINE TRIALS. 305 vapors, and they may differ from the recorded data of the treatises taken as authority. 86. Gas and Vapor Engine Trials may thus demand spe- cial treatment in some cases. The specific heats of gas-mixtures may require to be determined ; the specific heats of vapors may be undetermined, or their recorded values may be inaccessible. In such cases it may become the duty of the engineer to as- certain their values by computation or by direct experiment. For example : In a trial of a gas-engine by Messrs. Brooks and Steward it was necessary, in order to determine the quan- tity of heat stored and wasted in the exhaust gases, to deter- mine the specific heat of the mixture of steam, carbon dioxide, and nitrogen thus: * The analysis of the gas used in the tests IS By volume. H Hydrogen, • -395 CH4 Marsh-gas, ....... • -373 N Nitrogen CSH,, etc Heavy hydrocarbons, . . . . .066 CO Carbonic oxide, • -P43 O Oxygen, H,0,, CO,, H,S, etc., Water-vapor, impurities, etc., . .027 By weight its composition is found to be— Cu. Densi- Kilos per W’t p. meters. ties, t cu. m. unit. H •395 X .087 = •035 .058 CH *373 X .694 = .258 .426 N X 1.215 = .099 .I63 C3He, etc X I.84 = .121 .200 CO •043 X I-2I5 = .052 .086 0 X 1.388 = .019 .031 H,0,, etc. ...... X ^.8 = ■ .022 .036 I.OOO X .606 = ~6o6 1,000 * Van Nostrand’s Magazine, 1883. f Schdttler: Die Gasmaschine, p. 77.306 ENGINE AND BOILER TRIALS. By “ density” is meant the weight of one cubic meter in kilogrammes. One cubic meter of the gas in question weighs O.606 kilos. Upon complete combustion the gas develops heat per cubic meter as follows: Calories.* Calories. From H............................29060 x .035 = 1020 “ CH4........................11710 x .258 = 3020 “ CsH#,etc.......................11000 x .121 = 1330 “ CO............................ 2400 x .052 = 125 per cu. m. 5495 and per kilog. gas = 9070 calories. In British measures, one cubic foot of gas develops 617.5 heat-units. To determine the amount of air supplied for complete com- bustion, it is necessary to ascertain the quantity of oxygen in chemical combination with the combustible constituents of the gas. by volume 2H + 0 2 + I = HaO — 2 by weight 2+l6 = 18 ch4 + 40 = CO, + 2H,0 by volume 2+4 = 2 + 4 by weight 16 -f- 64 = 44 + 36 C,H6 + 90 = 3CO, + 3H,0 by volume 2+9 = 6 + 6 by weight 42 + 144 = 132 + 54 by volume CO + 0 2 + I =.co, : - 2 by weight 28 + 16 = 44 The combining proportions are— By volume iH + *0 = iHaO iCH4 +20 = iC02 + 2H20 iC3H6 + 4iO = 3C02 +3H20 iCO + *0 = iCOa * SchfJttler : Die Gasmaschine, p. 80.GAS AND VAPOR ENGINE TRIALS. 30 7 By weight— iH + 80 = 9H,0 iCH4 +40 = Jj^CO, + \ HaO iC,H,+^0 = ^CO, + *H,0 1 CO + 7O = JfCO, The volume of oxygen required for the combustion of I volume of gas is— H .395 X i = .197 CH4 .373 x 2 = .746 CaH, .066 x 4i = -297 CO .043 x i — .022 1.262 Less O in gas .014 . . . .014 1.248 Taking oxygen as 21 per cent, in atmospheric air, the vol- ume of air needed is 1.248 .21 5.94 per volume gas. Since air weighs 1.251 kilos per cu. meter, the ratio by weight is 5.94 X 1.251 1 X .606 12.26 air to gas 1. From the combustion of 1 unit weight of gas with 12.26 air, there results 13.26 units weight of a mixture the composition of which will be— ((CH4) .426 x V"= T.171 CO, \ (CsHe) .200 X -\2- = .629 ( (CO) .086 X V" = •135 j (H) .058 X 9 = .522 H,0 ■{ (CH,) .426 x | = .958 ((Q.H.) .200 x * = .257 N ( from the air, . . 9.407 (in gas itself, . . .163 Impurities in gas, i-93 1.74 6.5 7 0.03 13.273°8 ENGINE AND BOILER TRIALS. Per unit weight of mixture the composition will be— COa.........................146 HaO................... . .131 N...........................721 Impurities,.................002 1.000 The volume which 13.27 kilos of products of combustion will occupy is found from the known volumes of the constitu- ent gases as follows: Cu. m. Kilos. per kilo. Cu. m. COa . . . 1.93 X .524 = I.OII HaO . . . 1.74 X 1.28 = 2227 N . . . . 9.57 x .823 = 7.876 Impurities, . .03 x ~-9 = .027 11.141 The products of combustion occupy 11.141 cu. m. to each kilog. of gas. To find the ratio per cu. meter of gas, we have simply to multiply by 0.606, the number of kilos in a cubic meter, and get 6.751. As 6.94 cu. m. of air and gas are.needed to every cu. m. gas, by a contraction of 2.7 per cent, combustion takes place. The specific heats of the products of combustion are deter- mined from the specific heats of the several component gases as follows : Specific heat at constant pressure (water = 1) : t .2169 X .146 (C02) = .0317 .4805 X .131 (H„0) = .0629 .2438 X .721 (N) = .1758 ~ .4 X .002 (impurities) = .0008 Specific heat at constant volume (water = 1): 0.2712. Cv = .1714 X .146 (C02) = .0250 " .3694 X .131 (HaO) = .0484 .1727 X .721 (N) = .1245 ~.3 X .002 (impurities) = .0006 0.1985.SCHEME OF THE TRIAL. 399 The ratio of these specific heats is the exponent of adia- batic expansion, and is found to be _ £*_ 0.2712 r ~ Cv~ 0.1985 1.366. Since there is always an excess of air present, these, values will be somewhat modified by that fact. From the meter records the ratio of air to gas by volume was found to be 6.63 to 1 ; by weight the ratio is 6.63 X 1.251 1 X .606 13.68. Since for complete combustion only 12.26 parts of air by weight are needed, there are 1.42 parts in excess. The specific heats of air being* Cp = .2375 and Cv = .1684, the effect of the excess of air will be to reduce the specific heat slightly. _ {.2712 x 13-26) + (.2375 X 1.42) _ ~ . c* - 14.68 “ -268 ’ (.1985 x 13-26) +(.1684 X 1.42) C' =------------14)68-------------= -I96 y Cp _ .268 Cv ~ .196 = I*37« 87. The Scheme of the Trial should be carefully pre- pared in advance, and should be so planned as to secure the needed data with certainty and accuracy. The first considera- tion is the purpose of the proposed trial, and the first work done the arrangement of a general plan that shall enable the observers to collect with accuracy and certainty all the needed data, and to record them conveniently and in most available form. The next matter to be studied is the reduction of all general and special operations of the trial to a complete and efficient system, in which every part shall be made as far as possible contributory to the efficiency and fruitfulness of every3io ENGINE AND BOILER TRIALS. other part; in which each observer shall be so stationed and so instructed that he may secure the data assigned him for collec- tion with least difficulty, risk, and uncertainty, and shall have his own work checked, and shall aid in checking the work of others, as completely as possible. No essential data should remain unchecked, and every subsequent calculation based upon them should also be made by at least two computers in- dependently. The plan of the work being settled upon, each detail should be studied by itself, and every provision that experience and foresight can suggest should be taken to insure perfection of the scheme. A preliminary and informal trial will then be likely to reveal any serious defect, which being corrected* the final and official trial may be fully expected to give thoroughly reliable results. 88. Competitive Trials of Engines are sometimes con- ducted by the engineer, either to determine which of two or more competing forms of engine is to be accepted by the pur- chaser, or by his client, or, as at exhibitions of various kinds, simply to ascertain the power and efficiency of two or more engines, with a view to deciding their relative merits as types of engine, or as representing the best practice of their builders. It is largely through this kind of competition that the best known systems of standard engine-trial have been developed. Examples of such are illustrated by the following regulations, adopted at the exhibitions of the Franklin Institute of the State of Pennsylvania: NOTICE:—Exhibitors of engines, desiring quantitative tests made of their exhibits, must make formal application for such tests in advance. Engines can be exhibited, but will not be tested unless formal application and agreement to the following code are completed within the specified time. Parties desiring tests made of their engines can have them made by making formal application therefor, and by subscrib- ing to and fulfilling the conditions of the Code.COMPETITIVE TRIALS OF ENGINES. 5II All tests will be quantitative, and will, once begun, not be abridged, save by special agreement with the judges. Tests of regularity of speed, however, will be made inde- pendently of other measurements. The Committee reserves the right to limit the number of engines tested and to elect which engines shall be tested, if time will not permit complete tests for all making formal application. Competitive tests will not be made, save on the joint ap- plication of the two or more parties desiring them, who must, previous to the tests, agree on the rating of the various points of the engine (see Article 9), and subscribe to the Code, agree- ing to abide by the decision of the judges without appeal. Conditions of Exhibition and Test. (1) The cylinders of the engines entered may be of any capacity and proportion of stroke to diameter. (2) Each cylinder shall be drilled and tapped by the builder, for indicator connections, by means of one-half (£) inch pipe in the usual manner, and to the satisfaction of the judges. Pet drainage-cocks must be on the cylinder. The cross-head or some other point must be drilled for the indicator-cord attach- ment. (3) Each cylinder shall be drilled and plugged at both ends so as to admit of being completely filled with water and emptied by means of a one-half (£) inch pipe, in order to determine the clearance and the piston-displacement of one stroke at each end. These data will be obtained both hot and cold. (4) The steam and exhaust valves will be tested under full steam-pressure, ninety (90) pounds per square inch by the gauge, unless some other pressure has been agreed upon for the test. (5) The tightness of the piston-packing will be determined by removing the back cylinder-head and subjecting the piston to full boiler-pressure on each centre. (6) Each maker is , requested to use such diameter of band312 ENGINE AND BOILER TRIALS. fly-wheel or of pulley as shall give a belt-speed of 4000 feet per minute. Should he require a different belt-speed, he will specially note the same, in communicating with the Committee. . (7) Each exhibitor will be required to furnish his own con- nections with the main steam-pipe, the main injection-pipe, and the main overflow pipe or tanks. (8) Each exhibitor will be furnished with space at the regular rates established for the exhibition, in which space he must build his foundations at his own cost, and subject to the approval of the Superintendent. (9) Each exhibitor will communicate to the chairman of the Committee such a description and drawings of the engine ex- hibited as will facilitate the labors of that Committee, together with his claims as to meritorious points for his exhibit. The following points will have special consideration : * 1. Economy of steam. 5. Simplicity of design. 2. Regularity of speed. 6. Perfection of proportions. 3. Concentration of power. 7. Finish of parts. 4. Durability of construction. Each exhibitor must file the following data, before the tests, viz.: Diameter of steam-cylinder to nearest hundredth of an inch. Diameter of piston-rod “ “ “ Diameter of steam-pipe “ “ “ Diameter of exhaust-pipe “ “ “ Diameter of fly-wheel “ u “ Width of the face of fly-wheel “ " “ Weight of fly-wheel in pounds “ “ “ Area of steam-ports, each to nearest hundredth of an inch. Area of exhaust-ports, “ “ “ “ Stroke of engine, “ “ “ “ Indicated horse-power of engine when believed to be working most economically. Revolutions of crank per minute. Weight of whole engine, exclusive only of fly-wheel. * These are the points referred to in the special notice concerning the value of which agreement must be had previous to the competitive tests.COMPETITIVE TRIALS OF ENGINES. 313 When a condenser is used and its air-pump driven by the engine, the following additional data will be required, viz.: Diameter of air-pumps to nearest one-hundredth of an inch, Diameter of injection-pipe “ “ “ Diameter of overflow-pipe “ “ “ Stroke of air-pump piston “ “ “ And if an independent condenser is used, i.e., not driven by the engine, give Diameter of injection-pipe to nearest one-hundredth of an inch, Diameter of overflow-pipe “ “ “ “ Drawings of condenser used, any other data peculiar to it, and a full description. Preparations for the Tests. (10) The steam for the tests will be furnished by the ex- hibition-boilers, and will come from boilers specially set apart for the purpose of the tests. It will be charged for at regular rates of three (3) cents per indicated horse-power per hour. Steam will be furnished to exhibitors one week before the tests are made, if desired. No charge will be made for the services of attendants or experts, or the use of apparatus, unless in some extraordinary case, when the cost will be fixed by the superintendent. (11) The steam-pressure used will be subject to the wish of the exhibitor, but shall not exceed ninety (90) pounds per square inch, by the gauge. A special standard gauge will be used during the tests, and subjected to careful tests before and after use. (12) The safety-valve will be set to blow off at ten (10) pounds above the pressure fixed upon. (13) The thermal value, the temperature, and the pressure will be taken by means of scale-calorimeters, thermometers, and standard gauges at the boiler, at the steam-chest, and at the exhaust, if the engine is non-condensing. The thermometers, calorimeters, etc., will be furnished by the exhibition, but the exhibitor must do such mechanical work, must furnish such piping, tools and materials, as are neces-3H ENGINE AND BOILER TRIALS. sary to make the required attachments, at his own cost, and subject to the orders of the Committee. (14) The temperatures of injection and of hot-well will be taken with standard thermometers, in the case of condensing- engines. (15) The water used will be taken from the city mains. The feed-water for the boilers will be weighed by means of scales and a large tank, and will be run into a smaller sup- plemental tank, from which it will be pumped into the test- boilers by means of a feed-pump actuated by steam from other boilers. The condensing water used will, in the case of condensing- engines, be measured after leaving, the hot-well, in two care- fully gauged tanks, alternately filled and emptied, the tempera- ture also being taken. The known weight of steam used will be subtracted from the overflow. The injection-water will be weighed in large tanks, and its temperature taken. The injection-water will not be delivered under pressure. (16) The number of revolutions of the engines will be taken by a continuous counter attached to the crank-shaft. The variations in speed for one minute will betaken at each quarter of an hour by means of an electric chronograph, con- nected with a standard clock, beating seconds. The variations in speed during one stroke will be taken by an acoustic chronograph at fifteen minutes' intervals. Special tests of speed alone, under varying loads, will be made if desired, and close attention will be had to this point in all cases. (17) A standard barometer and thermometer will be read at fifteen-minute intervals during the trial. (18) The vacuum of condensing-engines will be read by a gauge, carefully compared before and after the trials. (19) All of the gauges, indicators, and thermometers used shall be carefully tested before and after the trials, and theCOMPETITIVE TRIALS OF ENGINES. 315 party whose engine is tested shall have the right to be present in person or by agent at these tests. (20) The indicator-diagrams will be taken at fifteen (15) minute intervals, and will be read for— Initial pressure, Pressure at cut-off, Terminal pressure, Counter-pressure at mid-stroke, Maximum compression-pressure, Mean effective pressure, Point of cut-off, Release of steam, Exhaust closure. From the diagrams will be computed the indicated steam at the point of cut-off and at release, as also the actual steam from boilers per horse-power per hour. (21) The Committee will test the engine at the load desired by the exhibitor of it, unless circumstances shall render it impossible to meet his wishes. If the load does not exceed seventy-five (75) indicated horse-power, the net load will be measured by a transmitting dynamometer. (22) At the close of the regular trial the engine will have its belt taken off, and be run for one hour for friction-diagrams. (23) Unless otherwise arranged, the trials will last ten (10) hours. (24) No account will be taken of the coal burned, but the economy of the engine will be deduced from the actual steam used and water weighed to the boiler. The trial will begin with the established pressure. The level of the water in the boiler and the pressure of the steam will be kept as nearly constant as possible during the wrhole of the trial. The whole weight of the water fed to the boiler, subject to proper deductions for waste, and to corrections for variation of level in the boiler, will be multiplied by its thermal value as steam at the steam-chest, and divided by the product of theENGINE AND BOILER TRIALS,. 316 indicated horse-power of the engine, and the number of hours of the test. The resulting quotient will be used to divide twenty-five hundred and fifty-seven and sixty-nine one-hundredths (2557.69) British thermal units, * giving the efficiency of the engine as compared with the mechanical equivalent of the heat furnished to it, and therefore its efficiency, as a means of converting heat into work. The net horse-power of the engine will be used for compu- tation similarly to the indicated horse-power, and the result will be taken as the measure of the efficiency of the engine, both as a means of converting heat into work, and as a machine for the transmission of power. This latter shall be considered the true measure of the efficiency of the engine. 89. Regulations for Competitive Boiler-trials are illus- trated by the following, adopted at the same time as the pre- ceding : NOTICE.—Boilers may be exhibited and used at the Exhi- bition, but quantitative tests of their efficiency will not be made except upon formal application, and the acceptance of the subjoined code. Competitive tests will not be made unless at the joint re- quest of the parties desiring them and until such parties have agreed to and subscribed to this code, and fixed upon a rating for the points enumerated in Article 4. The Committee reserve the right to limit the number of tests made, should time and opportunity not permit the com- pletion of all the tests desired. Preliminaries to the Tests. (1) Capacity.—The boilers entered may be of any capacity having an evaporative power not less than seven hundred and fifty (750) pounds of water per hour. Each boiler must be so drilled and fitted with proper pipes and cocks that the judges may be enabled to determine readily * Joule’s Equivalent is here taken as 774.1 foot-pounds.COM PE TITIVE BOILER- TRIALS. 317 its whole water capacity by filling and emptying the boiler and weighing the contents. (2) Pipes and Valves.—Each exhibitor will furnish all the pipes and valves necessary to’ make connection with the main water and steam pipes in a proper manner, and subject to the orders of the Superintendent. He will also make any alterations in water and steam pipes required for the tests, furnishing all tools, piping, cocks, and mechanical labor at his own cost. (3) Space.—Each exhibitor will be furnished with space at the regular rates established for the Exhibition, in which space he must build his foundations and boiler-setting, and make connection with the chimney-flue, if required, at his own cost, and subject to the approval of the Superintendent. (4) Specifications.—Each exhibitor must furnish to the Chair- man of the Committee such description and drawing both of the boiler in position and of the details of the boiler as will facilitate the labor of that Committee, together with his claims as to the meritorious points of his exhibit. The following points will have special consideration : 1. Economy of fuel; 2. Economy of material and labor of construction ; 3. Evaporative power; space occupied ; 4. Simplicity and accessibility of parts; 5. Durability of whole structure. Exhibitors desiring a competitive test made must agree upon a rating for these points before it will be made. Exhibitors must also file the following data: Area of heating-surface to the nearest hundredth of a foot; area of grate-surface to the nearest hundredth of a foot; area of calorimeter-surface to the nearest hundredth of a foot: area of chimney-flue surface to the nearest hundredth of a foot; height of chimney desired; number of pounds of coal per square foot of grate to be burned per hour. Should the determinations of these preliminaries by the Committee differ in result from those of the exhibitor, he will be required to give all the details of his calculations, and an agreement must be reached before proceeding with the test.318 ENGINE AND BOILER TRIALS. Preparations for the Tests. (5) Coal.—Anthracite coal will be used and will be furnished free of charge, provided the steam made is used for the gen- eral purposes of the Exhibition. The same quality and size of coal will be used in all the tests, unless special arrangements be made for another kind of fuel. An analysis will be made of the coal used. The coal will be weighed to the boiler. (6) Water.—The water used will be taken from the city mains. The feed-water for the boilers will be weighed by means of scales and a large tank, and will be run into a smaller sup- plemental tank, from which it will be pumped into the boiler by means of a feed-pump actuated by steam from the boilers. The temperature of the feed-water will be taken by means of a standard thermometer in the supplemental tank. (7) Pressure.—The steam-pressure used shall not exceed ninety (90) pounds per square inch by the gauge, unless by special arrangement with the Committee. A standard gauge will be used, and also a standard ther- mometer immersed in a mercury-pocket in the steam-space. (8) Safety-valve.—The safety-valve will be set to blow off at ten (10) pounds above the pressure fixed upon. (9) Leaks.—Within twenty-four (24) hours preceding the test of the boiler it must be subjected to hydraulic pressure ten (10) pounds greater than its steam-pressure during the test, and proved to be perfectly tight. (10) Attendants.—The attendants in charge of the boiler tested must be approved by the party whose boiler is tested and by the judges. All attendants are to be subject to the orders of the judges during the progress of the test. (n) Ashes— All ashes will be weighed on being withdrawn from the ash-pit, and must not be damped until weighed. (12) Calorimeters.—The calorimeters used will consist of a barrel, scale, and hand thermometer.COMPETITIVE BOILER-TRIALS. 319 Two calorimeters will be used and simultaneous observa- tions made at fifteen (15) minute intervals. (13) Fires.—The exhibitor shall be allowed one day previous to the test to clean boilers and grates. The steam having reached the required pressure, the ash- pit shall be thoroughly cleaned and swept, and thereafter the fire maintained as nearly uniform as possible, the test closing with the same depth and intensity of fire as it opened. This point is to be decided by the judges, who may make allowances if it be clearly shown to have been impossible to maintain uniform fires. If in the judgment of the Committee the firing is ineffi- ciently or improperly done, the test may be terminated at any time, and a repetition of the test granted or refused. (14) Pyrometer.—The temperature of the gases of combus- tion immediately upon entering the chimney-flue shall be taken by means of a suitable pyrometer, read at fifteen (15) minute intervals, and close to the boiler. (15) Manometer, Barometer.—The vacuum in the chimney- flue shall be taken by means of a water-manometer, read at fifteen (15) minute intervals, if natural draught is used. If a forced blast is used the manometer will be placed on the conduit to the ash-pit. A barometer will be read simultaneously. (16) Duration.—Unless otherwise arranged, the tests will last ten (10) hours. (17) Economy and Efficiency of the Boiler.—The level of the water in the boiler and the state of the fire must be kept as nearly constant as possible during the whole of the trial. The weight of the water in the boiler for each one-quarter of an inch, on the glass water-gauge, will be carefully deter- mined and recorded previous to the test, and proper correction for unavoidable changes of level made. The weight of water fed to the boiler, subject to proper cor- rections, will be multiplied by its observed thermal value as -steam.320 ENGINE AND BOILER TRIALS. From this product thermal units of heat brought in by the feed will be subtracted. The remainder will be divided by nine hundred and sixty- five and seven-tenths (965.7) British thermal units* giving the number of pounds of water evaporated from and at 212 degrees Fahrenheit. This latter quantity will be divided by the weight of coal burned, less weight of dry ashes, giving the number of pounds of water evaporated per pound of combustible. This shall be taken as the measure of the efficiency of the boiler. (18) Nominal Horse-power.—The nominal horse-power of the boiler will be deduced by dividing the number of pounds of water evaporated from and at 212 degrees Fahrenheit per hour by 30. (19) Evaporative Power.—The evaporative power of the boiler will be determined by dividing the nominal horse-power of the boiler by the number of cubic feet of space it occupies. The space occupied by a boiler and its appurtenances will be regarded as the product of the square feet of floor-space occupied by its extreme height in feet. Steam-pump tests have been conducted at such exhibi- tions under the following regulations, written, originally, by Mr. Hill: Regulations for Test of Steam Pumps. (1) Steam will be furnished by the boilers used in the exper- iments upon automatic and slide-valve engines; the pressure will be taken in the pipe as near the stop-valve as convenient. The pressure in the boilers will be maintained as uniformly as possible at (75) seventy-five pounds per sq. inch above atmos- phere. (2) A calorimeter test of the quality of steam furnished will be made regularly every thirty (30) minutes. The steam-pipe will be tapped in the last horizontal joint toward the pumps for calorimeter connection. * The value taken here for the latent heat of steam at the boiling-point.STEAM-PUMP TESTS. 321 (3) The exhaust will be delivered to a surface-condenser having not less than 500 sq. feet of condensing surface; the condensing water will be obtained from the city mains; water of condensation will be collected in a tank placed under the outlet nozzle of condenser. (4) The suction tank will be placed below the level of pump; the distance from bottom of tank to centre of water-cylinder will be uniform. For all contestants the vertical head of water in suction-tank will be taken with a sliding-hook gauge, at regular intervals. (5) The delivery-tank will be placed on a staging directly over the water-cylinder of pump, the discharge opening of water- cylinder will be connected with a 6-inch vertical stand-pipe furnished with a direct-weighted safety-valve ; the height of stand-pipe from centre of water-cylinder to centre of orifice of safety-valve will be 10 feet. The safety-valve will be loaded to create a resistance per sq. inch equivalent to a dynamic head of 150 feet less the height of stand-pipe (10) feet. (6) The measuring-tank will be placed (vertically) between section-tank and delivery-tank; the measuring-tank will be divided by a vertical partition in the centre into two compart- ments. Each compartment will have a capacity of 300 cubic feet; the water will be delivered from the receiving-tank into the measuring-tank through a (6) six-inch swinging nozzle. The nozzle will be directed over one tank until it has been filled and the water breaks over the dividing partition, when it will be swung over the empty tank; in the mean time the tem- perature of the water in the full tank will be noted, the number of tank entered in the log, and the contents drawn off through an (8) eight-inch delivery-pipe into the suction-tank below; this operation will be repeated regularly during the run. The precise capacity of each compartment of the receiving-tank will be determined prior to the experiments by filling each to the crest of partition, and drawing off, weighing, and noting the temperature of contents. (7) The duration of run will be fixed at (5) five hours. Previous to the commencement of run, the steam will be turned322 ENGINE AND BOILER TRIALS. on and the pump will be operated until all parts have acquired the working temperature. (8) The pressure of atmosphere will be taken from a United States standard mercurial barometer. (9) Thermometers will be located as follows: No. 1 in barometer case to note the temperature of atmosphere. Nos. 2 and 3 in the two compartments of measuring-tank. No. 4 in calorimeter. (10) The time of commencement and close of run and periods of observation will be taken from a chronometer clock placed near the pump under experiment; the periods of obser- vation will be indicated by a double stroke of the signal-gong; one minute previous to each observation a single stroke of the gong will be made calling the assistants to their stations. Every (15) fifteen minutes a full set of observations will be made and entered in the log. (11) A revolution counter will be connected to standard on piston-rod. * (12) Previous to experiments, each exhibitor will hand to the Board of Experts a complete schedule of dimensions of steam and water cylinder, internal diameter of steam and ex- haust pipes, area of steam-ports, internal diameter of suction and delivery-pipes and volume of clearance in steam-cylinder. (13) The economy will be determined by the water of con- densation collected in the tank under condenser, corrected by the average of result obtained from calorimeter observations; and the cost of the work in coal (Pittsburgh No. 1) at this upon assumed boiler efficiency of (9) nine pounds water evap- orated per pound of coal burned on the grates. (14) The duty will be stated in gallons lifted one foot high. 90. Standard Systems of Boiler-trial have been already discussed and described at such length that it is unnecessary to add anything more here than to remark that, in every case of real importance, the careful and skilful management of the boiler-trial as a part of the whole work, in the measurement of the efficiency of the system of heat-production and utilization, becomes an essential element of success. The best standardSPECIAL METHODS OF ENGINE-TEST. 323 methods, as a whole and in every detail, should be adopted. Unless the measurement of the quantity and quality of the steam supplied be accurately made, it is quite impossible to obtain a correct measure of the efficiency of the apparatus in which it is utilized by conversion into work and power. 91. The Heat-energy, the Quantity and Quality of Steam used, and the availability of the heat stored in that steam and transferred to the engine with it, can only be exactly known when the weight, the wetness or dryness, the pressure, and the thermal properties of the steam are precisely ascer- tained. The weight of feed-water pumped into the boiler is the weight of the mixture of steam and water, if any water is entrained by the steam, which is sent to the engine. The heat so supplied, diminished by the usually simple waste from the exterior of the steam-pipe, is the amount received by that machine. The availability of that heat for its purpose depends upon the degree in which the temperature and the pressure of the steam exceed the temperature and pressure of the atmos- phere or of the condenser. The first point to be attended to is the testing of the steam to ascertain whether it be wet, dry and saturated, or super- heated ; and if not dry and saturated, to what extent it stores an excess per unit of weight by superheating, or a deficiency of heat iit consequence of its admixture with water. This is determined by the use of the calorimeter. Smoke-preventing apparatus is sometimes attached to boilers, and it becomes important to determine the quality of the products of combustion in this respect. This usually in- volves a boiler-trial and a comparison with ordinary furnaces. It will often be found that the prevention of smoke involves an excessive air-supply and a consequent waste of fuel and loss of efficiency. This may be partly compensated, however, by the improved performance of the boiler, due to cleaner and more effective heating-surfaces and the absence of soot deposits. 92. Special Methods of Engine-test are sometimes adopted in competitive trials of special forms, as illustrated by the following regulations prepared by Messrs. Hill and Holmes.324 ENGINE AND BOILER TRIALS. Code of Regulations for Tests of Automatic Cut-off Engines. (1) Steam will be obtained from a pair of locomotive fire- box boilers, furnished by the Commissioners, These boilers have a combined evaporative capacity of 2250 pounds of water per hour ; a heating-surface (combined) of 983 square feet; and a grate-surface of 12.7 square feet. Each boiler will be provided with a safety-valve, loaded to blow off at 85 pounds pressure above the atmosphere. Each boiler will have attached, independently, an accurate test-gauge, and if it can be pro- cured, an Edson recording-gauge. The height of the water will be indicated by a glass water-gauge on each boiler, in ad- dition to the usual test-cocks. (2) The feed-water will be weighed in the receiving-tank, and drawn off as occasion requires into the supplemental tank. The water will be supplied to the boilers by an independent steam-pump, having the suction connected with the supple- mental tank, and the discharge with check-valves of boilers. The steam to drive the boiler-feeders will be obtained from boilers independent of those furnishing steam for the engine under experiment. The water fed into the boilers will be de- termined in weight whilst in the receiving-tank. The receiving- tank will have a capacity of 2300 pounds water, at 175* Fahr.; the supplemental tank will have a capacity of 1000 pounds water at 150° Fahr. (3) The resistance will be obtained by a 100 horse-power blower, having a sliding iron gate fitted to its discharge orifice. The position of the gate having been determined, it will be fastened at this point during the experiment. (4) A pair of indicators will be attached to the cylinder of engine, one at each end. The indicators will be moved in such a manner that the diagrams shall be coincident with the motion of the piston. .