EFFECT OF FUELalMPENGEMENF-SURFACE TEMPERATURE ON NOESEI SMOKE, AND POWER OF A COMPRESSIONJGNITIO‘N ENGINE Thus“ for “he Degree of PL, D. MECHE‘EAN STATE UNEVERSETY Lawrence Richard Daniel, Jr. 1958 ....... IIWITIIIW W 1mnwmlmnn'mml 1 'l 3 1293 01093 0083 This is to certify that the thesis entitled Effect of Fuel-Impingement—Surf ace Temperature on Noise, Smoke ,and Power of a Compression-Ignition Engine presented by Lawrence Richard Daniel, Jr. has been accepted towards fulfillment of the requirements for &_ degree in M91? 0 ‘* /. (/ 5/4"} ~«/’ (‘4. L L '3 V/\ Major professor 0—169 LIBRARY Michigan State University Mm EFFECT or FJJSL-IILI‘lICGEJMJNT-S mum: T mmmums ON NOISE, SmOKE, AND 302m OF A COMPRESSION-IGNITION ENGINE By Lawrence hichari Daniel, Jr. AN ABSTHACT Submitted to the School for Advanced Graduate Studies of Lichigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF EHILOSOPHY Dewartment of Mechanical Engineering 1958 Awmde, Lawrence Richard Daniel, Jr. AN ABSTRACT The intention of this investigation was to determine experi- mentally the effect of impingement-surface temperature on smoke, noise and power in a compression-ignition engine combustion chamber in which there is combustion-surface fuel impingement. A regular CFR Cetane engine was modified in such a way that, by use of a directional nozzle, the fuel spray could be directed either toward a combustion chamber wall or out into the open combustion chamber space. The combustion chamber consisted of a small cylindrical space located in the cylinder-head and was offset from the centerline of the bore. An investigation of airqflow in this chamber using paint- patterns and a small paddleawheel finally led to the development of a combustion surface in the.fonn of a protruding lip in the bottom of the combustion chamber. The fuel was injected onto this lip and the vapors produced thereon were picked up by the currents of air from the compression process. Spheroidization of the fuel was investigated on the assumption that within the engine a combustion surface might exist on which the fuel would spheroidize rather than spread as a smooth film. It was found that deposit formation on this combustion surface occurred so rapidly at higher surface temperatures that this system would not suc- cessfully operate within the temperature range at which spheroidization would seem to be a problem. Lawrence Richard Daniel, Jr. 2. Deposit formation caused increasingly more trouble as the temperature of the impingement surface was increased. It was concluded that the distance between the injector nozzle and the impingement sur- face was somewhat critical, in that too small a distance would allow diversion of the fuel spray by the deposits prior to its complete spreading on the lip, while too large a distance would allow a large portion of the fuel to autoignite and cause a louder combustion noise. It was found that the beneficial effect of an impingement surface on noise and smoke increased as the surface temperature in- creased. At the higher surface temperatures, however, deposits quickly formed and the beneficial effect of the surface was reduced. For this engine it was found that the Optimum surface operating temperature was in the neighborhood of 500°F. Above this temperature the smoke became worse, power dropped off and noise tended to increase, depending on the manner in which the deposits formed. Below this temperature'both noise and smoke quickly became unreasonable. The effect of compression ratio on the surface-impingement system in a compression-ignition engine such as this one was similar to that of the normal space-impingement system, For compression ratios between 16:1 and 22:1 it was found that smoke became worse, power in- _ creased, and noise decreased as the compression ratio was increased. Higher compression ratios than 22:1 gave excessive smoke. The original fuel-impingement compression—ignition engine as developed by Dr. J. S. Meurer, known as the M—system combustion chamber, utilizes fuel impingement in a hemispherical combustion chamber and Lawrence Richard Daniel, Jr. 3. evaporation of this surface.film into a controlled air-swirl. It was concluded that the system originated herein is not a true Mysystem combustion chamber. In the true Mpsystem the reaction rate is low at the beginning of combustion and increases towards the end of combustion while in this "lip" engine the maximum rate of pressure change occurs nearer the beginning of combustion. EFFECT OF FUEL-DIPINGE‘mfiNT-SURFACE TmPERATJRE ON NOISE, enema, AND POWER OF A COMPRnSSION-IGNITION moms By Lawrence Richard Daniel, Jr. A THESIS Submitted to the School for Advanced Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPdY Department of Mechanical Engineering 1958 ACKNOWLEDGMENT To Dr. Louis L. Otto, for his suggestion of the subject of this investigation, for his kindly concern in its successful completion, and for his considerate and understanding guidance through two and one-half years of graduate studies; To Professor Ralph Vanderslice for his willing participation and assistance during the photographic studies; To Mr. Carl Redman for his technical and procurement assistance, and Mr. Ray Pearson for the expeditious production of experi- mental equipment; To the Southern Fellowships Fund, Consumers Power Company, and Louisiana Polytechnic Institute for financial aid; To Michigan State University for financing the investigation; and finally, and most important, to his wife for her forebearance and encouragement; The author wishes to express his most sincere appreciation. ii AUTOBIOGRAPHY Lawrence Richard Daniel, Jr. Candidate for the Degree of Doctor of Philosophy Final Examination, December 15, 1958, 2:00 P.M., Room 108, Olds Hall Dissertation: Effect of Fuel-Impingement-Surface Temperature on Noise, Smoke, and PoWer of a Compression-Ignition Engine Outline of Studies: Major Subject: -Mechanical Engineering Minor Subjects: Mathematics, Applied Mechanics Biographical Items: Born: August 2, 1922, Shreveport, Louisiana undergraduate Studies: B.S. in Mechanical Engineering Louisiana State University, 1939~h3 B.S. in Civil Engineering Louisiana Polytechnic Institute l9h9-5h Graduate Studies: Master of Automotive Engineering Chrysler Institute of Engineering 19h6-h8 Experience: Engineering and Executive Officer, USS LCI(L) 759, l9hh—h6 Junior Engineer, Chrysler Corporation, l9h6-h8 Instructor, Assistant Professor, Associate Professor and Professor, Louisiana Polytechnic Institute, l9h8-Present Professional Societies: Society of Automotive Engineers, American Society of Mechanical Engineers, Louisiana Engineering Society, National Society of Professional Engineers, American Society for Engineering Education, Louisiana Teachers Association Honor Societies: Tau Beta Pi, Omicron Delta Kappa, Pi Mu Epsilon Registration: Professional Civil and Mechanical Engineer, Registration No. 1878, State of Louisiana iii TABLE OF CONTENTS IN TROD UCT IOIJ O O O O O O O O O O O O O DELINEATION OF VARIABLES AND DEFINITIONS . . . . PRESENTATION AND DISCUSSION OF RESULTS. . . . . GRAPES General Results. . . . . . . . . . Effect of Lip Temperature and Injection Advance at Constant Compression Ratio. Effect of Lip Temperature and Compression Ratio at Optimum Injection Advance for Sleeve-Impingement . . . . . . . General Comparison. . . . . . . . . SUMMARY AND CONCLUSIONS. . . . . . . . . . APPmmICE O O C O O O O O O O O O O O A. M—System Theory . . . . . . . . B. Development of Combustion-Chamber Configuration. . . . . . . . . C. Spheroidizing Tendencies . . . . . D. Equipment and Calibration . . . . . BIBL'IOC’P1$ PHX e e e e o e e e o e o o 0 iv EEO‘xH 1:3 145 SS 60 61 6h 83 97 113 LIST or FIGUREL Figure Page 1 Pressure-Time and Rate-Time Relationships, Motoring and Firing, for Space-Injection at 18 1/2:l Compression Ratio. Pips at 13°BTDC and 13°ATDC. Surface Temperature of Combustion Chamber, 830°F. Injection Commences 21°BTDC . . . . . . . . . 12 2 Pressure-Time and Rate—Time Relationships, Motoring and Firing, for Lip-Injection at 18 1/2:l Compression Ratio. Pips at 13°BTDC and 13°ATDC. Impingement-Surface Temperature 6hO°F. Injection Commences 21°BTDC . . . 13 3 Pressure—Time and Rate-Time Relationships, Motoring and Firing, for Sleeve—Injection at 18 1/2:1 Compression Ratio. -Pips at 13°BTDC and 13°ATDC. Impingement-Surface Temperature 580°F. Injection.Commences 21°BTDC . . . 1h h Motoring Compression Pressure Diagrams for Un- modified CFR Cetane Engine at 16.6, 18.1, 19.9, 22.1, 2h.9, and 28.5:1 Compression Ratio. Pips at 13°BTDC and 13°ATDC . . . 16 5 Pressure-Time and Rate-Time Relationships, Motoring and Firing, for Unmodified CFR Cetane Engine at 18 l/2:1 Compression Ratio. Pips at 13°BTDC and 13°ATDC. Injection Commences 13°BTDC . . . . . . . . . 21 6 Pressure-Time and Rate-Time Relationships, Motoring and Firing, for Fuel-Impingement System at 18 1/2:1 Compression Ratio. Im- pingement-Surface Temperature th°F. In- jection Commences 21°BTDC. . . . . . . bl 7 Pressure-Time and Rate-Time Relationships, Motoring and Firing, for Fuel-lmpingement System at 18 1/2:1 Compression Ratio. Im- pingement-Surface Temperature h60°F. Pips at 13°BTDC and 13°ATDC. Injection Commences 19 °B’I'DC - O O O O O O O O O O O O h2 , LIST OF FIQUFES (cont.) Figure Page 8 Pressure-Time and Rate—Time Relationships, Motoring and Firing, for Fuel-Impingement System at 18 1/2:1 Compression Ratio. Im- pingement-Surface Temperature 600°F. In- jection Commences 18°BTDC. . . . . . . AB 9 Bottom View - CFR Cetane Engine Cylinder-Head Modification . . . . . . . . . . . 66 10 Side View - CFR.Cetane Engine Cylinder-Head Modification . . . . . . . . . . . 67 11 Compression-Ratio Plug and Tie-Down Bolt . . . 69 12 Modified CFR.Cetane Engine. Note Tie-Down Bolt 0f Fig‘lre ll 0 O O O O O O O O O O 70 13 Compression-Ratio Plugs . . . . . . . . . 71 1h Piston and Block. Paint-Pattern of Air Swirl. . 73 15 Cylinder Head. Paint-Pattern of Air Swirl. . . 7h 16 Shrouded Intake Valve. . . . . . . . . . 75 17 Compression-Ratio Plug and Original MouthpInsert Prior to Grinding . . . . . . . . . 76 18 MouthpInsert Inserted Into Liner. Compare'With Figure 15 (No Insert) and Figure 17 . . . 77 19 PaddleAWheel USed for Determining Air Rotation . 79 20 Various MouthrInserts. . . . . . . . . . 80 21 Schematics of Combustion Chamber AiréFlow'in Modified CFR.Diesel. . . . . . . . . 82 22 HighASpeed Movies of Fuel Impingement on Surface at 535°F, at 6000 Frames Per Second . . . 85 23 HigheSpeed Movies of Fuel Impingement on Surface at 793°F, at 7500 Frames Per Second . . . 86 2h Fuel Impingement on Surface at 780°F, Early During Injection, 0.00005 Second . . . . 87 25 Fuel Impingement on Surface at 780°F, Just After Completion of Injection, 0.00005 Second . . 88 vi Figure 26 27 28 29 3O 31 32 33 35 36 37 38 39 ho hi LIST OF FIGURES (cont.) Page Fuel Impingement on Surface at 780°F (Close-Up), Just After Completion of Injection, 0 .00005 second 0 o o o o o o o o o o 89 Fuel Impingement on Surface at 6h5°F, Early During Injection, 0.00005 Second. . . . . 90 Fuel Impingement on Surface at 6h5°F, Just After Completion of Injection, 0.00005 Second . . 91 Fuel Impingement on Surface at 6h5°F (Close—Up), Just After Completion of Injection, 0.00005 Second. . . . . . . . . . . 92 Fuel Impingement on Surface at h80°F, Early During Injection, 0.00005 Second. . . . . 93 Fuel Impingement on Surface at h80°F, Just After Completion of Injection, 0.00005 Second . . 9h Fuel Impingement on Surface at h80°F (Close-Up), Just After Completion of Injection, 0.00005 Second. . . . . . . . . . . 95 Schematic of Regular CFR.Diese1. . . . . . . 98 Schematic of Modified CFR Diesel . . . . . . 99 Dimensions of Lip and Sleeve Installation . . . 101 Low Temperature Lip and Sleeve Assembly . . . . 102 Smoke-Meter . . . . . . . . . . . . . 107 Schematic of SmokeeMeter . . . . . . . . . 108 Installation of Thermocouple. . . . . . . . 109 General VieW'of Modified CFR.Diesel and Associated Equipment . . . . . . . . . . . . lll Set-Up for HighsSpeed PhotOgraphs of Fuel In- jection on a Surface. . . . . . . . . 112 Graph II III VI VII VIII LIST OF GRAPHS Compression Ratio vs Smoke Density and Power.for Regular CFR.Cetane Engine,‘With and Without Insulated Cap on Compression-Ratio Plug, as Compression Ratio Is First Decreased and Then Increased. Fuel Rate 9 ml./min. Injection at 13°BTDC. . . . . . . . . Compression Ratio vs Smoke Density and Power.for Regular CFR Cetane Engine, With and Without Insulated Cap on Compression-Ratio Plug. Fuel Rate 9 ml./min. Injection at 13°BTDC . Effect of Sleeve- and Space-Injection on Noise, Smoke Density, Power, and Lip Temperature USing Lothemperature Lip and Sleeve Assembly Effect of Sleeve- and Space-Injection on Noise, Smoke Density, Power, and Lip Temperature Using Intermediate-Temperature Lip and Sleeve Assembly . . . . . . . . . . Effect of Sleeve- and Space-Injection on Noise, Smoke Density, Power, and Lip Temperature Using Intermediate-Temperature Lip and Sleeve Assembly (Asbestos Insulation Between Lip and Mouthelnsert) . . . . . . . . Compression Ratio vs Noise, Smoke Density, Power, Lip Temperature and Injection Advance for LowaTemperature Lip and Sleeve Assembly at Best Power. Fuel Rate 10 ml./min. . . . . Compression Ratio vs Noise, Smoke Density, Power, Lip Temperature, and Injection Advance for Intermediate-Temperature Lip and Sleeve Assembly at Best Power. Fuel Rate 10ml.,/min............ Compression Ratio vs Noise, Smoke Density, Power, Lip Temperature, and Injection Advance for Intermediate-Temperature Lip and Sleeve Assembly (Asbestos Insulation Between Lip and MoutheInsert) at Best Power. Fuel Rate 10 ml./min. . . . . . . . . . . . viii Page D6 D7 D9 50 51 52 53 LIST OF GRAPES (cont.) Graph Page II Lip Temperature vs Noise, Smoke Density, and Power at Best Power. Compression Ratio 18 l/2:l, Fuel Rate 10 ml./min. . . . . Sh LIST OF TABLES Tables Page I Comparison of Three Places of Injection Inter- mediate-Temperature Lip and Sleeve Assembly with.Bottom of Lip Insulated from Mouthp Insert by Asbestos, Compression Ratio 18 l/2zl, Fuel Rate 10 m1./min. . . . . . 11 II Engine Warm-Up Data, Using High Temperature Lip and Sleeve Assembly, Lip-Injection, Compression Ratio 18 l/2:1, Injection Advance 18°BTDC, Fuel Rate 10 ml./min. .. . . . . . . . 18 III Data of Regular CFR Cetane Engine,'With and Without Insulated Stainless Steel Cap on Compressions Ratio Plug as Compression Ratio is Changed from 22.1:1 to 15.3:1 and Back to 22.1:1. Injection Advance 13°BTDC, Fuel Rate 9 ml./min. . . . . . . . . . . . . 22 IV Data on Regular CFR Cetane Engine, With and Without Insulated Stainless Steel Cap on Compression- Ratio Plug as Compression Ratio is Changed from 28.5:1 to 13.h:1. Injection Advance 13°BTDC, Fuel Rate9ml./min. . . . . . . 25 V Comparison of Three Places of Injection. High- Temperature Lip and Sleeve Assembly, Compres- sion Ratio 18 l/2:1, Fuel Rate 10 m1./min. . 26 VI Comparison of Two Places of Injection for Three Types of Lips. Compression Ratio 18 l/2:1, Fuel Ra-te 10 mlo/Inin O O O O 0 O O O O 29 VII Comparison for Sleeve—Impingement at Three Com- pression Ratios for Lothemperature Lip and Sleeve Assembly, Fuel Rate 10 m1./min. . . . 35 VIII Comparison for Sleeve-Impingement at Three Com- . pression Ratios for Intermediate-Temperature Lip and Sleeve Assembly. Fuel Rate lOml./min.............36 IX Comparison for Sleeve-Impingement at Three Com- pression Ratios for Intermediate-Temperature Lip and Sleeve Assembly with Bottom of Lip Insulated from Mouth-Insert by Asbestos. Fuel-Rate 10 ml./min. . . . . . . . . 37 X INTRODUCTION Ever since the early days of the diesel engine, engineers have been concerned with the formation of a combustible mixture within its combustion chamber. While the Otto, or spark-ignition engine, uses the major portion of the intake and compression strokes in which to form a combustible mixture, the«iiesel has considerably less time to perform this necessary function. In the diesel, or compression— ignition engine, the injection of fuel is begun just before the end of the compression stroke only to be terminated a few degrees later in the beginning of the expansion stroke. it could be estimated, there- fore, that the diesel has in the order of one-twentieth the time of the spark-ignition engine to form a combustible mixture. This is further complicated by the.fact that, while the combustible mixture is completely formed at the time of its ignition in the spark-ignition engine, in the diesel the last portion of the fuel to be injected is sprayed into a zone of combustion, glowing hot from the action of the initial autoignition. The early combustion has already taken full usage of the most readily available oxygen, leaving tne last portion of the fuel to burn in a relatively fuel-rich zone. It is mainly the job of the injection system to so combine +he fuel and air that this fuel-rich.condition, and its attendant formation of smoke, does not occur before the maximum amount of air has been combined with the fuel. This is also the reason why it is said that a diesel engine under full power is smoke-limited and why the richest.fuel-air mixture 2. ratio for a diesel is considerably leaner than that of an otto engine under the same.full-power conditions. During early investigations it was generally accepted that the best mechanism of formation consisted of immediate vaporization and mixing with air as the fuel was injected into the cylinder or combustion space. The control of the combustion reaction was then under the direct influence of the rate of inflow of the fuel. Delay of combustion (ignition delay) caused by a chemical delay character- istic of the fuel was something which had to be put up with and the more that could be done to Shorten this delay the better. During the ignition delay period more and more fuel is being injected into the combustion chamber. Because of this accumulation of fuel when combustion begins, a large amount of the fuel is consumed in a short time causing a high rate of cnange of pressure. This high rate of change in pressure may shock load some of the engine parts and set them to vibrating, transmitting noise to the surroundings. Be- cause of the heterogeniety of the autoignition process, pressure differences may be set up Within the combustion chamber which.may be superimposed upon the already vibrating masses. Thus it is that many factors, such as injection processes, natural frequency of the vibrat- ing parts, mass of the parts, and the like, enter into whether or not a fuel knOCks in a particular engine. There seems to be no fixed value of rate of change of pressure wnich differentiates between a knocking and a non-knocking combustion process. Each individual engine design has its own value of rate of change of pressure at 'which audible knock begins. 3. It has been.found that in the case of the more volatile fuels, smoke increases with.decreased ignition delay, while in the case of less volatile.fuels this trend is reversed.1 As the time for the beginning of injection was advanced less smoke was produced.2 However, if the injection was advanced too far, smoxe production was increased because of spray impingement on the combustion chamber sur- faces.3 Using a "nearly ideal micro- and macro~mixture" formed during the period of ignition lag produced a loud characteristic diesel knock and heavy exnaust smoke.)J These same investigators found that if, for improving mixture formation, either the spray velocity or the air velocity or'botn were increased, the combustion noise became louder. If the fuel rate at the beginning of injection was reduced the engine ran smoother, but there was an increase in exhaust smoke. Throughout this confusion, fuel characteristics were always paramount and any comparison of engine performances without their in- clusion was almost useless. In particular, the spark-ignition fuels with their long—delay characteristics were in general eliminated fran use in a compression-ignition engine. All the while the gap between the fuel used in the spark- ignition engine and the compression-ignition engine was widening. Autoignition was necessary in one engine wnile it was nighly undesir- able in the other. This separation was not too unde81rable because that fuel not readily adaptable to the diesel was usually usable in the otto engine. Nevertheless, the proouction of two distinCtly h. different.fuels is much more expensive than the production of only one, and toward this end a great deal of research has been.directed. A true multifuel engine, capable of burning either gasoline or diesel oil, would be eagerly accepted. This engine must have the power and economy of contemporary engines, and it must be quiet and clean- burning like the spark-ignition engine without the necessity of using the highly relined fuel required of this latter type. In June, 1955 there was presented to the Society of Automotive Engineers an explanation and solution to some of the problems of diesel engine combustion. Dr. J. S. Meurer of Machinenfabrik Augsburg Nfirnberg, Nurnberg, Germany presented a paper entitled "Evaluation of Reaction Kinetics Eliminates Diesel Knock" and demonstrated its practical applications with the operation of a highly successful engine. That this engine was quiet and relatively smokeless was witnessed by all. Dr. heurer's theories have now withstood three years of extensive research by industry. This engine successfully burned all.1uels in the range from gasoline to lube oil and as a result has served as an extreme impetus to research into the realm of multifuel engines. Just recently (October, 1950) there was presented a series of six papers on multi- fuel engines before the Society of Automotive Engineers National Diesel Engine Meeting. Since all types of fuels can be used in these engines it seems then that the gap between spark- and compression- ignition engines has finally closed. The M-system combustion system, as Dr. Meurer's theory is called, consists basically of fuel impingement on the combustion~ chamber walls. Prior to the impingement a small portion of the fuel autoignites during its passage from the nozzle tip to the combustion surface. The remaining fuel is deposited as a liquid film on the surface. Here evaporation is delayed as compared with an injection system in which.fuel is forced outward into the hot compressed air. This fuel vapor is picked up and consumed in a comparatively orderly manner by a rapid air swirl within the combustion chamber. The temperature of the combustion surface is extremely important in that it controls the rate of evaporation, lip wetting, and fuel cracking. This variable, combustion-surface temperature, is the primary interest of this investigation. The problem chosen for this investigation is to formulate a satisfactory qualitative analysis of the combustion process for fuel- impingement combustion as the temperature of the impingement surface is varied. Basically it includes an experimental development of a fuel—impingement combustion chamber.for a compression-ignition engine and a physical interpretation of the effects of surface temperature on smoke, power, and noise. DELINEATION OF VARIABLES AND DEFINITIONS In order to successfully investigate the effect of surface temperature on sm0ke, noise, and power, it is necessary to obtain means to vary and measure each to a certain degree of accuracy depend— ent upon the magnitude of their variations. Thus, it was considered useful to record such uncontrollable variables as atmospheric pressure and intake—air volume. However, such a small variation existed in the amount of air consumed under varying circumstances, including the vari- ation in compression ratios, that this variable was discounted during calculations. No specific correction concerning the effect of atmospheric pressure on smoke and noise is known and although recorded, this vari- able was also discounted during calculations. Incidentally, the pressure variation for the entire time of testing was no greater than two per cent. Low engine speed will produce the most pronounced diesel knocx. Since the CFR diesel wnich.was to be used in this investigation was regulated at 600 rpm, it was decided to use this speed. In order to eliminate another variable it was decided to maintain this as the only speed used during the tests. Considerable disagreement exists in the literature regarding the effectiveness of the various smoke-measuring devices. Since re- productivity, continuous reading, and only comparative results were necessary, it