(5) Two engine-counters will be employed, one to indicate the revolutions of the main shaft of engine, and one to deter- mine the revolutions of the jack-shaft.SPECIAL METHODS OF ENGINE-TEST. 325 (6) The dynamometer (transmitting) will be keyed to jack- shaft, between the pulley receiving the belt from the engine, and the pulley carrying the blower belt. (7) A steam-gauge will be screwed into the steam-pipe as near the stop-valve as convenient. (8) The pressure in the chest will be determined by a chem- ical thermometer immersed in a cup of mercury, screwed into the steam-space of the chest. A test-gauge will also be screwed into the steam-chest to determine the effect of part closure. (9) The temperature of the feed-water will be taken on a mercurial thermometer located in the supplemental tank. (10) The temperature of the cylinder clothing will be taken on a thermometer with the bulb in contact with the outer cov- ering of the cylinder. (11) The pressure of the atmosphere will be taken with TJ. S. standard mercurial barometer ; the temperature of atmos- phere will be read on the thermometer in barometer case. (12) The time will be determined by a chronometer clock placed near the engine under experiment. (13) The time of noting observations will be indicated by a double stroke of the signal-gong ; one minute previous to each observation a single stroke of the gong will be made, calling the assistants to their stations. (14) Previous to experiments, all pipe connections with the boilers will be carefully closed, leaving open only the steam- pipe connecting with engine, and feed-pipe connecting with the pumps. (15) Each exhibitor will hand to the Board of Experts, previous to the experiments, a complete summary of the dimensions of his engine, including the volume of clearance, steam and exhaust port area, and weight of reciprocating parts. (16) The duration of experiments will be fixed at eight hours. Previous to the beginning of experiments, the boilers will be steamed up to the running pressure, and the height of water brought to the thread tied around the middle of the glass tubes in the water-gauges. All water supplied to the boilers326 ENGINE AND BOILER TRIALS, thereafter will be weighed and charged to the engine. The height of water at close of experiment will be made to coincide with the thread on the glass tubes. (17) Every fifteen minutes a full set of observations will be made and entered in the log. (18) During the economy test, the engine will be run with full opening of stop-valve. (19) The economy of the engine will be determined upon the consumption of water per I. H. P. per hour, and the cost of the power (in coal) one-ninth this upon an assumed evapo- rative efficiency of boilers of nine pounds of water per pound of coal. Code of Regulations for Tests of Slide-valve Engines. (1) Steam will be supplied from the boilers used in the test of automatic engines. The general dimensions are stated in paragraph 1 of the Code of Regulations for Experiments upon Cut-off Engines. (2) The economy will be determined upon the consump- tion of water per I. H. P. per hour. The water will be de- livered from the exhaust-heater into the receiving-tank, where it will be weighed and entered in the log of the engine under experiment. The water will be drawn from the receiving-tank into the supplemental tank connected with the suction of the pumps feeding the boilers. The steam to drive the boiler- feeders will be obtained from boilers independent of those fur- nishing steam for the engine under experiment. The receiv- ing and supplemental tanks will be the same as used in the cut-off experiments. The dimensions are enumerated in para- graph 2 of the Regulations for the Test of Cut-off Engines. (3) A calorimeter-test of the quality of steam furnished will be made regularly every 30 minutes. (4) The power will be absorbed by a 100 H. P. pressure blower. This will have an adjustable gate fitted to the dis- charge-orifice to regulate the resistance. The area of opening will be fixed during the run. (5) Diagrams from each end of cylinder will be taken. TheSPECIAL METHODS OF ENGINE-TEST. 327 motion of indicator-drum will be such as to produce a diagram coincident with the movement of piston. (6) The counter indicating the revolutions of engine will be connected direct. The counter showing revolutions of jack- shaft (carrying dynamometer) will be driven by positive con- nectors at a reduced speed. (7) The dynamometer (transmitting) will be keyed to jack- shaft between the pulley receiving the belt from the engine, and the pulley carrying the blower-belt. The indications of the dynamometer will be read from a station in close proximity to the instrument. (8) A test-gauge of approved make will be screwed into the steam-pipe as near the stop-valve as convenient. The initial pressure in the cylinder will be compared with the pressure in the pipe. (9) Thermometers will be used as follows: No. 1 to show the temperature of atmosphere ; 2, in the feed-water tank; 3, in the steam-chest of cylinder; 4, in the calorimeter. The thermometers to be U. S. standard instruments, thoroughly tested before the experiments, and of uniform scale. No. 1 will indicate temperatures from 32 to 120 degrees Fahr. ; Nos. 2 and 4, from 32 to 250 degrees; and No. 3, from 32 to 600 degrees Fahr. (10) The pressure of atmosphere will be read from a U. S. standard compensated aneroid barometer. (11) The time of commencement and close of run, and in- tervals of observations for the log will be taken from a chro- nometer clock, placed near the engine under experiment. The time of noting observations will be indicated by a double stroke of the signal-gong. One minute previous to each observation a single stroke of the gong will be made calling the assistants to their stations. (12) Previous to the experiments all pipe connections with boilers will be carefully closed, leaving open only the steam- pipe connecting with the engine and feed-pipe connecting with the pumps. Great care will be taken that all steam generated in the boilers be delivered to the engine.328 ENGINE AND BOILER TRIALS. (13) The duration of run will be fixed at five (5) hours. Previous to the beginning of experiment, the boilers will be steamed up to the running-pressure (75 lbs. above atmosphere), and the height of water brought to the thread around the tube in glass water-gauge. All water delivered to the boilers there- after will be regularly entered, by weight, in the log. The condition of pressure and height of water will be maintained as nearly uniform as possible during the run, and made to coin- cide with the initial Conditions at close of run. (14) During the economy-test the engine will be operated with an open stop-valve. (15) At close of economy-run the main belt will be thrown off, and the engine throttled to run at load speed for the fric- tion-diagrams. (16) Previous to the experiments each exhibitor will hand to the Board of Experts a complete summary of the dimen- sions of his engine, including volume of clearance, steam, and exhaust-port area (least), weight of reciprocating parts, and estimated I. H. P., at 75 pounds pressure in the pipe. (17) Every fifteen minutes a full set of observations will be made and entered in the log. (18) The cost of the power in coal will be taken at one ninth the consumption of water per I. H. P. per hour upon an as- sumed boiler efficiency of nine pounds water evaporated per pound of coal burned on the grate. Code of Regulations for Tests of Mounted {Portable') Engines. (1) Steam will be furnished each engine by its attached boiler. Each exhibitor will be required to hand to the Board of Experts, previous to the experiments, a schedule of the length, width, and height from grates to crown of fire-box; total heating-surface; number, length, and external diameter of tubes ; thickness of water-leg; diameter and vertical and hori- zontal distance apart of stay-bolts, diameter and length of bar- rel, total area of openings through fire-bars, area of openings through ash-pit door, thickness of iron in shell and fire-box,SPECIAL METHODS OF ENGINE-TEST. 329 cubic feet of water carried to the gauge-line, cubic feet of steam room. (2) Before the commencement of experiments the boiler will be steamed up to the running-pressure, using........for fuel. Each exhibitor will have weighed to him a sufficient quantity for the economy-run. The management of the fire and the use of the fuel will be entirely under the control of the exhibitor. All fuel remaining in the pile at close of run, and all unburnt wood on the grates, will be weighed back to the credit of the exhibitor. The ashes under the grate will be weighed back dry. (3) A calorimeter-test of the quality of steam furnished by the boiler will be made regularly every 30 minutes. (4) The dynamometer will be keyed to main shaft of en- gine ; the power will be taken off from a pulley attached to loose side of dynamometer; the resistance will be created by a 40 H. P. pressure blower, the discharge-orifice of which will be fitted with an adjustable gate; the area of discharge-opening will be fixed constant during the run. (5) One revolution-counter will be employed, having a positive connection with the valve-stem of engine. (6) The feed-water will be weighed in the receiving-tank, and passed thence to the supplemental tank, from which it will be drawn by the boiler-feeder. The water will be deliv- ered from the city mains (unheated) into the receiving-tank. Each engine will heat its own feed-water. (7) The duration of run will be fixed at five (5) hours. Previous to the experiment, the engine will be run without load until all parts have acquired the working-temperature and the water brought to the thread tied around the tube of glass water-gauge. All water fed to the boiler from com- mencement to close of run will be regularly weighed and en- tered in the log. The pressure of steam and height of water at close of experiment will be made to coincide with the initial conditions. (8) Thermometers will be located as follows: No. 1, in330 ENGINE AND BOILER TRIALS. barometer-case, to indicate the temperature of atmosphere; No. 2, in feed-water tank ; No. 3, in calorimeter. (9) The pressure of the atmosphere will be taken from a U. S. standard compensated aneroid barometer. (10) The pressure of steam in the boiler will be read from a reliable steam-gauge, independent of that belonging to the engine. (11) Previous to experiment, all pipe connections with boiler or engine will be detached, except the pipe from steam- dome to cylinder, and the suction-pipe from feed apparatus to supplemental tank. (13) The economy will be determined upon the consump- tion of coal per I. H. P. per hour. (14) Before the experiments begin, each exhibitor will hand to the Board of Experts a complete summary of the di- mensions of engine, including volume of clearance, area of steam and exhaust ports, internal cross-section of steam-pipe, and weight of reciprocating parts. The valve-motion will be shown by a single indicator-diagram from each end of the cyl- inder, taken at a uniform piston-speed. (15) During the economy-run the engine will be operated with an open stop-valve. (16) At close of economy-run the main belt will be thrown off, and the engine throttled to run at load speed. Friction- diagrams will then be taken from each end of cylinder. (17) Every fifteen minutes a full set of observations will be made and entered in the log. (18) The time of commencement and close of run, and peri- od of observation, will be determined by a chronometer clock placed near the engine under experiment. The time of noting observation will be indicated by a double stroke of the gong. One minute previous to each observation a single stroke of the gong will be made, calling the assistants to their stations.CHAPTER IX. EXAMPLES OF ENGINE-TRIALS. 93. Examples of Engine-testing, as illustrating current and standard practice, will better complete a treatise on this sub- ject than any further extended descriptions of details and of methods of observation, of computation, and of preparation of reports. In the following pages are given, as fully as is possi- ble without occupying too great space, illustrations of this character, as obtained by reference *to the reports of the more expert and most experienced of contemporary engineers, or to reports of earlier work which have been regarded by engineers as best representing good practice in special departments. In all cases the engineer must himself judge whether to err, if at all, in making such tests and in preparing his report, in the direction of extended and complete—and hence costly— investigation and deduction, or in that of brevity and possible incompleteness. The general rule should be to secure all data essential to the purposes of the trial, and, incidentally, to secure all additional facts and data that he may find attainable without incurring objectionable expense. If, in any case, a doubt arises, it will usually be wisest to err on the side of com- pleteness and accuracy. Thus, when called upon, as an ex- pert, to ascertain whether the terms of a contract specifying simply the duty of a pumping-engine have been fully complied with, he need only measure, usually, the coal consumption, the quantity of water pumped by the machine, and the head against which the water is raised. To attempt more would sometimes be unnecessary, and might involve considerable un- authorized expense. But the expert engineer may often, with- out appreciable additional cost, obtain valuable data relating to the distribution, the utilization, and the wastes of heat, of 331332 ENGINE AND BOILER TRIALS. energy, and of steam and fuel: he should in such case en- deavor to obtain all such data and make them useful. The following selected illustrations cover the ground very completely, and will probably be quite sufficient for their purpose. 94. Illustrations of the Trial of Stationary Engines abound in the current periodicals, and may be referred to by the engineer seeking to make comparisons. As a model of brevity in reporting such a trial the following is selected. It is the report of Mr. Flower on a trial of a small Corliss engine designed by Mr. Edwin Reynolds. “ GENTLEMEN: I have made an economy test of your engine and boilers as directed by you, and beg leave to report thereon as follows: Date. Test of engine made.......................Aug. 3d, 1882. Description of Reynolds’Corliss............................. Engine. Diameter of cylinder...................... 14 in. Length of stroke......................... 36 “ Clearance (assumed)......................025 Nominal horse-power at 82 Rev............ 68 Trial. Trial began at............................ 7.30A.M. “ ended “............................... 4.06 P.M. Duration of trial........................ 8 h. 36 m. Revolutions. Revolutions of engine during test......... 35,372 “ “ per minute............ 69.22 Temperature of engine-room............... 990 Gauge-pressure. Maximum pressure in boiler.................. 72 pounds. Minimum “ “ ................ 52 “ Average “ “ ................ 65 “ Variable boiler-pressure................. 80 " Pressure per Average initial pressure on piston........ 61.2 “ Indicator. “ total “ “ .......... 27.08 “ “ gross effective pressure on piston. 25.58 “ Per cent, of boiler-pressure appearing as initial............................... 94 Counter-pressure Back-pressure due to friction through ports .45 pounds. per Indicator. “ “ “ cushion.................. 1.05 “ “ “ total on piston................ 1.50 “ Indicated Maximum gross effective horse-power....... 66.00 Horse-power. Minimum “ “ “ “ ..... 41.40 Average “ “ “ “ ..... 49-30 Average totaT‘ “ “ “ ..... 52.20TRIAL OF STATIONARY ENGINES. 333 Friction Maximum friction horse-power 27.21 Diagrams. Minimum “ “ “ 22.88 Average “ “ “ 24.32 Distribution Average total horse-power 52.20 of Load. “ gross effective horse-power 49.30 " net “ “ “ 24.98 Dynamo, Horse- Edison’s dynamo required.... 4.58 h. p. power of. Brush “ “ 11.54 “ Water used, Temperature of feed-water 203 0 actual. Total water pumped into boiler 11,520.5 pounds. “ “ “ “ “ per hour.... 1,340.0 “ Moisture in steam 3 per cent. Steam per hour, Dry saturated steam per hour 1300 pounds. actual. Dry steam per indicated horse-power, per hour 24.9 “ Dry steam per gross effective horse-power per hour 26.36 “ Steam used, as Steam account edfor by indicator per hour shown by In- per horse-power, total 24.37 “ dicator. Efficiency of cylinder ; •97 Coal per hour Coal per hour per horse-power, anthracite... 303 per H. P. Combustible “ “ “ 2.60 Cost. Cost per day of 10 hours, coal @ $6.25 ton. $4.94 Coal. Coal “ “ anthracite 158 pounds. Indiana block Coal per hour per horse-power 362 “ coal. “ per day of 10 hours 1 ,890 “ Cost “ “ @$3-75 ton $3-54 Maximum Dia- Indicated power of heaviest diagram 66 h. p. gram No. 31. Cut-off in parts of stroke 3.60 “ from commencement of stroke... 10 inches. Initial pressure 64 pounds. Possibilities of Same initial pressure as above . Engine. Diagram, £ cut-off, engine will develop.... Same cut-off as No. 31, and 74 lb. initial 72 h. p. pressure Same cut-off and same initial pressure as No. 70 h. p. 31, with 82 rev. per minute will develop.. 77 “ “ When No. 31 was taken, all the machinery that could be put on was on. The average power used was much less than No. 31, being 49.3 horse-power.334 ENGINE AND BOILER TRIALS. “ As is shown in body of report, the power of the engine may be increased by increasing the revolutions to 82 per minute (that being the rate of speed as given by the builder), by allowing a later cut-off, or by a higher initial pressure. “ A higher initial pressure may be had by increasing the boiler-pressure ; the average during test was 65 pounds, and you are allowed 80 pounds by the inspector. “ A higher boiler-pressure and a more uniform pressure than was had during test is desirable. “ The measure of economy of an engine is the amount of water used per hour per horse-power. From that point of view, your machine is far above the average. “ As the load on engine increases above 53 to 55 horse- power, the economy will decrease, unless the initial pressure is higher, or a higher speed of revolution is given to engine. “ The economy of engine by coal is not as good as it should be, and can be improved. 303 lbs. coal (anthracite) per hour per horse-power is high, but the fault is not with the engine, for the water used per hour per horse-power is only 24.9, and an evaporation of 10 lbs. actual would give an indicated horse- power for 2.5 lbs. coal; the boiler should evaporate 10 lbs. water per lb. anthracite coal.” The following is an example of a very full report by Mr. Hill on the trial of a Corliss engine designed and built by Mr. Harris : “The engine, 24" diameter of cylinder and.60" stroke of piston, is condensing, and fitted with the ordinary jet-con- denser and reciprocating air-pump. The injection-water is obtained by a lift of I57 from the Mississippi River, upon the bank of which the mill stands ; and during the trial the con- densing water entered the injection-pipe at a temperature near the freezing-point. The steam-valves were formerly closed by the usual weights ; but previous to the trial, vacuum dash-pots were added to insure a prompt closing of the valve when liber- ated from the hook. The engine is furnished with a pulley fly-wheel 20' diameter and 32" face; driving back to the line- shaft with a 30" double leather belt.TRIAL OF STATIONARY ENGINES. 335 “ The exhaust of engine is closely connected to a condenser by a io" pipe, and steam is conveyed from the boiler by a 7" pipe. “ Steam is furnished by a pair of tubular boilers set in battery, and each of the following dimensions: 60" diameter of shell, 12' long fifty 4" tubes. Each boiler is fitted with a vertical steam-dome, 30" diameter X 36" high, and over these and joined to them by short legs is a horizontal steam-drum, 24" diameter and 14" long. “ The steam-pipe is joined by branch pipes to the side of the horizontal drum. “ The feed-water is taken from a drop-leg in the overflow- pipe from the condenser, and conducted to the suction of a single-acting plunger-pump driven from the engine by belt. Into the breeching or front smoke connection has been intro- duced a fuel economizer, consisting of 250' of 2\/uiron pipe, through which the feed-water is forced to the boiler. “ The furnace is arranged to burn slabs and hard wood, although by the record it would appear to be well adapted for coal (the fuel used during the trial of engine). The lack of a suitable bridgewall, and the very large furnace-doors and grate- surface are not calculated for maximum economy with coal as a fuel, and it is eminently probable that with a different con- struction of furnace the efficiency of the boilers during the trial of engine would have been higher. “ The entire net power of engine is expended in driving the machinery of the mill, which consists of twelve run of 54'' buhrs, and three run of 48" buhrs ; two crushing rolls, each with 3-12" X 30" cylinders; five rolls, each with 2-12" X 30" cylin- ders, and one roll with 2-12" X 18" cylinders. The bolting, machinery consists of one chest with two reels; two chests with three reels ; one chest with six reels, and one chest with eight reels; in all twenty-two bolting reels and forty-eight con- veyors. “ The cleaning machinery consists of two ‘ cockle’ machines ; one ‘ scouring’ machine; one ‘separator,’ and two brushing machines. Of the purifying machines there are seventeen;336 ENGINE AND BOILER TRIALS. and one shaking machine; four flour-packers; four stand of wheat elevators; four stand of flour elevators, and twenty-one middlings elevators ; one small and two large exhaust fans. “To this should be added the machinery of the grain ele- vator, which is driven by belt from the third story of the mill; and the line-shafting, connecting belts, pulleys, and gearing, forming the general machinery of the mill. “ In the following tables are given the principal measured and calculated data of engines and boilers. The clearance was not measured, but estimated at three per cent, of piston-dis- placement, this being the usual clearance in similar engines of like dimensions. “ The factor of horse-power due mean area, and velocity of piston for each mean effective pound pressure, has been calcu- lated as follows: The area of a24"piston is452.39 sup.ins. and the area of the rod (3.375") is 8.9462 sup. ins.; and the mean area of piston is, therefore, 8.9462 452.39 - — = 447-9*7sup.ins.,. and the factor of horse-power 447-917 X 596.166 33000 8.20446. “ The valve functions have been measured on the diagrams. The volume of steam accounted for to release is obtained by taking the mean area (feet) of piston into the piston travel (feet) per hour to point of release, to which is added the hourly volume of clearance. The volume of steam retained by exhaust-closure is obtained by taking the mean area of piston, in feet, into the travel of piston, in feet per hour, from exhaust- closure to end of stroke, to which is added the hourly volume of clearance. “ The dimensions of boilers and fire-grates are furnished by your engineer, from which have been deduced the heating- surface, grate-surface, and calorimeter of tubes, and ratios ofTRIAL OF STATIONARY ENGINES. 337 heating to grate-surface, and grate-surface to cross-section of tubes. Dimensions of Engine. Diameter of cylinder...................... Stroke of piston.......................... Revolutions per minute during trial....... Piston speed “ “ “ “ ....... Factor of H. P. due area and velocity of piston ............................. Piston stroke to release in parts of stroke.. “ “ exhaust closure in parts of stroke.............................. Clearance (estimated) in parts of stroke.. Volume of steam to release per hour....... “ “ retained by cushion per hour................................ Diam. of air-pump......................... Stroke “ “ ........................ Diameter of driving-pulley................ Face “ “ “ ................ Weight “ “ “ ................ 24 inches. 66 “ 59.616. 596.166 feet. 8.204. 99.370. 6.067. 3.000 115,038.04 cu. ft. 10,189.02 cu. ft. 12 inches. 15 - 20 feet. 32 inches. 40.000 pounds. Dimensions of Boilers. Number................................... 2. Diameter of shells........;.............. 60 inches. Length “ “ ....................... 12 feet. Tubes, each boiler....................... 50-4 inches. Heating-surface shells (2)...... 250.56 “ “ tubes (100)..... 1,245.64 “ “ heads (4).... 40.72 “ “ total.. 1,536.92 sup. ft. Grate “ ....................... 51.75 sup. ft. Calorimeter of flues...................... 1,256.64 sup. ins. Heating to grate-surface..................... 29.70 Grate-surface to calorimeter.................. 5.93338 ENGINE AND BOILER TRIALS. “ The trial of engine for economy of performance and trial of boilers for evaporative efficiency were made simultaneously; all preparations having been completed, the trial began at 9.15 a.m., and terminated at 7.15 p.m.; duration of trial, ten hours. “ The test of boiler efficiency was with coal. “ The load was that usually carried in the daily operation of the mill, and through the care of the chief miller, was held quite uniform during the ten-hours’ run. It is possible that the mean power developed is slightly greater than usual, from the fact that the operatives were cautioned to avoid breaks in the load; and that they obeyed the injunction is best attested by the indicator-diagrams, which exhibit but slight variations in the load during the economy-trial. “ The diagrams were taken by independent indicators, one to each end of cylinder. Forty (40) pound springs were used, and the drums were moved by well-constructed bell-cranks and reciprocating connections hung on a stout gallows frame. The joints of the levers and connections were carefully made, and means were provided to take up wear and avoid lost motion. “ The strings on the indicator-barrels were only long enough to couple with the pins on the short stroke-reciprocating-bar, and the recoil-springs were adjusted as nearly as possible to the same tension. The length of diagrams was uniformly 4"78- “ During the trial a pair of diagrams were taken regularly every fifteen minutes, making eighty-two diagrams ; from which have been obtained the initial pressure in cylinder, piston-stroke to cut-off, ratios of expansion by pressure and by volumes, terminal pressure, counter pressure at mid-stroke, utilization of vacuum, and mean effective pressure on the piston, from which is obtained the mean power developed. “ The vacuum in the condenser and the pressure in the boilers were taken from gauges in the engine-room regularly every fifteen minutes.TRIAL OF STATIONARY ENGINES. 339 “ The temperature of water to the condenser was taken in the river at the mouth of the injection-pipe. The temperature of overflow from the condenser was taken in the measuring- tank. The temperature of feed to the boiler was taken in the feed-pipe near the check-valves. “ The water delivered to the boilers was measured in the following manner: Two oil-barrels were carefully washed inside and placed on the same level in the engine-room ; to the bot- toms of these was connected, by branch pipes, the suction-pipe of pump, each branch being provided with an open way-cock to shut off the flow when the level had been reduced to the lowest gauge-point. The pipe from the hot-well to the pump was cut and carried out over the barrels; a connection made by branches to each barrel, and a stop-valve in each branch regu- lated the flow of water into the tanks. The tanks or barrels were numbered i and 2, and were alternately filled to the over- flow notch in the rim, and emptied to the centre of the branch pipe in the side of barrel, and the contents discharged into the pipe leading to the pump. “ Whilst the No. i barrel was running out, the No. 2 barrel was filling with water from the hot-well; and directly the first barrel was emptied to the lower gauge-point, it was turned off and the second barrel turned on ; and so on during the entire trial, the empty barrel being shut off before the full one was turned on, to prevent transfer of water from the full to the empty barrel. Directly each barrel of water was turned on, the time was entered in the log, and a tally made by the assistant in charge of the tanks. From time to time my record of tanks discharged was compared with the assistant’s tally, to avoid error in the count. “After the trial, the capacity of each tank was determined by filling to the overflow notch, noting temperature, drawing off to the lower gauge-point, and weighing. The temperatures of the tanks of water discharged into the^ suction-pipe of feed- pump having been regularly noted during the trial, the weight of water delivered to the boiler was deduced from the number340 ENGINE AND BOILER TRIALS. of tanks discharged into the weight of tanks at mean observed temperature. “ The calorimeter-tests of water entrained were made by drawing off from the steam-drum, near the pipe to the engine, a given weight of evaporation, and condensing it in a given weight of water, noting the temperature of the water before and after the steam was turned in, and the pressure of evapo- ration each time an observation was made. The thermal val- ues due the ranges of temperature and the weights of steam and water, together with the thermal values of saturated steam at observed pressures, constituted the data from which has been estimated the heat-units resident in a pound of evapora- tion during the trial, from which has been deduced the water entrained in the steam as 12.84 Per cent, of the total water pumped into boiler. Twenty calorimeter-observations were made during the ten hours’ trial. “ The revolutions of the engine are nominally 60 per min- ute ; but from the ten hours’ continuous record by counter, the mean revolutions per minute were 59.616. “ The coal fired during trial of engine was Wilmington,, mined in the northern part of Illinois, and, from the evapora- tive efficiency developed, of very fair quality. “ The ash-pit and fires were cleaned before the trial, and the ash and clinker accumulated during the ten hours’ firing weighed back dry. The non-combustible by weight constituted 7.3 per cent, of the total coal fired. Previous to commence- ment of run, the water-level in both boilers was marked on the glass gauges, and the fires levelled and thickness noted ; the same conditions of fires and water-level obtained at the end of trial. “ In the following tables are given the observed and calcu- lated data illustrating the performance of engine and boilers. All data from the diagrams are means of eighty-two readings, and all other data are means of forty-one readings. “ The economy of engine by steam and by coal is developed upon the mean quantities charged per hour.TRIAL OF STATIONARY ENGINES. 341 Data from Trial of Engine. Duration of trial........................ Mean pressure by boiler-gauge above atm “ initial pressure above atm....._____ “ terminal “ absolute............ “ counter “ “ ......... “ cut-off in parts of stroke apparent.. “ “ “ “ actual........ “ vacuum by gauge........... “ “ “ diagrams....... “ temperature of injection.. “ “ of hot-well... “ effective pressure........ Indicated horse-power.......... Ratio of expansion by volumes.. “ “ “ “ pressures. Economy of Engine Total water per hour to boilers.............. Water (steam) per hour to calorimeter........ “ entrained per hour in the steam......... Net steam per hour to engine................. Steam per indicated horse-power, actual,..... “ “ “ “ by the diagrams Percentage of steam accounted for............ Coal burned per hour......................... Coal per indicated horse-power per hour...... “ “ “ “ evaporation 9 to 1 Combustible, per indicated horse-power, per hour Performance of Boilers. Duration of trial............................ Pressure by gauge.......................... Temperature of feed to heater................ “ “ “ “ boiler................ Elevation of feed by heater.................. Percentage of gain by heater................. 10 hours 92.876 lbs. 89.376 “ 12.018 “ 2.696 “ 15-560 18.019 26.40 inches 24.05 “ 33-840 92.725 32.9792 lbs. 270.5796 5-549 8.643 5,037.128 lbs. 10.000 lbs. 655.583 lbs. 4.371-545 lbs. 16.156 lbs. 13.035 “ 80.682 535. lbs. 1.9772 lbs. 1.7950 “ 1.8328 “ 10 hours 92.876 lbs. 92.725 114.324 21.599 1.723342 ENGINE AND BOILER TRIALS. Total water pumped into boilers ... 50,371-28 : lbs. a “ entrained in the steam (12.84 $) • • .. 6,467.70 ii a steam furnished ... 43,903-58 it a coal fired • • 5,350 it a non-combustible weighed back 390 it a combustible '. it Steam per pound of coal .. 8.206 it << “ “ combustible 8.852 it a “ “ coal from temp, of 212° ) ■ it and pres, of atm. f ** *' Steam per square foot of heating-surface.... .022 it Coal “ “ “ “ grate-surface it Percentage of ash in coal.......................... 7.3 Coal burned during trial, Wilmington (Illinois). “ During the economy-trial of engine, the flour manufactured was, by the miller’s report, 217 barrels high grade, and 2 per cent, added for low grade, or 221.34 barrels produced in ten hours. The mean indicated power of engine was 270.56 horse- power, and the hourly expenditure of power per barrel of flour produced was 27°'^ = 12.224 H. P. 22.134 “ The coal burned for whole trial was 5350 pounds, and coal per barrel of flour produced becomes ■ — - = 24.198 pounds. 221.34 “ Whilst the experiments (firing, slabs and hard wood) were in progress, the engine was indicated for distribution of the power in the mill. “ The first (A) load was with all the machinery on, and op- erating under the ordinary conditions. The second (B) load was with all the machinery on except the machinery in eleva- tor-building. The third (C) load was with all the machinery on except the flour-packers. The fourth (D) load was with all the machinery on except the cleaning machinery and flour- packers. The fifth (E) load was with all the machinery on except the crushing-rolls. The sixth (F) load was with all the machinery on except the purifiers. And the seventh (G) load was with all the machinery on except the grinding-buhrs.TRIAL OF STATIONARY ENGINES. 343 “ The changes of load were made quickly, in order to preserve the conditions of ordinary performance in the special machin- ery driven; and the power developed for each load has been estimated from six diagrams, three from each end of cylinder. “ The indicated loads were as follows: First load (A).........................267.503 H. P. Second load (.B)....................... 262.585 “ Third load (C)......................... 363.706 “ Fourth load (D)........................250.726 “ Fifth load {E)......................... 246.740 “ Sixth load (F)......................... 242.645 “ Seventh load (G)....................... 117.149 “ “ Each of these loads is made up of the friction of engine in all parts; extra friction of engine due to the load, friction of all the driving machinery in the mill, and power required to drive the special machinery, including friction; in like manner the differences between the maximum load and reduced loads nearly represent the power required to drive the special ma- chinery not on, including its own friction. “ Hence the difference between the maximum load and lesser loads represents slightly more than the power actually absorbed by the special machinery not driven. “ The distribution of the power in the mill is thus as follows: Total indicated power of engine load (A) Friction of engine alone............... Extra friction due load................ Grinding-buhrs......................... Cleaning machinery..................... Elevator .............................. Crushing-rolls......................... Bolting-reels, conveyors, fans, and general machinery................... Middlings-purifiers.................... Flour-packers.......................... 267.503 16.409 12.544 150.354 12.980 4.918 20.763 21.860 23.868 3-797 267.503344 ENGINE AND BOILER TRIALS,. “ I have attached to this report one pair of diagrams taken during the trial, and numbered 14, upon which have been drawn theoretic curves from the terminal pressures and points of release. The lack of coincidence between the actual and theoretic curves is due, in my opinion, to a slight leak past the piston or out of the exhaust; in all probability, the latter. The engine being very new, and a certain amount of wear be- ing requisite to make good joints between the valve faces and seats, it is probable that this leak will in time remedy itself. However, it does not appear that the failure of the diagram to satisfy the conditions of theory has any marked effect on the economy of the engine, for the actual consumption of steam and coal per indicated horse-power per hour are the least I have ever obtained from a single-cylinder engine.” The preceding illustrations exhibit the methods of report and the results of trial of good examples of ordinary practice with the common simple engine of moderate size and under usual working conditions. As illustrating what can be done with a good compound stationary engine, the following data are presented, as given the Author by Mr. Corliss a short time before his death, as the results obtained from a compound condensing-engine of about 500 I. H. P., driving a cotton-mill: Result of a Seven Days’ Trial of the Corliss Compound Engine at Nourse Mill. Commencing Oct. 15th, and ending Oct. 22d, 1884. 4 Starting Fires. Coal while run- ning. Wood used during run- ning time. Value of same at 40 %. Total new fuel fed to fur- nace each day. Cinders used during day. Wood. Value at 40 % of Coal. Coal. Wed., Oct. 15, 1884.. IOOO 400 2647 6838 200 80 9965 Thur , 16. “ .. 833 333 2535 7200 10068 Fri., “ 17, “ •• 30 12 2800 7200 IOOI2 Sat., “ 18, “ .. 3200 3600 6800 1671 Mon., “ 20, “ .. 800 320 3200 7200 10720 Tue., “ 21, “ .. IO 4 3200 6904 IOI08 Wed., “ 22, “ .. 3200 4300 30 12 7512 3018 Totals and averages for 7 days 2673 1069 20782 43242 230 92 65185 TRIAL OF STATIONARY ENGINES. 345 Total fuel fed to fur- nace each day. Cinders found at end of day. Total Fuel used. Run- ning Time. Fuel used per hour. Indi- cated Horse- power. 1 Fuel per hour per I. H. P. Aver- age Rev. Wed. Oct. 15 1884... Q965 863 9102 II H. 44 M. 775.76 498.93 i-55 56.96 Thur. “ 16 “ ... 10068 685 9383 II “ 41 “ 803.13 496.37 1.61 57-io Fri. “ 17 “ IOOI2 730 9282 II “ 40“ 795.64 495.09 1.60 57.08 Sat. “ 18 “ ... 8471 729 7742 9 “ 44“ 795.41 483.80 1.64 57.46 Mon. “ 20 “ ... 10720 742 9978 II “ 42“ 852.82 509.46 1.67 56.84 Tue. 'v< 21 “ ... IOI08 717 9391 II " 4°“ 804. gS 504.24 i-59 56.99 Wed. “ 22 “ ... IO53O 455 10075 II “ 41“ 862.36 501.94 1.71 57.17 Totals and averages for 7 Days 79 H. 52 M. 812.38 499*13 1.62 57.10 General Summary of 7 Days' Trial of Nourse Mill Engine. Commencing Oct. 15th, and ending Oct. 22d, 1884. Fires were started on clean grates Wed., Oct. 15th, 1884. Wood 2903 lbs. Equivalent value in Coal at 40 percent.,.................................. Ii6ilbs. Coal for starting fires,...........................20782 “ Coal used while running,...........................43242 “ Total amount of fuel fed to furnaces, 65185 “ Deduct cinders found at end of run, 455 lbs.; esti- mated at 80 per cent, value of new coal, . 364 “ Total fuel used during the seven days, .... 64821 “ Running time,....................................79 H. 52 M. Fuel per hour,...................................811.62 lbs. Average indicated horse-power from 636 cards, . 499.13 Fuel per hour per indicated H. P.,............... 