was decided to construct a device suitable for this 7. investigation. The indications obtained therefrom ranged from 6.1 to 1.3 when the exhaust changed from what might be considered a “rather dark" to a_“clear" condition. The density of exhaust smoke is there- fore somewhat proportional to the smoke-meter readings. Two methods were chosen for comparing noise. A tape-recorder was most usefulibr'audio-comparative results over a period of time but this could not be incorporated on a written page. A commercial noise- meter was used for direct readings in decibels and these values were listed under the "Noise" heading on the data sheet. In a normal engine the fuel may come into contact with the combustion surfaces. Because of this it was decided to start the range of the lip temperatures as near to that of a normal combustion chamber surface as possible. This would be in the order of 380°F and higher. The upper limit of the temperatures would depend upon the progress of the inVestigation. Compression ratios of 28.5:1 down to 16:1 would be all that were necessary. Lower than 16:1 would certainly produce a noisy con- dition and the higher ratios are conducive to smoke formation. The main investigation was actually centered in the range of 18:1. All variables which could be controlled were made constant. This included intake air (150°), coolant temperature (212°), and fuel rate (10 m1./min., in general). The.fue1 rate was set at a condition which produced heavy smoke in some cases wnile in others the exnaust was relatively clear. Because this system of combustion has previously been shown to be effective with most internal-combustion engine fuels, only one type of fuel was used for most of the tests, a commercial diesel fuel, Octane #hz minimum. In the description of the place of injection, the following nomenclature is used: ' Sleeve-impingement or sleeve-injection. Injection onto the sleeve and lip immediately adjacent to the nozzle. Lip-impingement or lip-injection. Injection somewhere out on the lip at one-half inch along the lip from the sleeve unless otherwise noted. The distance between the impingement surface and the nozzle tip is somewhat greater than in the case of sleeve-injection. Space-impingement or space-injeCtion. Injection so that there is no impingement on any combustion surface. This implies injection toward the passage between the cylinder and the lip and sleeve assembly. The liner is that portion of the combustion chamber which has been forced into a hole bored in the cylinder head. The mouth-insert is that machined part which is used in the bottom of the liner to control +he.flow of air and/or gases to and from the cylinder space. It serves a secondary purpose of keeping the sleeve and lip assembly in place. The compression—ratio plug is that machined part which is in- serted in the top of the liner. It serves as a means of closing the combustion chamber and of varying the compression ratio by the use of different sizes of plugs. In the case of the regular, unmodified CFR Cetane engine the compression-ratio plug is that part which is normally used to change the compression ratio. This latter arrangement is more 9. elaborate than that of the modified engine but it operates in essen- tially the same manner. 'When the word "scale" is used, it indicates the force in pounds exerted by the torque arm of the dynamometer. Since the engine rpm is constant, the scale readings are a direct indication of the power produced. The nozzles used in the injector for this investigation con- sisted of the normal pintle-type nozzle with which the CFR engine is regularly equipped and a multiple-orifice nozzle in'WhiCh all except one of the orifices were closed. This latter arrangement supplied a method by which.the direction of injection could be Changed, consisting essentially of rotating the nozzle in the injector or rotating the in- jector in its mounting in the engine. The orifice diameter was 0.0118“. The oscilloscope pictures were obtained by seven different ex- posures. In each case the time variable began on the right and moved to the left. The ordinate of the top two curves was pressure and that of the bottom two was the rate of change of pressure, or dp/dt. The top and bottom curves pertain to the engine under firing conditions while the center two curves are for the motoring condition. Pips appear at 13°BTDC and l3°ATDC. Approximately at the two and at the four centimeter lines up from the center are seen horizontal traces. The bottom trace represents 578 psi while the top trace represents 1057 psi, each measured from the center. No scale is set up for the rate diagram.but its value can be obtained by use of a constant which is derived in the Appendix D. 10. The different types of lips are described as: Lowhtemperature lip - lip and sleeve assembly using no insulation between it and the liner. Intermediate-temperature lip — lip and sleeve assembly using annular grooves, or spaces, as an insulation method. High—temperature lip - lip and sleeve assembly using asbestos as an insulation between it and the liner. The term "combustion chamber" refers to that separate chamber, apart from the space immediately above the piston, into which the fuel is injected. It is that volume enclosed by the lip and sleeve assembly above the mouth-insert and below the compression-ratio plug. PRESENTATION AND DISCUSSION OF RESULTS GENERAL RESULTS Effect of Impingement Surface Table I and Figures 1, 2, and 3 show very clearly the effect of varying the place of injection from space to lip to sleeve, re- spectively. This variance was obtained by attaching a flexible fuel TABLE I COMPARISON OF THREE PLACES 0F INJECTION. INTEanIATE-TmPENATURE LIP AND SLEEVE ASSEMBLY wITH BOTTOM OF LIP INSULATED FROM MOUTH-INSERT BI ASBESTOS, COMPRESSION RATIO 18 l/2:l, rum. RATE lo NIH/MIN. _ T— 1 _- Space Lip Sleeve Injection Advance, °BTDC 21 21 21 Noise 75.0 7h.5 73.? Smoke Density 5 .5 3 .8 h .0 Power (Scale) 9 .5 9 .7 9 .3 Lip Temperature, °F 830 6&0 580 Maximum Pressure, psi 1,060 980 910 Average maximum Rate, psi/sec. 203,000 162,000 81,h00 Picture Number 1 2 3 l2. IIII-ni . '~-' _ I l l I -*—-——Tine Figure 1. Pressure-Time and Rate—Time Relationships, Motoring and Firing, for Specs-Injection at 18%:1 Compression Ratio. Pips at 13°BTDC and 13 ATDC. Surface Temperature of Combustion Chamber, 830°F. Injection Commences 21°BTDC 13. -<—-~Time Figure 2. Pressure-Time and Rate-Time Relationships, Motoring ands Firin , for Lip-Injection at 18—:1 Compression Ratio. Pi at 13 BTDC and 13° ATDC. Impingement-Surface Temperature 6 0° F. Injection Commences 21°BTDC. t.................. In...» . I”: an... M1»... I I 1h. ~r———Time Figure 3. Pressure—Time and Rate—Time Relationships, Motoring and Firing, for Sleeve-Injection at 18%:1 Compression Ratio. Pips at 13°BTDC and 13°ATDC. Impingement-Surface Temperature 580 F. Injection Commences 21°BTDC. line to the injector and rotating the injector assembly while the engine was in operation. The three pictures are taken consecutively with.very little time lapse between them. Figure h is a set of motoring curves used to determine the effective compression ratio throughout the tests. These curves were obtained by motoring the unmodified CFR Cetane engine at various com- pression ratios. From these it can be seen that the compression ratio of the first three pictures, as indicated by the second curve from the top on each, is in the order of 18 l/2:1. The magnitudes of the maximum combustion pressure in Figures 1, 2, and 3 were 1,060, 980, and 910 psi, respectively, and the maximum of the average rates of pressure change were approximately 203,000, 162,000, and 81,h00 psi/sec, respectively. The first set of readings was taken from the maximum of each of the top curves and the second set from the maximum of the average trace, or mean, of the bottom curves. Thus, in the case of rate curves with a large number of fluctuations, the average ordinate is used rather than the maximum of any one fluctuation. It can be plainly seen by the pressure-time curves that the rate of change of pressure during the combustion process is greater in space-injection than in lip-injection which, in turn, has a greater rate than sleeve-injection. Care must be taken not to confuse the two calibration marks, one at 13°BTDC and the other at 13°ATDC, with pressure variations. The second curve from the bottom is the motoring rate-time curve. Its only purpose is comparative. 16. --——-— Time Figure 1;. Motoring Compression Pressure Diagrams for Unmodified CFR Cetane Engine at 16.6, 18.1, 19.9, 22.1, 214.9 and 28.5:1 Compression Ratio. Pips at l3°BTDC and 13°ATDC. 17. The amount of noise produced by space-injection and lip- injection, 75.0 and 7h.5, respectively, would probably preclude their acceptance as commercial machines. A noise reading of 7h.5, in general, separates the realm of general quietness and noisiness herein. This is, of course, relative and might not be similarly judged by another observer. Reducing the injection advance for space-injection would quiet the engine but with a reduction in power and increase in smoxe. A comparable change for lip-injection would produce the same changes as in the case of space-injection. Tests snowed that an injection advance which would quiet the engine to an acceptable level would re- duce the power of both space—injection and lip-injection into the range of the power produced by sleeve-injection while in neither case was the exnaust as clear as in the latter. The investigation was, therefore, mainly centered around sleeve—injection. Note that there is a row in Table I under the heading of Lip Temperature. The lip temperatures for space—, lip—, and sleeve— injection are liSted as 830°F, 6h0°F, and 580°F, respectively. All three temperatures are measured by a thermocouple placed in the center of the lip. For space-injection no cooling film of fuel is impinged on the lip so the temperature recorded under'this condition is natur- ally nigher than for lip— or sleeve-injection. For lip-injection, the fuel comes into contact with the lip over the outer half, or less, of lip area, so at least part of the lip is insulated and cooled by the fuel film and its vapors. The temperature listed for lip-injection 18. is therefore less than for space-injection. Sleeve-injection implies injection onto the sleeve and lip immediately adjacent to the nozzle. Only a very short distance of intervening space separates the nozzle from the lip. The fuel spreads onto a much larger portion of the lip than in the case of lip-injection; therefore, the recorded lip temper- ature is the lowest of the three temperatures listed. Note that the names for the last two types of injection, lip— and sleeve-, corre- spond to the first place of impingement of the fuel after leaving the nozzle. warm—Up Requirement and Deposit Formation Table II, a warmpup run on the high temperature lip with lip- TABLE II ENGINE WARM-UP DATA, USING RISR-TmPERATURE LIP AND SLEEVE ASSEMBLY, LIP-INJECTION, COMPRESSION RATIO 18 l/2:l, INJECTION ADVANCE 18° BTDC, FUEL RATE 10 NL./DIN. Time After Smoke Power Lip Temper- Noise Start.