1.626 lbs. Average revolutions per minute,..................57.1 Per cent, of ash and clinker,....................11.9 The results of a series of trials of a single-acting compound engine, as given in the following table, illustrate well the system and the conciseness which characterize the work of the expert engineer, as well as the efficiency attainable with this class of engines when well designed, well constructed, and operated under favorable conditions:346 ENGINE AND BOILER TRIALS. Steam per Indicated H. P. Single-acting Compound Engine. Non-condensing. Condensing. Boiler-pressure. Horse- Boiler-pressure. 60 lbs. 80 lbs. 100 lbs. 120 lbs. power. 120 lbs. 100 lbs.. 80 lbs. 60 lbs. 22.6 210 18.4 23.0 21.9 170 18.1 18.8 24.9 23.6 22.2 140 18.2 18.5 20.0 25 7 23-9 22.2 115 18.2 18.6 19.6 20.5 26.9 25.2 24.9 22.4 100 18.3 18.6 !9-7 20.3 27.7 25.2 .25-1 24.6 80 18.3 18.6 19.9 20.1 30-3 28.7 29.4 28.8 50 20.4 20.8 20 7 20.4 The engine was of 14 and 24 inches diameter of cylinder, 14 inches stroke of piston, and unjacketed. All steam passing into and through the engine was weighed and measured. Gauge- pressures are given. This engine is usually rated at 150 H. P. The steam was probably dry, but not superheated. 95. Tabulated Deductions and General Conclusions from engine-trials, as above illustrated, should usually be pre- sented in as concise and legible form as possible, and so arranged as to make it easy to interpret the data and to verify the results both as to facts and reasoning. Thus, one of the most complete investigations ever made in this field was that of Mr. Willans on the efficiency and wastes of his triple-expansion engine.* He describes in his report a series of economy-trials, non-con- densing, made with one of his central-valve engines, with one crank, having three cylinders in line. By removing one or both of the upper pistons, the engine could be easily changed into a compound or into a simple engine at pleasure. Check-trials were made by Mr. MacFarlane Gray, Prof. Ken- nedy, Mr. Druitt Halpin, Professor Unwin, and Mr. Wilson Hartnell. The work theoretically due from a given quantity of steam at given pressure, exhausting into the atmosphere, was first considered. By a formula of Mr. MacFarlane Gray, which agreed with the less simple formulas of Rankine and Clausius, the weights of steam required theoretically per indicated horse-power were ascertained. A description is given of the main series of trials, of the ap- * Proc. Brit. Inst. C. E., Mch. 13, 1888. Sci. Am. Supp., May 20, 1888.DEDUCTIONS AND GENERAL CONCLUSIONS. 347 pliances used, and of the means taken to insure accuracy. The missing quantity of feed-water at cut-off, which, in the simple engine-trials, rose from 11.7 per tent, at 40 lbs. absolute pressure to nearly 30 per cent, at no lbs., and at 90 lbs. was 24.8 per cent., was at 90 lbs. only 5 per cent, in the compound trials. In the latter, at 160 lbs., it increased to 17 per cent., but on repeat- ing the trial with triple expansion, it fell to 5.46 per cent, or to 4.43 per cent, in another trial not included in the table. The compound engine must always give a smaller diagram, considered with reference to the steam present at cut-off, than a simple engine, and a triple a smaller diagram than a compound engine. But even at 80 lbs. absolute, the compound engine had an advantage, not only from reduced initial condensation, but from less loss from clearance, and from reduced leakage. These gains became more apparent with increasing wear. The greater surface in a compound engine had not the injurious effect some- times attributed to it, and the author showed how much less the theoretical diagram was reduced by the two small areas taken out of it in a compound engine than by the single large area abstracted in a simple engine. The trials completely confirmed the view that the compound engine owed its superiority to re- duced range of temperature. At the unavoidably low pressures of the trial, the losses due to the added passages, etc., almost neutralized the saving in initial condensation ; but with increased pressure—say to 290 lbs. absolute—there would be considerable economy. The figures of these trials showed that the loss of pressure due to passages was far greater with high- than with low-pressure steam, and that pipes and passages should be pro- portioned with reference to the weight of steam passing, and not for a particular velocity merely. After comparing the data of initial condensation in cases where the density of steam, the area of exposed surface, and the range of temperature were all variables, with other cases (1) where the density was constant and (2) where the surface was constant, the author concluded that, at four hundred revo- lutions per minute, the amount of initial condensation depended chiefly on the range of temperature in the cylinder, and not348 ENGINE AND BOILER TRIALS. upon the density of the steam or upon the extent of surface, and that its cause was probably the alternate heating and cool- ing of a small body of water retained in the cylinder. The effect of water intentionally introduced into the air-cushion cylinder showed how small a quantity of water retained in the cylinder would account for the effects observed. At lower speeds, surface might have more influence. The favorable economical effect of high rotative speed was very apparent. Starting with 40 indicated horse-power, 130 lbs. absolute pressure, four expansions, and a consumption of 20.75 lbs. of water, the plan of varying the expansion, as compared with throttling, showed a gain of about 7 per cent, at 30 indicated horse-power, but of a very small percentage when below half- power. . If the engine had an ordinary slide-valve, the greater friction, added to irregular motion, would probably neutralize the saving; while if the engine were one in which initial conden- sation assumed more usual proportions, the gain would be prob- ably on the side of variable pressure. The diagrams showed that the missing quantity became enormously large as the ex- pansion increased. Judging only by the feed-water accounted for by the indicator, the automatic engine appeared greatly the more economical, but actual measurement of the feed-water disproved this. The position of the automatic engine was rela- tively more favorable when simple than when compound. The tabulated figures are given on page 349. M. Delafond, testing a single-cylinder Corliss engine, built at Creusot, with similar care and thoroughness, comes to the fol- lowing conclusions as fairly deducible from the data so ob- tained : * (1) The effective work is equal to Te— — ot + 0 Ti\ where T{ is the indicated work; but the coefficients a and 0 are not absolutely constant, varying with the pressure of steam. * Essais Effectives sur une Machine Corliss, etc.; Paris, Dunod, Editeur, 1884; p. 60.DEDUCTIONS AND GENERAL CONCLUSIONS.. 349 Trials of Triple Expansion Engines. Intended mean admis- sion pressure....Lb. 40 90 no 130 150 160 170 Simple. Compound or S. S. c. c. C. T. T. T. Triple. S. c. c. Actual mean admis- sion pressure. ..Lb. Percentage ratio of 40.87 92.6s 87-54 106.3 109.3 130.6 149.9 *5*-9 158.5 158.1 172.5 actual mean pres- sure,referred to low- pressure piston, to theoretical mean pressure 98.26 16.51 !ioo 9*-3 29.14 100.7 33-5 OJ 0 bo 94.2 36.31 94.6 38.59 84.54 95.9 39-55 85'. 3 85.2 Ind. horse-power 31.61 35-69 35-36 38-45 Feed-water actually used per indicated H. P. H.- Simple Lb. Compound Lb. Triple Lb. Steam required theo- 42.76 26.89 24.16 26 21-37 20.35 19-45 19.19 retically per I. H. 19.68 19-*9 18.45 P. H Lb. 34 67 19.24 19.86 17.9 17-65 16.25 15-23 15.16 14.87 *4-9 *4-36 Percentage efficiency. 81.1 7i-5 82.2 68.8 82.5 80.0 78.3 77 77-4 77.6 77-8 Percentage of feed- water missing at cut-off in high-pres- sure cylinder Ditto intermediate 5-33 6.84 5-OI cylinder 5 9-5 n.7 TC . I 14.84 17 12.06 *5-33 Ditto low - pressure cylinder 11.7 24.8 152 29.56 16.25 20.6 22.12 21.3 22.11 24.21 Percentage of feed- water missing at end of stroke in low- pressure cylinder... 10.4 18.83 14-25 21-53 16.59 17-55 20.69 18.01 *9-55 18.81 19.25 (2) The best economy was measured under the following conditions : With condenser; “ jacket; “ moderate pressure; “ “ expansion. In the best cases, the expenditure of steam, per effective and per indicated horse-power, per hour, was respectively 9k»50 and 7k-75 (about 17 and 21 pounds). (3) The steam-jacket is advantageous for high ratios of ex- pansion and high pressures; its effect decreases with reduced pressure and expansions, and becomes insignificant at low pressures and small ratios of expansion. (4) Compression is useful in non-condensing engines, and350 ENGINE AND BOILER TRIALS. the more so as the final pressure is made to approximate initial steam-pressure. (5) The best results were obtained in these cases at 120 to 170 I. H. P. At higher powers the cost in steam rapidly rises. Above 175 horse-power, the condenser is of no advantage, and high compression and the use of a good feed-water heater are advisable.* * * § (6) Initial condensation increases with increase of pressure, and lessens with diminishing expansion, becoming insignificant at full-stroke. The jacket reduces this loss; but the presence or absence of the condenser has no effect, this cylinder conden- sation being a result of expansion. (7) The cylinder condensations and re-evaporations are of complex character; the jacket increases the re-evaporation; pressure of 3J or 4^ atmospheres gave largest evaporations. (8) Moderate pressures are best; f as they give small initial condensation and considerable re-evaporation.^: (9) High piston-speed and the use of steam in the jacket of higher pressure than in the engine are advisable. (10) Working non-condensing at pressures of 3J to 5J atmos- pheres, with small expansion, the permanent presence of water in the cylinder could not be detected.* The following tables, prepared by M. Isherwood from the data obtained by a committee of the Societe Industrielle de Mulhouse at a series of trials of a condensing compound engine, illustrate well the fulness sometimes considered desira- ble in such cases. § But it will be observed that even here such important data as the ratios of expansion, release, and com- pression, and the quantity of cylinder condensation were not obtained. * This conclusion should, in the view of the Author, be based on a limit of steam-pressure (perhaps above 75 lbs. by gauge), f For single cylinder or simple engines. X The Author questions the logic of this deduction. § Bulletin de la Soc. Ind. de Mulhouse, Jan.-Feb. 1880. Journal Franklin Institute, Oct. 1885.\ DEDUCTIONS AND GENERAL CONCLUSIONS. 351 Experiments on a Condensing Compound Engine, Industrial Society of Mulhouse. a a 3 a tuD C B2 m * decimals of an hour, rotal number of doubl the engine........... boiler. the condenser . above the atmosphere. Pressure in the conden above zero............ of the engine............... Position of the throttle-valve. small cylinder when the steam was cut off... fraction completed of the stroke of the piste small cylinder when the steam was released. small cylinder when the steam was cushioned. Fraction completed of the stroke of thejpistor large cylinder when the steam was cut off----- large cylinder when the steam was released.... Fraction completed of the stroke of the pistor large cylinder when the steam was cushioned. Number of times the steam was expanded............ per hour ................................... Number of pounds of condensing-water admitted to the condenser per hour........................ ....... Temperature in degrees Fahrenheit of the condensing- water when admitted to the condenser.............. Number of pounds of condensing-water and water of steam condensation withdrawn from the condenser per hour.......................................... Temperature, in degrees Fahrenheit, of the condensing- water and water of steam-condensation when taken from condenser.................................... Number of Fahrenheit units of heat consumed per hour. Pressure on piston of small cylinder at commencement of its stroke, in pounds per square inch above zero. Pressure on piston of small cylinder at point of cutting off the steam, in pounds per square inch above zero... Pressure on piston of small cylinder at the end of its stroke, in pounds per square inch above zero...... Mean back-pressure against piston of small cylinder dur- ing its stroke, in pounds per square inch above zero_ Back-pressure against piston of small cylinder at the point where the cushioning began, in pounds per square inch above zero .................................. Indicated pressure on the piston of the small cylinder, in pounds per square inch............. .............. Net pressure on the piston of the small cylinder, m pounds per square inch................................ Total pressure on the piston of the small cylinder in pounds per square inch............................. July 8, 1879. Morning. July 8, 1879. Afternoon. 1 3.00222 3 24139 16211. 17253- 3248.068561 4265.391060 74038.567197 78893.841895 ■ 77*53-139*83 84499-77745o 1 91.694 92.164 1.810 1.907 89.994448 Wide open. 88.711972 Wide open. 0.25 0.42 0.98 0.98 0.925 0.925 0.45 0.45 0.91 0.91 o-75 9.6444 0 75 6.2569 14.222813 14.222813 1081.888922 I3I5-9I4I79 24661.273057 24648.018873 48.001 48.010 25732.004711 26068 994305 86.932 1220557.870799 96.728 1471790.924665 99.787254 •102.966053 88.280999 91.459798 33.423600 45.184067 35.343690 46.449021 34.846000 42.614000 27-855379 30.678629 24.227924 27.046174 60.200000! 73.300000Economic Results. Horses-power. Steam-pressures in Large Cylinder per Indicator. 352 ENGINE AND BOILER TRIALS. July 8, 1879- Morning. f Pressure on piston of large cylinder at commencement of its stroke, in pounds per square inch above zero.... Pressure on piston ol large cylinder at point of cutting off the steam, in pounds per square inch above zero_ Pressure on piston of large cylinder at the end of its stroke, in pounds per square inch above zero........ Mean back-pressure against piston of large cylinder dur- ing its stroke, in pounds per square inch above zero.. Back-pressure against piston ot large cylinder at the point where the cushioning began, in pounds per square inch above zero..................................... Indicated pressure on the piston of the large cylinder, in pounds per square inch.............................. Net pressure on the piston of the large cylinder, in pounds per square inch.............................. Total pressure, in pounds per square inch above zero, on the annular surface of the piston of the large cylinder remaining after subtracting from the area of that pis- ton the area of the piston of the small cylinder... Indicated horses-power developed in the small cylinder.. Net horses-power developed in the small cylinder..... Total horses-power developed in the small cylinder... Total horses-power developed in the small cylinder by the expanded steam alone............................ Indicated horses-power developed in the large cylinder.. Net horses-power developed in the large cylinder..... Total horses-power developed in the large cylinder by the annular surface of its piston remaining after sub- tracting from the area of that piston the area of the piston of the small cylinder........................ Total horses-power developed in the large cylinder by the expanded steam alone............................ Aggregate indicated horses-power developed by the - engine ...................... ........................ Aggregate net horses power developed by the engine— Aggregate total horses-power developed by the engine, exclusive of cushioning............................. Aggregate total horses-power developed by the ex- panded steam alone in both cylinders inclusive of cush- ioning............................................. Horses-power developed by the engine at the friction brake applied to the wheel on the engine shaft ..... Per centum of the total horses-power developed by the engine utilized as indicated horses-power........... Per centum of the total horses-power developed by the engine utilized as net horses-power................. Per centum of the total horses-power developed by the engine utilized as horses-power at the friction brake... f Number of pounds of feed-water consumed per hour per indicated horse-power............................... Number of pounds of feed-water consumed per hour per .net horse-power .................................... Number of pounds of feed-water consumed per hour per total horse-power developed by the engine........... Number of pounds of feed-water consumed per hour per horse-power developed by the engine at the brake.... Number of Fahrenheit units of heat consumed per hour per indicated horse-power........................... Number of Fahrenheit units of heat consumed per hour per net horse-power................................. Number of Fahrenheit units of heat consumed per hour per total horse-power developed by the engine....... Number of Fahrenheit units of heat consumed per hour per horse-power developed by the engine at the brake. 34.490000 21.156000 9.600000 3.756000 2.355°°° 17.006220 i5-747273 i9.556220 23.i35964 20 123093 50.000578 28.101654 40.738193 37.722401 30.603792 32.491077 63.874157 57-845494 80.604370 60.592731 55 717593 79.24403 71.7647X 69.12477 16.937819 18.703080 13.4222x2 19.417366 19108.790286 21100.310264 **142.576895 21906.148580 July 8, 1879. Afternoon. 43.200000 27.740000 12.561000 3.756000 2.355000 22.300000 21.041053 24.850000 25.113672 22.143736 60.013510 28.560045 52.658120 49.685305 38.333920 40.19431i 77-77*79* 71.829041 98.347430 68.754356 67.499569 79.07862 73.03601 68.63379 16.920199 18.320085 13.380260 *9-495*49 18924.482602 20490.193161 14965.219982 21804.449220DEDUCTIONS AATD GENERAL CONCLUSIONS. 353 o co o £ Number of pounds of steam present per hour in the small cylinder at the point of cutting off the steam, calculated from the pressure there............................. Number of pounds of steam present per hour in the small cylinder at the end of the stroke of its piston, calculated from the pressure there............................. Number of pounds of steam condensed per hour in the small cylinder to furnish the heat transmuted into the total horses-power developed by the expanded steam alone in that cylinder.............................. - Sum of the two immediately preceding quantities....... Number of pounds of steam present per hour in the large cylinder at the end of the stroke of its piston, calculated from the pressure there........................ .... Number of pounds of steam condensed per hour in the small and large cylinders, and in the receiver to furnish the heat transmuted into the total horses-power devel- oped in those cylinders by the expanded steam alone after the closing of the cut-off valve on the small cylin- der ............................................... . .. L Sum of the two immediately preceding quantities...... July 8, 1879. Morning. July 8, 1879- Afternoon. 607.871477 1005.726509 879.050774 1170 906554 76.530424 955.581198 805.995933 78.900853 1249.807407 1047.498116 162.065479 968.061412 185.699642 1233.197758 rt £ r* 43'-' C70 Heat lost in ash and otherwise unaccounted for 9,810 1.67 577,900 100.00356 ENGINE AND BOILER TRIALS. Engine.—The work done, 21.55 indicated h. p., corresponds to 55,300 thermal units per hour, or 12.0 per cent, of the whole heat taken up by the water. The efficiency of a perfect heat- engine working between 383° and 212° F. would be 0.205. Such an engine receiving the same amount of heat as the Paxman engine, namely, 460,300 thermal units per hour, would turn into work 93,200 thermal units per hour. The actual efficiency of the engine therefore, compared with such a perfect engine, is 59 per cent. The heat received by the engine per indicated h. p. per hour was 21,350 thermal units. The brake h. p. of the engine was 18.95 * its mechanical efficiency was therefore 87.9 per cent., the indicated h. p. expended in driving the engine itself being 2.61. Boiler and Engine.—The combined efficiency of the furnace, boiler, and engine, as represented by the consumption of fuel per horse-power, works out to 9.6 per cent., 55,300 thermal units being turned into work per hour, with an expenditure of fuel having a value of 577,900 thermal units. The coal used per indicated h. p. per hour was 1.89 pounds, and per brake h. p. per hour 2.15 pounds. Steam per Indicator-cards.—The amount of steam shown by the indicator-diagrams (Figs. 18 and 19) was as below: Percentage of whole 1CCU Steam in h. p. cylinder at a pressure of 150 lbs. per square inch above the atmosphere, which corresponds to a point at 0.39 of the stroke, a little after cut-off in all cases. 65.0 Steam in 1. p. cylinder at a pressure of 10 lbs. per square inch above the atmosphere, which corresponds to a point at 0.67 of the stroke, well before release in all cases... 78.8 96. Examples of Trials of Portable Engines are, perhaps, best found in the annual reports of the competitive tests of such engines at the various agricultural exhibitions, where they are most frequently seen and subjected to trial. These trials are of peculiar interest, as exhibiting the fact that even the smallest engines may, by skilful design, construction, and man- agement, be made to give admirable economy. The following are the data and the results reported at Newcastle, G. R., by the committee of judges, aided by Messrs. Sir Frederick Bramwell and W. Anderson :* * Journal Agricult. Soc. of England, vol. xxiii; 1887.EXAMPLES OF TRIALS OF PORTABLE ENGINES. 357 O O O ! ^i® 0 mvo O' vo ! "cT cT moo m ^ m to z o z Id to c C/3 z o co to S <5 C/3 O o O c O'fOu m H oi cTd ■ o o o hJ m o> m vo mm*”|2 m m 'o*' «N> I- o - ID ^ CO ►_ •<*- o moo moo - w mm1 vo n mvo O' t'W* • • «(«Hf« . . o m w m C oo iosc nw-*" • m n u h h m 0 m O' VO 4J NVO d io|®Hs< c7) ■*■ mvo m 6 00 N w N 00 m vo in«m«*c n mvo • c« : rt-Q ) g xj J • 10 c fs£ M ^ O O rt JO to, :x 3 ; U o' ^ « <0 C OGff c .s y « d*— = e.S c<" XT c” E 5 c | «i ss-S'S fill 5 3 w £ 3 °-2-9 « < - 3 3 fl i- H--S X o'w'” to 2 o o = O .. I— V<-| M-l U o ° o O-* , oj d a; « Z a! o3 rtj 41 'u u t2 6 3 3 3 < * -55“ 2 be g ^ ^ £ 5 3 5 3 u JZSO T5 o *3 be be be !2 u ” « rt ?s ; _ a> t> c < re fh tubes to normal grate-area.. I .122! -2741 .127I .092I . t641 . t71 I] .1711 -274! * This includes 8.37 square feet of heating-surface, due to the eight Paxman water-tubes in the firebox.Principal Dimensions of Boilers.—Continued. 358 ENGINE AND BOILER TRIALS. Compound Engines. CD ©5 « 0>H N Tft ® . . . O' • e*e bcS,o ■^-00 -t moo hi c Js 0 N N " £ g”0 i» 0 ®9 m m moo 00 ^ 0 ’ (ON 0» G ® g-jj* ©9 O"0 c .* 't moo mm “«? • • & O' • ttj® JB ®*o m L inrOO' CO eo ©9 VO O 00 -t- r i,S >■ io«m^t^m .(.5- S ‘ mNoovH ? fc E " Jslgi i® eo 't- t'' O' n-T~^ to O (!« t JC. • • • w ■*■ ■ H» bt,« t N -t C» m « 0» c GO """" S1* Simple Engines. eo vo 0 hi m f*vo "2 5 c •+«R5h? Sj-I " «- - si'3 wo eo O"0 m • h m t moo m .= JTJ _ H Kg’0 00 0 eo * Ms m m m -r ir n .E S\s si’5 w^oo 00 O ■** lb * 00 t- mvo 00 ~ -g •§ eo •49 3-7 63-1 i932 ii34 12.83 ii No damper to ash pan, throttle- valve in chimney. eo Sitci'O 0 0 JJ 'g c . • - • moo > bt ci >- M 0) -e-VO N OJ sGO N « H H ^ £ J EE g-o Catalogue number Area of chimney in sq. feet Area of blast-nozzle in sq. inches Ratio of heating-surface to normal grate-area Weight of water in boiler when quite full in lbs Weight of water at normal level in lbs Steam-space in cubic feet Height of bottom of gauge-glass above firebox in ) inches ) Arrangement of ashpan damper j * This includes 8.37 square feet of heating-surface, due tp the eight Paxman water-tubes in the firebox,Results of Experiments connected with the Boilers.—Continued. EXAMPLES OF TRIALS OF PORTABLE ENGINES. 359 co O w H pu co to oo 0 to m O' m n iJ-CClO'NNrcitO'tM co O' IO N vO to vS- 0 co 47 8x8 O' N VO s & H • • « • - CS VO CO m OO N t>« 00 M VO W H VO CO CO to CO 8117 VO to to co VO M C^. CO M to 3125 to cn in rn vo N 0 w 3108 VO 00 O C-. ct CO vo’ o M CO 0« 147 N ■tr O' vo vo oo_ 3114 O' CO Pt 00 H S S' 3111 O' oo IO H vo co co w 0 N C CtJ O an i + n vo moinMni/iHio N • ......... - O' N t^oo -^-00 00 w. to o w co w h M 00 H 0 vr» h oo to 0 htONfoi^roM oo • H • • CO • • 1 O' so^ c VO lO co l 1 S O' IO m N VO VO O M O' P» M w H m fv n oo co O' VO 00 00 IO 00 PH O' O' H w 00 0 OO ffjH o IO O' ** M co IO N MVfilflNHO'O'n « N« H CO N W ^vo M rn N f* CO CO CO VO O' m 1-c N * CO M ■ LO : N VO VO N ID O' OO tovo VO 00 00 00 f«N ■*■ VO t"» VO • o CO VO Slow -^-00 o CO 00 t-N CN ID LO* 0) H C t^OO M CO « *-• M N W N N 01 0- oiP-rorOHH H M m " " 00 VO CO to W 0 to Ct ^ CO N H 00 VO O' H ^ o N CO 0 O' • O co uo ~T M. M. ^ ^ M W ts N ^00 -VO to to VO VO VO VO 52 to oo h O' • c-1 »- 1-1 f g "rt • z v % % Z *-> . . JD o .o -Q 3 O - - —• ■— ■—1 r—* 8 S o “ :«>§igs• :g; S3£^^|ssl'« •z 'e c •r.-Q v- > 53 3 £ , S3 4> © O > rt lutSoTjaJ-al- ro >3J'Cj30J’O',3Qr3Sy C^_ ■SI«?Isi8SsSi1 «S«3ji^gOOwJi .g •gSa’S^'a^^S^S'!: i s i s a | a g g'-f s s QHUUU^Qffl H ci CO 4 tovo C^OO O' o M N * The indicator-pipes supplied to this engine by the maker were very small.360 ENGINE AND BOILER TRIALS. 5z w w £ H W 5 6 C/2 o u < o u 2: o tfi 2 c cu s o u u ~C- CM c c b s 00 VO & "Tf 00 £ So 3 •o cl 5 5 N Q * £ — o 1) •*-* £ o cu 4J.U > w. ? '+1 _ a-S •a i . erct age M 0 M O' M co N 8 ■Ph g m d r O - in co O' m 2 U1 vn CO co ■ct co « CO £ co 0 S' 00 0 O' 1/1 co ? c £ co CO <5 Cl l-t CO in 0 co ^ M M CO rC S'NmO ° d m d O' Cl d C O Zb. > 1) :-°0-S • d • D C £ ’ • J2 O ' Cu- £ • 7? 73 • O 3 _ Sf s •«10 • >> • x> • v bO D 73 c cox: - •;3 c ^ ^'5 boo <0 e “ Cn-- ^3 m y x> .!=: co w c ^ 3 o «a c bo o ^ C T3 '§ 2 §_ CL 3 -r, « ■•5 2 I 5) G P« £ B G G bC*L c ^ 5 *3- 2.2 G XJ D 3 £ c % 3| L - bo c 3 & .b: c _ rt - - "3 ^3 o||«S- 1^11 s 5 2 S 8 f"*oo O' o M <0 CO M coco O' M O' 00 co Tj- CO X5 o o £ o c : c o ! .2 • bo 1/1 o 2 .i-e-s SuS I zue D c y v o : aJ •£ a cta o . . g : g •2 c !« c 2^ 3 XI -O a g Cj 33 o 0 £ « c: : o H362 ENGINE AND BOILER TRIALS. It will be seen that the prize simple engine at Newcastle consumed 2.678 lbs. of coal per brake horse-power, while the prize compound engine consumed only 1.902 lbs. of coal per brake horse-power, a gain of 32 per cent., or nearly one-third. In the preceding table, the engine No. 2927, tested at Car- diff, and the two prize engines and compound engine No. 3113, tested at Newcastle, are compared. The third line gives the absolute temperature of the steam in each case ; the fourth line the fall of temperature, on the supposition that the steam leaves the cylinder at a temperature proper to 1 lb. back-pressure, that is, 2150; the fifth line is the quotient of the division of the fourth by the third, and shows the proportion of work to be expected; the sixth line is the reciprocal of the fifth reduced to one as the standard of engine No* 2927, and represents the proportion in which the steam should have been consumed, that being of course inversely as the amount of duty to be expected. We see that simple engine No. 3125 should have demanded about 7 per cent, less steam, and compound engine No. 3124 23i Per cent, less than engine No. 2927. In reality the simple engine, as will be seen by the eighth line, took 13 per cent, less, while the compound took nearly 30 per cent, less than the engine No. 2927. Considered apart from their boilers, it will appear that simple engine No. 3125 and compound engine No. 3124 each in round numbers exceeded by some 6 per cent, the duty which, having regard to the increase of the pressure of steam above that of the engine tried at Cardiff, and taken here as a standard, would have led one to expect, while engine No. 3113 used an amount of steam which was about 6 per cent, more than the foregoing calculation anticipated ; so that the result fell a little below that of compound No. 3124, working at loo lbs. less pressure. These trials appear to point to the conclusion that, with our present state of knowledge, it is probable that pressures between 150 and 200 lbs. per square inch will give the best practical results with compound engines of these types. The last column in the balance-sheet shows the percentageGENERAL CONCLUSIONS. 363 which each source of loss bears to the total amount of heat generated. Heating the fuel, and the air necessary for its com- bustion, and displacing the atmosphere (items 4 and 5) take 6J per cent.; while the cost of dealing with the excess air amounts to per cent. The loss by cooling is, however, the most seri- ous of all, and, although this engine was, as regards the usual parts, lagged with exceptional care, amounted to per cent. The losses which cannot be certainly accounted for amount to less than 3! per cent. A portion of these were probably due to the increased rate of cooling while the engine was at work, for the cylinders, piston-rods, valve, spindles, and the working- parts generally were hotter, and therefore emitted more heat, than when at rest. Reverting to the balance-sheet and to its credit side, it will be seen that items 1 to 5, involving an absorption of 7 per cent, of the heat produced by the fuel, are inevitable losses; but item 6, which relates to the excess of air, and comprises the two heads of heating that excess, and of displacing the atmos- COMPARISON BETWEEN THE THEORETICAL AND ACTUAL ECONOMY DERIVED from an Increase of Steam-pressure. Cardiff. Newcastle-on-T yne. Catalogue Number...................... 1. Steam-pressures above atmosphere,lbs. 2. Temperature of steam............F.° 3. Corresponding absolute tempera- ) tures........................ . .F. 0 j 4. Falls of temperature to 2150 or 675° ) absolute.......................F. 0 ) 5 Proportions which the falls bear to ^ the original absolute temperatures. 6. The reciprocals of the above ratios, to which reciprocals the fuel act- ually consumed should correspond, • reduced to engine No. 2927 as unity............................J 7. Water actually consumed per brake ) horse-power per hour (not including > jacket-water)..................lb. ) 8. Relative proportion of water used... Simple. Simple. Compound. 2927 8125 3124 3113 ! 80 95 150 250 324 334 365 406 784 794 825 866 109 119 150 191 •139 .150 . 182 .220 I .927 •763 .632 30.22 26.40 21.33 21.38 I 00 u> .706 .707364 ENGINE AND BOILER TRIALS. phere for its reception, gives a further amount of loss = 6.34 per cent., which is preventable. In the case of this engine, No, 3125, we have an excess of air weighing 12.31 lbs. for each lb. of fuel burnt, being practically equal to the air which is theoreti- cally needed,—while in engine No. 3114 the excess was only 1.67 lbs., and in engine No. 3113, 4.02 lbs. It is clear, there- fore, that if 3125 had been worked with no greater excess than 3114, the 6.34 per cent, of loss of item 6 would have been re- duced by 5.49 per cent., leaving only .85 per cent. Analysis by Messrs. Pattinson and Stead, Middlesbrough, of Powell-Duffryri s Coal used at the Newcastle Trials. Samples were collected at intervals during the trials, ana the coal analyzed was an average of these: Carbon, . . . 88.40 available Hydrogen, . 3.65 - 0.32 = 3.33H Oxygen, . . . 2.55 = 0.32H = 2.87HaO (water) Nitrogen, . . . 0.64 Sulphur, . . . 0.76 = 1.36 per cent, pyrites Ash, . . . • 3-i7 Water, . . . . 0.83 100.00 Sulphur in ash, . 0.04 Calorific value in British Thermal Units. Carbon, . . .884 X 14,544 units = 12,856 units Hydrogen, . .6333 X 61,200 “ = 2,037 “ Pyrites estimated at 47 Total per one pound of coal, . . 14.930 units Weight of air required to burn one pound of coal, 11.38 lbs. 98. Trials of Locomotive Engines are more difficult of prosecution than are those of any other class of steam- engine. The conditions of its operation are such that it is very difficult to secure measurements of coal and of water consump-TRIALS OF LOCOMOTIVE ENGINES. 365 tion, exceedingly difficult to obtain a good arrangement for taking indicator-diagrams, and next to impossible to determine the quality of steam made while in regular work. It is com- monly expected that the engineer conducting the trials will report on the following points : (1) The dimensions of the engines, as to diameter of cylin- der, stroke, diameter of boilers, exhaust-nozzles, etc. (2) Their weight and the distribution upon driving-wheels. (3) The weight of the train hauled. (4) The weight of coal consumed in hauling the same train over the same route by each engine. (5) The quantity of water evaporated by each engine in doing the work. (6) The relative amounts of smoke and cinders which es- caped from the smoke-stacks. (7) The temperature of the gases escaping. (8) The tractive resistance of the train at the same places as indicated by a dynamometer during the trips of each engine. (9) The pressure of steam in the cylinders of the several engines, as shown by indicator-diagrams, the pressure indicated in the boilers being recorded at the same time. (10) The time occupied in making each trip and between points, which should be as nearly uniform as possible. (11) The temperature of the air at starting, in the middle, and at the end of each trip. (12) The temperature of the water in the tenders. Such trials should usually be made as nearly as possible under the ordinary conditions of every-day work. The engines are weighed in working trim, with steam up and ready to start, and also with steam off and water blown out. The coal is weighed by taking the weight of tender empty and loaded, and noting the difference in weight as that of coal con- sumed on the run, returning the balance at its end. The water is commonly measured by using a float in the tank, the rise and fall of which, and the area of water-surface, being known, the volume and weight of water become easily determinable. The water may also be weighed, as well as the coal. The rela-366 ENGINE AND BOILER TRIALS. tive quantities of smoke and cinder ejected can only be esti- mated from observation. The engine should be given a pre- liminary provisional trial to see that everything is in working order. The following is an abstract of a good example of a report describing work of this kind under the direction of Mr. Leavitt, the trial being conducted by Professor Coon: The object of these tests was to determine the relative efficiency of Strong’s locomotive boiler and cylinder and valve gear, and their ease of working and liability to derangement, as compared with the best type of American locomotive in common practice at the present time. To this end three locomotives were tested, viz.: Engine No. 444, fitted with Strong’s twin-furnace boiler and a four-valve cylinder and valve gear; engine No. 383, having an ordinary straight-top boiler, with fire-box over instead of between the frames, anthracite- coal grates, and fitted with cylinder and valve gear similar to No. 444; engine No. 357, having an ordinary boiler similar to that on engine No. 383, save that it has a “ wagon top” of eight inches, and the link-motion common in American prac- tice, with plain slide-valves having a good balancing device. The leading particulars of the three locomotives are as fol- lows : Engine 444. Engine 383. Engine 357. Cylinders, etc. Cylinder, diameter and stroke Diametf*r of piston-rod 20 ins. by 24 ins.. 3 Jins i 19 ins. by 24 ins 3J ins 20J by 24 ins. 2§f and 2$$ ins. Length of connecting-rod, centres Transverse distance between cylinder, centres 8 ft. 3 ins 7 ft Distance from centre of main drivers to centres of cylinders 12 ft. 10 ins Number of valves per cylinder Type of valves 4, 2 steam, 2 exh.. Gridiron 4, 2 steam, 2 exh.. Gridiron One. Balanced slide. Number of ports per valve 10 10 Size of ports 4# ins. by 5 in.... Full travel of valves in i-fa in Lap of valves /5 in Lead of valves, steam J in. constant /sin. constant 2J ins J in. constant.... Lead of valves, exhaust xg in. constant.... Throw of errantries Tractive force per lb. of mean effec- tive pressure on piston Cylinder clearance in cubic inches... Cylinder clearance in per cent, of pis- ton displacement 154.8 pounds 481 6.38 per cent 131.3 pounds 448 6.58 per cent 149.11 pounds. 568. 7.35 per cent.TRIALS OF LOCOMOTIVE ENGINES. 367 Wheels and Journals. Driving and truck wheel centres (all tires of steel) ................... Front truck 4-wheeled swing beam.. . Rear truck 2-wheeled swing and radi- us bar............................... Nominal diameter of driving-wheels.. Calipered diameter of driving-wheels. Diameter of front truck-wheels...... Diameter of rear truck-wheels ...... Total wheel-base of engine.......... Rigid wheel-base of engine.......... Driving axle-journals (diameter and length)............................ Front truck axle journals (diameter and length) ....................... Rear truck axle journals (diameter and length)............................ Main crank-pin journals (diameter and length)............................ Coupling-rod journals (diameter and length).............................. Weights, etc. Weight on first pair drivers, in work- ing order........................... Weight on second pair drivers, in working order....... ............. Weight on third pair drivers, in work- order....... ..................... Total on drivers, in working order__ Weight on front truck, in working * order............................. Weight on rear truck, in working order Total weight of engine, in working order................ .............. Boilers, etc. Height of boiler-centre above rail.. Kind of boiler...................... Material for boiler-plate........... Diameter of barrel inside smallest ring Diameter of fire-boxes and combustion chambers, corrugated............... Length of grates.................... Width of grates..................... Number of tubes, all iron........... Diameter of tubes, outside.......... Length of tubes ..................... Grate area, square feet............. Heating-surface, fire-box. square feet. Heating-surface, combustion chamber, square feet....................... Heating-surface, tubes, square feet— Heating-surface, total, square feet-- Ratio of heating-surface to grate area. Smallest inside diameter of smoke- stack............................... Height of top of smoke-stack above rail.............. ................ Working steam-pressure per sq. inch.. Tender. Eight-wheeled, double trucks (diam- eter of wheels)...................... Capacity of tender (gallons)........ Capacity of tender (coal)............ Weight of tender loaded............. (Same tender used on all tests.) Engine 444. Wrought-iron.. Yes........... Yes......... 62 ins...... 62$$ ins____ 30 ins...... 42 ins...... 30 ft. 2 ins.. 5 ft. 7 ins.. in. by 10 ins. 6 ins. by 11 ins.. 7 ins. by 9 ins . 5 ins. by 6 ins.. 4f ins. by 4 ins.. 30.000 pounds. 30.000 “ 30.000 90.000 27.000 21.000 138.000 7 ft. 3 ins....... T win-furnace_____ O. H. steel....... 58 ins............ 38J ins. inside .. 42! ins. outside.. 306........... if ins ....... 11 ft. 5 ins... 62 square ft. i55......... . 93....... 1600..... 1848..... 29.8 to 1. 16 ins... 14 ft. 3 ins., 160 lbs....... 33 ms......... 3000.......... 10.000 pounds. 70.000 “ Engine 383. Cast-iron. Yes....... None____ 66 ins... 65H ins 22 ft. 9 in. 7 ft. 9 in.. None......... 74,640 pounds. 24,880 “ None......... 99,520 pounds. Straight-shell . O. H. steel.... 55 ins......... 11 ft • ••'...... 3 ft. 4$ ins..... 229.............. 2 ins............ 11 ft. 4$ ins____ 37.12 square ft. 151.6............ 1234.3... 385.9... 37 3 to 1. 160 lbs.. 33ins.......... 3000........... 10.000 pounds. 70.000 “ Engine 357. Cast-iron. Yes. None. 68 ins. 66f ins. 22 ft. 1 in. 7 ft- None. 63,280 pounds. 27,440 “ None. 90,720 pounds. Wagon-top. O. H. steel. 54 ins. ft. 3 ft. 6f ins. 248. 2 ins. ft. 2 ins. 39.2 square ft. 142-3- 1429.8. 1572.1. 40.1 to 1. 140 pounds. 33 ms: 3000 10.000 pounds. 70.000 k‘368 ENGINE AND BOILER TRIALS. All the locomotives were subjected to exactly the same work, under similar conditions. The route was a continuous succes- sion of curves as sharp as 14 degrees, and grades as steep as 96 feet per mile. The water supplied to the tender on each trip was gauged as follows: On each side of the tender, and at the centre of gravity of the water space, long glass gauges, the height of the tender, were attached, with a blank wooden scale behind. The tender was filled nearly full of water and placed on the track scales, the height of water in the glass gauges being marked on the scale. These were the o marks. The water was then drawn off five cwt. at a time (560 pounds), and corresponding marks made on the scale, each division thus representing 560 pounds of water. The readings of both scales were taken immediately before and after taking water, and at the end of the run. The same tender (that of engine No. 444) was used on all the trials, without alteration. All the coal for each run was weighed in barrows on a plat- form scale, and any coal remaining in the tender at the end of the run was deducted from the original amount, it also being weighed. At the beginning of each run, before any coal was charged to the experiment, the engine was allowed to start with a uniformly good fire. It was not practicable to get the weight of the ashes. The boiler-pressure was taken at five-minute intervals on each run. The temperature of the feed-water at the three tanks where water was taken did not vary half a degree from 64.3° F. throughout the trials. Engine No. 357 has a boiler feed-pump attached to one cross-head, any deficiency of water being supplied by an injector. Engines Nos. 444 and 383 were supplied with water solely by injectors. All indicator-cards were taken on up-grade. Two observers took simultaneous cards from each end of both cylinders, while a third, in the cab, noted the steam-pressure, position of throttle- lever and reverse-lever, the exact time the cards were taken,TRIALS OF LOCOMOTIVE ENGINES. 369 and the exact time of passing the mile-posts, and the time of stopping and starting at stations. The indicator-rig, for reducing the piston-motion for the indicator-barrel, was a modified true pantagraph motion. The strings used were hard-braided linen, about 8 inches long. Cards taken at 60 miles per hour are not more than .03 inch longer than those taken at one mile per hour. No wind-shields were used, and not the slightest difficulty was experienced in taking accurate cards at over 60 miles per hour. Through the courtesy of the Pennsylvania Railroad, their dynamometer car was used. Attention is invited to the tables of coal consumed and water evaporated. On the first four trips with Engine 444 some journals on the front truck heated, and on the third trip a main crank-pin heated, so that a helper was considered desir- able. Subsequently no parts warmed at all on any of the engines. If the consumption of coal of the three locomotives be com- pared, each on two trips when they were using the same grade of coal, to wit: Locomotive No. 444, on trips No. 4 and No. 10; locomotive No. 383, on trips No. 8 and No. 14; and loco- motive No. 357, on trips No. 12 and No. 13,—it gives the average for the three respectively, as follows: % Average for engine No. 444, . * . 6,537 pounds coal “ “ “ “ 333, • • 7,441 “ “ “ “ 357, - • 3,087 —which is a difference of 646 pounds between Nos. 383 and 357, or an advantage of 8.7 per cent, in favor of engine No. 383, and a difference of 1550 pounds between Nos. 444 and 357, or an advantage of 23.7 per cent, in favor of No. 444. It is also to be borne in mind that engine No. 357 has 2 square feet more grate area and nearly 200 square feet more heating-sur- face and much better steam room than No. 383. With equal boilers there would be still greater difference in the coal. In support of this, compare the two runs of engine No. 383 on May 2 and May 10, and engine No. 357 on May 7 and May 9,370 ENGINE AND BOILER TRIALS. as to water required from Mauch Chunk to Glen Summit, all the way up grade, and no blowing-off took place. On these four runs the load was precisely the same, about 421600 pounds, besides engine and tender. The mean consumption of water from Mauch Chunk to Glen Summit for the two runs men- tioned, for the two engines, was— For No. 383,.........................17,942 pounds “ 357>........................21,585. “ —a difference of 3643 pounds in favor of No. 383, or 20.3 per cent. Coal-consumption and Water-evaporation. Date. Trip. Kind of Coal. Pounds Coal Consumed. Pounds Water Evaporated. Pounds of Water per Pound Coal. Apr. 25 1st Locomotive 444. Anthracite, mixed sizes; mostly screenings; dirty 8.114 51,940 6.40 26 2d Anthracite, mixed sizes; mostly screenings; dirty 7,698 52,132 Not taken 6-77 “ 27 3^ Anthracite, egg size; clean; had hot pin and helper 6,386- “ 28 4th Anthracite, egg size; clean 6,562 5 x,9oo 7.91 “ 29 5th Bituminous, ‘“Blacksmith’s” wet; had helper 7,216 53,8i6 7-45 May 4 9th Anthracite, pea size; clean 8,002 50,680 6-33 5 10th Anthracite, egg size; dirty 6,511 50,708 7.78 6 11 nth 15th Bituminous, lump size; Westmoreland Company’s Mines; had helper twice Anthracite, lump size; Hillman Mine 5,614 6,948 48,062 51,422 <1 00 01 0 ON “ 18 16th Bituminous, Barclay; broken sizes 7,53° 53-97° 7. l6 “ 19 17th Bituminous, Barclay; broken sizes 7»x54 52,234 7-30 Apr. 3° 6th Locomotive 383. Anthracite, lump; Hillman Mine 8,643 45,472 5.26 May 2 7th Anthracite, lump; Hillman Mine 8,311 43,512 5-23 3 8th Anthracite, lump; Franklin Mine 7,666 42,364 5-53 “ 10 14th Anthracite, lump; Franklin Mine 7,217 4i,734 5-78 May 7 12th Locomotive 357. Anthracite, lump; Franklin Mine 8,260 47,824 5-79 9 13th Anthracite, lump; Franklin Mine 7i9H 49,112 6.20 The Dynagraph-car Diagrams. The results will be given of diagrams taken in the Pennsyl- vania Company’s dynamometer car from Sugar Notch to Fair- view on May 19 and 20, and from Mauch Chunk to Glen Summit on May 19. Wherever the word “ ton” is used it will mean 2240 pounds.TRIALS OF LOCOMOTIVE ENGINES. 371 Weight of engine (No. 444) and tender: Tons. Sugar Notch to Fairview,............................ 87 Mauch Chunk to Glen Summit,......................... 85 Weight of coaches (including dynagraph car): Sugar Notch to Fairview, May 19,.................... 125 “ “ “ “ 20,................. 174 Mauch Chunk to Glen Summit, May 19, ... . 200 Per cent, which weight of train is of weight of engine and tender: Sugar Notch to Fairview May 19,.................. . 69.6 “ “ “ “20,...................50.0 Mauch Chunk to Glen Summit, May 19, .... 42.5 Traction of train only, as given by the dynamometer-diagrams (mean): Pounds. Sugar Notch to Fairview, May 19,....................6,208 “ “ “ “20,....................7,930 Mauch Chunk to Penn Haven Junction, May 19, . 5,381 Penn Haven Junction to White Haven, May 19, . 4,635 White Haven to Glen Summit, May 19, .... 7,540 Tractive force due to indicated horse-power: Pounds. Sugar Notch to Fairview, May 19,.................11,198 “ “ “ “ 20,................................... 12,220 Mauch Chunk to Penn Haven Junction, May 19, . 8,813 Penn Haven Junction to White Haven, May 19, . 7,549 White Haven to Glen Summit, May 19,..............10,945 Tractive force due to engine and tender (the difference between traction due to indicated horse-power and traction due to train): Pounds. Sugar Notch to Fairview, May 19,.................4,990 “ “ “ “20,..................4,290 Mauch Chunk to Penn Haven Junction, May 19, . 3,432 Penn Haven Junction to White Haven, May 19, . 2,914 White Haven to Glen Summit, May 19, .... 3,405372 ENGINE AND BOILER TRIALS. In the following table, column i gives the per cent, which the weight of engine and tender is of the weight of the train, while column 2 gives the per cent, which traction due to engine and tender is of traction due to train : Sugar Notch to Fairview, May 19, 1. 69.6 2. 80.0 “ “ 44 44 20, 50.0 54.0 Mauch Chunk to Penn Haven Junction, May 19, 42.5 63.0 Penn Haven Junction to White Haven, May 19, 42.5 62.9 White Haven to Glen Summit, May 19, . . . 42.5 45.1 Strain-diagram A fairly represents the action of this loco- motive. The portion shown was taken on a 96-foot grade and on a 10-degree curve, and at a speed of 13.1 miles per hour, when the locomotive was working at its best. Strain-diagram B is a portion of that taken on May 20, with engine No. 444, the portion shown being taken at precisely the same portion of the road as diagram A, viz.: on 96-foot grade and 10-degree curve, but at a speed of 27.2 miles per hour. The revolutions of the drivers of engine No. 82 can be accurately taken from the strain-diagram, every cusp on either side of the curve repre- senting a revolution. It is obvious from this diagram (A) that one end of one cylinder was doing more work than the other end of the other cylinder. Hence the great oscillations in the diagram. It is also to be noted that the train, as a whole, had its rate of oscil- lation about every six or seven revolutions of the drivers. Speed of trains: Miles per Hour, Engine No. 82,................................ 13.1 Engine No. 444,............................... 27.2 Net tractive force at time diagrams A and B were taken: Pounds. For engine No. 82,............................15*097 For engine No. 444,........................... 8,718 Resistance or tractive force, in pounds, per long ton: For engine No. 82 (diagram A),................ 53.5 For engine No. 444 (diagram B),............... 50.1TRIALS OF LOCOMOTIVE ENGINES. 373 Cylinders, 20 in. x 26 in.; drivers, 50 in. diameter; weight of train, 281.7 long tons; 96-foot grade; 10-degree curve; speed, 13.1 miles per hour; net horse-power, 527.4; net tractive force, 15,097 pounds; tractive force per ton, 53.5 pounds. 19000 16000 17000 16000 15000 14000 13000 12000 11000 10000 sooo 8000 7000 6000 5000 4000 3000 1000 0 5 second intervals t--1--r*—1-r=—1--1--1--1—i—i---1—r—«—i—1—r—i—r—T 1000 Feet Speed of train 13.1 miles per hour. Fig. 122.—Strain-diagram “A,” Locomotive No. 82. 0 —r Weight of train, 147 long tons; 96-foot grade; 10-degree curve ; speed, 27.2 miles per hour; indicated horse-power, 952.4; net horse-power, 632.3; net tractive force, 8718 pounds; trac- tive force per ton, 50.1 pounds. 11000 10000 7000 * 6000 5000 4000 0 T 5 second intervals —1---------1---------T 0 )______________1000 Feet_____________ Speed of train 27.2 miles per hour. Fig. 123.—Strain-diagram “ B,” Locomotive No. 444. For the above strain-diagrams, A and B, the net horse-power, due to tractive force of 15,097 pounds and 8718 pounds for the respective speeds are: For engine No. 82, net horse-power, 527.4 ; for engine No. 444, net horse-power, 632.3 ; or the net374 ENGINE AND BOILER TRIALS. horse-power of engine No. 82 was 83.4 per cent, of net horse- power of engine No. 444. The indicated horse-power at the time diagram B was taken is as follows : Mean effective pressures, in pounds, per square inch : P. R. End. Front End. Right-hand cylinder,.....................88.64 85.84 Left-hand “ 90.21 82.48 Total,...........................178.85 168.32 Indicated horse-power, P. R. end,..................484.3 “ “ front “.....................468.1 Total indicated horse-power,.............. 952.4 Horse-power due to traction of No. 444 engine and tender, 952.4 — 632.3 = 320.1. Per cent, which traction of No. 444 engine and tender was of traction of train, 50.6 per cent. Per cent, which weight of No. 444 engine and tender was of weight of train, 50.0 per cent. As the weight of train drawn by engine No. 444 was in part estimated, it is probably not correct within 0.6 per cent. The weight of train drawn by engine No. 82 was obtained exactly. The following is a resume of experiments on locomotives, made by M. Marie, engineer of the Paris and Lyons Railroad, on the heavy grades leading to the Mont Cenis Tunnel, which may be compared with the preceding : Water evaporated by pound of coal, .... 8.88 Consumption of coal per indicated horse-power, 2.88 “ “ u effective “ . 3.27 Average speed per hour during trials,..........17 04 Efficiency of boiler,.................65 per cent. Efficiency of engine, as compared to “ perfect” engine working under the same range of temperatures, . . . 53 “RESULTS AND CONCLUSIONS. 375 Dimensions of Locomotive. Cylinders, 21^x26 in. stroke. Drivers, 49! in. diam. Heating-surface—fire-box,........... 104 sq. ft. “ —tubes...............2,045 “ Total,................... . . 2,149 sq. ft. Grate area,......................... 22.4 “ Weight of engine and train, .... 366,474 lbs. The coal was of good quality, yielding 14,600 British thermal units when burnt in oxygen. The amount of ash was 6.5 per cent., and the coal contained 1 per cent, of moisture. The average point of cut-off during the experiments was at 19 per cent, of the stroke. 99. The Several Results and Conclusions to be derived from these, as from locomotive-trials generally, are very obvi- ous. The comparatively small quantity evaporated by the fuel is evidence that the necessarily large amount of work demanded of the locomotive boiler is obtained at great sacrifice of effi- ciency. Much larger figures than those above given are often quoted, as, for example, in the French report referred to above ; but it is probably generally the fact that some priming has produced a misleading result.* The second important matter is the consumption of water, an especially serious item in the performance of locomotives. In the trials above detailed, the weight of water used ranged from 24 to 40 pounds per I. H. P. per hour. The latter is a fair result; the former is remarkably good. The coal account gives from 3 to 5 pounds per I. H. P. per hour. Four pounds seems to be a good average amount. Little need be added to what has already been said in reference to the data and the deductions from the dynamometer records. The traction ranged, in the case given, in the neighborhood of 50 pounds per ton, or about 2.2 per cent. ; and the power exerted was from 600 to nearly 1000 horse-power. The results reported from the French trials quoted are re- * See Clarke’s Manual, p. 799.# Sy6 ENGINE AND BOILER TRIALS. markably and exceptionally excellent. Later constructions of compound locomotives, only, have rivalled them. It will be noted that the boiler had very high efficiency, 65 per cent., and that the engine had a total efficiency above one-half that of the ideal, perfect, engine operating under similar external con- ditions. The general results of comparisons of performance of simple and compound locomotive engines show an evident gain by the latter, to the extent of from 15 to 20 per cent., in fuel and steam consumption ; which gain is often partly compensated by a somewhat greater consumption of oil. The saving in coal con- sumed is often less than that of steam used ; the two quantities being, in some reported cases, 15 and 20 per cent, respectively. The pressure of steam adopted in these comparisons is com- monly 10 to 12 atmospheres. 100. Trials of Marine Engines are conducted under some- what more favorable conditions than attend trials of locomo- tives, but they are also to some extent embarrassed by the peculiar surroundings of the motor apparatus. Some of the most interesting and fruitful investigations ever made have, not- withstanding these difficulties, been made in this direction. The now well-known trials of the U. S. R. M. steamers, designed by Mr. Emery, are examples of such, and their reported per- formance is here presented.* The “ Rush,” the “ Dexter,” and the “ Dallas” are similar as respects the hulls, the screws, and the boilers; but the engines are different: that of the “ Rush” being compound ; that of the “ Dexter,” high-pressure condensing; and that of the “ Dallas,” low-pressure condensing. The vessels are each 129J feet between perpendiculars at water-line, 23 feet extreme breadth of beam, and 10 feet depth of hold. The draught of water aft is about 8 feet 10 inches. The hulls are of wood. One of the vessels averaged upward of eleven nautical miles per hour for six consecutive hours on her trial trip, and neither of them averaged less than ten knots. Each vessel has one boiler 11 feet wide on base and 9 feet * Reports to Navy and Treasury Departments ; 1874-5.TRIALS OF MARINE ENGINES. 177 high, three furnaces in each boiler, located between water-legs. The products of combustion return through tubes within the shell. The boiler of the “ Dallas,” designed for low-pressure steam, is 13 feet 9 inches long. The boilers of the two other vessels were designed for high-pressure steam, and are each 12 feet long. The steam-chimney is connected to the boiler by a large tube. The boiler of the “ Dallas” has 160 tubes, 3J inches in diameter and 9 feet 3 inches long. The boilers of the two other vessels have each 158 tubes, 3} inches in diameter and 9 feet 8 inches long. The “ Rush” is propelled by a compound engine, with ver- tical cylinders and intermediate receiver, the pistons being separately connected to cranks at right angles. The cylinders are steam-jacketed, felted, and lagged, and are, respectively, 24 and 38 inches in diameter, with 27 inches stroke of piston. The steam is distributed to the high-pressure cylinder by a short slide-valve with cut-off plates sliding on the back. The distribu- tion of steam to the low-pressure cylinder is effected by means of a double-ported slide-valve with lap proportioned to cut off the steam at about half-stroke. The surface condenser contains 900 square feet of condensing-surface. The air-pump is oper- ated from the cross-head of the low-pressure engine. The cir- culating-pump is of the centrifugal type, operated by a small engine, directly connected. The screw is 8 feet 9 inches in di- ameter, with mean pitch of 14J feet. The engine was intended to be operated regularly with a steam-pressure of 80 pounds, but during the trials, hereafter referred to, it was reduced to correspond to the pressure carried on the trial of the ■“ Dexter.” The “ Dexter” is of the inverted type, with a single cylin- der 26 inches in diameter and 36 inches stroke of piston. The cylinder is not jacketed. Steam is distributed by a short slide- valve, with adjustable cut-off plates. The condenser is located outside the frame, but it and the pumps are duplicates of those in the “ Rush.” The engine and boiler are designed to be op- erated with a maximum steam-pressure of 70 pounds. The “ Dallas” is of the inverted type, with a single cylinder378 ENGINE AND BOILER TRIALS. 36 inches in diameter, with 30 inches stroke of piston. The cylinder is not steam-jacketed, but is covered with non-conduct- ing composition and lagged. Steam is distributed by a short slide-valve, with adjustable cut-off plates. The surface condens- er is located under starboard frames, and has the same con- densing surface as those in the other vessels. The air- and cir- culating-pumps are also substantially the same. The engine and boiler are designed to be operated with a maximum steam- pressure of 40 pounds. The experiments were made with the vessel secured to the wharf. The coal was broken on the wharf to proper size (the vessel's bunkers having been closed and sealed) and filled into bags to a certain weight. The bags were sent on board, as ordered by the engineer on watch, he making record of the number of bags and the time of receipt ; a similar record being made by one of the men on the wharf. At the end of the hour the number of bags on the fire was reported and entered in the appropriate column. The ashes were measured into buckets, of which the mean weight was ascertained and tallied as they were hoisted out. The feed-water was measured before its return to the boiler; for this purpose a tank of boiler-plate was constructed, having a plate dividing it vertically into two equal parts. In the upper edge of the plate was cut a notch eight inches long, by which the height to which each half of the tank could be filled was determined. The mean of the weight of water in the half- tanks was I129I- pounds, at a temperature of 720 Fahrenheit. In the computations for each experiment, the weight of water is reduced to correspond with mean temperature. One of the feed-pumps was disconnected from the check-feed valve, and its discharge-pipe led to a receiving-tank placed over the two halves of the measuring-tank, into which this pump forced the water from the hot-well. The receiving-tank had two cocks, one over each half-tank, so that either could be filled from it at will.TRIALS OF MARINE ENGINES. 379 The other feed-pump had its suction-pipe detached from the hot-well and connected with the bottoms of the two half-tanks, through a cock on each, so that the contents of either could be drawn out and discharged. The method of measuring the water was as follows : One side having been filled, the cock above it on the receiving-tank was closed and the other over the empty half opened. When the water in the full one had settled to the edge of the notch, its cock in the feed-pipe was opened and the contents pumped into the boiler (care being taken to empty one in less time than it required to fill the other) ; when empty, its feed-cock was closed. When the water in the tank reached wTithin a few inches of the notch, a gong in the engine-room was sounded to call attention, and when it reached the notch the gong was struck twice ; at this instant the assistant engineer in the engine-room noted the reading of the counter, and an attendant in the fire-room noted and reported the height of water in the glass gauge on the boiler, as shown by a scale secured to it. The attendant at the tank also noted the time of filling, and the temperature when half emptied. By this system of checks all errors of record could be de- tected, and it was possible to preserve and utilize any continu- ous run which came to an end through derangement of the engine. All parts of the tanks, pipes, and cocks were plainly visible to the eye, and had any leaks occurred therein they must have been detected. A number of indicators were tested with steam before the trials, and a. pair selected correct by a standard gauge. Indi- cator-diagrams were taken every twenty minutes, and the data for the columns of the log, except coal and ashes, every half hour. It was ascertained that the pistons were tight by removing the cylinder-covers and letting on full steam-pressure. During the first and principal experiments with each vessel the boilers were worked at their maximum power with natural draught at the dock, the fires cleaned regularly, and the cut-offs adjusted to carry a steam-pressure of about 70 pounds during3^0 ENGINE AND BOILER TRIALS trial of the “ Rush” and “ Dexter,” and about 35 pounds dur- ing that of the “ Dallas.” At the conclusion of the principal experiments on each ves- sel, shorter experiments were made to determine the effect of varying the degree of expansion at the approximate steam- pressures of 70 and 40 pounds. In the case of the “ Dexter” the cut-off was shortened for one experiment as much as the gear provided would permit; and for this vessel, as well as for the “ Dallas,” the cut-off was gradually lengthened, during other experiments, as far as the boiler would supply steam. The long runs having demonstrated the evaporative quali- ties of the boilers, record was made, during the short runs, of the water used only. While these runs were in progress an officer was stationed at the tanks and one in the fire-room, in addition to the usual number on watch, to avoid the possibility of error. The data obtained from these engines have been carefully classified and arranged by Prof. Cotterill.* They will be given presently. Another good illustration of a marine-engine trial is the following, the report quoted being that of Sir F. J. Bramwell on the “ Anthracite.” As full an abstract is given as is needed to bring out the most salient parts and essential methods. In studying these results, it may be borne in mind that the effi- ciency of an ideal engine of similar working conditions, but free from wastes other than thermodynamic, would be about 0.26, and the weight of steam and fuel required, allowing an evaporation of 9 to 1, would be about 8 pounds and 0.9 pounds respectively, f The difference, 9 pounds of feed-water and 0.9 pounds of fuel, between the ideal and the real engine measures the wastes of the latter. The engines are of the “ direct-acting inverted” type, with' surface condensation. Two cylinders are used ; the after cylin- der has two diameters of J>ore: the upper (the smaller one) is * Cotteriirs Steam-engine, p. 292 et seq. \ For details of computation see Rankine’s Steam-engine, pp. 396-406, 410- 411.TRIALS OF MARINE ENGINES. 381 the high-pressure, and receives the steam from the boiler dur- ing the first half of the down stroke; the lower (the larger diameter) is the medium, or “ intermediate/' and is supplied at the up stroke with the steam which in the high-pressure did the work of the preceding down stroke. The exhaust from the bottom of the after cylinder passes into a chamber, from which is afforded the supply to the low-pressure (the forward) cylin- der. Thus there is obtained in two cylinders an expansion of thirty-two times. The surface condenser is composed of a number of close- topped, galvanized, wrought-iron tubes, standing vertically from a tube-plate, and having within them smaller tubes open at both ends, and proceeding upward from a lower tube-plate, so that the water from the sea passes up through the central tubes and down the annular spaces to the inlet of the circulating-pump. The exhaust steam comes into contact with the exterior of the tubes, the condensed steam being drawn off by the air- pump, and returned to the hot-well, which surrounds the upper part of the condenser. The space between the high-pressure piston and the upper side of the intermediate piston is in connection with the cham- ber which supplies the low-pressure cylinder. The cylinders and their covers are heated by steam circu- lating through wrought-iron pipes cast into the thickness of the metal, and are very efficiently cleated, so as to prevent loss of heat. The boiler is the Perkins boiler, formed of successive hori- zontal rows of wrought tubes (3 inches external diameter), con- nected at frequent intervals by vertical thimbles, the whole series being contained in a wrought-iron double casing, having the space filled in with vegetable black. The boiler is supplied with distilled fresh water. The drawings show the high-pressure cylinder to be 8 in. bore, the “ intermediate" 16 in. bore, and the low-pressure 23 in. bore, but the cylinders were all somewhat smaller than the foregoing dimensions; the high-pressure cylinder is 7J in. diameter, the intermediate is 15-^f in., and the low-pressure is382 ENGINE AND BOILER TRIALS. in. The stroke in both cylinders is i ft. 3 in. The diam- eter of the piston-rods (the areas of which have to be deducted from the area of the intermediate piston, and from that of the underside of the low-pressure piston) is 2f in. Preparations for the trial had been made by weighing out 50 cwt. of “ Nixon's navigation hand-picked lumps," into 50 one-hundredweight sacks. These were ranged on deck. The bunkers, which were full, were sealed up both above and below. A spring-balance was hung up on deck, close Jo the stoke- hold hatch, and an assistant caused each sack of coal to be re- weighed just before it was lowered for use. The sacks were afterwards separately weighed to obtain the net weight of the coal. Fifty pounds of dry wood were served out, and two sacks of coal; and with these the fire was laid (the grate has an area of about 15 square feet). The fire was lit................................ at 6.28 A.M. Steam was up and the engines were turned round at 718 A.M. The height of water in the boiler-gauge was noted, and also the height in the hot-well; the still- cock being shut, was sealed in that position. The steam stop-valve was sealed in its wide- open position. The engines were started and the vessel got un- der weigh....................................... at 7.20 A.M. The throttle-valve was put into the position which the engineer knew, from experience, would cause the engines to run at about 130 revolu- tions per minute after they became thoroughly heated up, and the handle was sealed into this position, the link motion being in full gear ahead. The engines were provided with a Harding’s counter, such as is used in the Navy, and there were pressure-gauges to show the boiler-pressure and the pressure in the chamber supplying the low-pressure cylinder, and the condenser wasTRIALS OF MARINE ENGINES. 383 provided with a vacuum-gauge. Four Richards indicators were fitted, viz.: one to the high- pressure end of the after cylinder, one to the intermediate end of that cylinder, one to the top and one to the bottom of the forward, the low-pressure, cylinder. The first set of diagrams was taken............ at 8.22 A.M. The first reading of the counter............... at 8.30 A.M. From this tirne until.......................... 5.45 P.M. the counter was read at the hours and half- hours, and sets of diagrams were taken at the quarter past the hour and at the quarter to the hour. The time when each sack of coals was lowered into the stokehold was noted, and also the time when the stoker commenced to use the contents of each sack. The last shovelful of the 15th sack w^as put on... at 5.18 P.M. and it was decided to stop the trial as soon as the coal then in the fire was exhausted. The engines ran on until they stopped of them- selves, and indicator-diagrams were taken, first at each quarter of an hour and then at each five minutes during the time they were gradu- ally stopping. The quarter-hour diagrams were taken until.... 6.30 P.M. when the engines were making 124 revolutions, and the five-minute diagrams were taken until the engines came to a stand................. at 7.23 P.M. or 12 hours 3 minutes after their start in the morning. The water in the boiler was pumped to the same level in the gauge as that at which it had stood in the morning, and the height of water in the hot-well was noted. The mean revolutions from 8.30 A.M. to 6.30 P.M., 10 hours, were 130.77 per minute, and from the first start to the same time being 11 hours 10384 ENGINE AND BOILER TRIALS. minutes, the mean revolutions were 130.4 per minute. From the start at 7.20 A.M. to 6.3O P.M., 11 hours and 10 minutes, the engines developed an average gross indicated horse-power of 80.55, but from 6.30 to the time (7.23 p.m.) that the engines stopped of themselves, from the fire having burnt itself out, the power was gradually diminishing. We estimate the 50 lbs. of wood as of about one-third the value of coal as fuel, say........................ 17 lbs. The coal, 15 cwt.................................. 1680 “ 1697 lbs. The loss of water for the whole 12 hours was 23^ gallons. The amount of lubrication was small, involving an expendi- ture of about one gallon of lard-oil, while cylinder and slide lubrications are in the Perkins system inadmissible and, with the metal used, unnecessary. At the conclusion of the trial the assistants took away the four indicators, and the spring-balance with which the coals were weighed. All these were tested, with the result that the balance and the 100-lb. spring (used in the high-pressure cylin- der-indicator) and some of the lighter springs were absolutely accurate, and that the variation in the others is too trifling to call for any allowance in calculating the mean pressures. The mean pressures of the various diagrams were ascertained by dividing the areas of the diagrams obtained with the planim- eter by the lengths of the diagrams. The data obtained were as follows, as subsequently recom- puted and arranged by the board appointed by the U. S. Navy Department to examine the vessel, the extraordinary pressures and ratios of expansion adopted attracting attention and mak- ing this work important: Data and Results from the Experiment by Mr. Bramwell on the “ Anthracite.” Economic results: Pounds of coal consumed per hour per indicated horse-power................................. i./l 14TRIALS OF MARINE ENGINES. 385 Pounds of coal consumed per hour per net horse-power................................... 1.9634 Pounds of coal consumed per hour pef total horse-power................................... 1.4291 Pounds of combustible consumed per hour per indicated horse power......................... 1.6259 Pounds of combustible consumed per hour per net horse-power............................... 1.8653 Pounds of combustible consumed per hour per total horse-power............................. 1-3577 Pounds of feed-water consumed per hour per indicated horse-power........................ 17.8304 Pounds of feed-water consumed per hour per net horse-power.............................. 20.4560 Pounds of feed-water consumed per hour per total horse-power............................ 14.8893 Fahrenheit units of heat consumed per hour per indicated horse-power................ 20,021.7027 Fahrenheit units of heat consumed per hour per net horse-power...................... 22,969.9810 Fahrenheit units of heat consumed per hour per total horse-power.................... 16,719.1503 Weight of steam accounted for by the indicator: Pounds of steam present per hour in the first cylinder at the point of cutting off the ste&m, calculated from the pressure there.......... 989.3756 Pounds of steam present per hour in the first cylinder at the end of the stroke of its pis- ton, calculated from the pressure there.... 890.6505 Pounds of steam condensed per hour in the first cylinder to furnish the heat transmuted into the total horse-power developed in that cylinder by the expanded steam alone..... 45.1639 Sum of the two immediately preceding quan- tities ....................................... 935.8144 Pounds of steam present per hour in the second3&6 ENGINE AND BOILER TRIALS. cylinder at the end of the stroke of its piston, calculated from the pressure there.. .... Pounds of steam condensed per hour in the first and second cylinders to furnish the heat transmuted into the total horse-power de- veloped in those cylinders by the expanded steam alone.............................. Sum of the two immediately preceding quanti- ties....................................... Pounds of steam present per hour in the third cylinder at the end of the stroke of its pis- ton, calculated from the mean of the pres- sures there for the down-stroke and up-stroke of the piston............................ Pounds of steam condensed per hour in the first, second, and third cylinders to furnish the heat transmuted into the total horse- power developed in those cylinders by the expanded steam alone..................... Sum of the two immediately preceding quanti- ties....................................... Weight of water vaporized in the boiler from the feed temperature: Pounds of steam evaporated per hour in the boiler on the supposition that this weight was equal to the weight of steam accounted for by the indicator at the end of the stroke of the piston of the third cylinder plus 121.9992 pounds condensed in that cylinder by other causes than the development of the power; this 121.9992 pounds is calculated from the weight of 147.2538 pounds condensed per hour in the third cylinder during the experi- ment made at the New York Navy-yard on the machinery of the “ Anthracite/’ divided by the ratio 1.207, °f the difference between 1,0047334 124.8752 1,129.6086 1,118.3780 199.1154 1,3174934TRIALS OF MARINE ENGINES. 