(min) Density (Scale) ature, °F 3 3 .6 7 .2 535 714 .o 12 5.8 7.3 790 75.3 21; S .9 8 .2 630 7h .6 36 5 .6 8 .5 630 7‘4 .6 NB 5.8 7.9 750 7h.9 72 5 .O 9 .1 7&5 7t .8 78 5 .3 o .3 720 71. .7 19. injection, is indicative of the variations encountered in this investi- gation. To be particularly noted is the trend of the lip temperatures, first increasing to a maximum (790°) followed by a reduction in temper- ature and occasionally by another increase. This is understandable when it is considered that the lip is initially clean and therefore uninsulated from the hot gases. This lip, because it was designed to run at high temperatures, was very susceptible to early deposit forma- tion. Consequently, the deposits quicxly formed, diverting the spray before it thoroughly impinged on the lip, and reduced the cooling ef— fect of the liquid fuel. This loss of cooling effect, combined with the clean uninsulated surface of the lip, allows the heat of the com- bustion gases to quickly penetrate the lip and raise its temperatur . Eventually deposits do form on the lip and their insulating value succeeds in lowering the temperature of the lip, hereafter to fluctuate somewhat, depending upon the amount of deposits remaining on the lip. For the lower temperature lips less trouble is encounted by deposits and therefore, the cooling action of the fuel spreading out and forming a thin cover is the controlling factor. The only sure indication of impingement of the fuel on the lip is obtained by chang- ing the place of injection. Any decrease in the temperature indicates better impingement on the lip since the thermocouple is located in its center. No appreciable increase in temperature when the direction of injection has been changed from lip r Sleeve to space indicates that deposits have built up and caused diversion prior to complete impirge- ment. 2d. Noise depends on the manner of diversion and the time of in- jection, the earlier and the less dispersed injections producing the louder diesel knock. Smoke depends to a large extent on the control which the lip exercises on the fuel, a well spread out highly dispersed injection producing a minimum of smoke. Comparison with Standard CFR Although Figure 5 was taken using a different pressure pick- up (different calibration) than was used for the rest of the investi- gation, it is included herein for its general interest. This picture was taken of the events occurring under standard conditions in an un- modified CFR.diesel engine at a compression ratio of 18 l/2zl. Since the fuel rate, and power, were different than in the circumstances under which all the other pictures were taken, no quantitative com- parison can be made. In particular, it should be noticed that the large-ranged fluctuations of the rate of pressure rise vs. time diagram are absent as compared with Figures 1 and 2. This is due to the pintle-type of injector used, while the remaining pictures are indica- tive of the behavior of an orifice-type nozzle. The preceding state— ment was verified by use of an orifice-type nozzle in place of the pintle-type in the regular CFR engine. The orifice-type nozzle evi- dently delivers fuel in such a manner as to induce large, almost instantaneous, variations in the rate of pressure rise. Referring again to Figures 1, 2, and 3, we see that a controlled condition such as sleeve—impingement can considerably reduce both the magnitude of the fluctuations of the rate of pressure rise and their mean value. 21. ~*————Tine Figure 5. Pressure—Time and Rate—Time ielationships, Motoring and Firing, for Unmodified CFR Cetane Engine c 18%:1 Compression Ratio. Pips at 13°BTDC and 13°ATDC. Injection Commences 139ch . 22. Impingement Effect in Standard CFR The data shown in Table III was taken on the regular CFR Cetane diesel using a pintle-type nozzle. The information desired TABLE III DATA ON REGULAR.CFR CETANE ENGINE, WITH AND WITHOUT INSULATED STAINLESS STEEL CAP ON COMPRESSION-RATIO PLUG AS COMPRESSION RATIO Is CHANGED FROM 22.1:1 TO 15.3:1 AND BACK TO 22.1:1. INJECTION ADVANCE 13°BTDC, FUEL FLON 9 NL./uIN. _—_‘_~A __ Insulated Stainless Steel Cap Standard Compression- On Compression-Ratio Plug Ratio Plug Compression waer Smoke Ebwer Smoke Ratio (Scale) Density (Scale) Density 22.1:1 10.0 h.1 10.3 h.6 19.9:1 10.0 3.0 10.5 3.6 18.1:1 9.9 _ 3.0 10.5 2.7 15.6:1 10.0 2.3 10.3 2.2 15.3:1 9.7 2.3 10.0 2.1 16.6:1 9.6 2.5 10.1 2.3 18.1:1 9.5 3.1 10.3 2.6 19.9:1 9.6 3.0 13.1 3.1 22.1:1 9.h h.l 10.1 3.6 ‘4 ‘ “— here was to determine the effect of providing a hot surface for the fuel to impinge upon in case it was successful in traversing the com- bustion chamber without complete evaporation. This is accomplished by attaching a stainless steel dism insulated by asbestos to the com- pression-ratio plug. It was found that this surface attained an average temperature of the order Of 800°F while the bare plug averaged approximately 360°F. 23. Actually, none of the M—system principles (Appendix A) are applied here because (1) the amount of fuel autoigniting is not limited, (2) oxidation does not begin gradually, and (3) little or no controlled evaporation delay is introduced by this system. All in- jected fuel, except that which might impinge on the far surface is free to evaporate as rapidly as possible with little control over per- missible pressure rise. It is nevertheless interesting to note the effects. Graph I indicates the trends of smoke and noise vs. compression ratio. In each case, with and without the insulated cap, the trend was toward more power'during the compression ratio reduction than during the compression ratio increase. This can be explained when it is noted that the runs started at a high compression ratio and progressed to the lower compression ratios. This was followed immediately with a set of runs taken as the ratios were increased. For this latter set it was necessary to reheat the engine components to a temperature com- patible with the higher compression ratios. This represents a loss in availability of the fuel for useful work. Although it seemed at the time that a sufficient waiting period had elapsed, the graph snows othe wise. This is brought up here because it is wiSned to emphasize the time involved for equilibrium conditions to be achieved. Two- hour warm-up periods were not unusual. An explanation of the smoke trend is necessary. Note that there is less smoke at the lower compression ratios. dlliot2 has ex- plained that "short ignition delay generally increases smOke production because a larger portion of the fuel is injected into an inflamed mixture. Under these conditions the production of locally overrich regions is favored and thermal decomposition is more likely to occur." This is obviously what happened here.for as the compression ratio is increased the ignition delay is certainly decreased. The uninsulated plug shows more power than the insulated plug. This is at least partially due to a poorer volumetric efficiency with the insulated plug. Another very important factor is time of combustion and rate of pressure rise. The tape recorder revealed more noise for the bare uninsulated plug. This indicates a larger rate of pressure rise which, if occurring just after TDC, would probably produce more power than that produced by a gradual pressure rise. Another concurrence with the statement that decreased ignition delay produces more smoke is Shown in the range of compression ratios less than 19:1. Here the smoke is worse for the hotter condition dictated by the insulated cap. In order to confi m or deny the smoke trends existing in Table III and Graph I, a rerun was made over the entire range of usable compression ratios. This infonuation is snown in Table IV and its plotted form.is given in Graph II. Again, the insulated plug gave .less power than the uninsulated plug at all compression ratios, and again there was somewhat of a cross-over in the smoxe trend at a com- pression ratio of approximately 20:1 with the insulated plug producing more smoke at the lower compression ratios than the uninsulated plug. 'A possible explanation could be that at the lower compression ratios -L . the insulated plug provides a higher ambient temperature into which 25. TABLE IV DATA ON REGUIAR CFR CETANE moms, WITH AND WITHOUT INSULATED STAINLESS STEEL CAP ON COMPRESSION-RATIO PLUG AS COMPRESSION NATIO IS CHANGED FROM 28.5:1 TO 13.h:1. INJECTION ADVANCE 13°BTDC, FUEL RATE 9 EAL/MIN. Insulated Stainless Steel Cap Standard Compression- On Compression-Ratio Plug Ratio Plug Compression Fewer Smoke Fewer Smoke Ratio (Scale) Density (Scale) DenSity 28.5:1 8.h 6.0 8.6 5.9 2h.9:1 9.2 5.0 9.5 S.h 22 .1:1 9 .7 h .0 10 .3 u .2 19.9:1 10.1 3.6 10.5 3.7 18.1:1 10.1 3.1 10.5 2.7 16.6:1 10.0 2.h 13.1; 21: 15.3:1 9.8 2.3 10.2 2.1 13.h:1 9.h 2.0 9.6 2.0 the fuel is injected thereby reducing the ignition delay and producing more smoke. At the higher compression ratios, obtained in this engine by drastically shortening the length of the combustion chamber, the predominant influence could possibly now be the impingement of the fuel onto the immediately adjacent compression-ratio plug, with the insula- ted cap providing the hotter surface.for more efficient fuel vaporiza- tion and combustion. This would indicate that impingement upon the less-hot uninsulated plug delayed evaporation a sufficient time to foul the combustion pattern. The anomaly at the highest compression ratio Shown could very easily be due to a misreading. 26. Effect of Higher Lip Temperature Table V is a comparison of space—, lip—, and sleeve-injection for a higher temperature lip than was used to obtain Table I and TABLE V COMPARISON OF THREE PLACES OF INJECTION. HIGH—TmiPERATURE LIP AND SLEEVE ASSEMBLY, COMPRESSION RATIO 18 l/2:l FUEL RATE lO ML./NIN. Space Lip Sleeve Injection Advance, °BTDC 15.5 15.5 15.5 ' Noise 76 75 7h Smoke Density 5.0 5.2 h.3 ‘ waer (Scale) lO.h 9.8 9.2 Lip Temperature, °F 855 710 690 Figures 1, 2, and 3 and at a smaller injection advance. The same general trends existed fer noise and smoke with the exception that lip—injection seemingly produced a smokien condition for the hotter lip. In general, however, the noise was lower and there was less smoke for impingement than for non-impingement. This lip and sleeve assembly gave much difficulty with quick deposit formation, so it could quite possibly be that a diversion of the impinged spray was the cause of this apparent trend to slightly more smoxe for lip-impingement. In particular it should be noted that the trend in power is dif- ferent, and is less for impingement than for non-impingement. Had a larger injection advance been used, this could have been to a large 27. extent modified such that sleeve- or lip—impingement would produce almost as much power as space-impingement when all three were operat- ing under ideal conditions of injection advance. Note also the trend of scale readings in Table 1 which were taken at a constant injection advance of 2l°bTDC. This latter data indicates that perhaps the optimum injection advance for sleeve—impingement is greater than 21° for this particular lip and sleeve combination. EFFNCT OF LIP TENPERATJRE AND INJECTION ADVANCE AT CONSTANT COMPRESSION RATIO 1 . Low Lip Temperature . Table VI is a comparison of two places of injection (sleeve and space) for three types of lip and sleeve combinations with the engine operating at two injection advances. The three types of lip and sleeve combinations are used to control the temperature of the im- pingement and non-impingement surfaces. The two injection advances are intended to compel operation under conditions more favorable for space-injection, 11°, and more favorable for sleeve-injection, 21°. These are not necessarily optimum conditions under any of the circum- stances tested. For each lip and sleeve combination these data were taken as quickly as possible after equilibrium conditions had set in and before an appreciable amount of deposits had formed. headings were first taken for space-impingement followed by a quick rotation of the injector to produce sleeve-impingement. The sequence was then repeated as a check. It was important to note that the deposits formed by sleeve-impingement were swept clean and oxidized during the space- impingement operation. The aforementioned formation of deposits does not in any way preclude the successful use of an impingement surface but it does in- dicate that this variable has become pronounced during the reduction of smoke and noise. 29. one 2m 0mm 0% R? 0mm ofiA 93 So mom 33 can a. donates...