3 s; the temperatures of the initial steam in that cylinder on its piston, and of the back-pres- sure steam against it at the commencement of the stroke in that experiment and in the present one. In the navy-yard experiment the temperature of the initial' steam on the piston of the third cylinder was 245.76 de- grees Fahrenheit, and the temperature of the minimum back pressure against the piston was 150.25 degrees Fahrenheit; difference 95.51 degrees Fahrenheit. In Mr. Bramwell’s experiment the temperature of steam of the initial pressure on the piston of the third cyl- inder was 230.60 degrees Fahrenheit, and the temperature of the minimum back pressure against it was 151.47 degrees Fahrenheit; difference, 790.13 Fahr. And = 1.207, * 79-13 the ratio used above.. ..................... Difference between the weight of water vaporized in the boiler and the weight of steam ac- counted for by the indicator: Difference in pounds per hour between the weight of water vaporized (1455.9126 pounds) in the boiler and the weight of steam ac- counted for by the indicator in the first cyl- inder at the point of cutting off the steam.. Difference in per centum of the weight of water vaporized in the boiler between that weight and the weight of steam accounted for by the indicator in the first cylinder at the point of cutting off the steam....................... Difference in pounds per hour between the weight of water vaporized in the boiler and the weight of steam accounted for by the in- dicator in the first cylinder at the end of the stroke of its piston.......................... 1,439.4926 450.1170 31.27 503.6782388 ENGINE AND BOILER TRIALS. Difference in per centum of the weight of water vaporized in the boiler between that weight and the weight of steam accounted for by the indicator in the first cylinder at the end of the stroke of its piston.................... 34*99 Difference in pounds per hour between the weight of water vaporized in the boiler and the weight of steam accounted for by the in- dicator in the second cylinder at the end of the stroke of its piston.................... 309.8840 Difference in per centum of the weight of water vaporized in the boiler between that weight and the weight of steam accounted for by the indicator in the second cylinder at the end of the stroke of its piston.................... 21.53 Difference in pounds per hour between the weight of water vaporized in the boiler and the weight of steam accounted for by the in- dicator in the third cylinder at the end of the stroke of its piston........................ 121.9992 Difference in per centum of the weight of water vaporized in the boiler between that weight and the weight of steam accounted for by the indicator in the third cylinder at the end of the stroke of its piston.................... 8.47 The results of the trials of the “ City of Fall River,” which follow, exhibit the effect of varying conditions of operation as a simple and as a compound engine.* This steamer was a side-wheel freight-boat of the Old Colony Steamboat Co., ply- ing between New York, Newport, R. I., and Fall River, Mass., having a compound vertical-beam engine, H. P. cylinder 44//X8/, L. P. cylinder 68"Xi2', built by W. & A. Fletcher, North River Iron Works, New York, 1883, and so constructed that the high-pressure cylinder could be entirely disconnected, leaving a simple beam engine, having a steam-cylinder 68" X 12'* * Report on Trial of the “ City of Fall River,” Jour. Franklin Inst.; July, 1881.Results of Experiments. TRIALS OF MARINE ENGINES. 389 •Dia ‘apix Fair. Ahead. Ahead. Fair. Ahead. Even. Fair. •J3MOd-3SJOq jad jnoq jad JajB^ VO W c« ~ *? « N. : : jO VO • • •J3JBM. JO ajn jb jad mai- paa j « 'O H t*» ►« • • O O O' O' « ; • •spunod ui ‘jnoq jad jajB^vv. VO 00 ''f ^ *-! 0* m co >0 t-» • VO t'. 00 00 N vo tC tC tC 10 ! ! N N N N rO •jaMod-asjoq jad jnoq jad pso;} lbs. 2.04 2.0217 2.0388 2.8 ,.S4 •spunod ‘jnoq jad peo3 . 0 r* . m 0 . 5 N O . N co . m m ro . 1-^ • co co co ’ - . . 00 VO • 0 I I vo in • ro co co •+ ■+ •jaMod-asjOH co to h » co vo w *1 T in tC tC vo in in •jnoq jad paad§ . vo m -4- « ro ^ *J jg O' ^ 00 vo 00 to *3 rr vo m m vo in m C/5gM M M M M M M •aSnBS jad tUBats ajnssajd aSBjaAy § # a ?. <8 s •auiij Suiuun^ • m m 00 10 'f vo O QrocoM^ON'*- •OhmONOO J3mmwwi-imm •suot ssojS ‘juacuaoBidsiQ 00 00 00 00 00 00 00 Tj- 0 -vf CO N if N O' O' O' <> O' M w' H tl H M M uajBM jo jqSnBjQ O r^mr^vovo vo *; 0000000 •sapra ajniBis ‘aouBjsiQ O' O' O' O' O' 0 0 r-* • t"* t>» vo vo Ports. New York to Fall River. Fall River to New York. New York to Fall River. Fall River to New York. Fall River to New York. New York to Newport... Newport to New York. Style of Engine. Compound. Compound. Compound. Compound. Simple Simple Simple. .^.. Date. 1883. May 3.. May 4.. May 9.. May 10. June 7.. June n. June 12. 'ON d!JX >1 n ro m vo fs390 ENGINE AND BOILER TRIALS. In all cases the fires were well burnt down at the end of each trip, and, when the boat arrived at dock, fires were banked and coal put on to keep them alive while steam is blown off. Dur- ing the day, about noon, more coal was put on the fires. An hour previous to departure fires were hauled down, and spread with fresh coal, to make steam, and ordinarily no further firing is necessary until half an hour after starting. On each trip indicator-cards were taken every half-hour. Water was meas- ured by meters, readings taken every hour. The meters were tested by measuring water, under the same pressure as when feeding boilers, into a barrel, and weighing four cubic feet at a time ; variations of such tests being from 61.4 to 61.5 lbs. per cubic feet. On June 10, the cut-off on the simple engine was shortened, making it easier to keep steam and to run with wide throttle. All water-measurements, power-calculations, and coal-measurements of trips Nos. 1, 2, 3, 4, 5 were reported to the Author by Messrs. Adger and Sague, the observers. The power and coal measurements of trips Nos. 6 and 7 were made by the W. & A. Fletcher Company. Final Results. Compound engine, 14 trips between New York and Fall River, May 15 to June 2. Average time, 11 hours I2T6¥ min- utes ; coal, 20.65 tons. Simple engine, 12 trips between New York and Fall River, June 4 to 10. Average time, 11 hours 57TV minutes; coal 27.42 tons. Deducting 3 tons per trip for banking, spreading fires, don- key boiler, and kitchen (all of which is included in the amount of coal given), makes the actual consumption of coal per trip while the engine was running: for compound engine, 17.65 tons; and for simple engine, 24.42 tons. The hull of this steamer was of the following dimensions: Length on the load water-line........... 260 ft. Length over all......................... 273 “ Breadth of beam on load water-line...... 42 “TRIALS OF MARINE ENGINES, 391 Breadth of beam over guards......... Depth of hold moulded............... Draught of water, light............. Draught of water, loaded 600 tons... Depth between-deck, from top of plank- shear to top of upper frame......... 73 18 “ 9 “ 3 in- The paddle-wheels were of the feathering variety, and of the following proportions : Diameter outside of buckets............. 25 ft. 6 in. Number of buckets....................... 12 Width of each bucket................... 40 in. Length of each bucket................... 10 ft. Distance from centre of wheel-shaft to centre of eccentric actuating paddle- levers.................................. 12 in. Length of arm on bucket from axle to lever-pin............................. 21 in. The engine was found to have an efficiency of mechanism of about 83, and the paddles about 80 per cent.; their total efficiency being thus 66 per cent., or two-thirds. It was of the McNaught type. The boilers were tubular and contained— Area of grate-surface in each boiler...... 115 sq. ft. Area of water-heating surface in each boiler 3,345 “ Area of steam-heating surface in each boiler 205 “ Ratio of water-heating to grate surface... 29 Ratio of total heating to grate surface... 30.87 Weight of each boiler............. 51J tons (net) Weight of water in each boiler.... 27 “ “ The figures in the table are deduced from their performance : The thermodynamic efficiency of the steam as used in the compound engine on May 10 was computed according to the method given by Rankine.* The pressures of admission and of release and the mean back-pressure were obtained from the cards and the corresponding temperatures, densities, and latent heats arrived at by using the formulas given.f * Steam-engine, § 284. f Ibid., §§ 206, 255.392 ENGINE AND BOILER TRIALS. Results of Boiler-trial. Position of Boiler. Date of Test. Length of test (hours)................ Total coal burned (lbs.).............. Total refuse, ash, etc. (lbs.)........ Total combustible (lbs.).............. Percentage of refuse, ash, etc........ Total water evaporated (lbs.)......... Average steam-gauge pressure.......... Average height of barometer........... Average temperature of feed-water (Fhr.) Average temperature of atmosphere! Fhr.) Average temperature of chimney gases (Fhr.)............................. Number of pounds of coal per hour per sq. ft. of grate................... Number of pounds of water evaporated from the temperature of feed per lb. of coal................. ............. Number of pounds of water evaporated from the temperature of feed per lb. of combustible........................ Number of pounds of water evaporated from and at 2120 F. per lb. of combusti- ble................................... For’d. Aft. For’d. Aft. For’d. Aft. May 4 May 4 May 9 May 9 May 10 May 10 o3 18922 3699 15223 19-55 154106 68.5 30.70 102°.3 74° 13 21314 3427 17887 16.08 183785 68.5 30.70 IOI° 74° *2-5 18294 35i8 14776 19.23 151057 70 30.70 97°-1 78° 12-5 22083 3206 18877 14.52 182019 70 30.70 97° 78° 12.5 18186 3449 14737 18.97 *44391 70 3°-5 67° 77° J2-5 21650 3503 18147 16.18 176576 70 3°-5 97° -3 77° 435° 00 0 485° 495° 493° 416° 12.657 14-257 12.726 15-292 12.646 15.069 8.14 8.62 8 257 8.24 7*939 8.156 10.117 10.27 10.22 9-639 9-797 9-732 u-59 11.77 n-75 11.08 11.266 11.192 The following are the data and results: px = absolute pressure of admission = 11808 lbs. per. sq. ft. /a = absolute pressure of release =- 1363.68 “ “ p2 = mean absolute back-pressure = 704.16 “ “ tK = absolute temperature of feed-water = 558°.36 Fahr. The corresponding temperatures, densities, and latent heats are designated by the same subscripts. tx = 7740.50 Fahr. ta = 6S2°.32 Lx — 131841.14 A = 19000.39 Dx — .1909 D3 = .02606. From these data the following results were arrived at by considering the cylinders as non-conducting and the engine perfect: * The ratio of expansion r = 6.7167. Energy per cubic foot of steam admitted UDX = 27183.43 foot-lbs. * Steam-engine, pp. 388, 389.RESULTS AND DEDUCTIONS. 393 Heat expended per cubic foot of steam admitted HXDX = 163716.507 foot-lbs. Mean effective pressure, or energy per cubic foot swept through by piston, UDX ----1 = 4047.5 lbs. per sq. ft. Heat expended per cubic foot swept through by the piston, If D ——- = 24377 lbs. on square foot = pressure equivalent to T heat expended. Efficiency of steam = — ~tt 1=1 -l66. tLxDx rlx Net feed-water per cubic foot swept through by piston = — = .0284. r Cubic feet to be swept through by piston for each indicated horse-power per hour = I^-QQQQ-----------= 489.2 cubic feet. r r M. E.P.X = 4047.5 ^ ^ Feed-water per I. H. P. per hour = 489.2 X .0284 = 13.89 lbs. Actual feed-water = 17.00 lbs., nearly. 13.89 Difference, 3.11 lbs. = 22 per cent. due to cylinder condensation and leakage waste and other wastes not taken into account. This is an exceptionally excel- lent result. These wastes are usually much greater. 101. Results and Deductions and Graphical Records of these trials are rich in matters of interest to the engineer. The data obtained in the trials of the engines designed by Mr. Emery are as follows : * * Cotterill, pp. 294-296.Distribution of Heat. 394 ENGINE AND BOILER TRIALS. Total Expendi- ture of Heat and Steam. Thermal Units per i'. WtJ-O to coco \0 rf co w O' ci O' rr H O Tt in O' oo ci m vO co r^oo co rj- co co co co in in in O m in in in co *-< 'T ^ O" O' m Lbs. Steam per I.H.P. per Hour. in 0"0 MN N M M M O I'* Tf co « ci ci n H fsCO'Td in d O O *m d Cl d d d O O' O' O vO t^vO CO Ml d d d d CO u. 1/5 m M M COCO CO Tt CO d H H H H O' O T in in h tn a] f • O Tt co in w co O in in in O' d vO coco O W u as H o ££ £ • d ei M M Cl CO rrd d M H CO CO co -T £ W « < X H Heat- ing Feed. • o o I t>. O M. d ><* CO CO CO O O O N Cl o r^co co co co OOOO d N't vO vO vO vO \0 o SH V) w V) Incom- plete Expan- sion. II .2 18.0 CO ^ Cl O' W COM N M Ml d d O in h vO O' in co O' O' O' M —t M l-l M Ml OO Ml O' O' CO O o h CO Ml d d d d O 1 « • O d O O' O' *T Tt in rJ-O O Tt COCO vO rf Ji $ i r-H • co ci N JNH Tt CO Cl Cl Cl in coO m m W l-l 1-1 tM l-l O O O' O' N H H H H [X. X ° W H , z Useful Heat. cn T O 6 ci o d co co O Cl 't In cnr> O't^ co co co co in d m O O' co O' O O' w co co ’T CO O' in in N T cc d d m d mi T T T T T ul Heai ) PER CE Total. Loss in a Perfect Engine. O rfH 6 d d d 'rt- in Cl O "t Is OO Cl Cl Cl CO CO Cl OO "3-co -Ten oo co O d Cl d Cl CO m m oo in O co co in co co co co co co co is D| Sh Useful l Work. I o o O coco iO NN H MOON d O co d M O' l-l M M M T't't O' co O' O' O'CO co (/) 06 < J D u Ratio of Expan- sion. «!■# «*»-+>* w tNin m|oo d oo m ci H* ooHiHt OM^in T H«>-*»Hooesi® in co co d d ■ 5 < PH J Speed of Piston. O O co in co co M M (H O m in h vO oo h co Ml l-l d Ml in co co m d in O' mi d "T Ml 11 d d d co in co d i-i Tt" CO O d Ml d d CO CO CO u z 5 Boiler Pres- sure. Ho* Hr oaH1 in -T ci O' O' O' H®’ in m rf- in O' O' O' ■'t" f A , »-f># i-H* * \£, in in in T O' O' O' O' O' o O O CO d in in T T T Pu ' ' t ' )escription of Engine. X u < a Compound engine, low-pressure cylinder, ^jacketed. Operated as a simple engine without jacket. Operated as a sim- ple engine, with jacket in use. | Operated as a com- pound engine, with | jacket in use. c/5 < ►J < Q Simple engine, not "jacketed. i-i / % t ^ r y h ci co rf in O N GO O' O mi d rt* tn ODistribution of Heat.—Continued. RESULTS AND DEDUCTIONS. 395 55 . gws £e£ Thermal Units i.ffr. per i'. w t-i m co _ M HH O' Tt rf rf rf O" CD vC rf co O co rf rf o O t^O'O f rr^-i-tvO t> O'N co w t^* 0"0 to o r» CO CO rf rf rf rf too rf rf rf W o & ^ W 0 ZS « 5 Sg* H * Lbs. Steam i.fTr. per Hour. O NO i-N « « MNO Cl N 01 01 CO rf m co « w e» minO'O « tn co rf O O' O O n N rf coo co r^ to h o Mctwwwwcocowaw u. * r^o • ; d r^O O m r^f^O'O'r^-T Excess Back- pres- sure. O' O'N iO ^ CO co in *f rf \ \ M 1-1 O NOiCCON't O 0 co co io co co co co « co N N O *tCO . . qooo n nh r^oo 'T>ncoN 8 C « K fe OOOOCO NN • • t>. r'l r^o t^O to tooo co r*. Incom- plete Expan- sion. M M 01 01 fr O' »-* *o o M H N N N N • • m rf co hh o o tortr> O ind Nto f'-vO »o 0"t't N«CI*hWNNWmNm Ex- haust Waste. O O f-> O' rf M o co 0-0 e< n m a n • • oi O' O' CO cooo O' r^ao co to to n co O co coo N n -+■ HMHNHMMMNHf) a * ^ W h ^ w o a Q ~ u. w Sg m Tt O' n O O CO CO O O O0 H OO o CO O' O O O tn rf d"d co co O O *1- m 0>0 O O *o rf rf rf co co rf rf rfrf-f'fT}-ifcocOcOrfco cn . tJ 5£ « rt Dg 1^00 W Tf co co CO O' H hi CO co 0"t0 N O' 9 c'u’bfl O' o O r^o o o’ 01 01 O O CO 01 hi o vO o»o 1> c Pucd N CO CO N 01 CO CO CO CO CO CO CO CO CO CO NON rf rf CO O QO r^o 'tO'NCO 01 O W rf rf vO O » w o hi o O O' O O' r^O O' O O' M t-1 hi hi M hi hi H H « << PU d Ratio of Expan- sion. co O h hi i M O to oo o O' He’He’soHtHH' --+<# 'teON tow vO rf- rf vO tocON 01 t-i r> m in Speed of Piston. 0"0 f> io rf O' 0 tocOhiOOMOOii-iQvo coO COO'D h in torfoi corfO'O *-iO O >-i CO CO O' co CO COOl NCONNNWNNNCON Boiler Pres sure. H^HnssHi Hn r+* CO 01 hi irnO rf hi vOOIOcO'OOlOcO'OcoO' oo co co in m co tn oo oo O in in m co O co oo tn 55 H X W Q o bo c oj *Sc^ eg . Cl Cl O d O' CO Cl of Other Losses. 0O O' O' I— O' T ao O co 0 in O. in in Cl f" 0 4 M t-H h z w u «ti Excess Back- Pres- sure. O O M O N N T T w Tf 'T 4 - I gs < n ffi s Heat- ing Feed. in^O't r^vo m u-> ao in in in m 4 4 O' 10 4 4 ^ 0 C/) w in m O .-} Incom- plete Expan- sion. 8‘^z 6* iz O'ZZ b'X>z O' I'* M CO co co 00 M Cl mao t-H CO Ex- haust Waste. r^vo w 00 t-H M CO Cl O O in co 0 4o tJ- m co d M t-H h. X° h . z £ i 5* M O 1^ Cl O 4 tH M tj- h- co co rtiO H-O CO CO 0 M. 4 •-< O O' rfvO vO O ul Heai 5 PER CE Total. Loss in a Perfect Engine. co Tj-oo ao O m in in cncON N in in i-n. O' Cl Cl t-H *T M O O rf t-c m ao in in h [i] w 5 n con n h ao m t-H in tT CO ^ m co h < Ph J Speed of Piston. TfCO Q Tf m O O Cl Cl Cl Cl in t-H O W Cl Cl rfO Cl Cl cooo co m Cl Cl cu u Z 5 PH Boiler Pres- sure. ao w O' f'* m in N N 00 O' cl. RESULTS AND DEDUCTIONS. 397 The expenditure of heat in the last column is reckoned from the temperature of the feed-water. The number obtained by dividing 42.75 by the expenditure of heat thus reckoned is the true efficiency of the engine. Experiments 42-45 are excep- tions, made without vacuum. In calculating the expenditure of heat, the boiler has been supposed to supply dry steam ; the results obtained are too large, though not much too large, as there is no reason to believe the amount of priming consider- able. The columns headed “ Useful Heat Expended” show the useful work done, together with the corresponding necessary loss, expressed as a percentage of the total heat expended. The first of these columns is the absolute efficiency of the en- gine, and the third the efficiency relatively to a perfect engine working between the same limits of temperature. The five remaining columns show heat unnecessarily lost— (1) By the exhaust waste, by transmission of heat to the exhaust steam, and by external radiation less the heat given out by piston friction and the effects of compression. (2) By incomplete expansion, by the amount of work which the steam discharged from the cylinder might do by expand- ing down to the pressure of the condenser. (3) By misapplication of heat in heating the feed, raising the temperature of the water by direct heat instead of by com- pression of the exhaust steam. (4) By excess back-pressure, the difference between the actual back-pressure and the pressure corresponding to the temperature of the condenser. (5) By other losses, by clearance and wire-drawing and by misapplication of heat during expansion. \ All the results are given as percentages of the total expen- diture; but by multiplying by that expenditure, and dividing by 100, they may be expressed in thermal units per I. H. P. per minute; or, by multiplying by the consumption of steam and dividing by 100, they may be expressed in pounds of steam per I. H. P. per hour. These computations have been made very carefully by Pro-39§ ENGINE AND BOILER TRIALS. fessor Cotterill, and interesting conclusions are reached by their study: The large losses by exhaust waste, 27 per cent., when in the first set of these trials the steam-jacket was dispensed with, and the exaggeration of that loss by increased ratios of expansion; the reduction of this loss in the next set of four trials, by the use of the jacket; the increase of waste invariably, with increase of surface exposed ; the great gain in this direc- tion by compounding, as seen in the final set of five “ Bache” trials; while the reduction of exhaust waste is partially com- pensated by increased liquefaction in the high-pressure cylinder. The net final advantage of compounding all these effects and variations of condition are well shown by these data. The work may be studied in detail in the treatise from which the figures are quoted. The trials of the “ Dexter” developed the gain by increased piston-speed which might have been antici- pated ; and those of the “ Rush” exhibited, again, the gain due to compounding. The cylinders of the compound engine of the “ Rush” were steam-jacketed, and those of the non-compound engines were not steam-jacketed. A new non-compound engine with steam- jacketed cylinder and a boiler designed for high-pressure steam having been completed for the revenue-steamer “ Gallatin,” a series of trials of the machinery of that vessel, with and with- out steam-jacket in use, for comparison with the trials detailed in the report, were made, and the data are similarly arranged for comparison in Nos. 25 to 45 of the table. The first twelve or fifteen trials illustrate again the good effect of steam-jacket- ing in reducing wastes and permitting a great increase in the best ratios of expansion at any one pressure in the compound engine. The “ Gallatin” trials show similar effects in the non- compound engine. This latter engine consisted of a pair of single cylinders 34 inches in diameter and 30 inches stroke ; and the trials were conducted substantially as were those of the other ships. Examining the table, it is seen that all the earlier of this set of trials exhibit in a very decided manner the good effect of the jackets, reducing waste by cylinder condensation,’ and increasing the ratios of expansion at maximum efficiency,'RESULTS AND DEDUCTIONS. 399 and also the gain due to increasing pressures. A gain is ob- served in the experiments in which the jacket is filled with steam- of pressure exceeding that within the cylinder, but it is not great. The final set of three trials as a non-condensing en- gine, in effect, and both with and without jacket, exhibit con- siderable reduction of cylinder condensation ; while the good work of the steam-jacket is very observable. The work of the engineers on the trial of the “ Anthracite,” as given in the preceding article, having been challenged, a second trial was made, March 19th, 1881, obtaining very simi- lar results, the coal amounting to 1.795 pounds per indicated horse-power per hour, including the fuel used in starting fires. These results are beautifully exhibited in the accompanying chart (Fig- 124). Graphical Records, such as these, are peculiarly valuable, both as exhibiting the progress of the trial and as a check upon the written log. As is seen in the chart, the several curves, each made to an exact scale laid down on the margin, show the principal data, in their absolute values at any given time, and also their variations with the progress of the trial. Com- paring this set of curves with the figures given in the log and tabulated in the preceding article, it is easy to trace out any desired set of relations and to check the one by the other. The accuracy of the observations is also to a certain extent indicated by the smoothness of the line. Any seriously incorrect value would be immediately detected by its location outside the gen- eral trend of th*e curve of which it should locate a point. The lines showing revolutions, \Vork, and coal-consumption are al- most perfectly straight from end to end ; those showing speed and power exhibit more strikingly the slowing down at the end of the trial. The whole is a good model of this kind of record. Another set of illustrations of the beauty, convenience, and value of graphical records is found in those representing the re- sults of trials of the Italian ironclad “ Lepanto,” which follow (Fig. 125). The “ Lepanto” is a steel ship of upwards of 18000400 ENGINE AND BOILER TRIALS. I. H. P. of 400 feet length,72Jfeet beam, 28J feet draught, 46 feet depth, and of about 14000 tons displacement.* The vessel has eight “ drum” marine boilers and sixteen of the locomotive type ; and blast is supplied by twenty fans to the 24 furnaces of the one set and the 32 furnaces of the other. There are four sets of compound engines. The follow- ing are the principal data : Marine. Locomotive. Grate area in boilers,..............478.4 sq. ft. 675.2 sq. ft* Heating-surface,....................15*360 “ 26,720 “ Ratio,..............................32.1 39.6 3 steam-cylinders (each engine), diam., . . . . 54 in. Stroke of pistons,................................39 Revolutions per min.,.............................96 Maximum I. H. P.,............................... 18,000 Condenser surface,................................31,300sq.ft* 2 series of diam.,................................20J ft. Blades, in number,............................... . 3 Pitch,............................................20% ft. Surface of blade, each screw,.....................80 sq. ft. The condensed and tabulated data of two of these trials are given in the table opposite. These trials were made in the Gulf of Genoa, under the usual external conditions of work at sea. All the engines and boilers worked well. The blast was introduced into the fire- rooms, which were sealed to retain the air, under pressures varying up to 2\ and ?>i inches of water; while the consump- tion of fuel was from 45 to 70 pounds per square foot of grate per hour. The curves, Fig. 125, exhibit the performance of this great ship most admirably. The E. H. P. (effective horse-power) curve, aa, corresponds to a displacement of 14,784 tons, the mean displacement of the “ Lepanto” at the various trials. bb is the I. H. P. curve. dd is the “ indicated thrust curve,” from the I. H. P. curve* * Major Soliam ; Trans. Inst. Naval Archits., 1888.RESULTS AND DEDUCTIONS. 401 Steam Trials of the Italian Ironclad “ Lepanto.” Trials. Sea........................................ Wind...................................... Mean draught..............................ft. Area of midship section................sq. ft. Displacement............................tons Wetted surface.........................sq. ft. Mean speed of ship.....................knots Indicated horse-power..................... Number of boilers used.................... Number of engines used.................... Mode of action of engines................. Area of fire-grate used................sq. ft. Heating surface used.................j jlw . 1u ( Oval boilers Mean steam-pressure in lbs. per ) Locom *< s<^' *n‘ ( Engine-room Mean air-pressure in j Oval boiler stokeholes inches of water. ( Locom. “ “ ~ a ( In H. P. cylinders Cut'off ) In L. P. ' “ Ratio of expansion........................... Mean pressure in lbs. per j H. P. cylinders sq. in. I L. P. Mean vacuum in condensers... ............ins Revolutions per minute..................... Apparent mean slip............. ... .per cent Mean speed of piston per minute...........ft I. H. P. per sq. ft. of grate.............. Heating surface per I. H. P. in sq. ft. j Coal used per hour, in tons .................. Coal used per I. H. P. per hour, in lbs. ..... Coal burnt per sq. ft. of grate j Oval boiler lbs. per hour. ( Locom. “ “ Steam used per I. H. P. per hour as shown by indicator-cards............................... A. Calm Light N. O. 30' 4" L999 14,860 36,500 725 1.004 2 Oval 2 Compound 94.1 3,488 3,840 50 ‘48* Natural o. 1 0.6 11.1 15-3 6.8 28.6 38.8 6.4 252.2 10.7 3 48 3-82 0.9 2.02 21.3 16.1 B. Rather rough Fresh N. O. 3o' 3" I, 993 14,810 36,430 13*3 5,7H 8 Oval 4 Direct 478.4 13,952 15,360 37 34 0-94 o. 1 556 15.4 28.6 68.73 4-6 445 25 II. 9 2-45 2.69 6.9 2-75 32.3 18.2 The dotted line at the bottom of curve dd shows the increase of thrust due to the friction of the forward engines, acting at low power with the after engines. According to this the initial load friction of the engine would be about 7.5 per cent, of the load at full power. ff is the “ curve of the net resistance of the ship,” from the E. H. P. curve.402 ENGINE AND BOILER TRIALS. The undulation characteristic of the E. H. P. curve, aa, and of the net-resistance curve, ffy at about 16.5 knots, is reproduced on the I. H. P. curve, bb, and on the indicated-thrust curve, dd. Curve cc gives the ratio --- * * = p, viz., the propulsive I. H. P. coefficient or the “ net total efficiency of propulsion,” which slightly increases at the higher speeds when it approaches to the standard value 0.50. Curves mm and nn give the “ coefficient of performance” for displacement and midship section. Curve gg gives the ratio between the net resistance of the ship and the indicated thrust.Scale for Speed RESULTS AND DEDUCTIONS. 403 Curve hh gives a similar ratio when the initial friction of the engines is taken from the indicated thrust. Curve rr in Fig. 3 gives the I. H. P. in function of revolu- tions. Some of the most remarkable work done by marine engines has been seen in the performance of torpedo-boats, at high Fig. 125^.—Curves of Speed and Power, “ Lepanto.” speed, with high steam-pressure, forced draught, and high evaporation.* Thus, in the case of a Thorneycroft boat in which the water-tubular boiler is used, with engines develop- ing 89 indicated horse-power, the evaporation duty was 13.4 lbs. of water per pound of coal, and the fuel-consumption was * See Engineering, Feb. 22, 1889, p. 117.404 ENGINE AND BOILER TRIALS. 2.22 lbs. of coal per indicated horse-power per hour. In another experiment, with an air-pressure of 0.27 in. and the engines developing 282 indicated horse-power, the evaporative duty was 12.48 lbs. of water per pound of coal, and the coal- consumption 1.98 lb. of coal per indicated horse-power per hour. On another occasion, with an air-pressure of 0.49 in. and the engines developing 449 indicated horse-power, the evaporative duty was 12 lbs. of water per pound of coal, and the coal-con- sumption 1.99 lb. per indicated horse-power per hour. On a fourth trial, with 2 in. of air-pressure and the engines working with one boiler, namely, 775 indicated horse-power, the evapo- rative duty was found to be 10.29 lbs. of water per pound of coal, and the coal-consumption 2.26 lbs. of coal per indicated horse-power per hour. On the natural-draught trials the temperature of the chimney gases was 421 deg. Fahr.; and on the full-speed trial, when the boiler was supplying steam for 775 indicated horse-power, the temperature was 777 deg. Fahr. The evaporative value of the coal was found by calculation from its chemical constituents to be equal to 15.41 lbs. of water per pound of coal from and at 212 deg. Fahr. The efficiency of the boiler on the natural-draught trial was therefore 87 per cent. The efficiencies of nearly 78 per cent, with an air-pressure of 0.49 in., and over 60 per cent, with a 2-in. air-pressure, are also rejected. The weight of the boiler, with all its fittings and mountings and water, was 9.84 tons, 77.8 indicated horse-power per ton of boiler at full power—a result which compares favorably with that obtained with the locomotive boiler. 102. Pumping-engine Trials offer, perhaps, the best op- portunities to secure thoroughly complete records, and to effect satisfactory solutions of the problems arising in this branch of engineering. The following, which are presented purely as illustrative examples, are good illustrations both of method and result: A trial of a small pumping-engine built by the late George H. Corliss and supplied to the city of Providence, R. I., in 1882PUMPING-ENGINE TRIALS. 405 was made. The results were exceptionally good and the report is concise and a model in its way. It is as follows, and is sub- mitted by the city engineer :* Three days previous to the trial, a test was made to ascer- tain the actual quantity of water delivered into Sockanosset Reservoir, which is situated about one mile from the engine- house, as compared with the theoretical displacement of the plungers of the pump. This was determined by means of a weir located at the gate-chamber of the reservoir. Observa- tions were taken at this weir in a thorough and careful manner while the engine was pumping at the rate of 9065000 gallons per 24 hours ; and it was found that, for every 100 gallons dis- placed by the plungers of the pumps, 99y!~o gallons were de- livered into the reservoir. This is the most favorable result that has been brought to our knowledge. At different times, May 19th and 20th, the engine pumped at the rate of upwards of 12000000 per 24 hours. The trial was commenced Monday morning, May 22d, and ceased Saturday evening, May 27th. At 6.50 A.M., May 22d, clean fires were started under the three boilers used during the trial. There was no steam up at the time, as the fires had been allowed to run down on the previous Saturday afternoon. During the trial, the fires were banked each night at the end of the day’s run, with the excep- tion of the last day, when they were run down, as was done the previous Saturday. The average time run per day for the six days was 12 hours 27 minutes and 30 seconds. The coal used was “ Cumber- land,” or bituminous, coal, and the wood used was estimated to be equal to 40 per cent, of its weight in coal. In calculating the duty, no allowance was made for the ashes, clinkers, etc., taken from the grates and ash-pits during the trial or at its comple- tion. During the trial the engine pumped 28360162 gallons, or at the rate of 9105604 gallons per 24 hours, and developed a duty of 113271000 foot-pounds for every 100 pounds of coal, considering the total amount of coal consumed, or up- * Report of Chief Engineer; City of Providence, 1882.406 ENGINE AND BOILER TRIALS. wards of 13 per cent, in excess of the duty guaranteed in the contract; or if the coal used in kindling the fires and bank- ing is deducted from the total coal consumed during the trial,, leaving only the amount used while the engine was in opera- tion, the duty on that amount would be 138035000 foot-pounds per 100 pounds of coal. ... During all the tests that had been made, the machinery had worked with ease, without interruption from any cause,, and so smoothly as to inspire entire confidence in its reliability* The table opposite shows the daily and aggregate duty, and a summary of the principal records of the trial: The following are the essential facts and data of the trial of a pumping-engine designed by Mr. H. F. Gaskill for the city of Saratoga Springs, N. Y., as reported by Mr. Chas. T. Por- ter in June, 1883, and are abstracted from his report of July, 1883. The boilers were of the cylindrical fire-tube type, the engines compound. The methods of test were substantially those described as standard. A steam-jet gave a mild forced draught. Dimensions and Performance of Boilers. Type of boiler, cylindrical tubular. Number of boilers...........................2 Diameter of boilers............................... 66 in. Length of boilers................................. 18 ft. Number of tubes in each boiler.............. 87 External diameter of tubes......................... 3 in. Arrangement of tubes: horizontal and vertical rows. Least distance between tubes and shell of boiler 4.5 in. Height of crown of boiler above tubes....... 24 in. Heating surface in both boilers, as follows: One half the shells, 311; tubes, 2,460. Total 2,771 sq. ft. Furnace, width........................ 6 ft. * depth.......................... 5.75 ft. “ length of opening between grate-bars 5 ft. “ “ “ these openings uncovered.. 4.25 ft.Daily and Aggregate Duty and a Summary of the Principal Records. PUMPING-ENGINE TRIALS. i u h D a C’O . OV V •O— rt v rt a S O u *z. JdH o CJ o.S o.S ’O'o 5* « w c * § a S y rt 3 rs o ^ o o ^1- o M hH M o o' M M CO "3- vo O o' S’0 £, a *g 02 § o o O' o o -cf „ S' 5 o o w 9 5 < o Oz *spunod UI J9A;9D9)I saipur ui rannoH^v W M o o* •spunod ui uiBais 8* •J39J UI PB9H '8J33[UIQ puB saqsy jo *iu9D j9v OJ s O c S 2 5>ii V O U r* bc’t bO * < 407 Average gallons raised per day, 4,726,694. Average gallons raised per revolution, 174.89.ENGINE AND BOILER TRIALS. 408 Furnace, width of each grate-bar............. “ “ “ air-spaces................. “ square feet of grate-area, under both boilers.......................... “ of which the proportion in air-space is only.......................... Horizontal flues, as follows: Three times the length of each boiler.. 54 ft. From wall between boilers to chimney. 24 “ Total............................. Internal diameter of common flue and chimney................................ Height of chimney above flue................. Square feet of heating surface for each square foot of grate-area........................ Square feet of heating surface for each indi- cated horse-power............................ 1.75 in. •5 “ 51 .22 78 ft. 3 ft. 75 “ 54.3 14.9 Performance of Boilers, on the Test for Duty, 48 Hours. Coal burned................................. 16,860 lbs. “ “ per hour, on each square foot of grate.............................. 6.9 lbs. Water evaporated............................ 155,961 “ “ “ by combustion of 1 pound of coal........................ 9.25 lbs. Average temperature of feed-water................ 71.5 deg. “ pressure of steam, by gauge........... 73-66 lbs. Number of thermal units contained in 1 pound of steam................................... 1,211.1 Equivalent evaporation from 2120, under one atmosphere........................................ 10.916 lbs. Evaporation per hour from each square foot pf heating surface............................ 1.175 “ The engines had a detachable valve-gear; the valves between the high- and low-pressure cylinders and the exhaust-valves are gridiron slides.PUMPING-ENGINE TRIALS. 409 All the cylinders and their heads are steam-jacketed. The water formed by condensation in the jackets is returned to the boilers. Cylinder Dimensions. Distance between centres of cylinders....... 45.5 in. Length of stroke in all cylinders........... 36 in. Number of high-pressure cylinders........... 2 Diameter of “ “ “ .......... 21 in. “ “ “ “ piston-rods............ Area of each piston, average of both faces... Piston displacement......................... Waste-room, in clearance and passages....... Proportion which this adds to piston-displace- ment....................................... Addition to length swept through by piston. Total amount of displacement and waste- room........................................ 342.83 sq. in. 12,342 cu. in. 494 “ .04 1.44 in. 7.428 cu. ft. Number of low-pressure cylinders.......... 2 Diameter “ “ “ .......... 42 in. Number of rods in each piston............. 2 Diameter “ “ “ ............. 3.5 in. Area of each piston, average of both faces... 1,375.8 sq. in. Piston-displacement.......................49,528.8 cu. in. Waste-room in clearance and passages...... 1,347 “ Proportion which this adds to piston-displace- ment ................................... .0272 Addition to length swept through by piston. .979 in. Total amount of displacement and waste- room .................................. 29.442 cu. ft. Proportion which is added by this waste-room to the total capacity of high-pressure cylin- der................................ .105 Performance of Engines on Forty-eight-hour Test for Duty. Average number of resolutions made per minute.... *9*37 “ piston speed, in feet, “ “ “ .... 116.224io ENGINE AND BOILER TRIALS. Pressure of the atmosphere, in pounds on the square inch........................................... 14.5 Average horse-powers exerted in high-pressure cylin- ders ............................................ 109.2 Average horse-powers exerted in low-pressure cylin- ders.............................................. 76.55 Average horse-powers exerted, total............... 185.75 Pounds of coal burned per hour.................... 351 “ “ “ “ “ horse-power per hour____ 1.9 “ “ water evaporated per hour............... 3,250 “ “ “ “ “ horse-power per hour 17.5 “ “ “ “ “ hour for each horse- power exerted in the high-pressure cylin- ders............... 30 Total average back-pressure in high-pressure cylin- ders, pounds....................................... 12.5 Pounds of water per hour accounted for by indicator: 1. At point of cut-off in high-pressure cylinders. 2,061 Proportion of the quantity evaporated.....___ .634 2. At point of release in low-pressure cylinders. 2,880 Proportion of the quantity evaporated/....... .886 Temperature of the steam in all jackets, degrees.... 318.7 “ “ high-pressure exhaust (average).... 204 “ “ low “ “ ............ 153 The boilers were large, and the high duty was obtained from them at a slow rate of combustion and of evaporation. The coal was hand-picked and left only 4.73 per cent, of ashes and cinders. The whole quantity burned, assuming the fires to have been in the same condition at the close as at the commencement of the trial, was 20330 pounds, which shows a duty of 106838000 foot-pounds for each 100 pounds of coal consumed. The above assumption, however, was not fully warranted, since by omitting the first twelve hours the remain- ing forty-eight hours show a duty of 102340000 foot-pounds for each 100 pounds of coal consumed, and this may be takenPUMPING-ENGINE TRIALS. 4i r as the real duty. It exceeded the stipulated duty by nearly twenty-eight per cent. Studying the indicator-diagrams, it was found that 0.366 of the steam was condensed in the high-pressure cylinders, and exists in the state of water at the point of cut-off. During the expansion in the high-pressure cylinders, in ad- dition to the re-evaporation of water formed by the conversion of heat into work, about one half was re-evaporated. At the end of stroke in the large cylinder 88.6 per cent, of the steam from the boilers is found in the state of vapor. As a general rule, the higher the terminal pressure in the first cylinder the greater is the fall in passing into the second cylinder. While this fall affords a measure of the heat lost at that point, it suggests what the condensation of the entering steam must be in cylinders in which, although their surfaces have just been exposed to the same cool vapor, the pressure does not fall, because the supply of steam is unlimited. The economy attained, although excellent, is far short of that which such engines are capable of; the economy in the high-pressure cylinders, taken alone, is inferior to that obtained in first-class non-condensing engines; and further economy is to be obtained by preventing, in a greater degree, the transfer of heat from the steam in the steam-pipe to the condenser with- out doing work. This can be done either by employing a higher piston speed or by moderate superheating of the steam. A combination of these would, doubtless, according to Mr. Porter, effect a further increase of from twenty to twenty-five per cent* in the duty obtained. Dimensions and Performance of Pumps. Number of pumps...................... 2 Aggregate length of the two chambers in each pump................................... 7 ft. 6 in. Width of the two chambers in each pump . 2 ft. 3 in. Height of the two chambers in each pump. 2 ft. 11 in. Capacity of each pump-chamber, in cubic feet................................ 25412 ENGINE AND BOILER TRIALS. Diameter of plunger, inches............... “ “ rod.......................... Area of plunger, mean of two faces, square inches................................. Stroke of plunger, inches................. Displacement of plunger, in cubic feet.... “ “ “ “ gallons....... Number of double strokes of each plunger per minute............................. Mean velocity of plunger, in feet, per minute Number of valves acting together.......... Diameter of each valve-opening, inches____ Total area opened by valves, square inches. Lift of each valve, inches................ Mean velocity of water through valves, in feet, per second....................... Weight of each valve, pounds.............. Weight of each valve for each square inch of opening, pounds..................... Resistance to current on each square inch of opening, pounds..................... Totol loss of efficiency in pounds on square inch...........................(416 -f- .26) X Mean excess of pressure in the delivery. main, pounds on square inch............ Proportion of power lost in passage through valves................................. Time occupied by valves in closing, seconds Motion of plunger while valves are closing, inches................................. Proportion of stroke lost in closing of both admission- and delivery-valves......... Net delivery from both pumps per double stroke, gallons........................ Net delivery from both pumps per double stroke, pounds............................ 20 4 307-88 36 6.41417 48 1937 116.22 84 1.3125 113.6 •3125 5-25 .5625 .416 .26 = 1.352 84.57 .016 .04 .07 .004 190 1,584PUMPING-ENGINE TRIALS, 413 Delivery per day at eighteen revolutions per minute, gallons...................... 4,924,800 Number of double strokes made in 48-hour test.................................... 55>779 Net foot-pounds of work done on each double stroke.............................. 309,338 Net foot-pounds of work done by consump- tion of 100 lbs. of coal...................102,340,000 In contrast with the results of trial of more modern types of pumping-engine, the following are data obtained from test of a well-designed and well-constructed engine of the Cornish type, as given the Author by the City Engineer of Providence, R. I., the official having charge of the engine: Record of a Week’s Run of the Cornish Engine, Providence, R. I., 1882. Date. Hours run. Number of strokes. Strokes per minute. Average length of stroke. Total head against pump. Temperature of water in pump-well. Deg. Fahr. Weight of c.ft, of water, av. temp. Wood used to start fires. Coal value of wood used. Monday, Feb. 6th h. m. 13 22 5505 6.864 Feet. 10.79 Feet. 163.57 34° lbs. 62.378 lbs. 866 lbs. 289 Tuesday, Feb. 7th 12 50 5458 7.088 10.88 167.43 34 60.378 Wednesday, Feb. 8th.. 12 52 5466 7.080 10.91 168.83 36 62.380 Thursday, Feb. 9th Friday, Feb. 10th 12 56 5468 7 046 10.90 168.74 37 62.381 13 01 5433 6.956 10.85 169.00 37 62.381 Saturday, Feb. nth.... 12 51 5459 7.080 10.95 170.23 37 62.381 Totals and averages.... 77 52 32789 7.018 10.88 ^7-93 36° 62.380 866 289 Date. Coal used for banking. Coal used starting fires and pump- ing. Coal value of total fuel consumed. Ashes. Per cent, of ashes. Gallons pumped. Rate of pump- ing per 24 hours. Duty calcu- lated on total fuel consum- ed in foot- pounds per 1 ioq lbs. coal.. lbs. lbs. lbs. lbs. Gallons. Monday, Feb. 6th 8747 9036 395 4t^°5 3,382,944 6,074,114 51.065,000 Tuesday, Feb. 7th 750 7679 8429 569 6/5% 3,382,038 6,324,851 56,019,143 Wednesday, Feb. 8th.. 486 7681 8167 526 6lV0 3,396.335 6,335U32 58.548,000 Thursday, Feb. 9th 474 7818 8292 617 llws 3,394,463 6,299,004 57,603,853 Friday, Feb. 10th 512 7749 8261 620 7iVh 3,357,264 6.190,090 57,274'500 Saturday, Feb. nth.... 500 7600 8153 748* 9lVu 3.404,421 6,358,452 59,27 6,657 Totals and averages.... 2722 47274 50338 3475 6A 20,317,465 56,522,364 Area of plunger 8.319 sq. ft. This area js used by the Water Department. Loss of action determined by weir, 8T409o% Duty calculated on actual quantity delivered. * Included in this amount was found 53 ibs. unconsumed coal.414 ENGINE AND BOILER TRIALS. The duty of small steam-pumps has been found to range very low. A vacuum-pump tested by Mr. Emery in 1871 gave a duty on the above basis of millions; one tested by Mr. J. F. Flagg at the Cincinnati Exhibition in 1875, reduced to the same basis, gave a maximum duty of 3t2qV millions.* Several vacuum and steam pumps gave duties reported as high as 10,000,- 000 to 11,000,000, small steam-pumps doing no better than vacuum-pumps. Experiments made at the American Institute Exhibition of 1867 showed that medium steam-pumps do not, on the average, utilize more than 50 per cent, of the indicated power in the steam-cylinders, the remainder being absorbed in the friction of the machine, but more particularly in the passage of the water through the pump.* All steam-pumps, nearly, require that the steam-cylinder shall have 3 to 4 times the area of the water-cylinder to give sufficient power when the steam is accidentally low ; hence, the net, or effective, pressure forms a small percentage of the total pressure; and this, with the large extent of surface exposed internally and externally, and the total absence of expansion, makes the waste very great. A pump tested by Mr. Emery required 120 pounds weight of steam per indicated horse-power per hour, and it is believed that the cost will rarely fall below 60 pounds. As only 50 per cent, of the indicated power is utilized, ordinary steam-pumps rarely require less than 120 pounds of steam per hour for each horse-power utilized in raising water; which is equivalent to a duty of but 15,000,000 foot-pounds per 100 pounds of coal, as- suming 10,000 thermal units per pound, as in the following. The following examples of pumping-engine data illustrate a very accurate systemf proposed by Mr. Barrus: This duty of engines is expressed by the following formula: Duty = Foot-pounds work done Thermal units of heat consumed [CVwN—L] X [H + s + A] 1000000 Thermal units of heat consumed. X IOOOOOO = *Am. Machinist, Sept. 1878, p. 2. f Lond. Engineering, Feb. 15, 1889, p. 170. PUMPING-ENGINE TRIALS. 415 which = volume of piston-displacement, one stroke, cubic feet. = weight of one cubic foot of water. = number of strokes during trial. = head in feet corresponding to indication of pressure- gauge on force-main. h = heat in feet corresponding to indication of vacuum- gauge on suction-main. (This is a minus quantity where there is a head of water on the suction-main and pressure-gauge is used.) s = vertical distance in feet between the centres of two gauges. L — total leakage of plungers during trial, estimated from results of leakage test with pump at rest. C = correction for air admitted into the pump = propor- tion of the stroke during which the pump is sub- jected to the full discharge pressure, measured from the indicator-diagram. Thermal units of heat consumed = weight of water supplied to boiler by main feed-pump X total heat of steam of boiler-pressure above temperature of main feed- water, plus weight of water supplied by jacket-pump X total heat of steam of boiler-pressure above tem- perature of jacket-water, plus weight of any other water supplied by total heat above its temperature of supply. The total heat of the steam is corrected for the moisture or superheat which the steam may contain. For moisture, the correction is subtracted, and is found by multiplying the latent heat of the steam by the percentage of moisture, and dividing the product by 100. For superheat, the correction is added, and is found by multiplying the number of degrees of superheating (i.e., the excess of the tem- perature of the steam above the normal temperature of saturated steam) by 0.48. No allowance is made for heat added to the feed-water which is derived from any source except the engine or. some acces-416 ENGINE AND BOILER TRIALS. sory of the engine. Heat added to the water by the use of a flue heater at the boiler is not to be deduct- ed. Should heat be abstracted from the flue by means of a reheater connected with the intermediate receiver of the engine, this heat must be included in the total quantity supplied by the boiler. The following examples are given to illustrate the method of computation. The figures are not obtained from tests ac- tually made, but they correspond in round numbers with those which were so obtained. First Case.—Jacketed compound fly-wheel engine. Jacket- water returned to the boiler by gravity. Jet condenser with air-pump, operated by main engine. Feed-pump driven by main engine supplied with water from hot-well, which receives drip from intermediate receiver. No heaters. 1. Boiler-pressure by gauge, .... ioo lbs. 2. Capacity of pump-displacement one stroke (V),..................... . 12.5 cub. ft. 3. Number of strokes during trial (W), . 140,000 4. Pressure by gauge on force-main, . So lbs. 5. Vacuum by gauge on suction-main, . 4.8 in. 6. Vertical distance between gauges (s), 10 ft. 7. Temperature of water in pump-well, 60 deg. 8. Leakage of pump determined by trial at rest (Z), 546,000 lbs. 9. Kind of pump-diagram, . Rectangular (or C — unity) 10. Weight of water supplied by feed- pump, .............................. 188,000 lbs. 11. Weight of water supplied from jackets, 9,000 “ 12. Temperature of main feed-water, . 100 deg. 13. “ jacket-water, . . . 290 “ 14. Percentage of moisture in steam, . . 2.5 Additional Data based on the Above. 15. Weight of one cubic foot of water at 60 deg. (w),.......................... 62.4 lbs.PUMPING-ENGINE TRIALS. 417 16. Head corresponding to pressure in force-main [8° * 144] = H, . . 184.6 ft. 62.4 17. Head corresponding to vacuum in suc- tion-main [4.8 x 1.13] = h, . . . 5.4 “ 18. Total heat of i lb. of dry steam at ioo lbs. gauge-pressure, reckoned from o deg. Fahr.,..................... 1,216.5 th. un. 19. Total heat of 1 lb. of steam at 100 lbs. gauge-pressure containing 2.5 per cent, moisture,..................... 1,194.6 “ 20. Total heat of 1 lb. of steam at 100 lbs. gauge-pressure, containing 2^ per cent, of moisture, reckoned from temperature of main feed-water (100 deg. Fahr.),................... 1,094.6 “ 21. Total heat of 1 lb. of steam at 100 lbs. gauge-pressure, containing 2\ per cent, of moisture, reckoned from temperature of jacket-water (290 deg. Fahr.),.......................... 902.2 “ 22. Heat consumed by engine, 188000 X 1094.6 + 9000X902.2 . . . =213,904,600 “ Applying these quantities in accordance with the duty for- mula we have: Duty = " N V w L ~ ( H h s\ _(140000 x 12.5 x 62.4) — 546ooo_ X \i84.64-54+io/ X1000000 213904600 21730800000 X IOOOOOO . 1 = ---—-----------7---------= 100593268 foot-pounds. 213904600 ^ r Seconi Case.—Jacketed compound direct-acting duplex engine. Jet condenser. Independent air-pump, which exhausts through a heater. Feed-water supplied by an independent418 ENGINE AND BOILER TRIALS. donkey-pump, which exhausts through the heater. Jacket- water returned to boiler, without passing through heater. 1. Boiler-pressure, by gauge, .... 120 lbs. 2. Capacity of pump-displacement, one stroke (V)........................3.75 cub. ft. 3. Number of strokes during trial {N)> . 76,000 4. Pressure by gauge on force-main, . . 100 lbs. 5. Vacuum by gauge on suction-main, . 9.3 in. 6. Vertical distance between gauges (.y), 8 ft. 7. Temperature of water in pump-well, 80 deg. 8. Leakage of pump, determined by trial at rest (L), ................. 354,540 lbs. 9. Kind of pump-diagram, . Rectangular (or C = unity) 10. Weight of water supplied by feed- pump, ............................ 56,000 lbs. 11. Weight of water supplied by jackets, 6,400 “ 12. Temperature of main feed-water, . . 215 deg. 13. “ “ jacket-water, . . . 280 “ 14. Percentage of moisture in steam, . . 3 per cent. Additional Data based on the Above. 15. Weight of 1 cubic foot of water at 80 deg. (w\.......................... 62.2 lbs. 16. Head corresponding to pressure in force-main, = (H), . 231.5 ft. 17. Head corresponding to vacuum in suction-main, (9.3 X 1.13) = (A), . 10.5 “ 18. Total heat of 1 lb. of dry steam at 120 lbs. gauge-pressure, reckoned from o deg. Fahr.,..................... 1,220.2 th. un. 19. Total heat of 1 lb. of steam at 120 lbs. gauge-pressure, containing 3 per cent, of moisture,................ 1,194*2 “ Total heat of 1 lb. of steam at 120 lbs. gauge-pressure, containing 3 per 20.PUMPING-ENGINE TRIALS. 4*9 cent, of moisture, reckoned from temperature of main feed-water (215 deg. Fahr.),........... 978.3 th. un. 21. Total heat of 1 lb. of steam at 120 lbs. gauge-pressure, containing 3 per cent, of moisture, reckoned from temperature jacket-water (280 deg. Fahr.),........................... 912.2 “ 22. Heat consumed by engine, 56000 X 978-3 + 6400 X 912.2 . . . .= 60,622,880 “ Applying these quantities to the formula, we have: Duty = [(76000x3.75x62.2) — 35454Q] x (231.5 -)-8-f-io.5)xioooooo 60623880 4343115000 x IOOOOOO . . , -------= 7164.374 too.-pounds. Third Case.—Jacketed fly-wheel compound engine. Inter- mediate receiver fitted with reheater supplied with live steam. Main steam-pipe provided with separator. Water drained from jackets, reheater, and separator, into a closed tank under boiler- pressure, from which the water is supplied to the boiler by a small steam-pump. Jet condenser fitted with independent air. pump with exhausts through a heater to the atmosphere. Main supply of feed-water drawn from hot-well and fed to boiler by injector, discharging through the heater. The main feed-water and the auxiliary supply enter the same feed-pipe just before its connection to the boiler. The auxiliary pump exhausts through the heater. Number of plungers, two: diameter of each plunger, 19 in.; length of each stroke, 36 in. ; diameter of each piston-rod, 3^ in. 1. Boiler-pressure by gauge, .... 120 lbs. 2. Capacity of pump-displacement, one stroke, Each plunger = area 19 - j area 3j x 3 (F) = s.8o6 cub. ft. 144420 ENGINE AND BOILER TRIALS. 3. Number of strokes of one plunger during trial (N),................. 4. Pressure by gauge on force-main, . . 5. Vacuum by gauge on return-main, 6. Vertical distance between centres of gauges 0),........................ 7. Temperature of water in pump-well,. 8. Leakage of plunger determined by trial at rest (Z),................ 9. Correction for admission of air into the pump (C)y..................... 10. Weight of water supplied by main feed-pump,........................ 11. Weight of water supplied by auxiliary pump from the jacket, reheater, and separator-tank, .............. 12. Weight of water discharged from jackets,.......................... 13. Weight of water discharged from re- heater, .......................... 14. Weight of water discharged from sep- arator, .......................... 15. Temperature of water supplied from hot-well to injector,.............. 16. Temperature of water discharged from injector and entering heater, . 17. Temperature of feed-water leaving heater,........................... 18. Temperature of jacket-water previous to entrance to tank, ..... 19. Temperature of reheater-water pre- vious to entrance to tank, . . . 20. Temperature of separator-water pre- vious to entrance to tank, . . . 21. Percentage of moisture in the steam leaving separator, according to calo- rimeter-tests, ................... 280,000 80 lbs. 4.8 in. 10 ft. 60 deg. 546,000 lbs. •95 188,000 lbs. 12,000 lbs. 7.000 “ 2.000 “ 3,000 “ 110 deg. 180 “ 215 “ 290 “ 300 “ 340 “ 0.5 per cent.PUMPING-ENGINE TRIALS. 421 22. Weight of 1 cubic foot of water at 60 deg. (w),...................... 23. Head corresponding to pressure in force-main, —-----— = (//),. . . 62.4 7 24. Head corresponding to vacuum in suction-main, 4.8 X 1.13 = (A), . . 25. Total heat of 1 lb. of dry steam at 120 lbs. gauge-pressure, reckoned from o deg. Fahr.,................ 26. Total heat of 1 lb. of steam at 100 lbs. gauge-pressure, containing 0.1 per cent, of moisture, = 1220.2 — [.005 X 867.5 (latent heat)], . . . . 27. Total heat of 1 lb. of steam at 120 lbs. gauge-pressure, containing 0.5 per cent, of moisture, reckoned from temperature of main feed-water cor- rected for heat derived from injector = 1215.9 — [no+ (215.9 — 180.6)] = 1215.9-145.3,................... 28. Total heat of 1 lb. of steam at 120 lbs. gauge-pressure, containing 0.5 per cent, of moisture, reckoned from temperature of jacket-water (290 deg.), = 1215.9 — 292, .... 29. Total heat of 1 lb. of steam at 120 lbs. gauge-pressure, containing 0.5 per cent, of moisture, reckoned from temperature of reheater-water (300 deg.), = 1215.9—302.1, . . . . 30. Heat lost by cooling of 1 lb. of the separator-water from its tempera- ture in the boiler (349.9 deg.), to its temperature of discharge to tank (340 deg.), = 352.6 - 342.7, . . 62.4 lbs. 164.6 ft. 81.1 “ 1,220.2 th. un. 1,215.9 1,070.6 “ 923-9 913-8 “ 9.9 U422 ENGINE AND BOILER TRIALS. 31. Heat consumed by engine = (188000 X 1070.6) + (7000 X 923.9) + (2000 X 913-8) + (3000 X 9.9) . . . 209,597,400 th. un. Applying these quantities in accordance with the duty for- mula, we have: Duty = P C V w N \ ( H h ,95x5.806x62.4x280000 /x \i84.6-[-5.4+1QjJ x 100000000 209597400 19274062080 X 1000000 „ „ = —z-LZ-------------------= 91957544. 209597400 ^ Where the lift is small, and especially if the quantity to be raised is large, the centrifugal pump, driven at high speed by fast-running engines, is generally employed. Such arrange- ments are also customary in steam-vessels. Centrifugal pumps are not economical under heavy lifts or where the cost of power is serious. Mr. Hansen gives the following, probably low, estimate for the power demanded by the best-known pumps of this type : T T T „ 10 VH1-5 VH15 1. -t -l • 1 • ----- /• /r j 2x33000 6600 where V is the number of gallons raised per minute through the height, H feet.* The following table represents the results of trials of Ger- man naval ship-pumps of the centrifugal typef, as translated by Mr. Hansen: * Engineering, February 22, 1889, p. 182. f Busley : “ Die Schiffsmaschine,” 1883.PUMPING-ENGINE TRIALS. 423 Work of Centrifugal Pumps. Number of Experi- ment. Name of Ship. Duration of Trial. Steam- cylinder. Centrifugal Pumps. Lift. Minutes. Seconds. Number. Diameter. Stroke. Number of pumps. Diameter of disk. Diameter of suction-pipe. Diameter of delivery-pipe. Suction. Delivery. i Total. 1. 2. 3- 4- 5- 6. 7- 8. 9- 10. 11. 12. J3* H- in. in. in. in. in. ft. ft. fr. 1 Sachsen 4 00.0 2 11.81 11.81 2 3i-5o 13-39 14.17 5-9i 10.17 16.08 2 Wuitemburg.. 3 50.0 2 12.20 11.81 2 31-5° 13-39 14.17 5.12 9.22 14-35 3 Leipsig 2 57-5 2 19-57 12.36 2 43-70 12.36 12.36 11.65 2.62 14.27 4 Bayern 4 10.0 2 10.63 9-I3 2 29.92 12.20 12.20 7.61 7.81 15-42 5 Bismarck 5 17-5 7.87 7.87 15-75 6 Blucher 12 25.0 7.90 6.89 14.79 7 Gneisenau 12 30.0 7.22 3.81 11.03 8 Moltke 6 45 0 8-53 5-91 14-44 9 Stosch 18 5-o 2 11.81 9.84 2 27.56 8.27 8.27 6.64 6.99 13.63 10 Stein 5 4i-5 2 10.63 9-37 2 27.56 12.40 12.40 8.27 3.28 n-55 11 Olga 2 8.0 2 9.06 9-45 2 27.56 11.81 11.81 9-35 1.48 10.83 12 Marie 6 0.0 2 9.06 8.27 2 23.62 8.27 14.96 8-53 5-25 13.88 13 Blitz 1 49° 1 1 9.84 9.84 4-79 6.46 11.25 14 Mo we 8 0.0 2 6.30 5-5i 2 12.60 4.72 4.72 4-59 4-59 9.19 Quantity of Water Lifted. Steam Engine. Pump. Number of Exf ment. Total. Per minute. Boiler-pres- sure. Opening of Steam-valve. Revolutions per minute. Mean Pressure on Piston. | 1 Indicated I u V £ a V Cfl O E Brake Horse- power. Horse-power in water lifted. Useful effect. Velocity of water in pipe. Vacuum in suction-pipe. 1. i5- 16. *7- 18. 19. 20. 21. 22. 23- 24. 25. 26. gals. gals. lb. per lb. per per ft. per lb. per sq. in. sq. in. 08 cent. sec. sq. in. 1 7,678 *9*9-5 28.45 1.00 260.0 13 •07 45 9-37 20.8 5-25 3-56 2 6,754 *750.5 28.45 1.00 247.0 *5 •23 52 18 7.62 14.6 J 4-79 1 4.40 [313 3 10,912 3692.6 22.47 1.00 211.0 12 •05' 95 29 16.00 16.8 5-94 J 3-4i I3.84 4 7,920 1900.8 28.45 1.00 343-3 11 . 12 31 07 8.91 28.9 6.27 J3-7° l3-84 5 5,214 1004.0 28.45 1.00 350.0 14.10 4-73 33-7 3-3i 6 23,408 1885.8 28.45 1.00 400.0 16.37 8-45 51-6 6.20 7 22,880 1830.4 28.45 0.22 337-o 12.13 6.00 50.0 6.04 8 3,938 609.0 28.45 0.13 332 • 5 10.55 2.71 25-7 2.00 9 29,282 1620.7 28.45 1.00 385.0 6.71 11.61 6.40 U.12 10 7,4i4 1310.5 27.02 1.00 324-5 4-59 4.17 1 7•** 11 5,434 2583-9 69.98 1.00 433-o 30 •72 79 40 8.47 10.7 9.06 9-39 12 8,580 1430.0 51.20 1.00 370.0 12 •32 24 46 6.03 24.6 "i 3-15 3.84 *3 1,738 957 ° 42.67 0.25 325.0 12 •37 10 75 3.26 3°-3 4.82 1.71 14 1,276 159-5 99-56 1.00 420.0 0.27 3-5i 424 ENGINE AND BOILER TRIALS. 103. The Farey and Donkin System of trial has already been described (§ 83) in the preceding chapter. The measure- ment of the heat discharged from the condenser has been seen to furnish the simplest and most convenient and exact method possible of making a thermodynamic study of the efficiency of the engine. Professor Unwin, as just stated, has applied this system to such a study of a pumping-engine of the Worth- ington form with the “ equalizers” attached, forming what has been called the “ high-duty ” type of that machine. The fol- lowing are the reported results:* It was arranged that there should be an eight-hours' trial of the en- gines only, and a twenty-four-hours’ trial of engines and boilers conjointly. The jacket drains were rearranged so that the jacket condensation could be measured. The Engines. — The engines are compound, pumping a large volume of water on a low lift The high-pressure pistons are 27 in. in diameter, and the low-pressure pistons 54 in. The stroke is variable, the maximum from cylinder- head to cylinder-head be- ing 44 in. During the trials the stroke remained very constant and about 43 inches. The engines work rams 40 in. in diam- eter, and the same stroke as the steam-pistons. Com- pensating cylinders absorb work during the first half of the stroke, and give it back during the second half. There are two to each engine, 11 in. in diameter, loaded by air-pres- sure to about 120 pounds per square inch. The pumps lift \ Mean Diagram from diagrams taken from Engine A. \ at 12.30 p.m. Nov. 5th. 1888 p Saturation curve is drawn for the mean weight of feed water used per stroke during the trial 10 20 30 40 50 Volume of Cylinder in cubic feet Fig. 128.—Mean Diagrams. 9150.11. Fig. 127.—Diagrams. 9150.A Fig. 126.—Indicator-diagrams. * London Engineering, December 7, 1888.THE FARE Y AND DONKIN SYSTEM. 425 water from a well communicating with the river and deliver it through two 3-ft. mains to the reservoirs, nine miles distant. The head during the trials measured by the difference of pres- sure in the suction and dis- ibs. charge pipes, was from 50 ft. to 65 ft. The head was measured by mercury col- umns fixed in the engine- house, communicating with the suction and delivery mains in accordance with the provision of the contract. The suction-gauge com- Fig. 130.—Chart of Trial.42& ENGINE AND BOILER TRIALS. municated with the suction-pipe just below the floor, and the pressure-gauge was set to give pressures reckoned from the floor-level. The sum of the mercury-gauge readings is taken as the effective lift. The pressure-gauge communicates with the delivery-main at a point beyond the stop-back valve. Con- sequently the resistance of that valve is reckoned as part of the engine friction, and is not credited to the useful work done by the pumps. The engine-cylinders are jacketed, and the steam is also taken through a jacketed reservoir between the cylinders. The jacket-water was weighed. The condensers are injection con- densers with horizontal air-pumps. The pumps were very carefully measured, with the follow- ing results: Diameter and Areas of Cylinders and Pumps. Diameter at 60 deg. F. Diameter at 316 deg. F. Area of Pis- | ton. Area of Rod. Effective Area. Means. in. in. sq. in. sq. in. sq. in. H. P. cylinder A 26.98 27.C2 573-4 17.7 555-7 Front 26.98 27.02 573-4 23.8 549-6 I H. P. cylinder B 27.02 27.06 575-1 17.7 557-4 r 553*5 Front 27.02 27.06 575-1 23.8 551-3 J L. P. cylinder A.... 53-99 54-07 2296.2 7.0 2289.2 ] Front 53-99 54-07 2296.2 17.7 2278.5 1 Q L. P. cylinder B.... 54.02 54.10 2298.7 7.0 2291.7 r22o5.1 Front 54.02 54.10 2298.7 17-7 2281.0 J Pump plungers 39-9° 1250.0 16.8 1233.2 Front 39-9° 1250.0 0 1250.0 j 4i- The Boilers.—The boilers were single-flued Cornish boilers. Three were used in the trial on October 29, and four in the trial on November 5 and 6. The boilers were 28 ft. in length and 6 ft. in diameter, with a single flue 3 ft. 6 in. in diameter for the greater part of the length. During the trials of November 5 and 6 the length of the grate was 4 ft. 6 in. Hence the grate-area of the four boilers was 60 square feet. The feed-pipe was disconnected, and the safety-valves open on the idle boilers.THE FAREY AND DONKIN SYSTEM. 427 The coal was weighed under supervision on platform-scales, which had been tested, and the weights of coal brought into the house were from time to time again tested on a Denison balance. Measurement of the Feed.—The feed was supplied from the delivery-main at a nearly constant temperature of 51 deg., the ordinary feed arrangements which supply the boilers with hot water from the jackets and hot-well being disconnected. The feed was delivered into a small gauge-tank with overflow-pipe provided with a float and counter. The capacity of this gauge- tank was determined three times by weighing the water ; and the closely accordant measurements gave a mean value of 394 pounds for the capacity. No corrections are necessary for tem- perature, and no error is introduced by any possible difference of level or condition. The feed-tank delivered by a stop-valve into another tank, from which a small Worthington feed-pump delivered the water into boilers. The Worthington pump took its steam from the boilers in use, and exhausted into the tank, from which it pumped. The whole of the steam used was therefore recondensed and re- turned to the boilers. Of the heat supplied by the boilers to work the feed-pump, nearly all was returned to the boilers. A small portion, viz., that due to the useful work of pumping and that lost by radi- ation from the tank, was no doubt lost. So far a small error telling against the main engines is introduced. The water-level at the commencement of each trial in the boiler gauge-glasses was carefully observed, and the water-level was brought to exactly the same marks at the end of the trials. The time at which each tankful was supplied to the boilers was noted, and also the feed-water temperature. Pyrometer ob- servations were made in the flues. Anemometer observations of the air supplied to each boiler were taken every half-hour during the twenty-four hours* trial, the anemometer having been previously tested. Measurement of the Air-pump Discharge.—The air-pump428 ENGINE AND BOILER TRIALS. discharge was led into a wooden tank with stilling-screens. From this it was discharged through a sharp-edged circular orifice freely into the air. The diameter of the orifice was carefully tested after the trials, and the coefficient of discharge from similar orifices is known to be 0.599. The temperature and head over the orifice was noted every 5 minutes in the first trial and every minutes in the second. The temperatures relied on in this report were taken by a fixed zero thermometer, with open scales, recently verified at Kew. Measurement of Length of Stroke.—As the stroke is variable, an arrangement of indicating-fingers was attached to each engine, and the length of stroke on each engine was noted every quarter of an hour. Indicated Power.—The indicated power was taken by four Richards indicators, chosen because they give fairly large dia- grams. These indicators were sent to Kensington after the trials and tested under steam, against a steel-tube pressure- gauge recently made, and specially tested by Messrs. Schaffer and Budenburg. No important error was found at any part of the scale with any of the springs. But with the light springs of the low-pressure-cylinder indicators there was a little frictional sticking or else a little slackness of the paral- lel-motion joints, which under a steady pressure introduced a small uncertainty of indication at one or two points in the range. Probably this would be less still when the indicator- piston was in motion, as when drawing a diagram. The indi- cator-pipes were large and were clothed. Diagrams were taken «very half-hour from all the cylinders. Trial of Engines. This was a twenty-four-hours* trial, the coal-consumption being measured, as well as the efficiency of the engine. The engines had been started in the morning, but, before beginning, the fires were cleaned and all ashes removed; also all coal was swept from the boiler-house floor. Four boilers were used, and the fires were not drawn ; but the condition of the fi^es was nearly identical at the beginning and end of the experiment.THE FAREY AND DONKIN SYSTEM. 429 The trial commenced at 10.22 A.M. on the 5th and ended ex- actly at 10.22 A.M. on the 6th. The barometer varied a little during the twenty-four hours, the mean being 29.78 in. (corrected), corresponding to 14.627 lbs. per square inch. The temperature of the injection varied from 48.6 deg. Fahr. to 49.5 deg. Fahr., the mean being 49.2 deg. Fahr. The mean boiler-pressure was 60.29 lbs. per square inch (74.92 lbs. per square inch absolute). The mean vacuum shown by the mercury-gauge on the engine was 27.76 in., or 13.63 lbs. per square inch. The total head of water on the pumps was about 55 ft. at starting and 53.5 ft. at the end of the trial; the mean head was 53.68 ft. The air-pressure in the compensating air-vessel varied from 118 lbs. to 122 lbs. per square inch (above atmosphere). Speed and Length of Stroke.—The speed was remarkably constant, the mean speed being 17.282 double strokes per minute. The engines made 24,886 double strokes in the twenty-four hours. The length of stroke was even more con- stant than in the previous trials. The mean length of stroke was 43.06 in. for engine A and 43.05 for engine B. Indicated Horse-power.—The reduction of diagrams taken every half-hour during the first eight hours, and every hour afterwards, gave the following results. The variation of the diagrams was very small: Indicated Horse-power. Engine A.—H. P. back 31.662 “ L. P. “ 3I-I45 62.807 'i u H.P. front 34-176 a L.P. u 31-685 65.861 Engine B.— -H. P. back 35-856 << L. P. a 28.073 63.929 a H. P. front 35-236 a L. P. a 27.684 62.920 128.668 126.849 Total indicated horse-power of both en- gines, ............................... 255-5I7430 ENGINE AND BOILER TRIALS. The Pump.—The mean lift was 53.68 ft.; mean length of stroke, 3.5879 ft.; number of strokes per minute, 17.282. Hence the pumps lifted 13,407 gallons per minute, or 804,396 gallons per hour, or 19,305,504 gallons in the twenty-four hours. The pump horse-power is 217.06. Consequently the mechanical efficiency of the engines and pumps is 0.8495, slightly greater than in previous trials. The Feed and Jacket Water.—The feed-water had a mean temperature of 51.07 deg. The total feed-water used was 108,537.4 lbs., or 4522.39 lbs. per hour. The jacket-water was measured for six hours on the 5th and for one hour on the morning of the 6th. The rate of discharge appeared to be the same. The amount of drainage from the jackets was 706 lbs. per hour. Consequently, reckoned per indicated horse-power per hour, the quantities were: Total feed (at 51.07 deg.) per indicated horse- power per hour, ..............................17.700 Jacket condensation,.............................2.763 Used in cylinders,........................14*937 Air-pump Discharge.—The mean head over the orifice was 1.7033 ft., and the mean temperature 74.965 deg.* The total air-pump discharge was 2586 lbs. per minute, or 2522.4 lbs. of injection-water and 63.6 lbs. of condensed steam. Heat Rejected by the Engine per Indicated Horse-power per Minute.—The heat required to raise the whole air-pump dis- charge from 49.2 deg. to 74.965 deg. We get for the heat re- jected 260.7 thermal units per indicated horse-power per minute. This is Donkins coefficient. The more accurate estimate of the heat rejected is as follows: Thermal Units. Heat due to 2522.4 lbs. of injection-water per min- ute raised from 49.2 deg. Fahr. to 74.965 deg. Fahr.,...................................................64,990 * Another set of readings, with another thermometer, gave this temperature 75*r3 deg. Fahr.THE FAREY AND DONKIN SYSTEM. 431 Heat due to 63.6 lbs. of feed-water raised from 51.07 deg. Fahr. to 74.965 deg. Fahr.,...................1,519 Heat due to 11.78 lbs. of jacket-water raised 256.3 deg. Fahr.,..................................‘..............3,020 69,529 Heat rejected per indicated horse-power per minute, . 272.1 Add converted into work,........................... 42.7 314.8 Which neglects the loss by radiation. Heat used, reckoned from the Boiler-pressure.—The total heat of the steam, considered dry, reckoned from the feed-tem- perature at the mean boiler-pressure is 1156.5 thermal units per pound. Consequently the heat delivered from the boiler to the engine was 341.1 thermal units per indicated horse power per minute. The difference between this and the previous esti- mate, of 314.8, represents loss by radiation, error due to the presence of priming-water in the steam, and errors of observa- tion. If we suppose the jacket-water pumped into the boiler at the temperature of the steam (as it returns to boilers in a closed circuit), and the rest of the feed taken from the hot-well, thus removing the abnormal conditions which were present in the trial, 17.8 thermal units, or 5.2 per cent, of the heat used per indicated horse-power per minute, would be saved. Then the heat required by the engine would be, in normal conditions of working, 323.3 thermal units per indicated horse-power per minute. The following table gives the results: Double strokes per minute,..............17.282 Boiler-pressure,...................... . 60.29 lbs. per sq. in. Feed-water per minute,................... 75-37 lbs. Jacket-drains per minute,.................11.77 “ Temperature of steam,....................307.36 deg. F. Pressure on pump,.........................23.26 lbs. per sq. in. “ in compensators,..................120 “ “432 ENGINE AND BOILER TRIALS. Mean pressure in high-pressure cylinders, 32.92 lbs. per sq. in. Mean pressure in low-pressure cylinders, 6.905 “ Temperature of injection,...............49.2 deg. “ “ air-pump discharge, . . 74.965 “ Head over orifice,......................1.7033 ft. Air-pump discharge per minute, . . 2586 lbs. Injection-water per minute, .... 2522.4 “ Heat passing through engine per indicated horse-power per minute: Thermal units from boiler in saturated steam through cylinders from feed-temperature, . 287.8 Latent heat of jacket steam, . . . . 41.45 329.25 Heat rejected in air-pump discharge, . 260.24 Converted into work,..................42-75 Radiation and error,..................36.26 329.25 Indicated horse-power,..................255.5x7 Pump, “........................217.06 Mechanical efficiency,.................. -8495 Feed per indicated horse-power per hour through cylinders,..............14.937 lbs. Feed per indicated horse-power through jackets,............................. 2.763 Piston speed per minute,................124 ft. Measurement of Coal used.—The floor having been swept clean, the coal was brought in in quantities of about 8 cwt., and the time of finishing each lot was noted. The ash-pits were cleaned before the trial, and afterwards nothing was removed till the end. The fires were cleaned before the trial began, and again at 4 A.M. on Tuesday morning. The fires were not touched at the end of the trial, but the ash-pits were immedi- ately cleaned, and the whole of the ashes were treated thus : First the clinkers were separated and weighed. The rest of the ashes were sifted through a sieve with $ in. mesh. All thatTHE FAREY AND DONKIN SYSTEM. 433 passed through the sieve is treated as incombustible ash, although probably one-third of it is unburned carbon. What did not pass through the sieve is treated as unburned fuel. Analysis in similar cases has shown that the cinders retained by the sieve are almost entirely carbon. The coal account, then, stands thus: Pounds. Pounds. Gross weight of coal brought into boiler-house, 11,180 Left on floor at end of trial,.....................99 Cinders sifted out of ashes,.......................132 231 Total coal used,.......................... 10,949 = 456.2 lbs. per hour. Pounds. The residue consisted of clinkers,................ 66 Incombustible ashes,..............................366 432 The clinkers and ashes amount to 3.9 per cent, of the coal used. The rate of combustion was 7.24 lbs. of coal per square foot of grate, or 0.19 lbs. per square foot of heating-surface, per hour. The coal used per indicated horse-power per hour was 1.785 lbs., a very good result, as the feed was supplied at 51 deg. Fahr., and the rejected heat from the jacket-drains wasted. The evaporation was 9.914 lbs. of water from 51.07 deg. at 307.36 deg. per pound of coal including clinkers and ashes. This corresponds to an evaporation of 11.867 lbs. per pound of coal from and at 212 deg. Calorimetric Value of the Coal.—The heating power of the coal has not been directly determined, but good Welsh coal is known to contain about 89 per cent, of carbon and 4 per cent, of hydrogen, the rest being oxygen, nitrogen, and ash. The calorimetric value of such a fuel is 14500)0.89 + 4*2^ X .04} = 15387 thermal units per pound.434 ENGINE AND BOILER TRIALS. But this is reckoned for a dried sample of coal, and makes, no allowance for the latent heat of the steam produced in com- bustion. There would be produced by combustion 0.36 lbs. of water per pound of coal; and the latent heat of this would be 348 thermal units: so that the available heat of a pound of dry coal would be 15,039 thermal units. The coal as taken from the yard would contain at least 1 per cent, of moisture, so that the available heat of I lb. of the coal as weighed and used would be: Thermal Units. Heat due to 0.99 lb. of coal,.................14,888 Less latent heat of 0.01 lb. of water, .... 10 14,878 Available heat, 14,878 thermal units per pound of coal as weighed and used. Taking this value, the total heat due to the combustion of the coal is 26,557 thermal units per indicated horse-power per hour, or 442.6 thermal units per minute per indicated horse-power. Of this 341.1 has been shown to be delivered to the steam. There remain 101.5 thermal units per indicated horse-power per minute to account for as losses in the boilers. The efficiency of the boilers is 0.77. The coal gave to the steam 11,466 thermal units per pound of coal used. Anemometer Observations. — Observations at each boiler every half-hour gave the following volumes of air entering per minute in cubic feet at the temperature 79.5 deg. of the boiler- house. Boiler,...............................J K L M Quantity of air in cubic feet per minute, . 420 438 486 360 Hence the total quantity of air used was 1704 cubic feet per minute, or 225 cubic feet per pound of coal. The weight of the air used was 7489 lbs. per hour, or 16.42 lbs. per pound of coal. As the coal requires nearly 12 lbs. per pound for perfect combustion, the quantity of air used was moderate. The mean temperature of the flue from the pyrometer ob- servations was 422 deg.THE FAREY AND DONKIN SYSTEM 435 Tabulating the results stated, we get: Per Hour. Per Indicated Horse-power lbs. per Hour, lbs. Coal used, . . 456.2 1.785 Air used, 29.310 Less ashes and clinkers, 7,945.2 . . 18.0 Total weight of furnace gases, . . 7,927.2 31-03 Heat Used and Lost in Boilers.—The thermal units of heat developed in the furnaces were applied thus: Thermal Units per Indicated Per Horse-power Cent. per Hour. Total heat due to coal used,.......................26,557 100 Given to steam,...............................20,466 77.1 Carried off in furnace gases,..................2,657 10.0 Probable loss due to opening firedoors to stoke, 265 1.0 Due to carbon in ashes,......................... 284 1.1 Radiation and unaccounted for,.................2,885 10.8 If there was any priming-water, the heat given to steam would be less. On the other hand, probably, the losses due to moisture in the coal and to air entering the furnaces during stoking are underestimated. Duty of the Engines.—The work done by the engines dur- ing the twenty-four hours’ trial was 106010000 foot-pounds per 112 lbs. of coal. It has been stated that for the purposes of the trial the ordi- nary conditions of the engines were altered, and heat rejected which is ordinarily used. Correcting for this, the duty of the engines in normal conditions of work must be 111.5 millions according to the results of the trial. To accompany this report, drawings are sent as follows: Drawing 1.—A mean diagram (see Fig. 128) drawn from436 ENGINE AND BOILER TRIALS. the diagrams taken on engine A at 12.30 P.M. On this has been plotted a saturation-curve for the mean speed per stroke during the trial. Since the indicated power varied so little, this saturation-curve must be very approximately the true curve for the actual diagrams. The re-evaporation during the stroke is very marked, as was to be expected from the large jacket condensation. Drawing 2.—Mean diagrams (see Fig. 129) from all the dia- grams of both engines taken at 12.30 P.M. are plotted so as to show the effective thrust of the engines at each point of the stroke. A curve of cosines is drawn giving the ± thrust of the compensators. Combining this with the engine-diagram, the resultant thrust is obtained. The effect of the inertia, how- ever, is neglected. It will be seen that the resultant thrust is remarkably uniform, and probably the effect of the inertia of the moving pistons and plungers is to increase the uniformity of this thrust. Drawing 3.—The principal observations taken during the trial have been plotted in this diagram (see Fig. 130) with time abscissae. The diagram shows the general regularity of the working of the engines during the trial. 104. Gas-engine Trials, and Reports on their results, are substantially similar to those for steam-engines ; but here engine and boiler are one, and all heat-energy is generated by the combustion of the fuel within the working cylinder; this com- pelling special methods of measuring it. The most complete and fruitful example of such a trial is described in the. report an abstract of which follows.* Some of its deductions are given in another chapter (§84). The report on these trials, by Messrs. Brooks and Steward, embodies a very careful examination, both theoretically and experimentally, of the performance of that form of motor, made with a view to determine not only the actual efficiency and economy of the machine, but also the extent and the pro- portions of the losses met with in its ordinary operation. A series of results had been obtained during investigations made *Van Nostrand’s Magazine, 1S83.GAS-ENGINE TRIALS AND REPORTS. 437 under the direction of the Author, and which included trials of various forms of gas-engine, in which the distribution of heat in useful and lost forms of energy was determined with care. In these cases, the consumption of water-gas varied from 21.2 to 23.4 cubic feet per hour and per horse-power in engines of 6 or 7 indicated horse-power, up to 23.5 to 24.5 with engines of two horse-power or less. The friction of mechanism'ranged from 4 to 5 per cent, of the total energy of combustion, and from 40 per cent, power in the smaller to 20 per cent, in the larger engines; the waste at the exhaust was from 12 per cent, of the total heat of combustion in the small to 24 per cent, in the large engines, and from 100 to 200 per cent, of the quan- tity transformed into useful work. The water-jacket carried off from 45 to 55 per cent, of all the heat supplied by the combustion of the gas. For example: the distribution of the heat of combustion, in one case worked for the Author by his senior assistant, Mr. Cartwright, was as below: Useful dynamometric work,..........14.27 Work of the pump,..........................0.42 Friction of mechanism,.....................4.10 Lost in exhaust,..........................23.55 Ditto in water-jacket, ...................46.90 Radiation, etc.,...........................10.76 Total heat supplied,................100.00 This engine developed seven horse-power at the brake, and indicated 8.9 H. P., consuming 21.2 or 27.6 cubic feet of gas, accordingly as the indicated or the dynamometric horse-power was made the basis of the calculation. It seemed to the Author desirable that this method of in- vestigation should be further developed, and that a comparison of the actual with the thermodynamic performance of the gas- engine should be made, systematically determining all the data needed to make such a comparison complete, and as nearly exact as possible. This work was undertaken by Messrs.438 ENGINE AND BOILER TRIALS. Brooks and Steward. Messrs. Schleicher, Schumm & Co., the builders of the engine, prepared one of their io horse-power Otto engines for trial, and forwarded it from Philadelphia* This engine was set up, as described in the report, and connected as shown in the plan, Fig. 131. The American Meter Company supplied meters, including one of unusual size, for the purpose of measuring the air, as well as the gas supplied, a measurement never before undertaken, so far as the Author is informed. The Meter Company also afforded all needed facilities for testing the meters, before and after the trials. The results of the investigation are given with all necessary detail in the body of the report. It will be seen, as one result of the precaution taken to measure the supply of air, that the relative volumes of air and gas are found not to be precisely determinable from figures obtained without the use of an air- meter. This precaution was also found to have value as per- mitting a correct determination of the effect of varying the supply of air and of gas independently, either with or without change of proportions (Section 5). The determination of the proper proportion of air to gas is important and interesting (section 9); and the comparison of the lines of the indicator with theoretic curves is still more interesting and novel, as well as very instructive (sections 12 and 13). The fact that combustion is progressive, even into the expansion period, is probably here, for the first time, ex- hibited by direct investigation (section 15). The analysis of the efficiency of the engine affords a means of making a comparison of the thermodynamic with the actual efficiency of this class of heat-engine. It is seen that the total heat accounted for thermodynamically, consisting of that transformed into work and that expelled with the exhaust, amounts to 34 per cent, of the total heat actually supplied, and that the other wastes, by way of the water-jacket and otherwise, amount to 66 per cent. The thermodynamic efficiency is therefore about 4^r and the actual efficiency y^V, or 52 and 17 per cent., respec- tively. (1) The Engine and Accessories.—Below are the dimensionsGAS-ENGINE TRIALS AND REPORTS. 439 of the principal parts of the engine, and of such accessories as are involved in the calculations:* Stroke................................... 14 in. (356 mm.) Diameter of piston................... ... 8.5 “ (216 “ ) “ “ piston-rod..................... 1.75 “ (44 “ ) “ “ connecting-rod (crank end)... 2.5 “ (63 “ ) “ “ connecting-rod (piston end).. 2.25 “ (57 “ ) “ “ crank-shaft.................... 4 “ (102 “ ) “ “ fly-wheels..................... 66 “ (1680 “ ) “ “ brake-pulley................... 30 “ (762 “ ) Length of brake-arm....................... 16.5 “ (420 “ ) Weight of both fly-wheels................ 1650 lbs. (750 kilos) Clearance (compression-chamber) 38 per cent, total cylinder volume. The ground-plan (Fig. 131) shows the general arrangement of the apparatus employed, A meter was used to measure the gas used by the engine, inclusive of the igniting flames. As the engine takes gas suddenly and at intervals, it is necessary to insert a flexible rubber bag in the gas-supply-pipe between the meter and engine, to act as a gas reservoir, and so relieve the meter of all strain. The air was also measured by a three-hundred-light meter, and a pair of large rubber bags was inserted in the air-pipe. A small fan-blower kept these bags constantly filled, the pressure being controlled by a check-valve in the pipe near the blower. A three-way cock in the air-pipe under the engine allowed the air to be taken either through the large meter or directly from the room. The water required for the jacket was measured by a meter placed near the gas-meter, and its temperature, both be- fore entering and after leaving the water-jacket, was measured by a standard thermometer. The three meters were tested before they were put in place. A pyrometer was placed in the exhausfcpipe as near as pos- *For complete description see U. S. Letters Patent, No. 196,473, dated October, 1887.440 ENGINE AND BOILER TRIALS. sible to the engine, giving the mean temperature of the dis- charged gases. For the purpose of measuring the work of the engine a Prony brake was employed. The indicator was placed directly upon the cover of the ex- haust passage. A speed-counter was attached to the link moving the slide- valve, to record the number of double revolutions. (2) Summary of Tests.—The observations were usually made at intervals of five minutes during the tests, oftener when any marked variation was noticed. The gas-pressure was about 30 millimeters.(ij inches) water column, and the air-pressure, when the large meter and blower were used, averaged 50 milli- meters (2 inches). The “ horse-powfer in gas burned ” was calculated from the analysis of gas, and is the dynamic equivalent of the heat capacity of the gas. The “ horse-power lost by exhaust ” andAt Varying Powers. At Full Power. GAS-ENGINE TRIALS AND REPORTS. 44I O O O O toco 00 tj- . N O co • • co coco cm O au ” to orNin c CM rl-cOH o CM Z --- 3 *1" O "o r cm O O > 1 N W'tH r -f moo O 0 O H OO 10 *3- M tO M OeX) • CO • • . . 0 • CM rj- rf OOO OO O r* ^to O CO CM to CM Cl O Oao N'O m 00 CM to ^ 0 w r^co • CO • • 00 0 to COTfO^COOO *TO coco CM m CM OO M O f"> r^* *h O to to 0- CM m r^ao • CM • • • • • co co i- 0 r^co cm to COO OCO cm to CM CM OO M O 0 m 1^ cm too 00 VO to M t^CO • CM • • • • • co co tfco m M COO OCO 3 2 3' a | “i s rj X) i • • O O' M I - 6 M « • • N Brake Horse- power. O' vO 01 tn oo ei Tt- • ID co cd vO • a ^ co m -in Indi- cated Horse- power. CD O w vO O • • M m m • • oo m -r .in * 9 Pressure in Cylinder LBS. PER SQ. IN. ABOVE Atmosphere. Mean Effec- tive. oi m oi CD O' • 01 cd O • .in CD CD -CD Mean Ter- minal. O rt ■ .in m in • .in Mean Initial. O' m w m r> • «oi O' .CD M . . M Jacket-water. Rise of Temp. o F m O' CD 01 O O vO O' m Ol oO O O' O m cO Quantity in lbs per minute. 2.O9 2.08 2.04 2.01 2.00 Gas used per hour corrected for probable error of meter. D- co m O m co O' 01 O* 6 6 O vO n O O CD »—1 Gas used by meter in cu. ft. per hour. OO OO vO 01 CD SO m Tj- 0 i-t m m m O' VO CD M . W Revolu- tions of Engine per min- ute. O M ** OO CD O' M O n* O' O' 0 0 Tf rf rt m <3- Load on Brake in lbs'. O 0 -t co m co m O . . . 0 00 m 01 rf md ^ oi Duration of Trial. j O O in m m So O O m cD 01 M cdcdtT 00000 ^ O in 0 O }£> << O M CD 01 O *-< 01 01 CD D" M M M ~ ri ri > > V p c a a, C/5 C o V ctf £ £ c 3 o o D 3 C | «£3 cU a o u> *446 ENGINE AND BOILER TRIALS. present. In one minute 1834 cubic feet of gas were used, which at 628.7 thermal units per cubic foot would furnish altogether 890,000 foot-pounds of work, if it could all be ren- dered available. For this there is obtained: Foot-pounds. On brake 4.889 h.p. or........................161,337 Engine friction 0.674 h.p. or.................22,242 In cooling water 2.09 X 106.9 X 772 or . . 172,500 Leaving for exhaust, waste, and radiation . 4 . 533,921 Or reducing these numbers to percentages of the heat of combustion: Per cent, given by brake,....................18.12 “ lost in engine friction,................2.50 Per cent, accounted for in indicator-diagram, 20.62 “ given to jacket-water,...............19.37 “ lost in exhaust, etc.,...............60.00 Comparing these figures with those obtained previously, it will be found that (1) the efficiency in this case is about 3 per cent, or 4 per cent, greater—3 or 4 per cent, more heat is con- verted into work in the cylinder; (2) less heat is given to the jacket-water and more is carried into the exhaust; that the gases retain the heat instead of its being given to the jacket-water and this increases the efficiency of the expansion. Taking Card No. 10, we get the following values of the pressures and volumes in the cylinder: Pressure absolute. Volumes in cubic ft. Beginning of compression, . . . 14.7 0.1888 End of “ . . . 54-7 0.0738 Beginning of expansion, . . . 167.7 0.0802 End of “ . . . 28.7 0.3102 Hence, since these curves are of the form pvn = constant, we get for the values of n— P'or compression curve: 547 _ /o. 1888V1 # 14.7 ~ '00738/ ’ n = 1.399.GAS-ENGINE TRIALS AND REPORTS. ‘ 447 For the expansion curve : 167.7 /0.3I02\W 28.7 “ \0.08021 n — 1.305. The expansion curve lies between an adiabatic and an iso- thermal, being nearer to an adiabatic. Hence the loss of heat to the jacket must be rather less than the heat developed during expansion. This is conformable to the fact observed of the rather low percentage of heat given to the jacket. The following are the reported results of a similar trial made for the British Society of Arts.* Trial of an Atkinson Gas-engine. I Date Sept. 21 Sept. 22 Sept. 22 2 Trial A B C 3 Duration 6 hours 3 hours £ hour 4 Power full half empty 5 Revolutions per minute 131.1 129.6 I3I-9 6 Explosions “ “ 121.6 69.1 23.8 7 Mean initial pressure 166.0 166.5 145.5 8 Mean effective pressure 46.07 47.60 48.59 9 Indicated H. P 11.15 6-59 2.3 10 Brake-load net ... 130.5 66.0 11 Brake H. P 9.48 4-74 .... 12 Mechanical efficiency 0.850 0.719 .... 13 Gas per hour, main 209.8 127.1 47-2 14 “ “ “ ignition 4-5 5.9 — 15 “ “ “ total 214-3 133-0 — 16 Gas per indicated H. P. per hour, main 18.82 19.29 20.50 17 “ " “ “ “ total. 19.22 20.18 — 18 Gas per brake H. P. per hour, main... 22.14' 26.80 .... 19 , “ “ “ “ " “ total.... 22.61 28.10 — 20 Water per hour .... 680 lbs. 260 lbs. .... 21 Rise of temperature 52.2° 67.8° .... 22 H. P. in driving engine I.67 1.85 2.3 23 Mean pressure during working stroke, equivalent to work done in pump- ing strokes, about 1.0 .... .... 24 Corresponding indicated H. P 0.26 .... .... * Journal, Feb. 15, 1889, p. 220.448 ENGINE AND BOILER TRIALS, The graphical record is as below: ;|jf PJ !§iit ffljf T5| , | ■—[ Indicated i—, Horae Power 1 | r Horae Revolutions per Minute pM# ja Explosions per Minute lilll: WMi £ Work done in millions of Foot Pounds per % honr ^ - - | tteat carri^ yV ^ ^ N ' Rise of temperature of water through jacket ^ 1 * 1 1 1 1 1 Heat cum«d*wey bi iuehet. water iwr hour , . 11.30 45 12.0 15 30 45 1.0 15 30 45 2.0 16 30 45 3.0 15 30 45 4.0 16 30 45 5.0 16 30 Fig 132.—Gas-engine Trial. From the log is obtained the following: DISTRIBUTION OF ENERGY. Heat turned into work as shown by indicator-diagrams, 22.8 Heat rejected in jacket-water,.........................27.0 Heat rejected in exhaust, lost by imperfect combustion, and otherwise accounted for, ...................50.2 100.0 The actual expenditure of heat was at the rate of 11,250 thermal units per indicated h. p. per hour, which corresponds to the absolute efficiency of 22.8 per cent, just given. It is very interesting to notice that the heat expenditure per indi- cated h. p. per hour is little more than half that of the steam- engine, a difference due, of course, to the greater range of tem- perature within which the engine works. The efficiency of the engine, as compared with a perfect engine working between the same limits of temperature, and 'receiving the same amount of heat, is 28.2 per cent. The limits of temperature being assumed, the ideal mean diagram would give the following:GAS-ENGINE TRIALS AND REPORTS. • 449 Ideal Distribution. Foot-pounds per Explosion. Percent- ages. Calorific value of the gas used per explosion: o 000896X 19200X772 13,280 IOO Heat turned into work 3,390 3,590 5,030 1,270 25 * 5 27.0 37-9 9.6 Heat rejected in jacket-water Heat rejected in exhaust Heat unaccounted forT 13,280 100.0 There seems little doubt that the largeness of the percent- age unaccounted for is due to the fact thatcombustion was not completed. • The same series of trials included an Otto engine built by the Crossley Works, which gave the following data: Trial of Otto Gas-engine. 1 ■ 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Date Sept. 19 A 6 hours Full 160.1 78.4 196.9 67.9 17.12 177-4 M 74 0.861 Sept. 20 B 3 hours Half 158.8 41.1 196.2 73-4 9-73 89.9 7-41 0.762 Sept. 20 C i hour Empty j 161.0 10.2 148.0 66.7 2.19 Sejjt. 27 £ hour With and without counter-shaft. 162.3 & 164.8 19.0 & 10.5 72.3 & 74.1 4.40 & 2.50 Trial Duration Power Revolutions per minute Explosions per minute Mean initial pressure Mean effective pressure Indicated H. P Brake-load net Brake H. P Mechanical efficiency Gas per hour, main “ “ “ ignition “ “ 44 total 351.8 3-5 202.6 3-2 49.0 355-3 205.8 16 17 18 19 20 Gas per indicated H. P. per hour, main “ “ “ “ 41 “ total. 20.55 20.8 22.38 . 20.76 21.2 Gas per brake H. P. per hour, main— “ “ “ “ “ “ total “ “ net H. P. available for electric lighting per hour, after allowing for counter-shaft, as per trial D, main.. 23-87 27.34 24.10 j- 27.4 27.77 36.8 21 22 23 24 25 Water per hour Rise of temperature H. P. in driving engine Mean pressure during working stroke, » equivalent to work don^ in pump- ing strokes, about. Corresponding indicated H. P 713 lbs. 128.o° 2.38 [ °55 480 lbs. 102.30 2.31 2.19 2.50Absolute 450 ENGINE AND BOILER TRIALS. Heat Account. Foot-pounds per Explosion. Percent- ages. Calorific value of the gas per explosion: 0.00223X19800X772 34,040 100 Heat turned into work 7,515 14.700 12,100 22.1 43.2 35.5 Heat rejected in jacket-water Heat rejected in exhaust 100.8 Fig. J33 shows an indicator-diagram obtained from each of the two engines, and also the ideal diagram with which they are compared, both, in the latter case, being reduced to a com- mon scale, and the one superposed over the other.* * Journal Brit. Soc. Arts, Feb. 15, 1889.VAPOR AND BINARY-VAPOR ENGINE TRIALS. 451 105. Vapor and Binary-vapor Engine Trials have been seldom made in such manner as to yield results at all reliable. The trial of an engine designed by Du Trembley is reported by Rankine to have given the following results.* The following are means, computed from results given in M. Gouin’s report, on the performance of the steam and aether engines of the “ Bresil ” : PRESSURE IN LBS. ON THE SQUARE INCH. In boiler or Back Mean evaporator. pressure. effective. Steam,...............43.2 7.6 11.6 -'Ether,.............31.2 5.3 7.1 Total M. E. P. reduced to the area of one piston, the areas and strokes of the pistons having been in this case the same, ....... 18.7 It appears that the proportions of the power obtained in the cylinders, respectively, were : In the steam cylinder, = .62 ; 18.7 7.1 In the aether cylinder, —— = .38. 18.7 The gain of power by the addition of the aether-engine is not quite so great as this shows; because, had the steam cylin- der been used alone, the back pressure would have been in all probability about 4.6 instead of 7.6 ; so that the mean effective pressure in the steam cylinder would have been 14.6 instead of 11.6; and the proportion of the power of the steam-engine to that of the binary engine would have been 14.6 I87 = 77’ leaving 1.00 — .77 = .23 * Steam-engine, p. 447.452 ENGINE AND BOILER TRIALS. of the power of the binary engine, as the gain due to the aether- engine. The consumption of fuel was either or 2 44 | ^s* C°a^ Per *nc^cated horse-power per hour, according as certain experiments made under peculiarly adverse circumstances were included or excluded. Rankine adds : “ The binary engine is not more economical than steam- engines designed with due regard to economy of fuel; but by the addition of an aether-engine, a wasteful steam-engine may be converted into an economical binary engine.” A binary-vapor engine, tested by Mr. Haswell, in which the auxiliary fluid was carbon disulphide, had the following con- struction : * First, a horizontal cylindrical-fire tubular boiler. Second , a tubular generator in form of a cylinder boiler, in which bisulphide of carbon (formula CS2) is vaporized, hav- ing attached in the vapor space an ordinary perforated dry pipe, all inclosed in a shell having a diaphragm plate between the outer and inner shells at both sides and at one end, thus form- ing an upper and a lower chamber around it. The opposite end is inclosed with a deep disk or bonnet, forming a communication between the lower and upper series of tubes, for the proper cir- culation of the steam with which the CS2 is vaporized. Third, a horizontal non-condensing jacketed steam-engine. Fourth, conduit-pipe, steam-jacketed from the generator to the cylinder of the engine, the jacket of the conduit communi- cating with the jacket of the cylinder, and from thence the con- densed steam led by a pipe to a steam-trap communicating with the feed-pump of the boiler. Fifth, an automatic pressure-reducing valve, for controlling the admission of steam to the shell surrounding the generator, operated by the pressure assigned to the generator, holding the vapor-pressure uniform, by admitting more or less steam to the shell as the variation of the load on the engine may require. * Trans. Am. Soc. C.E., 1887.VAPOR AND BINARY-VAPOR ENGINE TRIALS. 453 Sixth, a reducing valve for controlling the pressure in the jacket around the vapor-conduit and cylinder. Seventh, a coil-heater through which the condensed CS2 is forced back into the generator. Eighth, a surface condenser. Ninth, three small independent steam-pumps, and a con- nection to a water-main from which the water of condensation is obtained. The generator is charged to a little over one half its ca- pacity. Steam is led by a pipe to and through the automatic regu- lating valve, where it is reduced in pressure and temperature; thence to the generator through a perforated pipe between the shells below; thence flowing around the lower half of the generator; thence through the lower tubes; thence through the upper series; and thence between the shells above, thus circulating through the entire generator, CS2 taking up the heat; the steam is condensed and gravitates to the bottom of the outer shell; from thence to the boiler feed-pump, with the condensa- tion from the jacket of the conduit and cylinder, delivered through the steam-trap, and from thence returned to the boiler. Steam is also admitted through the reducing or regulating valve, to and through the jacket of the conduit to the jacket of the cylinder, where it is restricted to a reduced pressure, and as it is at a temperature due to this pressure, it is at a tempera- ture in excess of that surrounding the generator, thus imparting an increased temperature to the vapor and superheating it. The exhaust vapor from the cylinder passes around a coiled tube in the heater, thence through a surface condenser, from which it is drawn off by the second pump and delivered into an auxiliary condenser. The liquid CS2 gravitates from the auxiliary condenser to a reservoir. From thence it is drawn by the third pump and delivered through the coil in the heater, thence to the gener- ator, where it is again vaporized. A plant designed for the development of this design was tested.454 ENGINE AND BOILER TRIALS. The operation of the engine was continued five hours, which, as that period involved the cleaning of the fire, was held to afford time for a test. The reported data are as below: Pressure, steam—boiler,.....................75.8 pounds “ “ shell, . ...................15.3 “ “ vapor—engine,......................76 “ “ “ mean, by indicator, . . . 31.35 “ Water evaporated,...........................5.71 cubic feet Revolutions per minute,.....................100 Vacuum,.....................................9.85 pounds Coal consumed,............................ . 600 “ Horse-power indicated,......................86.64 From which it appears that steam at a pressure of 75.8 pounds per square inch passed through the automatic regulating- valve to the shell surrounding the generator at the reduced pressure of 15.3 pounds, due to a temperature of 250.4 degrees, produced a vapor in the generator of 76 pounds. The consumption of coal was thus reported as 1.385 pounds per indicated horse-power per hour. These results confirm the indications of thermodynamic science, that substantially as good work may be done with other vapors as with steam; but the steam-engine has actually given as good economical results as those here reported, and has many practical points of superiority. This trial was, how- ever, too short to be taken as fully satisfactory, and the history of these devices, so far as known, does not seem to encourage an expectation of the displacement of the steam-engine by their introduction. The data and results obtained by Mr. Barrus, by test of a Campbell ammonia-engine and boiler, as reported to the Camp- bell Engine Co., April 1887, were as follow:VAPOR AND BINARY-VAPOR ENGINE TRIALS. 45 5 Table No. i. Principal Dimensions of Boiler and Engine. Boiler—One Horizontal Return Tubular, set in brick-work. 1 Diameter of shell........................ 42 in. 2 Length of shell......................... 10 ft. 3 Number of 2 in. tubes below level of liquid.. 67 4 “ “ “ “ above “ “ “ 68 5 Inside diameter of tubes................. 1.75 in. 6 Length of grate (net).................... 2.75 ft. 7 Width of grate.......................... 3.33 “ 8 Width of metal and air-spaces in grate.. £ in. 9 Area of water-heating surface........... 369.3 sq. ft. 10 Area of steam-heating surface........... 318.8 “ 11 Area of grate-surface.................... 9.17 “ 12 Collective area for draught through 67 tubes 1.12 u 13 Rated horse-power of boiler on basis of 15 sq. ft. of water-heating surface per h. p... . 24.6 h. p. 14 Ratio of water-heating surface to grate-sur- face .................................. 40.3 to 1 15 Ratio of steam-heating surface to grate-sur- face................................... 33.6 to I 16 Ratio of grate-surface to tube area...... 8.2 to I 17 Diameter of smoke-stack.................. 20. in. 18 Height of smoke-stack above grate........ 30. ft. Engine—Porter-Alien Automatic Cut-off, Single Cylinder. 19 Diameter of cylinder.................... 11.5 m. 20 Stroke of piston......................... 20 “ 21 Diameter of piston-rod................... ij “ 22 Clearance (assumed)..................., . 10 per cent 23 Horse-power constant 1 lb. M. E. P. 1 rev. per minute............................. 0.01037 h. p. 24 Diameter of steam-pipe................... 4. in.456 ENGINE AND BOILER TRIALS. Table No. 2. Data and Results of Ammonia Tests of Whole Plant. Date 1887, March 8, March 9, April 16. 1 Duration of test hrs. 8 10 7-45 Total Quantities. 2 Weight of coal con- sumed lbs. 1400 1400 1098 3 Weight of ashes, clink- ers, and refuse u 139 90 4 Percentage of ashes, etc per cent. 9.9 8.2 Hourly Quantities. 5 Coal consumed per hour lbs. 175 140 147.4 6 Coal per hour per sq. ft. of grate “ 19.09 15.27 16.07 7 Quantity of injection- water used with nor- mal load cu. ft. 372.8 Averages of Observations. 8 Boiler-pressure above at- mosphere cu. ft. Approx. 100 95.5 86.6 9 Temp, of vapor in main pipe near throttle... . Deg. F. 304 301 10 Temp, of vapor in ex- haust-pipe u 180.8 11 Temp, of spray leaving boiler u 280 271 12 Temp, of feed-liquid en- tering boiler it 167.6 167 13 Temp, of escaping gases in front connection.. “ Approx. 560 547 S4i 14 Temp, of escaping gases entering stack u 390 394 15 Temp, of injection- water from hydrant.. u 49-5VAPOR AND BINARY-VAPOR ENGINE TRIALS. 457 Table No. 2. (Continued.) Data and Results of A mmonia Tests of Whole Plant. Date 16 Temp, of injection- 1887, March 8, March 9, April 16. water from river 17 Temp, of same leaving Deg. F. 42.7 the absorbers (( 104.2 18 Vacuum in feed-well... * 19 Revolutions of engine inches, XI.5 II per minute 20 Mean effective pressure revolu. 205.2 204.5 201-5 measured from indi- * cator-diagrams 21 Indicated horse-power lbs. 29.05 27.13 *26.99 developed by engine. H. P. 61.80 57-53 54-oo 22 Weather and outside } Fair Fair temperature j Averages of measurements Moderate Moderate of two sets of Sample Diagrams. 23 Boiler - pressure above atmosphere 24 Initial pressure above lbs. 96.5 88.2 atmosphere 25 Cut-off pressure above U 88.7 80.8 atmosphere 26 Release pressure above u 67.9 61.5 atmosphere 27 Compression pressure u 9.6 9.1 above atmosphere. .. 28 Back-pressure at mid- stroke below atmos- ii 1.7 0 phere (t 0.7 1.5 * Corresponding to the normal load of 56.39 H. P.458 ENGINE AND BOILER TRIALS. Table No. 2. (Continued.) Date................. 1887, March 8, March 9, April 16. 29 Back-pressure at lowest point below atmos- phere ............. 30 Proportion of direct stroke completed at cut-off ..'........ 31 Proportion of direct stroke completed at release............ 32 Proportion of return stroke uncompleted at compression..... Results. 