“ .13 :.m w.m O.m 4.9 m.m m.OH 0.0H ©.m 4.0H N.OH m.m o.m .3 en E 3 .3 on em 3 .3 em as E on an we we. on an. as. as 0.: ea ed as Aoamomv mospm hpflmcoo mxosm omaoz oommm o>ooam ocean oevmaw mosiw o>ooam mowmm msmmam comdm m>mwam oomdm o>ooam soapooan Mo oomdm am Ha Hm Ha Hm Ha oaemo mag hoods mopmopm< moooam smegma spas mocmmm mmasqmd amassed wcwpmHSmcH oz soapmasmcH o>ooam new man we odes 1H! .ZHE\.AE OH 384: dumb «Hum\a ma OHB mqmde aoomw>o¢ coapooncH 30. Graph III is a plot of the events occurring using the lowest temperature, or non-insulated lip and sleeve assembly. An interesting set of events occurred. First, the lip temperature increased as in- jection was changed from sleeve to space, a larger increase occurring at the larger injection advances. This is natural since larger pressures would be created when more of the combustion occurs in the vicinity of or prior to top-dead-center. For the 11° injection ad- vance more power is available for space- than for sleeve-impingement because the low temperature impingement surface delays evaporation of the impinged fuel until too late in the cycle for efficient usage, 'while injection into the hot compressed air is timed more nearly cor- rect for good power output. A reversal of this tendency would occur for the 21° injection advance, if the sleeve were hot enough to supply ample vaporization during the time of fuel impingement. The sleeve and lip are evidently too cold here.for this to happen, so again the power trend is for more power for space-injection. The noise trend is what might be expected, louder combustion for space—injection than for sleeve-injection. Even tnougn the sleeve has not been successful in producing comparable power, it has accom- plished its purpose of controlling the rate of combustion. The smoke trend is probably the most interesting and requires more explanation. Note that at 11° injection advance the trend is toward more smoke.for space-injection than.f0r sleeve—injection and that this trend is reversed at 21° injection advance. First, a long mixture time for space combustion is necessary for minimum snoxe, 31. 'thus point four is better (less smoke) than point two because the in— jection advance is considerably greater here. Next, for a cold sleeve and a long mixture time, impingement delays combustion so long that a smokier condition exists, thus point four is better than point three. Since the cold sleeve is a definite controlling factor points one and three are about the same with three being understandably better because of the time involved. The general trend for this cold lip and sleeve combination is therefore: for small injection advances more smoke in the non—impingement condition; for large injection advances more smoke in the impingement conditions. 2. Intermediate Lip Temperature. Graph IV represents a plot of the variations occurring using the intermediate-temperature lip, as the place of injection is varied from the sleeve to space. Even though the expected trends exist for the data as recorded, a careful study of the operating conditions in— dicates that certain corrections should be made here. The first correction would produce very little change. It is noted that the lip temperature for sleeve-injection is greater, 590°F, than in the case of the better insulated lip on the right on Table VI, 570°. It is quite possible then that diversion by deposit formation was beginning to occur. Depending upon the magnitude of diversion and its nature, there might be a change in smoke, noise, or scale readings. The unusually high value for noise, 75.1, for sleeve-injection def— initely confirms either a diversion or a skipping action. The cor- rection for noise and temperature should therefore be in the manner 32. shown as corrected (1). No indication of the direction of corrections necessary for smoke and power is apparent. This was an occurrence, not infrequent, which does not destroy the utility of the data. It was shown earlier that fuel impingement on a surface under controlled conditions did in fact decrease smoke production markedly. This was somewhat true, even for the normal CFR.diesel operating at the higher compression ratios with an insulated cap on the compression ratio plug. t seems apparent then that the increase in smoke pro- duced as the place of injection is changed from lip to space is not here compatible with the preceding statement. Subsequent checks showed that any impingement whatsoever on any of the lips used, except the coldest at a large injection advance, definitely reduced the amount of smoke even though noise and power were not necessaiily changed in any specific direction or perhaps not changed at all. Therefore, in this case, it is highly probable that the corrections (2) should be made. The power trend is as expected. At 11° injection advance, space-injection produced more power than sleeve-injection. At 21° injection advance, sleeve-injection produced more power than space- injection. 3. High Lip Temperature. Graph V, a plot similar to that of draphs III and IV, snows the events occurring under a hotter condition, this time with the same sleeve insulated with annular grooves as used to obtain Graph IV but with asbestos insulation between the lip and the mouth—insert uolaing 33' | the lip and sleeve assembly in place. The trends are typical and well r formed. Lip temperature rises for both injection advances as the place of injection is changed from sleeve to space. Power correspondingly increases as the place of injection is changed from sleeve to space for ll° injection advance but decreases for 21° advance. Smoke, at both injection advance angles, is worse for space injection than for sleeve injection. Noteworthy is the noise increase at 11° injection advance, 73.7 for lip to 7h.l for space. This relatively small in- crease can be eXplained by considering the temperature Which the lip and sleeve assembly and the space have at this time. Understandably the sleeve controls the noise for the sleeve—impingement condition and this explains the 73.7 Late injection into hot surroundings (space—impingement) decreases ignition delay thereby producing smoke, and this decrease in ignition delay explains the 7h.l That smoke is produced is verified by the space smoke reading of 5.7. EFFECT OF LIP’TEMPERATURE.AND COMPRESSION RATIO AT OPTIMUM INJECTION ADVANCE FOR SLEEVE-DIPDVGEIMNT A comparison of the preceding information obtained on the three lip and sleeve assemblies is not necessarily valid, although typical, partially explainable, variations do exist. In none of the previous cases have the optimum conditions of injection advance been sought out. Because of this it is mucn more revealing to investigate sleeve-impingement for each lip and sleeve assembly under optimum conditions of injection advance as the compression ratio is changed. This was done, and the data presented in Tables VII, VIII, and Ix are the results of this investigation. This information is shown corrected and in graphical form in Graphs'VI, VII, and VIII. The information which is required to plot these grap s was ob- tained through a long series of time-consuming runs in which the op- timum injection.advance was obtained for each compression ratio. This required a thorough warm-up followed by sufficiently long runs at each injection advance to allow equilibrium conditions to set in. At all times it was necessary to be exceptionally careful that deposit forma- tion had not altered too greatly the required impingement pattern. 1. Low Lip Temperature. Table VII represents the data obtained using the low-temperature lip at compression ratios of 16:1, 18 l/2:1 and 22:1. Although the injection advance at the 16:1 compression ratio is slightly misleading, the trends of the variations are in general correct. As the compression 35. TABLE‘VII COMPARISON FOR SLEL‘VhL-LMPINGWBNT AT THREE. COMPRESSION RATIOS FOR Low-Tmemmruns LIP AND SLEEVE ASSEMBLY FUEL RATE lO NIL/mm. =================== at: Compression Ratio 16:1 18 l/2:l 22:1 Injection Advance, °STDC 21 21 19 l/2 Noise 7b.? 7h.8 7h.5 Smoke Density h.2 h.8 5.6 Power (Scale) 9.7 10.0 10.0 Lip Temperature, °F 390 hlo £80 ratio increases power increases, smoke gets worse, noise decreases and lip temperature increases. Note that injection advance remained con— stant for the two lower compression ratios and then became less at this higher compression ratio. The general trend consisting of smaller in- jection advances for higher compre53ion ratios is correct. A Cheek of the original data sheet revealed a note to the effect that the injection advance for the 16:1 compression ratio run was "noise limited" which indicated that the engine was knocking considerably, and it seemed advisable not to further increase the injection advance. This was a case of audio misinterpretation. Thus, a logical correction at the lower compression ratio would be to increase the injection advance, the power, the noise, and the lip temperature, slightly, and to de- crease the smoke indication. These corrections are shown in approxi- mate, but nevertheless considered, amounts on Graph VI. 36. 2. Intermediate Lip Temperature. Table VIII represents the data obtained for the intermediate- temperature lip at the same three compression ratios used earlier. TABLE'VIII COMPARISON FOR SLELvE—IMPmCmaNT AT THREE COMPRESSION RATIOS FOR INTERMEDIATE-TEMPERATURE LIP AND SLEEVE ASSEMBLY. FUEL RATE 10 NIL/MIN. Compression Ratio 16:1 18 1/2:l 22:1 Injection Advance, °BTDC 20 19 18 Noise 73.8 7h.1 7h.l Smoke Density h.7 h.2 5.2 Power (Scale) _ 9 .5 10.1 10.2 Lip Temperature, °F h65 h60 535 Note that the lip temperature was higher, the noise was less and the intensity of smoke was greater at 16:1 compression ratio than at 18 l/2:1 compression ratio. This same effect was noted while running the highest lip temperature used in this investigation. On occasions 'when the engine was producing an unusual amount of noise, the smoke would begin to increase, noise would decrease, and the lip temperature would rise. Inspection invariably revealed diversion of the fuel spray by the deposits. It was concluded that the deposits were suf- ficiently arranged, suitably hot, and caused early enough diversion to produce an injection similar to Space-injection, while the hot ambient temperature of the surroundings suitably reduced the delay 37. period to increase smoke and quietness. High compression ratios notably reduced noise and increased smoke.for this same reason. Inspection of the deposits on the lip after the lowest com- pression ratio run revealed a "crinkly" deposit which was "diverted a little to the right". This then could most easily produce the con- dition mentioned earlier; more smoke, less noise and a higher tempere ature. Probable corrections are incorporated in Graph VII and again the indication is more power, worse smoke, less noise, and higher lip temperature as the compression ratio is increased. 3. High Lip Temperature. Table IX represents the variations occurring when a modified intermediate-temperature lip is used and shows the effect of a higher TABLE IX COMPARISON FOR SLEEVE—DIPINGRIMRNT AT THREE. COMPRESSION RATIOS FOR INTERIthIATFr-TWPERATURE LIP AND SLEEVE ASSEMBLY WITH BOTTOM OF LIP INSULATED FROM MOUTH—INSERT BY ASBESTOS . FURL RAM 10 ML./MIN. Compression Ratio 16:1 18 l/2:1 22:1 Injection Advance, °BTDC 20 l8 16 Noise 7h.h 7h.2 7b.2 Smoke Density h.2 h.7 5.5 Power (Scale) 9 .0 9 .1 9 J4 Lip Temperature, °F 570 675 6&5 38. temperature. This lip and sleeve assembly is Similar to the inter— mediate-temperature lip except that asbestos insulation is used between the bottom of the lip and the mouthsinsert holding the lip and sleeve assembly in place. Again a correction to the observed data is in order even though the same general trends exist here as for the other two lips. The lip temperature is greater at the intermediate compression ratio than at the highest compression ratio. The original data sheet shows that a relatively long time was required to establish equilibrium conditions which indicates that deposits might have formed. Data taken later at a larger injection advance also points to a lower temperature. No other change is indicated. Consequently, Graph VIII indicates the same trends as the other lip and sleeve assemblies with more power, worse smoke, less noise and higher lip temperature as the compression ratio is increased. h. Highest Lip Temperature. Considerably more data was obtained than is presented here. In particular, much information was obtained with a high—temperature lip and sleeve assembly which was completely insulated by asbestos. This lip operated at temperatures ranging from 700°F for sleeve in— jection (a very short while only) to lOSO°F for space injection. De- posits built up so quickly that reliable runs could not be made. In an effort to limit the deposit formation somewhat, the asbestos insulation between the lip and the mouthrinsert was replaced byfoundry cement, a commercial "plastic iron". This lip, although 39. running cooler, was also plagued with.deposits. Some impingement was obtained and these results indicated a high noise level, medium smoke, and medium power. 