33 Coal consumed per in- dicated horse-power per hour........... 34 Heat rejected to the ab- sorbers per indicated horse-power per hour. 106. Comparison of Results of Experience, as illustrated by the preceding facts and figures, leads to such final conclu- sions as follow: (1) Experiment, experience, and the philosophy of heat- engines combine to indicate that the limit of possible advance in their economical application is now so nearly approached that further progress must be expected to be both slow and toil- some. (2) That the range left for such further improvement upon the best and most efficient of existing engines is probably small, and the difficulties arising in the attempt to reduce it are in- creasing in a higher ratio than progress in its reduction. (3) That, while wasteful engines may be improved by vari- ous expedients, including the adoption of other working fluids lbs. 2.0 2.4 .189 .211 •773 .791 •307 •342 lbs. 2.832 2-433 2.729 Th. Un. 23,760COMPARISON OF RESULTS OF EXPERIENCE. 459 than steam, no other vapor has yet been found to give an eco- nomical performance in heat-transformation exceeding, or even equalling, that obtained with the best steam-engines. (4) That the gas-engine, with its higher range of tempera- ture variation, is the most promising competitor; but that it is not yet possible to judge whether the increase of temperature- range to be expected with the steam-engine, or the increased pressure-range of the gas-engine, with the possibilities of waste- reduction seen to be within reach, is likely to give the one or the other final superiority for small powers. The outlook in the case of steam, used as a working fluid, is well shown by the illustration given on the next page, from a paper by Mr. Parker.* The diagram shows the method of expansion of steam at an absolute pressure of 140 pounds per square inch (gi atmos.) : (a) when kept dry and saturated ; (b) when expanding adiabatically; (»• -<(■ N ts 0 0 vO S' cdvO cooo M 0 00 -<*-00 H m S» O' 0 S' O'VO IH w M ID00 ID VO VO In N S t^OO OOO'O'-'I-'NNM OOOOOOOO OOmhhhhm •anon Jad J3M.od -3SJOJJ pajBaipuj jad papuadxa jBafj oi "5 AJl h h lDiDOvO" N p [i, t' rD O'00 0 rDoo CD g O 00 NH SnOO VO Ov g M t (?) N m' t " H 0 oi ” vt-mmmmmmn wJactBMWNWH •qi jad uiBais isnBqxg aqj JJO paiJJBD c £ g[j] (IVO tlDWNH H t^OO M C O CO N CD Nl-VO ov rovo On O' fO 0 00 N 1^00 0 Uc.mmnmnmt'* u,°N aa O' oo oo oo oo O' fr.SO'O'O'O'O'O'O'O' fr. ^OOOOOOOOOOOOOOOO ^ IN ^ £) In tv f'OO 00 OvOwmNCOCOCO •rana^s jo *qj jad papuadxa jBafj cn "c £ From 212° F. 991 997 1,002 1.006 I,OII 1,018 1.024 1.029 From 2X2° F. 991 997 1,002 1.006 1,on i,ot8 1.024 1.029 raeais jo *qi jad uoisuBdxg Sai -jnp paijKdmi iBajj 3 "3 D ooooodoo 00000000 nreais jo qj jad jap -ui[X3 Suuajua jBajj cn c s From 212° F. 991 997 1.002 1.006 1,on 1.018 1.024 1.029 From 212° F. 991 997 1.002 1.006 1,on 1.018 1.024 1.029 •amuim jad ljo££ jo paadsqjiM jaMod-asjofj pavea -ipui jad najy uojsig c" & cn tv VO O'VO lO'tmiD 0 Tt-VO SO “)x N N 1DH O'MO^-n 00 0"f H O'VO to - cl iri s 0 n *? d 0" vo d d ■+ s Nl- Tj- LD id ID VC X VO t'OO 00 O' Ov 5 0 0 •asBapg ib ajnssajj c* 'S OOOOOOOO OOOOtDQtDO VO 00 O S ID 0 ID 0 M S m 0 SvfHIO OVH (V) ID VO 00 0 N VO W ID « M M (N 8 8 $&8 8 &8 S>8 rt wmmnncd c« h h m « « in u GAPPENDIX. 483 tx N O 00 v< (i ti n m 1 a# txvo 00 N O'O ----- — « *'0 txOO 0 w w mhhhmMMOJ m tx o m moo h vo O' m tx tx « « N Ct IH H 1 wOMVotxom^ O'dIHCO'O iJ-N M dltOdld M N « M N N N N N N V« o H 0) rt 41 - ~ HlipH f. d W u JJ j) ... *0^44 bo o o o ,c 0.SU2. *3 C tuo tx O' n moo O'oo 0 mooovo M- 83>8 ^SvScg 8 8^8^3 C« wwwwctm at wwwetctm “'‘o w m w ct « m 0 G 010484 ENGINE AND BOILER TRIALS. VI. COMPARISON OF THERMOMETERS. CelsiuL. Reaumur. Fahren- heit. Celsius. Reaumur. Fahren- heit. Celsius. Reaumur Fahren- heit. — 20 — 16 *“4 25 20.0 77.O 70 56.0 158.0 — 19 -15-2 — 2.2 26 208 78.8 71 56.8 159.8 -18 — T44 -0.4 27 21.6 80.6 72 57*6 161.6 -17 — 13.6 1.4 28 22-4 82.4 73 58.4 163.4 — 16 -12.8 3-2 29 23.2 84.2 74 59*2 165.2 — 15 — 12.0 5-0 30 24.O 86.0 75 60.0 167.0 — 14 — 11.2 6.8 31 24.8 87.8 76 60.8 168.8 -13 — 10.4 8.6 32 25.6 89.6 77 61.6 170.6 — 12 -9.6 10.4 33 26.4 91.4 78 62.4 172.4 — II -8.8 12.2 34 27.2 93-2 79 63.2 174.2 — IO -8.0 14.0 35 28.0 95-o 80 64.0 176.0- — 9 -7.2 15-8 36 28.8 96.8 81 64.8 177.8 -8 -6.4 17.6 37 29.6 98.6 82 65.6 179.5 — 7« -5.6 19.4 38 30.4 100.4 83 66.4 181.4 -6 * -4.8 21.2 39 31.2 102.2 84 67.2 183.2 — 5 —4.0 23.0 40 32.O 104.0 85 68.0 185.0 —4 -3-2 24.8 4i 32.8 105.8 86 68.8 186.8 —3 -2.4 26.6 42 33-6 107.6 87 69.6 188.6 —2 —1.6 28.4 43 34-4 109.4 88 70.4 190.4 — 1 —0.8 30.2 44 35-2 hi .2 89 71.2 192.2 0 0 32.0 45 36.0 113.0 90 72.0 194.0 1 0.8 33-8 46 36.8 114.8 9i 72.8 195.8 2 1.6 35-6 47 37-6 116.6 92 73*6 197.6 3 2.4 37-4 48 38.4 118.4 93 74*4 199.4 4 3-2 39-2 49 39-2 120.2 94 75-2 201.2 5 4.0 41 .O 50 40.0 122.0 95 76.0 203.0 6 4.8 42,8 5i 40.8 123.8 96 76.8 204.8 7 5-6 44.6 52 41.6 125.6 97 77.6 206.6 8 6.4 46.4 53 42.4 127.4 98 78.4 208.4 9 7.2 48.2 54 43-2 129.2 99 79.2 210.2 10 8.0 50.0 55 44.0 131.0 100 80.0 212.0 11 8.8 51.8 56 44.8 132.8 101 80.8 213.8 12 9.6 53-6 57 45-6 134.6 102 81.6 215.6 13 10.4 55-4 58 46.4 136.4 103 82.4 217.4 14 11.2 57-2 59 47.2 138.2 104 83.2 219.2 15 12.0 59-0 60 48.0 140.0 105 84.0 221.0 16 12.8 60.8 61 48.8 141.8 106 84.8 222.8 17 13.6 62.6 62 49.6 143*6 107 85.6 224.6 18 14.4 64.4 63 50-4 145*4 108 86.4 226.4 19 152 66.2 64 51*2 147*2 109 87.2 228.2 20 16.0 68.0 65 52.0 149 0 no 88.0 230.0 21 16.8 69.8 66 52.8 150.8 III 88.8 231.8 22 17.6 71.6 67 53-6 1526 112 89.6 233*6 23 18.4 73-4 68 54-4 154-4 113 90.4 235.4- 24 19.2 75-2 69 55.2 156.2 114 91.2 237.2APPENDIX. 485 Comparison of Thermometers—Continued. Celsius. Reaumur. Fahren- heit. Celsius. Reaumur. Fahren- heit. Celsius. Reaumur. Fahren- heit. 115 92.O 239 -O 127 IOI.6 260.6 139 III.2 282.2 116 92.8 240.8 128 102.4 262.4 140 112.0 284.0 117 93-6 242.6 129 103.2 264.2 141 112.8 285.8 Il8 94-4 244.4 130 104.0 266.0 142 113.6 287.6 119 95-2 246.2 131 104.8 267.8 143 II4-4 289.4 120 96.0 248.O 132 105.6 269.6 144 II5-2 291.2 121 96.8 249.8 133 106.4 271.4 145 116.0 293.0 122 97.6 251.6 134 IO7.2 273-2 146 116.8 294.8 123 98.4 253.4 135 108.0 275.0 147 117.6 296.6 124 99.2 255.2 136 108.8 276.8 148 118.4 29S.4 125 100.0 257.O 137 IO9.6 278.6 149 119.2 300.2 126 100.8 258.8 138 110.4 280.4 150 120.0 302.0486 ENGINE AND BOILER TRIALS. VII. DENSITIES AND VOLUMES OF WATER. Kopp; Corrected by Porter. Temperature. Volume, Kopp. Corrected Vol- ume. Differences. F. C. 39-2 4 I.OOOOO I.OOOOO 41.0 5 I.OOOOI I.OOOOI 24 58 88 51.8 10 1.00025 1.00025 34 59*o 15 1.00082* 1.00083 30 68.0 20 1.00169 1.00171 Ii5 139 161 27 77.0 25 1.00284 . 1.00286 24 86.0 30 I.00423 1.00425 22 95 0 35 1.00583 1.00586 181 20 104.0 40 1.00768 1.00767 200 219 237 255 273 290 307 324 34i 357 373 389 19 1130 45 1.00967 1.00967 19 122.0 50 1.01190 1.01186 18 131-0 55 1.01423 1.01423 18 140.0 60 1.01672 1.01678 18 149.0 150.0 65 70 1.01943 1.02238 1.01951 1.02241 17 17 167.0 75 1.02554 1.02548 17 176.0 80 1.02871 1.02872 17 185.0 194.0 85 90 1.03202 1-03553 1.03213 1.03570 16 16 203.0 95 1.03921 1*03943 16 212.0 100 1.04312 1.04332 Weights and Volumes. Temperature. Ratio of volume to that of equal weight at maximum density. Weight of a cubic foot. Temperature. Ratio of volume to that of equal weight at maximum density. Weight of a cubic foot. Temperature. Ratio of volume to that of equal weight at maximum density. Weight of a cubic foot. Fahr. 32 ■ ° 1.000129 Lbs. 62.417 Fahr. 210.° 1.04226 Lbs. 59.894 Fahr. 390.0 i-*5538 Lbs. 54.030 39-1 1.000000 62.425 212. 1.04312 59-707 400. 1.16366 53-635 40. 1.000004 62.423 220. 1.04668 59.641 410. 1.17218 53-255 5°- 1.000253 62.409 23O. 1.05142 59-372 420. 1.18090 52.862 60. 1.000929 62.367 24O. 1.05633 59.096 43°* 1.18982 52.466 7°. 1.001981 62.302 250. 1.06144 58.812 440. x.19898 52.065 80. 1.00332 62.218 260. 1.06679 58 5*7 45°- 1.20833 51.662 90. 1.00492 62.119 270. 1-07233 58.214 460. 1.21790 5* -256 100. 1.00686 62.000 280. 1.07809 57 903 470. 1.22767 50.848 no. 1.00902 61.867 290. 1.08405 57-585 480. 1.23766 50.438 120. 1.01143 61.720 300. 1.09023 57-259 49° • 1.24785 50.026 130. 1.01411 61.556 310. 1.09661 56.925 500. 1.25828 49.611 140. 1.01690 61.388 320. 1.10323 56.584 5*o- 1.26892 49-*95 150. 1.01995 61.204 330. 1.11005 56.236 520. 1.27975 48.778 160. 1.02324 61.007 340. 1.11706 55-883 530. 1.29080 48.360 170. 1.02671 60.801 35°. 1.12431 55.523 540- 1.30204 47-94* 180. 1.03033 60.587 360. i-13*75 55-*58 55° • *•3*354 47*521 190. 200. 1.03411 1.03807 60.366 60.136 370. 380. 1.13042 1.14729 54-787 54-4*1 APPENDIX. 487 VIII. TEMPERATURES AND PRESSURES, SATURATED STEAM. IN METRIC MEASURES AND FROM REGNAULT. 6 U 9 2 & a V H 32° 31 30 2Q 28 27 26 25 24 23 22 21 20 19 18 17 l6 15 14 13 12 II 10 9 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Steam-pressure. fi 9 2 Steam-pressure. In Centimetres. In Atmospheres 0. a E v w C.SC V S * 3 e&s* 2*.« « c«.a « b£ ^ 5 qj ag « • rt § 'cE^c «5*fJo s ui” ES^= • •r . *->,a D ^ s w CL-° « Q. K T3 rt o If Oi — -a O - aj rj 5-3-fi - O rt 0 0! Q. 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W W N O' O'OO vo vo m; O' O' c •vf O' h m « moo •1-00 •1- m o O ^ 0 m 6 00 O' O'OO 00 00 00 I O' VO > m m » O' 0 vS' ^8? mvo ov « « SAPPENDIX. 493 ft, ‘SS'g S8 5!;fS,'8&'8?f!> aasjaR'aa H « m' <4- moo vo m m oo oo c, 0 O'oo oo tv m o m m o> 0 so tv O' m m O' tv 00 N O' O' t) rdsmm "“HHssrr HS-E 8 SVSvS5*8 sIKtlHH: »?£HH 3 8 S' ‘S^Er'S'S I?? US’? 6 O' O' O' O' O'00 00 00 00 00 00 sssss II! niimin Iflllll !ll!l!l!ll lllllll Ill IIIIIIIMI ?il§8i§S8g Iflilllll! IlfSI 5s * SH fi? TsU^si RRSSRSf.Rft'S, HHgHH'l ‘ggg'l'g'S'2'S'S'S i m$r&n HkHH S?1S'?3'I ££<3 sfslslsss1 ill-sfsHI ftlHIsJ sS5 aammig sISSssHIE sssimr&s: vO it) n, jo w et hi O' O' O' O' O' O' O' ft? ih 8SHms?S SsSgSSsSSS HHH? KKR EKKR'g.'g.'g.'g.'g.'g. £ £ £ “ •n Hf SaTs mstmn s“»slsL"H £22&££$££& msm&s Km§1 00* ^^1c2^4 m ggSSsffSH? SHSSsSgS® IsHHHK HfigS s ggg SSsSSSHSi l^SSSSSi ft, <2 S'8 S, SPSS'S, Si'S, SS- to in in in in^ JnPROPERTIES OF SATURATED 494 ENGINE AND BOILER TRIALS. •qoui ajBnbs jad spanod ui ‘uinrioeA b »AoqB sjnsssjj a. P-StSSR'S. Volume. Aiisusp uimuixeui jo ajniBjaduwi *b j»5BM papusip jo }q3i3M junba jo auihioA OJ U1B9JS JO .OUiniOA JO OUB^J n m tn NMOO'O'OOO MOO uim m ^-vo 0 ^ m rnulHls r'H&kss •133J Diqno ui meats jo punod b jq m mmn HHH 'OvOvdvO'O'OvO'Ovdvo lovunmioio •spunod UI ‘UIB3JS jo jooj DiqaD b jo jq3i3M. 11! illllllll Hill Quantities of Heat. •uopBjodBAa jo spun ui i0z£ 9AOqB UOHBJOdBAO JO }B9q ]B?OX sSa In British Thermal Units. Total heat of evaporation above 320 = *y+ L. * SS&5ES ?C tt 1C 1C 1C K Latent heat of evaporation art pressure P - /-f E. sit tn O' QOO rr> \a S'gvg m mum n llltll External latent heat. Ft 5- m%%4. ‘g.'B/S. ^^ca‘a ■<*■ tj- ro tF&HBH'S HJ-HSS m m m m mmmmmm'»-'vj-'^-Tf CO CO CO CO CO CO co Ov O' tS « « N « O C* ■'t-'O 0 01 tJ-vo 00 00 00 00 flllltfill ifiiifmi mm mu VO Ov M Th t'. t^OO 00 N N W N flffllHIi Sisiifim !!!!!!! """" O' O' m o m e» owo w m o O fSaSSHSif HHIH VO'O'O N rsNh.N ££&£&$££££ &&&£&£££££ £. ssssssssss <8 eg eg eg eg eg 0 SO>H vl-SO ■+ ft &&SS II HI HHskHL’ msmS'Cvt-v)- m ro pi m m h h M VO HVO 1H vo M t^o o m 00 OO 00 00 £&?SSii2S2 IIIIJIIHr £HggH m 0 o n o t^.o m W M O O' K$5SH&«§ HsHsJrIH HSsrJ^sJ El's sis s O' O M M t^.00 00 00 N W H M mmnn - O' ro o o ro CM 0 o N M 0 00 rssr&smf a?^ s?s5 n o- m o oo m »-. o' 2mm ro ro ro co n rot mvo vo t^oo O' O HS8iaa5a§3i co ro co ro ro ro co ft, i t^OO O' 0 r^oo S.S.SSS'S.S'S.&S j S S o ?o o 0'S ?2 m M ro Tj- mv? is. 1 PROPERTIES OF SATURATED STEAM-{Continued). 40 ENGINE AND BOILER TRIALS. •qom ajcnbs jad spanod ui ‘uinriaBA b aAoqB ajnssajj ft. 00 O' 0 ** Cl mMf IT)VO tvoo O' O WMN NCldCtNClClClMrn 1 m « ro Mf 10 vo CvOO rorororororororo hhmwmhhh Volume. •Xjisuap uinai;xBtu jo ajmBjadraai ib j»ibm paqnsip jo jqStaM |Bnba jo arnhioA oj raBais jo aainioA jo oiib^j O'M fO w 0 00 tor.N CNN in N 0 rovO 0 -t-00 N vo VO f ro H O'00 10 MffAH NNWNmwm-mmm C1NC1NC1C1C1C1C1C1 HVO M N«M Mf 0 000 d. to Mf N Q NNNNNNNN oiqno ui uiBajs jo punod b jq m tnvo w 00 10 t^vO VO lOfOfO 00 Q N U100 N vo 0 to 0 N O N + m 0"0 mi- - VO VO inmiOMfMfMfMfro rorororororororororo VO CIOO OvNf VO Mf M OfvMfCU c ro ro ro Cl Cl N Cm 1 rororonmmroro •spanod ui kuiB3}s jo ;ooj oiqno u jo to 00 0 O' Ml- 0 m ro 10 v8^R Cl Cl N w w O'NrOO'fnNO h u-> 0 mi-r> m}-00 mNNvo VO 00 O' O Cl ro u->vO 00 O' in K O' N Ml-vo 00 Q Cl Mf fM t^oo 00 00 00 O' O' O' NNNNNMCINNCI N S N w ONf O 0 Mf 00 Cl to O' ro 0. ; ►* ci ro tovo noO fs.O't- ro to N CO 0-000000 *m n ci ro ro ro ro ro ro ‘ Quantities of Heat. •uonBjodBAa jo spun ui ‘ee£ OAdqB UOIJBJOdBAd JO jBaq ibjox N ^“VO h* WWW WWW 00 0 N Mfvo 00 0 N ro to r^oo 00000000 O' O' O' O' NWNNNNN0INK NNNNNNNNMN vo 00 O C4 -^VC 00 0 o&ooocoo 01 0i ro to ro ro o"i 1 NNNhNNNW 09 5 15 s V js H .1 u CQ c O £ ^ g«-r «|j^ c>3 II £-1 09 * I'm 0 W t^vo m o- lO to 10 00 00 00 0 O' fM Mf O' rovO CO O' O' j ^ ro £n £#*8 'S Mf'-O 00 VO VO vo VO vo r-» r>- C-m (■> 00 00 00 00 00 00 00 00 00 00 00 vo Mf 0 to O' - ro 00 vo Mf ci ovo Mf ■- Ovh ro uovc 00 0 C-i t^-CO 00 CO 06 CO O' O' 00 00 00 00 00 00 oc oo 0 C 2-S •C g 1+ • c ag*"* £2 > a || rt a; J * 1 1 Ui O' VO » « N O' 10 0 -1-mJ-tJ- f- t . Cm. 1 00 00 00 873.626 873.178 872.732 872.289 871.848 871.411 870.977 870.545 870.I16 869 688 row Cl too n N C , vo Mf N 0 O' r^vc vo cioo Mf 0 to w r^ rr OOOOOOO N SVC C vo vo VO VO vo VC VC VC ; 0000000000000000 15 |§2 Xij43 M vo m O' vO O m m Mf Mf 00 00 00 Mf O' rooo^ Cl vO_ CO w n_ Mf Mf m to LO VO VO VO N N N 00000000000000000000 to C^OO 0 1-1 Cl Cl M 0 rovo 0 rovo O' Ci 000000 O' O' O' 0 c 0000000000000000 15 g c J SjSS S «J3 s 0"0 f* vo m vo m rn ci O' O' O' NNN 1 N O' O' M vo u-100 Mf Mf Mf u-)VO 00 H (OVO O' ro I'm m 1 w vo w t-» ci c^noo ro O' 1 « h h 0 0 ff 0 00 00 d- O' O' O' O' 000 00 00 00 00 00 Mf Mf u~> O' u-1 in O' lo 0 mO tn m tvro Mf 0 tn hvo ci r^ro t^vo vo m in Mf Mf 0000000000000000 CmNNSNNNJm Required to raise the temperature of the water from 320 to 7'°. W H IA O' Mf O0 in Cl 00 Cm- Mf M ui to w pj O' ro ro m Cl VO O' Cl to 0-00 0 H N iom r^ Mf 0 vo ci O' to h Cl ro ro Mf to imo VO t^co rorororororororororo in to ci tn in ci Mf n NCINhOO'MO t-v ro 0 in h vo ci 00 W CO-O H H M M »hhm6incin roromrorororom *S99jJ89p jiaquwqBj ‘ajnjBjadraax VO 0 00 S Mj- O O' d m rn -t- -f ro ro m h OvowvO h OiO O h 00 0 >1 Cl ro Mf Mt ro ro ci vo ro O' to h n ro O' n h h ci Cl ro Mf Mf ui tnvo d. MfMf^-MfMfMfMfMfMfMf rorororororororororo vo s n ntn Mf o- h O 00 VO Mf H 0O MfW NN00 tO inn s fi-00 00 O' 0 0 H mroromrorofofn •qoui ajBnbs asd spanod a; ‘rannoBA b oAoqa aanssajj ft, 00 O 0 M H N H N Of to VO r^ 00 O' 0 ClClClClClClClNClfO h w m ^ 10vo t^oo mmc^nronronAPPENDIX. 497 ** irS’??!?'* ?§■?& vg Reg 8,8 §8 sin n n mi imuiaii t^ rn is 0 Tj- CN 0\MOMH O' O' fOVO 00 00 lONmm ooo o\ tr: 0 oo tvOO M OO VO covo ^VO H oo to $$8&8*g«£g«J R?SII ^ srejsssss cS &£% 0 oo \o m fo imfKSii “SHs *§!Hg$K3 Hll • || CO <*o ami II!!! Illlflllli ml titftKHf ^ 'o* N N WHi Wi issnsisi? * «s rHs^srIII I.S'iS’S siasmns N N M J v8^‘5 8.?8>8>^g.S ff §.&§.8.8.8.S& SPSS’S fllllslsll III! SlsSfllfll Ss $s 2 O' mO'Mn stHIKsiH °S-S2 § VS'S £<2 W5 S-'S, m§§$m$ SHS&HJIa $S«£ II rs^jsf&aas IS&Si mH&iSsS ‘S'SoS’o 2t2 8 2^gS'<23 ££ c^cScSc^cScScScScScS C» 00 oo'oo'oo1 ££££££££££ s SS ISSIHIHS HHH 8^*8 5 S'S S-2 3-Sf evapora- tion, H. s«5?IE4KItllliHls5ls!i mmimmsmussmi «j.Sg '8>8.?'&R.'8 SR? q.'g.S ^'g.S'S-S rS-TJ'S Sot'S S, l| m m « « n rocorott-tj-^-mm mvo vo vo tv tv tv 00 00 00 O' O' Same pres- sure as indi- cated by steam-gauge, allowing 14.7 pounds for atmospheric pressure. "SRS R8,S228,I8>8.Rg.R,8S!8 g2 R8 S’ Pressure above a oounds oer square inch. 8R8,S8-S&R.2£SVR(g. m f'-oo 0 cm m cm - 8.'§.8'5!S-3P"83oo>'o8r'2S'S?R‘8. <>2 2 2 5 5 as 2 2 SrSS'ftJg.gjISJSII Same prc sure as in« cated bi steam-gau allowing 1 pounds fr atmosphe pressure 3S«f||||||||| Pressure above a vacuum in pounds per square inch. 42XII. FORMULAS RELATING TO PROPERTIES OF STEAM. APPENDIX; 501 he 0 1 ^ 2" H ^ a •uinnoBA ^ »Aoqy I w olR X II * $ I a II So a> a *-» CO » n tx n f* m vo m vo m m omomo m m.mmNNM m o 0 O'oo oo t>. t-^vo vo mm^-^-m m w n m m o 0 O' O'oo oo t^vp vo m v§ **» M M i*. 't- o> moo m oo moo m tv n f» n < oca oo t-« t^vo s n t- n ti n f* m nnmmo 0 o> O'oo 00 i'. t>.vo vo m nmmoo O' Ovoo 00 f> tivo vo m m if 8 * M yQ n ^ O' moo m 00 moo m t>* n n ti m vo m vo m m 0 m 0 m O' +5itom 00 moo moo m n nmmoo o> O'oo 00 f>vo vo m m if if m m n n m m 0 O' O'oo 00 nn «vo mmt 8v °. VO m vo 0 m 0 m 0 m 0 if O if ©> if 00 moo moo n nn nnvo m vo m vo 0 momom 0 n nmmoo O' O'oo 00 s voo mmt if m m n n m m 0 0 gv g'tg ^ nn voo mmt if 8o 5-3 n O' if 00 moo moo moo n sn n«vo mvo mvo 0 m 0 m Q if ov •vf ov ^00 moo moo m 00 n m m 0 0 O' O'OO x ns vovo mmt if m m n n MMOOOvcgoofs t^y5 vg m m ->f if m N NNNNM M M M M M MMMMM MMmMM M M M M 0 OOOOO OOOOO 0 M O' vo m m 0 m o m 0 rn O' if O' if O' m oo moo m t>. n n m vo m vo m m omomo m m m m o 0 O' o>oo oo t^vo vo m m -<^if m m n n m Mooovgv oo wn g.vo vo m m if if m 6o 4-o r» if O' moo m oo moo mt** n n m vo m vo m m omomov f Of ovm « moo moo m m m o O O' O' oooo n fivo vo m m if if m m n n m m o O O'OO oo f- t^vo vo m m if if m m 0 m m m if m vo 0 m O m o m 0 if Of 0"f m mo moo n no nnvo m vo m vo Q momom 0 m woOOvOvoooofi fivo m m if if m connmm o 0 O' b*oo oo t^vg vo m m f if m m m o CO n O' if oo moo moo moo n nn nnvo m vo m vo 0 m Q m 0 if Of o if oo moo moo m oo m o O O' O'oo oo f"VO vo m m if if m m n n m o O O' O'oo i-* t^vo vo m mf-f-mm n 0 «•* m x fflNN s NfxNt^M vo m vo m m Omomov f 0"f O' m oo moo m n n n f* m o O O' ovoo oo r*. t^vo vo m m if if m m n n m o 0 O' O'oo oo n. t^vo vom m m ->f m —> n m m m ^ O' vo m m o m 0 m O m O' if O' if O' m oo moo m f* n t-» n m vo m vo *- m omomo m 5 0 0 O' O'oo oo t^vo m mf f mm nnmmo 0 O' O'oo oo r-* s»vo vom mif-f-mm n O 0 m N vo moo ni^n nn nnvo h vo m vo o m o m 0 if Of o> if oo moo moo n r». n n fi n 0 0 O' O'oo oo fi fivo vom m if if m m nnmmo O' O'oo oo fi fivo vomm if if m m n n m r-' w if Mvoomo m 0 m o if O' f o if oo moo moo n nn nnvo mvowvoo momom 0 O 0 O' O'OO oo ti f^vo vom if if m m n nmmoo O' gvoo oo r^vo vomm if ->f m m n n cJ vo •+ n 10 m m u-> vo -<}- n O t-~ m mHxvo n O mof, O h n O n in oo m mvo on ionO mvo w h ^ 6 n moo mm M M n n n « iMMO >o mvo vo vo VO oo vo if n o Mnnn oo mvo on m o mvo oo * N hs r^oo 00 00 o o o o n m 0 m 0 m omomo momom OmOmo m o m o m omomo m Q m o m o cn mt^mm vo vo r*. r^oo oooooo m m n n m mif-.oo oo o o o o m 057504 ENGINE AND BOILER TRIALS. XIV. COMPOSITION OF VARIOUS FUELS OF THE UNITED STATES. Pennsylvania Anthracite. Rhode Island “ Massachusetts “ North Carolina “ Welsh Maryland Semi-bituminous. Pennsylvania “ Indiana “ Illinois Bituminous ........... “ (Block) Bituminous....... Illinois and Indiana (Cannel) Bituminous Kentucky (Cannel) Bituminous--- Tennessee Bituminous........... Alabama Virginia California and Oregon Lignite............ 50.1 c. H. O. N. S. Mois- ture. Ash. 78.6 2-5 *7 0.8 0.4 1.2 14.8 85.8 10.5 3*7 92.0 6.0 2.0 83.1 7-8 9.1 .... 84.2 37 2.3 0.9 0.9 i-3* 6.7 80.5 4-5 2.7 1.1 1.2 17 8.3 75.8 20.2 4.0 59-4 38.8 1.8 70.0 28.0 2.0 52.0 39 0 9.0 62.6 35 5 1.9 58.2 37-1 4-7 59-5 36.6 3-9 48.4 48.8 2.8 71.0 17.0 12.0 415 56-5 25 54-0 42.6 1.0 1.2 1.2 55-0 41.0 4.0 74 0 18.6 7-4 So. 1 3-9 13-7 0.9 *•5 16.7 13.2 Spec. Grav. 1.85 78 Coal. KIND OF COAL. Pennsylvania...........Anthracite .........Cannel.......... .........Connelsville.... ......... Semi-bituminous . .........Stone’s Gas..... .........Youghiogheny. .. ............ Brown....... Kentucky...............Caking ......... “ .............Cannel ......... “ Lignite....... Illinois...............Bureau County . “ Mercer County.. “ Montauk...... Indiana................Block............ “ Caking....... “ Cannel....... Maryland...............Cumberland.... Arkansas...............Lignite......... Colorado................... “ ......... Texas................. “ .... Washington............ “ --- Pennsylvania..........Petroleum. Per Cent, of Ash. 3*49 6.13 2.90 15 02 6.50 10.77 500 560 9-50 2- 75 2.00 14.80 7.00 5-20 5.60 5-5o 2.50 5-66 6.00 13.98 5-00 9.25 4.50 4-50 3- 40 Theoretical Value. In Heat Units. In Pounds of Water Evaporated. 14,199 14.70 *3*535 14.01 14,221 14.72 i3*i43 13.60 13*368 1384 *3**55 13.62 14.021 1451 14.265 14.76 12,324 12.75 i4*39t 14.89 15*198 16.76 13.360 13-84 9*326 9-65 13,025 13.48 13*123 1358 12,659 13.10 13*588 14.38 14,146 14.64 13*097 1356 12,226 12.65 9*215 9*54 13*562 1404 13,866 14.35 12,962 *3-4* “*55i 11.96 20,746 21.47APPENDIX. 505 ANALYSES OF ASH. Specific Crrav. Color of Ash. Silica. Alum- ina. Oxide Iron. Lime. Mag- nesia. Loss. Acids S.&P. Pennsylvania Anthracite 1-559 Reddish Buff. 45-6 42-75 9-43 1.41 o-33 0.48 “ Bituminous.... 1.372 Gray. 76.0 21 .CO 2.60 0.40 Welsh Anthracite 1.32 40.0 44-8 12.0 trace 2.97 Scotch Bituminous 1.26 37-6 52.0 3-7 1.1 5.02 Lignite 1.27 19-3 11.6 5-8 23-7 2.6 33-8506 ENGINE AND BOILER TRIALS. XV. HORSE-POWER PER POUND MEAN PRESSURE. Diameter of Cylinder. Inches. Speed of Piston in Feet per Minute. 100 240 300 350 400 450 500 550 600 650 4 .038 .091 .114 -*33 .152 .171 .19 .209 .228 .247 4* .048 • **5 • *44 .168 .192 .216 .24 .264 .288 .3*2 5 .06 .144 .18 .21 .24 .27 -3° •33 •36 -39 5* .072 - *73 .216 .252 .288 ■ 324 •36 •396 -432 .468 6 .086 .205 .256 -299 -342 • 385 .428 •47* •5*3 •555 6* .102 •245 •3°7 -39* .409 .464 .512 •563 .614 .698 7 .116 -279 348 .408 .466 524 .583 .641 .699 •756 7i •*34 .32* .401 .468 -534 .602 .669 •735 .802 .869 8 *52 .365 .456 .532 .608 .685 .761 •8 37 .912 •989 8| .172 •4*3 • 5*6 .602 .688 • 774 .86 .946 1.032 1.118 9 .192 .462 577 •674 • 770 .866 •963 *059 *•*54 1.251 9* .215 -5*5 644 -75* .859 .966 1.074 1.181 1.288 *•395 10 .2381 •57* -7*4 •833 •952 1.071 1.190 1.309 1.428 *•547 iof .262 .63 .787 •9*9 1.050 1.181 *•3*3 1.444 *•575 1.706 11 .288 .691 .864 1.008 1. *52 1.296 1-44 *•584 1.728 1.872 **i •3*4 -754 -943 1.1 *257 *•4*4 1-572 1.729 1.886 2.043 12 •342 .820 1.025 *i95 1.366 *•540 1.708 1.880 2050 2.222 *3 .402 -964 1.206 1.407 1.608 1.809 2.01 2.211 2.412 2.613 *4 .466 1.119 1.398 1.631 1.864 2.097 2-33* 2.564 2.797 3.029 15 .535 1.285 1.606 1.873 2.131 2.409 2.677 2-945 3.212 3-479 16 .609 1.461 1.827 2.131 2.436 2.741 3-°45 3-349 3-654 3-958 *7 .685 1.643 2.054 2.396 2-739 3.081 3-424 3.766 4.108 4-450 18 .771 1.849 2.312 2.697 3-083 3.468 3-854 4.239 4.624 5.009 19 •859 2.061 2.577 3.006 3-436 3.865 4-295 4 724 5 *54 5-583 20 •952 2.292 2-855 3-33* 3.807 4.285 4-759 5.234 5-73* 6.186 21 1.049 2.518 3.148 3.672 4.197 4722 5-247 5-77* 6.296 6.820 22 1.152 2.764 3-455 4.031 4.607 5.183 5-759 6-334 6.911 7.486 23 1.259 3.021 3-776 4-4°5 . 5-035 5.664 6.294 6.923 7-552 8.181 24 1.370 3.289 4.hi 4-797 5.482 6.167 6.853 7-538 8.223 8.908 25 1.487 3.569 4.461 5.105 5-948 6.692 7-436 8.179 8923 9.566 26 1.609 3.861 4.826 5.630 6-435 7.239 8.044 8.848 9.652 10.456 27 *•733 4-159 5-*99 6.066 6.932 7-799 8.666 9-532 10 399 11.265 28 1.865 4-477 5-596 6.529 7.462 8.395 9.328 10.261 11.193 12.125 29 2.002 4.805 6.006 7-007 8.008 9.009 10.01 II.on 12.012 130*3 3° 2.142 5-*4* 6.426 7-497 8.568 9.639 10.71 11.781 12.852 *3-923 21 2.288 5.486 6.865 8.001 9.144 10.287 **•43 12-573 13.716 14.860 j* 22 2.436 5.846 7.308 8.526 9-744 10.962 12.18 13-398 14.616 15.834 33 2 590 6.216 7.770 9-065 10.360 **•655 *2-959 14.245 15-54 16.835 34 2.746 6.59 - 8.238 9.611 10.984 *2.357 *3-73 15.*03 16.476 17.849 35 2-9*4 6-993 8.742 10.199 ii.656 *3**3 14.57 16.027 17.484 18.941 36 3.084 7.401 9.252 10.794 12.336 13.878 15.42 16.962 18.504 20.046 37 3-253 7.819 9-774 11.403 13.032 14.861 16.29 17-9*9 19.548 21.177 . 38 3.436 8.246 10.308 12.026 *3-744 15462 17.18 18.898 20.616 22.334 SO 3.620 8.648 10.86 12.67 14.48 16.29 18.1 19.91 21.62 23-53 K> 3.808 9 -*39 *1.424 13328 15.232 17.136 19.04 20.944 22.848 24.752 it 4.002 9.604 12.006 14.007 16.008 18.009 20.00 22.011 24.012 26.013 41 12 4.198 10.065 *2-594 14693 16.792 ”^8.901 20.99 23.089 25.188 27.287 T* 4.40 10.56 13.20 *5-4 17.6 19.8 22.00 24 2 26.4 28.6 4.606 11.046 13.818 16.121 18.424 20.727 23.03 25-333 27.636 29.939 je 4.818 11.563 *4-454 16.863 19.272 21.681 24.09 26.399 28.908 3*-3*7 46 5-°43 12.086; 15.128 17.626 20.144 22.662 25.18 27.698 30.216 32.754 17 5-256 12.614' 15.768 18.396 21.024 23.652 26.28 28.908 ?*-536 34.164 48 5.482 12.846 16.446 19.187 21.928 24.669 27.41 30.15* 33 152 35-633 5-7*4 12.913 17.142 19.999 22.856 25.7*3 28.57 3*-427 34-284 37-*4* cn 5-95° 14.28 *7-85 20.825 23.8 26.775 29.75 32.725 35-7 38.675 5° 6.180 14.832 18.54 21.665 24.76 27-855 30.95 34-°45 37.08 40.205 5X C2 6.432 15-437 19.296 22.512 25.728 28.944 32.16 35-376 38.592 41.808 Cl 6.684 16.041 20.052 23-394 26.736 30.078 33-42 36.762 40.104 43 - 446 d 6.940 16.656 20.82 24.29 27.76 3*-23 34.7 38 *7 41.64 45-** 55 7- *98 17.275 21.594 25.193 28.792 32.39* 35-99 39 589 43-*88 46.787 e6 7.462 17.909 22.386 26.117 29.848 33-579 37-3* 41.041 44.772 j f 48.5°3 5U C7 7.732 i8.557 23.196 27.062 30.928 34-794 38.66 42.526 46.392 50.258 d7 c8 8.006 19.214 24.018 28.021 32.024 36.027 40.03 44.033 48.036 52-039 5° 8.284 19.902 24-852 28.964 33-*36 37.278 41.42 45-562 48.704 53-846 59 60 8.566 20.558 25.698 29.981 34.264 38.547 42.83 47**3 5*.396 55.679 750 •»*5 •360 •450 *540 .64i • 800 •87+ 1-002 1- X2I I.290. *'96» 2.16a 2- 357 2- 564 3 015 3- 495 4- 004 4- 567 5 *35 5- 780- 6.442 713& 7.86o 8.63a 9-44 10.279 11.053 12.065 12.99a 13-99* 15.015 16.065 *7145 18.270- I9-425 20.595 21.855 23-*3° 24 435 25 77° 27 *50 28.560 30.015 31.485 33- °° 34- 545 36 *35 37-77° 39.42° 41.1*5 42.855 44.625 46.425 48.240- 5°-*3° 52.05 53-985 55 965 57-99 60.045 62.13 64.245INDEX A ART. PAGE 206 Supply, Measurement of, • • • • • 33 51 Pump Diagrams, , . . • • 204 American Institute Boiler Trials, , • . • 40 79 Ammonia Engines, Trials of, . . . • . 105 455 Amsler's Planimeter, 220- Analysis of Fuels • 40 Gases, 5L 105 Apparatus for, , , • 47 10& " Anthracite,” Trials of the Steamer, • . 100 38a Apparatus, Brown’s, to test Indicator Drums, • 54 146 Elliott’s, for Gas-analyses, . • 49 113 for Boiler Trials, and for Engine Trials, 6, 20, 31 9, 37, 43 measuring Indicator Diagrams, 65 212 Wilson’s, for Gas-analysis, . • 47 109 Applications, Special, of the Indicator, . . • . 62 203 Atkinson’s Gas-engine, Unwin’s Trials of, • . 104 444 Attachment of Brakes (Dynamometric), . • 76 280 Indicators, .... 159 B Barrel or Tank Calorimeter, .... • . 42 86 Barms’ Calorimeter, . . . . • 46 99 Method of Report on Pumping-engine Trials, . 102 414 Trials of Ammonia-engines, . . 105 454 Binary Vapor Engine Trials, .... . . 105 45i Blanks for Indicator Diagrams, . . 56 181 Boilers, and Engines, Trials of, Purposes of, . 1, 21, 50 1, 38, 287 Efficiency, 11, 17 Logs of Trials of, ... . 34 58 Performance. .... 12 20 507508 INDEX. Boilers, Precautions at Trials of, . • ART. 33 PAGE 55 Records of Trials of • . 33 52 Reports on Trials of, , • 33 53 Sample Reports on Trials of, • • . 40, 49 76, 113 Standard Trials of, • . 32, 33 45, 46 Trials, Apparatus of, • • • . 20 37 at American Institute, . • • • . 40 79 Systems of, • . 17 34 Value of, ... • . 23, 27 42, 49 Brake, Amos’ and Appold’s, • 76 277 Balk’s, • • 76 278 Brauer’s, 280 Prony’s Dynamometric, • • 76 269 Proportioning and designing Prony’s • . 77 292 Bramwell’s (Sir F. J.) Trials of the S.S. “ Anthracite, Pf . 100 380 Brook’s and Steward’s Trials of Gas-engine, . • . 104 438 Brown’s Apparatus for testing Indicator Drums, • • 54 146 C Calibration of Dynamometers, • • . 75 267 Calorimeters, Barrel or Tank, • • . 42 86 Barrus’, . . • • • • . 46 99 Coil, . • • • • 45 95 Continuous, • • • • • . 46 98 described, . • • • 42 86 Errors of, . • • • • - 44 94 Hirn’s, ...» • . 42 57 Record of Tests by, . • • . 44 94 Theory of, . . . • 43 88 Chronographs, 68 223 “ City of Fall River,” Trials of S.S., . . 100 388 Coffin’s Planimeter, .... 67 222 Combustion of Gases, .... 86 307 Comparison of Indicators, . . • 54 150 Competitive Trials of Engines, . • . 88, 92 310, 323 Compound-engine Diagrams, . 61 194 Trials, . . • • 95 350 Computations of Power, • . . • • . 68 236 Conclusions from Engine Trials, • • 95 346 Condensation in Cylinders, and Leakage, • 7i 253 Consumption of Steam and Water, . • . 69 237 Cornish Pumping-engines, Trialsjof, • . 112 413 Costs of Steam Power, .... • 3 6 Counters, Speed, • 68 223INDEX. 509 Crosby’s Indicator, . . . • • • ART. . 53 PAGE 137 Curves, Constructive Hyberbolic, . . • • • 0 70 248 Cylinder Condensation and Leakage, • • • • . 7i 253 D Deductions from Engine Trials, . • • • 95 346 Diagrams, Blanks for Indicator, . . . 0 . 56 l8l Compound-engine, .... . 61 T95 Dynagraph, ..... . 96 373 Indicator, interpreted, . • • • . 57, 60 182, 189 Pump, • 63 204 Draught-gauges, • . 48 no Drum-testing Apparatus, .... 54 146 Duty, Air-compressor, 63 206 Apparatus to Measure,.... 65 212 Gas-engine, . 64 210 of Steam Engines, .... . 2, 103 3. 435 Pumps, 102 414 Peculiar Standards of, . . . • . 64 208 Dynagraph Diagrams and Results of Tests, . 96 373 Dynamometers and Indicators, . . • 50 126 Amos and Appold’s, . • 76 277 Balk’s, 76 278 Brauer’s, .... 77 278 Calibration of, . • • 75 267 Prony’s, designing, . • • 76, 77 269, 272 E Economy of Fuel, 41 Trials to determine, • 9 10 Efficiency and Power, combined, in Boilers, . • 30 43 of Heating Surfaces, . . . . 11 13 Steam Boilers, .... . 10, 11 11, 17 Variations of, . 28 42 Electric Indicator, 149 Elliott’s Apparatus for Gas-analysis, . 47, 49 106, 119 Emery’s Trials of U. S. R. M. Steamers, . 100 376 Engines and Boilers, Purposes of Trials of, . . 1, 79 1, 285 Barrus System of Trial and Report, . . 102 414 Competitive Trials of, . 88, 92 310, 323 Consumption of Steam by, 15 33 Duty, 3 Examples of Trials of, arts. 85, 93, 96, 98; PP- 304, 33L 356, 3645io INDEX. Engines, Friction of, .... ART. PAGE 262 Gas, Trials of, . .... 84, 104 303. 436 Net Work of, .... . 262 Systematic Trials of, ... . l8, 82 36, 96 Trials, Fitting up for, . 8l 294 Vapor and binary-vapor, Trials of, . . 105 45i Errors of Calorimeters, ..... 94 Evaporation, Factors of, ... 38 74 Examples of Locomotive Engine, Trials of, . . 98 164 Marine “ “ “ . IOO 376 Portable “ “ “ . . 96 356 Pumping •- “ “ “ . 80, 93 288, 331 Stationary “ “ “ . 94 332 Expansion, Ratios of, 70 252 F Factors of Evaporation, .... 38 74 Farey and Donkin’s System of Engine Trials, 83.103 299, 424 Final Conclusions from Tests of Engines, 106 458 Flues and Tubes, Proportions of, . 15 30 Fork, The Timing, 68 233 Friction of Engines, 72 262 Fuels, Analysis of, 25, 33 40, 51 Economy of, 26 41 Evaporative Power of, 24, 35 39.61 Tests of Value of, ... 22 39 G Gas-engine Diagrams, 64 210 Trials, arts. 84, 86, 104; pp. 303, 305, 436 Gases; Analysis of, .... 33> 47 5L 105 Elliott’s Apparatus for, 47, 49 108, 119 Wilson’s “ “ 47 107 Combustion of, . 86 307 Gaskill’s Pumping-engines, Trials of, . 102 406 Gauges, Draught, 48 no Graphical Records of Trials, .... IOI 399 H Hand Speed-indicator, # • •• 68 231 Heat, Development, Transfer, and Storage of, . . . 12 19 from Fuel, ...... 35 61 Conditions of Economy of, • . 13, 35 23, 61 Latent and Total, of Steam and Water, . • 37 73* INDEX. 511 ART. PAGE Heat, Specific, of Steam and Water, . • 36 71 Utilization of, • • 13 23 Heating Surfaces, Efficiency of, • • • • • II 13 Hirn’s Calorimeter, • • • 42 87 Indicator, 53 138 Hyperbolic Curves, Constructing, • • • 70 248 I Indicators and Dynamometers, • • • 5o 128 Attaching, . . . . . # • 55 159 Blanks for Diagram, 56. I8l Comparisons of, . 54 150 Diagrams and their Modifications, arts. 58, 59, 61 ; pp. 182, l86, I94 Essentials of good, 52 129 Forms of Interpretations, arts. 53. 57. 60; pp. 130, 182, I89 Measurement of Diagrams, . 66 212 Principles of Construction and Use, 5i I29 Reducing Motions for, • 55. 56 160, I79 Locomotives, . 55 l66 Marine Engines, • • 55 170 Special Applications, . • • 62 203 Standardization of, 54 142 Institute. Boiler Trials at the American # • 40 79 Instructions for Standard Boiler Trials, 33 46 K Kent’s Calorimeter, ••••••.. 45 96 L Latent Heat of Steam • • • 37 73 Leakage and Cylinder Condensation, . • . . . 71 253 Locomotive Engine Trials, Examples, . • • . • 98 364 Indicating, .... • • • 55 168 Logs of Boiler Trials 58 M Marine Engines, Indicator Attachment, . . . 55 170 Trials, Deductions from, . . . . IOI 393 McNaught’s Indicator, Examples, . . . . . 100 376 Measuring Diagrams, ..... 131 Gross and Net Power, . 74 265 Methods and Apparatus of Trials of Boilers, 4- 3L 82 7.43.296512 INDEX. Mosscrop’s Speed-recorder, . ART. 68 PAGE 222 Motion, Indicator reducing, . • • • • 55 160 N Nomenclature of Indicator Diagrams, . • • • • 58 182 O Objects sought in Test-trials, . • • • • 3 5 Otto Gas-engine Trials, . . , • • • • 104 444>449 P Peculiar Indicator Cards, • • • 64 2<_ J Performance, Specifications of Economical, • • 2 Boiler, .... • 12 ,40 20, 84 Planimeters, ...... 67 219 Portable Engines, Trials; Examples, 96 356 Porter’s (Mr. C. T.) Report on Gaskill Pumping-engine Trial, 102 40b Power and Efficiency of Boilers, 30 43 Computations of, ... 68 236 Measurement of Gross and Net, 74 265 Trials to determine, 14 27 Precautions in Boiler Trials, . 33 55 attaching Indicators, 56 179 Preliminaries to Standard Boiler Trials, 33 47 Prony Dynamometer, .... 76 269 Proportions of Flues and Tubes, 15 30 Variations of Boiler, . 29 43 Pump Diagrams, .... 63 204 Steam, Duty Trials, 89. 102 320, 414 Pumping-engines, Duty of, 2 4 Examples of Trials of, • 80 288 Q Quality of Steam from Boilers, . • . 4i 84 Quantities to be measured in Tests of Boilers, • • • 15 29 R Ratios of Expansion, for best effect, • • 70 252 Records of Test, Boilers, • 33 52, 53 by Calorimeter, • 44 94 of Pumping-engines, Barms’, • 102 414 Reducing Motions for Indicators, , 55 160 Regnault’s Steam Tables, 39 75 Reports on Test-trials, Character of, 5 8 of Boilers, . 33 53 Engines, Barms’, 102 414 INDEX. 513 ART. PAGE Results sought in Test-trials, . . . • 15, 40 29, 76 Reynolds’ Electric Indicator, . 149 Richards’ Indicator, 53 132 Rules for Trials, arts. 33, 88, 89, 92; pp. 46, 53, 310, 316 s Sample Boiler Trials, . 40, 49 76, 113 Schemes of Test trial, 16, 87 33> 309 Skeel and Van Buren’s Calorimeter, . 46 98 Specifications of Performance of Boilers, . 2 2 Speed-counters, ...... 68 223 Standardizing Dynamometers, 75 267 Indicators, . . . . 54 142 Standard Trials, Boilers, . . . . . 32 45 Engines, . . . . 79 245 Instructions for, 33 46 Stationary Engine Trials, Example, 94 332 Steam and Water used by Engines, • 15, 69 33. 237 Latent and Total Heat of, . 37 73 Power, Costs of, .... 3 6 Pump Trials, . 89 320 Duty Shown by, . 102 414 Quality of, 4i 84 Specific Heat of, . 36 7i Used for Various Purposes, . 15 32 Steamers, Trials of “ Anthracite,’’ . 100 376 “ City of Fall River,” . 100 388 Steward, Brooks and, Gas-engine Trial, 104 438 System of Engine Trial, Farey and Donkin’s . 83. 103 298, 424 T Tables of Boiler Performance, . 12 20 Efficiency, .... . 11 17 Regnault, ..... 39 75 Water Consumption by Engines, . 15, 69 33, 244 Tabor’s Indicator, 53 135 Tachometers 223 Tests of Indicators, 54 142 Theory of the Calorimeter, 43 89 Thompson’s Indicator, ..... 53 133 Tables of Water Consumption by ] Engines, 69 244 Timing-forks, 68 532 Total Heat of Steam, ..... 37 73 Trials, Apparatus used in Boiler, . . 6, 20 9> 73 Competitive, 88 3ii514 INDEX. Trials, Engine and Boiler, ART. . So PAGE 287 Examples of, . 80-105 288-451 Extent of Scheme of, 18 36 Farey and Donkin’s System, . 83, 103 298, 424 Fitting up for, 8l 294 Gas, .... . 84, 86 303, 305 Logs of Boiler, .... 34 58 Methods of 4 7 Objects sought in Test, . 3> 21 5, 38 Precautions at Boiler, 33 55 Purposes of Engine and Boiler, . . 1 6 Records of Boiler, 33 52 Reports on “ ... 33 53 Character of, 5 8 Results of Boiler, 40 76 Sample “ “ . 40, 49 76, 113 Scheme of Test, .... . 16, 87 33. 309 Standard Test, .... . 32» 79 45, 285 Instructions for, . 33 49 Steam Boiler, System of, 17 34 Pump . 89 320 to determine Economy of Boilers, 9 10 Power “ “ 14 27 Two Methods of, ... 82 297 U. S. R. M. Steamers, 100 397 Tubes and Flues, Proportions of, . 15 30 Typical Indicator Diagrams, . . 58 182 U Unwin’s Trials of Atkinson’s Gas-engine, . 104 440 Otto’s ‘ ‘ . . 104 449 Worthington Pumping-engine, . • 80 288 V Value of a Boiler, . . 23 39 Van Buren and Skeel’s Calorimeter, . . 46 98 Vapor-engine Trials, .... • • 85, 105 305, 451 W Water and Steam Consumption, 69 237 Specific Heat of Steam and, 36 71 Water-tube Boiler, Trial of, . 49 113 Webb’s Indicator, 53 140 Wilson’s Apparatus for Gas-analysis, 47 109 Work, Dynamometric or Net, 73 262STEAM ENGINE. Stationary—Marine—Locomotive—Gas Engines, Etc. THEORY OP STEAM ENGINE. . Translated from the fourth edition of Weisbach's Mechanics, By A. J. DuBois. Containing notes giving practicax examples of Stationary, Marine, and Locomotive Engines, showing American practice, by R. H. Buel. Numerous illustrations. 8vo, cloth, $5 00 THE STEAM ENGINE CATECHISM. A Series of direct practical answers to direct practical ques- tions, mainly intended for young engineers, and for examin- ation questions. By Robert Grimshaw. Fifth edition, enlarged and improved. 1887.........................18mo, cloth, 1 00 “ Not only young Engineers, but all who desire rndimental and practical instruction in the science of Steam Engineering will find profit in reading the ‘ Steam Engine Catechism1 by Robt. Grimshaw. ’*—Mechanical News. STEAM ENGINE CATECHISM. Part II. Containing answers to further practical inquiries received since the issue of the first volume. Second edition, enlarged. 18mo, cloth, 1 00 “ It deserves a place in every young engineer’s book-case. "—Engineering, London. STATIONARY STEAM ENGINES. Especially adapted to Electric Lighting Purposes. Treating of the Development of Steam Engines—the principles of Con- struction and Economy, with description of Moderate Speed and High Speed Engines. By Prof. R. H. 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