5. Deposit Effect on Smoke Density The smoke denSIty readings for Sleeve-injection at 21° in— jection advance and at 18 1/2:1 compression ratio onto a clean com- bustion surface, as taken from Graphs III, IV, and V, are 5.0, 3.7, and 3.6 for three lip temperatures in order of increasing temperature. A similar set of readings, as taken from Graphs VI, VII, and VIII, at 21°, 19°, and 18° injection advance at the same compression ratio taken after the combustion surface had been covered witn a considerable amount of deposits as a result of a long period of running is n.8, h.2, and h.7, respectively. A comparison would then be 5.0 vs h.8, 3.7 vs h.2, 3.6 vs h.7. This rather clearly indicates again the effect of the higher temperatures and their attendant deposit formation, even though some of the improvement may be due to injection advance. GENERAL COMPARISONS A comparison of smoke, noise, and power at the different lip temperatures should provide qualitative design information. In order to successfully Show the trends, it is necessary to use a specific compression ratio rather than averages of the three ratios investigated, since averages would tend to nullify or at least lessen the character- istic variables. Since noise is higher at the lower compression ratio and smoke is worse at the higher compression ratio, the 18 l/2:l com- pression ratio will oe used. Graph IX is a plot of the variables, sm0ke, noise and power, as the lip temperature is increased.from h00° to 600°. An area, rather than a point, has been plotted in order to indicate the variations 'which should be considered. This area is based on the experience of some 150 hours of engine operation. Considering the lack of informa- tion obtainable in the literature and the nature of the investigation, these values still might be within too small a range. Nevertheless, certain significant trends are apparent. As lip temperature increases the power available first increases and then de- creases. The indication is that the maximum is reached somewhere be- tween h00°F and 500°F lip temperature. The trend of the variation for both smoke and noise indicate that an optimum might exist in the neighborhood of 500°F. Figures 6, 7, and 8 were taken of runs at the three temper- atures just discusse‘: h10°, b60°, and 600°, respectively. They rather bl. ‘— Time Figure 6. Pressure—Time and Rate—Time Relationships, Motoring and Firing, for Fuel-Impingement System at 18%:1 Compression Ratio. Imgingement-Surface Temperature hIOOF. Injection Commences 21 BTDC. h2. fi-‘rv — T ime Figure 7. Freesure-Time and HateJTime Relationships, Motoring and Firing, for Fuel—Impingement System at 18%:1 Compression datio. Imgingement-Surface Temperature h600F. Pips at 13°BI‘DC and 13 ATDC. Injection Commences 19°BTDC. h3~ ”summon Ins"! Iillngt. <— Time Figure 8. Pres sure-Time and date-Time Relationships, Motoring and Firing for Fuel—Impingement System at 18§:l Compression Ratio. I ingement-Surface Temperature 600°F. Pips at 13° BTDC and 13 ATDC. Injection Commences l8O BTDC. 111.. clearly show the noise trend, or combustion roughness, with the inter- mediate temperature seemingly more smooth. Thus it has'been shown.for a surface-impingement system such as this at a constant compression ratio of 18 l/2:l, that a combustion surface temperature exists for which best power can be obtained almost simultaneously with.minimum noise and smoke intensity. As the com- pression ratio is increased from 16:1 to 22:1, it has been found that more power, more smoke, and higher impingement—surface temperatures are produced along with less noise. At higher compression ratios than this the smoke was considered unreasonable. GRA PPS I l I ll 3.? -H 03 g- —~,10 c: 0) .54 O 5 6 ' ‘ 9 ’3? '3 5 5f ‘6 ; 5 i 04 I ht / a 3— _. // 'Without Insulated Cap - - - With Insulated Cap 2 . . 1 15:1 17:1 19:1 21:1 23:1 Compression Ratio Graph I. Compression Ratio vs Smoke Density and PoWer for Regular CFR.Cetane Engine, With and Without Insulated Cap on Compression- Ratio Plug, as Compression Ratio is First Decreased and Then Increased. Fuel Rate 9 ml./min. Injection at 13°BTDC. h7. I r 1‘ 11, Power >3 .p -H g / ’- — —\ \ ‘3" ,/” ‘\1 ~10 m /’ \\ .x // \\ o / \ 5 // \ ‘\ ! \ I \ and 6 \\ { 9 / \ /’ ‘\ j; / :4 s / - g // .3 / a; /' a /’ o /, 0. Smoke ,/ / i h ' 3/ 1 (,3/ // /' / //’ 3 " /, _ / / Without Insulated Cap ,./”'_’ -—-—-—-With Insulated Cap 2 / l 1 1 13:1 17:1 ' 21:1 25:1 29:1 Compression Ratio Graph II. Compression Ratio vs Smoke and Fewer for Regular CFR.Cetane Engine, With and Without Insulated Cap on Compression-Ratio Plug. Fuel Rate 9 ml./min. Injection at 13°BTDC. 11° INJECTION ADVANCE Place of Injection Spec §l§eve III—TI _ __._ .__.. __ a“-.. - . 3, (A / I? __ - - 1 , -_ - . ———~ ___— y..-.___.____..._ __ rb-Ffi’77 -___.. j..._.._—_.———_ - _ _..- Graph III. P- u—---———..---—_..————- _.-4)—.- Noise ____71_ ___7__6.___ _ 118 . 21° INJECTION ADVANCE Place of Injection Sleeve Space 7 .75 7h _ 73 Smoke Density . 3 77 777 ._.____.____ _ _2_____ -_ -_____I____.______I .1. _ I _- _~___. Powerjscale). __ _ _ _...__._ l // 10 _ W J _--_ _-_ ,JEP -IflRPr‘i‘tWe Too _ 6QO.__ ._ -"_.7_;_-__299_ C7 7 1:00. ——..—-- --_._-_~._-__39_Q-_';___'."7 7 ' (131777777777 Effect of Sleeve-an). Space-Injection on Noise, Smoke Density, Fewer and Lip Temperature Using Lowaemperature Lip and Sleeve Assembly. fin 11° INQECTION ADVANCE Place of Injection , 1:9 . 21° INJECTION ADVANCE Place of Injection Sleeve Space Noise Sleeve Spgce _ _I -_ __ J . _ZZ_____-II __ I _ _ ___ _ 26 7S “Cowea‘QA L73 Observed '— ———--__.__-—_ . 73 VIA ___7_7_7 7 7 7 7 __SIqu Peasitr- ,_ _ -- 5......‘: .'—.;.E? _I__ h g _Hw‘_ CpFE;./”’ - _ I3 I_I____“W___r____C&fiRXVZj 2 77 7 777;-.17I 7: 77777777 7‘77 waer (Scale) 10 l " ’7‘ ”it“? - M II--- _ I ,9 -._-_--.._I Lip Temperature , ___. 70o - II _ Igwag I I__-______600 I 7 3 'P 7 L‘ VIZ-..“ - .-.-_-_ ___.__._.____ .5“)..- - - .-_*-_- 71"(‘67‘37‘6- __ LOO _ __ II C92 __ _ ___ 300 . _________ Graph IV. Effect of Sleeve— and Space-Injection on Noise, Smoke Density, Fbwer and Lip Temperature Using Intermediate-Temperature Lip and Sleeve Assembly. 50. ___11:_INIEOTION_AOMANCE 21° INJECTION ADYAN§§—— Place of Injection Place or 15390131011 Sleeve Space . Sleeve S ace ___. _______ ___N91se_I-_ - ______ .I_ _ __II.___ I. _IIIULIIIII_ __ II_IIII_IKII_IIIII ————~-.$ 73 Smoke Density p.-.— ...—-_ r 5 / LL _ ___I/WI— ,3 -__ 2 I" 1-- - - III.-. __IIIIIII -IIII_EmeRf%aEQ I . II 9 __II_I_I_-§I_IIII_ p _ __WM ‘ g Lip Temperature _ Q7.en-II 2;;:ff7777 am I__II__ I__ __III I__II_I_I_Jqu- mm Graph V . Effect of Sleeve- and Space-Injection on Noise, Smoke Density, Power and Lip Temperature Using Intermediate-Temperature Lip. and Sleeve Assembly (Asbestos Insulation Between Lip and Mouth-Insert.) 0\ Snake Density 1 Power "/———' . 10 Injection Advance 9 o ’3 .3 7.: z A 76 ’ s. P 957 “ a. g Smoke Density .4.) 2 75 g 5 5.. .Q' :1 7h 500 r - Lip Temperature hOO - 300 L“ 1 16:1 19:1 22:1 Compression Ratio Graph VI. Compression Ratio vs Noise, Smoke Density, Power, Lip Temperature and Injection Advance for Low-Temperature Lip and Sleeve Assembly at Best Power. Fuel Rate 10 ml./min. 23 22 21 20 Injection Advance, °BTDC S 51. ox Snoke Density 7h 73 Lip Temperature, °F 600 500 hop T Fewer . ‘ 10 a 9 Injection Advance 1; "a! a 7 t‘ e ‘8 Smoke Density Lip Temperature 6:1 19:1 2231 Compression Ratio Graph VII. Compression Ratio vs Noise, Smoke Density, Power, Lip Temperature and Injection Advance for Intermediate- Temperature Lip and Sleeve Assembly at Best Fewer. Fuel Rate 10 m1./min. 21 2O 19 Injection Advance, °BTDC 52. Ox Snoke Density Noise ‘1 U1 Lip Temperature, °F 7b 700 ‘- 73 600* Lip Temperature Injection Advance Smoke Densit rx~1IIg_‘_§‘~_‘__~__Noise Power (Scale ) Graph.VIII. 19:1 Compression Ratio 22:1 Compression Ratio vs Noise, Smoke Density, Power, Lip Temperature, and Injection Advance for Intermediate- Temperature Lip and Sleeve Assembly (Asbestos Insulation between Lip and Mouth-Insert) at Best Power. Rate 10 ml./min. Fuel 20 19 18 17 1...: 0\ Injection Advance, °BTDC 53. Smoke Density Noise 7h 73 Lip Temperature, .. ./é - 10 73 '9; I ; 7 _i’l 33 e A A .45 Smoke Noise J l L hOO 500 600 °F Graph IX. Lip Temperature vs Noise, Smoke Density, and Power at Best Fewer. Compression- Ratio 18 1/2:1, Fuel Rate 10 ml./min. Sh. SUMMARI AND CONCLUSIONS The intention of this investigation was to determine the effect of impingement-surface temperature on smoke, noise, and power in a fuel-impingement compression-ignition engine combustion system. A fuel-impingement system for a compression-ignition engine was successfully constructed and tested. The system, commonly called M-System, operated in the manner described by its originator, Dr. J. S. Meurer of Machinenfabrik, Augsburg-Ndrnberg, Nfirnberg, Germany. (See Appendix A.) Certain pertinent information pertaining to its behavior was obtained in addition to the original object of the investigation. Spheroidization of the.fuel spray at high surface temperatures was investigated. It was found that the engine did not operate in a sufficiently high temperature range.for which spheroidization would seem likely. (See Appendix 0.) Air swirl in an inclined cylindrical chamber, offset from the centerline of the cylinder bore, was investigated by means of paint- patterns and a small paddleawheel. (See Appendix B.) It was found that the direction of swirl in the offset chamber could be successfully controlled by various mouthrinsert configurations and by use of a shrouded intake valve; however, no method was obtained which would produce a high-rate continuous unidirectional swirl within the chamber. It was concluded therefrom that the predominant airqflow was up one side of the chamber and down the other. A protruding lip on the down— 56. stream.side would therefore provide a surface on which to impinge the fuel and from which the on-rushing air could pick up the vapors for combustion. The protruding lip was in all cases attached to a stainless steel sleeve. The various sleeves used were cylindrical in nature, their outside diameters and configurations being such that various means could be used to insulate the assembly from the liner into which it was fitted. The place Of.fuel impingement was varied by using a modified multi-hole orifice-type nozzle in which all holes were closed except one. This produced a directional nozzle, the angle of fuel flow being at 75° with the axis of the nozzle. Thus the place of injection could be changed by rotating the injector about its longitudinal axis. After running the engine, inspection of the deposit formation indicated that the fuel was spreading onto about one-half of the lip surface in a.re1atively long narrow path. Occasionally it indicated a flow'off of the lip and onto the piston. Because of this, it is felt that a specially designed nozzle would be a definite aid to the fuel- impingement system as deScribed herein. By this means the longitudinal flow of fuel could be reduced and the area of the fuel impingement could be increased thus allowing more effective use of the lip surface. Better results could most possibly be obtained by use of a hemispherical or cylindrical combustion surface with injection in the latter case in a circumferential direction. Thus the fuel will have little tendency to skip, or be diverted off into space. In any Skip- 57. ping, or’diversion action the fuel will be forced to return to an im- pingement surface. Throughout the entire investigation of the fuel-impingement system the formation of deposits on the impingement surface was a critical item. Deposit formation altered the amount of smoke and noise produced and the amount of power developed. Ironically, these variations were not always repetitive nor always in the same direction. Deposit formation occurred in a shorter time at the higher temper- atures. No long successful runs without diversion by deposits were made at higher surface temperatures than 600°F. It was found that the beneficial effect of a fuel-impingement surface increased as the surface temperature increased. At the higher surface temperatures, however, deposits quickly formed and the ef- fectiveness of the surface was reduced. For this engine, with all things considered, it was found that the optimum surface operating temperature was in the neighborhood of 500°F. Above this temperature the smoke became worse, power dropped off and noise tended to increase, depending on the manner in which the deposits formed. BelOW'thiS temperature both noise and smoke quickly became unreasonable. The effect of compression ratio on the surface-impingement system was exactly Similar to its effect on a space-injection system. As the compression ratio was changed from 16:1 to 22:1 the power and the smoke intensity increased while the noise level decreased. At higher compression ratios than this the smoke was considered unreason- able. 58. The results obtained from this particular engine design in- dicate that an optimum distance should exist between the nozzle orifice and the impingement surface. Too small a distance will allow quick diversion of the.fue1 by deposit formation while too large a distance does not properly limit the amount of fuel subject to autoignition in space. This latter occurence will produce excessive noise and more smoke. It was of particular importance to note that any impingement ‘whatsoever on the combustion surface, even its.furthermost edge, did in fact reduce the smoke.formation markedly while little change was affected in power and noise (depending, of course, on injection advance). Although the amount of fuel autoigniting is not changed appreciably 'when the place of injection is changed from the far edge of the lip to space, it seems most probable that the rate of combustion of the re— maining.fuel is quickly brought under control by surface impingement. In the case of space-injection the fuel injected after autoignition begins is injected into a high temperature zone created by burning vapors, and for this last portion the ignition delay is sufficiently shortened that combustion starts before a chemically correct mixture can form. The production of a fuel-rich zone and its accompanying smoke is therefore enhanced. For surface combustion the last portion is spread on to a hot lip which quickly controls the rate and type of evaporation. The combustion rate is therefore controlled sufficiently to allow prOgressive consumption of all the vapors. Use of gasoline in an engine of this nature is not precluded 59. because of its lower spheroidizing temperature (higher volatility). In a properly designed chamber the fuel will never leave an impinge- ment surface for long, and will therefore be held under its control. Thus the desired evaporation and gradual mixing of the fuel with air will be accomplished. That portion of the fuel which has autoignited earlier will then provide the ignition source for the remaining fuel which has been deposited on the impingement surface. The noise level will therefore be low Since the amount of fuel autoigniting is very small. It is concluded that the system originated herein is not a true III-system as set up by its originator. In the true Ill-system the reaction rate is low at the beginning of combustion and increases toward the end of combustion, while in this "lip" engine the rate-time diagrams reveal the maximum rate of pressure change to occur nearer to the beginning of combustion. The controlling effect of the “lip" nevertheless exists and less smoke and noise is produced at comparable power . APPENDIX .APPENDIX.A MrSYSTEM THEORY The rules set up by Dr..Meurer in the development of his engine which so successfully combats noise and smoke are: 1. Limit to a minimum the portion of the fuel involved in autoignition. 2. AllOW'the fuel to oxidize gradually. 3. Mix the fuel with.the hot air.fast enough to affect a stoichiometric airqfuel ratio before ignition starts and make sure that no more.fuel is mixed at any time than can burn with a permissible pressure rise. Regarding Rule 1, it is obvious that the reasoning here is to limit the rate of pressure rise in the beginning of combustion. Allows ing the combustion chamber to become full of the combustible mixture prior to autoignition will aggravate the Knocking tendency of the engine. Rule 2 needs more explanation. In the M—system engine the fuel is injected from a nozzle located in the cylinder head into a hemispherical combustion chamber located in the central portion of the top of the piston. The injector and combustion chamber are so located that the.fuel leaving the injector will spread on to the hemisphere before much intervening space has been traversed. It is during this transportation that Rule 1 is accomplished. Because of the nature of the evaporation from the hot com- bustion surface (the air and/or the combustion gases are even hotter) 62. the fuel evaporates more slowly than when in the air and at least part of the time in a zone deficient of oxygen. This process, controlled and slowed.down by the surface temperature, allows the accomplishment of Rule 2. Dr. neurer has cited references and has shown by the results obtained with his engine that "evidently the ignition point is influ- enced by the mechanism of mixture.formation, being low (or earlier) for vapors formed by heating fuel droplets with hot air, and high (or later) for vapors formed by heating fuel in the absence of any apprec- iable amount of air and subsequent diffusion in air." Rule 3 says “mix the fuel with the hot air fast enough to affect a stoichiometric air-fuel ratio before ignition starts and make sure that no more fuel is mixed at any time than can burn with a per- missible rate of pressure rise." According to the explanation for Rule 2, we.find that the vapors do not show an extreme tendency to autoignite, at least not in the time allotted. After.formation of a combustible mixture there will be a tendency to await ignition by the flaming particles formed during the accomplishment of Rule 1. Now if the combustible mixture or burned gases are progressively removed from the impingement surface the fresh vapors formed underneath can be made ready for combustion in a controlled manner. This leads to a controlled combustion state rather than the extreme thermal advance caused by spraying fuel into extremely hot compressed air. It is this last rule that provides for the reduction of smoke production. Likewise, the controlled rate of 63. formation of a stoichiometric airqfuel ratio combats an extreme rate of pressure rise, and its consequent knock, during the latter phases of combustion. In order to obtain the rate of mixing dictated by Rule 3, Dr. Meurer has used an intake-induced swirl and superimposed on this the squishing action of the close approach of the piston to the cylinder head to produce an even higher rate of rotation of compression air in the hemispherical combustion chamber. This type of action is shown in Appendix B, Figure 6. Primary variables upon which the success of this system de- pends are swirl rate and surface temperature, the latter of which comprises the subject of this research. L_- APPENDIX B J DEVELOPMENT OF COMBUSTION-CHAMBER CONFIGURATION In a fuel-impingement combustion system the necessary vapor- ization of the fuel is accomplished by the combined action of the hot impingement surface and the even hotter compression air. Either these vapors must be removed from the vicinity of the impingement surface and later mixed with air for combustion, or the combustion takes place in the vicinity of the surface and the burned gases must be removed prior to the combustion of the vapors being formed underneath. Any return of the burned gases to the zone of mixing or zone of combustion- tends to richen the mixture relatively in fuel and thereby cause smoke. No autoignition can take place in that part of the vapors closest to the impingement surface because the necessary mixing with air has not taken place. Indiscriminate highly turbulent mixing is not desirable in that it is necessary to remove the vapors or the combustion gases in a controlled manner such that smoke formation is not too great. If the vapors are held under the control of the cooler surface, and thereby mostly unaffected by the higher gas temperatures until suf- ficient air is in the vicinity for complete combustion, the uncon- trolled themal advance which leaves behind a carbon skeleton (smoke) can be eliminated. Positively controlling the manner in which the air passes over the vaporization surface can also control the rate of pressure rise by limiting the amount of mixture available for com- bustion at any one time. It is necessary then to direct the air into the vicinity of the injection surface in a controlled manner. Since swirl had been used in the parent design as set up by its originator, it was decided to try to adapt the equipment available here to such a system. The M-system, as this process is called, incorporated its combustion chamber in the top of the piston. Because. of the diffi- culties involved in obtaining temperature readings from a reciprocating mass it was decided for this investigation to develop a cmnbustion chamber in the cylinder head of the existing engine. The literature revealed several methods of ascertaining in- 5,6 formation on air-flow in a compression-ignition engine. None of these were completely satisfactory so two of them were used with certain modifications. In both publications a statement was made to the extent that, once established, a strong swirl persisted doggedly. This was the beginning of the development of the lip combustion ~ chamber. The centerline location of the valves in the available engine precluded a center location of the combustion chamber and the com- promise solution was an offset as shown in Figures 9 and 10. The piston side of the combustion chamber was to be as near the center of the cylinder as possible and the edge of the chamber was to pass tangent to the injector tip. If a directional nozzle were used this would allow tangential injection of the fuel onto the walls of the chamber. Il'l. ll. .IIIIIIIIIIIIIIIIIIIII IIII. - III..III-/ ,. \‘lll'li luull .II. .II: ||-.|.IIIIII|.I'I / mull/r / . i . ... .... _../.. . 12": 5 6+ 2 1"}; Bottom View - CFR Cetane Engine Cylinder-Head Modification . Fig. 9. P- I a . I I L. . a a . I I.. a i . . .. . _ _ a .J 9 L L I. I I l (a L. , L ... .\. I \ I: a I: l :o.:. .I. . .w . I a . I ..... n . Jul. I IE!) I I I v a 5’ I ?~.> vain. 5333.30: boominogaho ofimam 833 58 I to; beam .0." .wfim -‘ ION. .\ .x 9 GM} . _w‘-. u: ... . ... ..x .. . ...: _ if]. \u .. M... w. e .- .. .- ....U E .. r. a. \~ - . . _H ... r r "u. a a .. . ... _ . . . . . . . a M...” .. _ "a. v. . ..m . ... .. _ . i .. ... ... .. .. n . m.\ u— e _ _. - . i -. x _.. ... u \x _ .. w\ x. . . .. . .... . .... a . .... n N’: .. \ w.’ I.\ 4:.... . .. a \ 68. Elementary calculations indicated that suitable compression ratios (30:1 down to 16:1) could be obtained easily with a one inch diameter combustion chamber. Still other calculations revealed that a cast iron wall thickness of 3/16" would provide an adequate.factor of safety, so a 1 3/8" hole was'bored as close to the valves as practical. The edge of this hole was so located that upon insertion of the liner the.£hel leaving the injector nozzle would lay on almost circumferentially. A cast iron liner of such oversize dimensions as to provide a tight press fit was made and forced into place. A comp bustion-chamber plug was machined and a heavy steel plate was provided 'with holes in order that it might serve as a bridge to hold the plug in place. These parts and other obvious ones required for successful assembly of theicombustion chamber are shown in.Figures 11 and 12. The compression ratio could then be changed by adding washers on top of the plug. Later>during the overall investigation it was.found ex- pedient to change the form of these plugs rather than use the washers, and these plugs are shown in Figure 13. Since the original device to change the compression ratio was no longer operative, it was laid away and this space was used as in- dicated in Appendix.D. A series of tests were then begun in which.aluminum paint was daubed onto the piston in sufficient amount to form.globules. The engine was quickly assembled without the intake and exhaust pipes . Motoring was begun as soon as possible and after a few minutes the engine was shut down and the head removed. The first attempts gave a 69- !““““.;O‘,‘““‘tt‘V‘wHQHHU' U Fig. 11. Compression-Ratio Plug and Tie—Down Bolt :3 253a mo fiom €8.03 8.02 .efimfi 8.030 Es Beans: .NH .ME I.’ . Fig. 13. Compres sion-Ratio Plug s 72. faint visual history of the path of the air. This was considerably improved by the addition of drops of black paint, a good example of which is shown in Figures 11; and 15. By using a shrouded intake valve the direction of rotation of the air swirl could be easily changed, depending on the direction in which the shroud allowed the incoming air to enter the cylinder. The valve used had a 180° shroud and is shown in Figure 16. When an abundance of paint was used, a clear indication of the path of the air up into the combustion chamber was shown. This path indicated an abrupt change in flow of the air on one side or the other of the combustion chamber proper.- In an attempt to smooth out the flow an insert was developed and placed into the bottom of the combustion-chamber liner. This insert was then ground away in such a manner that the paint pattern indicated that a relatively smooth trans- ition was obtained as the air was forced from the space between the piston and head and up into the combustion chamber. The original form of the insert, sometimes called a mouth-insert, is shown at the bottom of Figure 17 and its final form inserted into the liner is shown in Figure 18. A combustion-chamber plug, or compression-ratio plug, as it is sometimes called, is shown in the top of Figure 17. Note here that the direction of swirl was counter-clockwise as viewed from below and that the combustion-chamber plug in the upper left-hand portion of the picture indicates the same rotation. The attempt here was to scoop up into the pocket the air flowing at the outer periphery of the cylinder and to allow that air passing nearer the center to go on by. Fig. 1b. Piston and Block. Paint—Pattern of Air-Swirl 73- Fig. 15. Cylinder Head. Paint—Pattern of Air—Swirl 7h. Fig. 16. Shrouded Intake Valve 75. Fig. 17. Compression-Ratio Plug and Original Mouth-Insert Prior to Grinding 76- Fig. 18. mouth—Insert Inserted into Liner. Compare with Fig. 15 (no insert) and Fig. 17 77. 78. Later on during the project it was.found that the air utiliza- tion of the engine was inadequate. This led to a new investigation of air motion within the combustion chamber. Since the paint-pattern method gave every indication of a well-directed air motion, it was de- cided that perhaps its velocity was insufficient for enough of the air to be provided in the proper place during the short time available for combustion. In order to ascertain the velocity of swirl within the combustion chamber a paddleawheel device was fabricated and installed in one of the combustion chamber plugs. (See Figure 19.) The shaft and plug had an almost airtight but yet relatively'frictionefree fit. A small roller thrust bearing was used to provide freedom from axial movement. Upon.motoring the engine the paddleawheel.device indicated that the total swirl during one cycle of the engine was less than one revolution. It seemed logical, therefore, that the low swirl rate was responsible for the poor air utilization of the engine. Several other shapes of insert were then tried, each having its own particular postulate in order to obtain sufficient swirl. These inserts, shown in Figure 20, attempted to do such things as allow the air to enter tangentially and spirally or to bodily transport the intake-induced swirl into the combustion chamber. Some produced re- sults comparable with the original design and others were worse. It became apparent that the intake-induced swirl was somewhat destroyed during the time it was being forced into the offset com- bustion chamber. This was doubtless due in part to the counter effects of the squish (squeezing action) occurring in the small clear— ance space as the piston approached the top center position. Fig. 19. PaddleAWheel Used for Determining Air Rotation 7.9 . Fig. 20. Various Mouth—Inserts 81. The best design turned out to be one in which the squish action was reduced by relieving the top of the piston in the form of an in- verted cone with its apex in the vicinity of the combustion chamber mouth and using an insert which would allow smooth transition from the clearance volume above the piston to the combustion chamber. Even this was considered inadequate. As can be seen from Figure 21(a) the air generally tends to enter the combustion chamber mainly from three sides. It was con- sidered possible that air entering tangential to the piston circum- ference on one side might somewhat cancel that entering from the other side with a result that the predominant air-flow direction was at an angle with the head. (See Figure 21(b)). If this was correct, then a combustion chamber shaped like Figure 21(c) would allow the air to enter in a somewhat vertical direction and leave in a more horizontal direction. If the direction of injection were changed from tangential to the combustion chamber in the circumferential direction, to downward and tangential in the axial direction, then this would provide the action necessary for controlled air motion. A compromise solution for the particular configuration available here is shown in Figure 21(d) . That this solution was adequate is verified in the main portion of this thesis . /////// , W? W//// / APPENDIX C SFHERDDIZDVG TENDENC IE3 Part of the investigation of the fuel-impingement combustion system consisted of an attempt to determine what happened when the .fuel in the form of small droplets was spread on the hot combustion surface. It is known that when water is dropped on a hot stove that the droplets seem to dance for quite some time without any sensible evap- oration. What would happen under conditions in which the droplets were shot onto the hot surface in the form of a fine spray in a very nearly tangential direction? Would the same phenomenon occur causing the fine spray to be delayed in its evaporation? ‘lould this be dif- ferent at atmospheric conditions than at high temperature and pressure? The.M-system theory is based on the assumption that the fuel is "slicked on" to the combustion surface and does not leave it as a liquid. The spheroidization of the droplets, or Leidenfrost phenomenon as it is sometimes called, could very well limit the maximum tempera- ture under which the impingement surface could perform. Above this temperature the fuel would be more susceptible to the action of the air on all sides and thus the combustion process would revert to something similar to that of the normal diesel in which the.fuel is injected into space rather than on an impingement surface. This would probably decrease the ignition delay such that more smoke would arise. The investigation into the Leidenfrost phenomenon 8140 proceeded as follows: First,.fuel was dropped upon a hot-plate as the temperature was progressively raised. On an inclined surface the Leidenfrost or spheroidizing action apparently occurred between 580°F and 620°F ‘while on a horizontal plate it began.between 680°F and 710°F. The rate of evaporation seemed faster on the inclined plate where the scrubbing action as the droplet moved across the plate was more apparent. This test was followed by impingement of the fuel by the in— jector nozzle onto the same hot-plate still at atmospheric pressure. Visual inspection under stroboscopic light indicated at least some 'wetting of the surface between 690°F and 780°F but the area became progressively smaller at the higher temperatures. High speed movies, in the order of 6,000 to 7,500 frames per second, were used in an attempt to further define the temperature at ‘which spheroidizing would take place. Even these did not suitably stop the action such that a complete visual analysis could be made. However, the pictures shown in Figure 22 are a sequence, at 535°F, which definitely indicates that wetting action is taking place. Figure 23,taken at 793°F, shows a definite bouncing tendency of the latter portion of injection. Finally, high speed stills, at l/20,000 sec., taken by means of the stroboscopic light, revealed that wetting occurs at h80°F while spheroidizing is progressively more visible at 780°F than at 6h5°F. (See Figures 2h through 32.) It should be noted here that at h80° 8S. Fig. 22. High-Speed Movies of Fuel Impingement on Surface at 535°F, at 6000 Frames per Second. II I IT. Fig. 23. High-Speed of Fuel Impingement on Surface at 793°F, at 7500 Frames per Second. 87. O eeooom 808.0 £038.39 828 3.3m £63 at Suede 5 passages Home ea eMHh 8. .3008 moooo.o .5300on me dogmas—co .334 push. «5.02. pm oversaw do enogmfidsH Hem...” .mm .mflm 8 688m mooooé doggone do coauoadaoo no»: one”. .Aablomoaov meow» pm mommaom no pooaowfidEH Home .8 . ..m .uaooow mooooé 30.333 gm 3.8m aaomzw so oomgm so passages Home .pm .mfim .388. 883.0 .8335 no 833950 some ans. ares ...» 033m :0 sausages Hose .8 .mE .888 808.0 .838an no 530.3500 93.2 push. «antennae $.me pm oomgm no poosowfiaaH Home .mm .mfim .383 808.0 .8383 maven has $02 ...... manta no snagged Hose .om .mE .9808 380.0 .ooapoOnoH mo ooapoaaaoo .39.? no.3. .903 pm oomuhsm no pace—egg Hush .Hm .wwm .388 808.0 acetone “8 830380 no»: 32. .Esusmoaov some a... 83.3w 8 anaemia H25 .Nm .mE 96. (Figure 32), there is seemingly no difference between the zones of im- pingement and non-impingement . The liquid here is spread thin and has not picked up the glare of the strobe light. In considering the effect of the temperature of the hot gases of the combustion zone, it was concluded that possibly the only apprec- iable effect was an increase in rate of evaporation of the globules formed by spheroidization. . The literature reveals some information of the effect of pressure on the rate of film boiling. This can be considered here be- cause when the rate of film boiling is high and the film is thin, ' spheroidizing occurs. This information indicates that as the pressure increases the maximum rate of heat transfer through the film is much greater and the temperature differential between the mass of the fluid and the surface is less at this maximum rate than it was at the maxi- mum rate at the lower pressure. It is just after this maximum rate of heat transfer occurs that spheroidization takes place. Absolute values have not been obtained but there is every indication that some Spheroidization does occur at the higher lip temperatures of the order of 616°}? and up. When the engine was tested under various conditions, it was found that lip temperatures of 600°F and above gave extreme difficulty due to deposit formation. Just as smoke formation limits the useful power of a diesel so does deposit f omation limit the useful tempera- ture of the lip. Because deposit formation precluded continuous op— eration at 6h5°F and above, it was decided that this portion of the problem is a matter for future investigation. .APPENDIX D EQUIPMENT AND CALIBRATION It was decided to use a regular CFR.Cetane engine as the fundamental unit for the investigation. Since this engine is standard- ized and is universally used in research.projects, it would be easy to duplicate and check the results in other localities. Using such standardized equipment would allow a comparison procedure rather than direct measurement of absolute variables. This engine in its standard form.is shown in the two schematics of Figure 33. In this form it used a pintle-type nozzle. After modification the engine can be pictured as shown in the two schematics of Figure 3h. Here a directional orifice—type nozzle was used, having been obtained by the modification of a multi-hole orifice-type nozzle. The spray cone of this nozzle prior to modification had an included angle of 150°. Closing off all except one hole produced a directional flow, the angle of injection at 75° with the centerline. Rotating the injector in its mounting, therefore, allowed changes in direction of injection. The combustion chamber liner(sxcylindrical tube) was so placed that the extension of the original injector mounting hole allowed the injector to be located in such a position that a directional nozzle could "lay on" the fuel either on the liner in a circumferential spiral direction upwards or on the liner and lip in an almost axial direction downwards. 98. §\\ [\Va‘mim 7 Quest? 0 Z / 1. Position for maximum compression ratio ___. 2. Position for 2: minimum compression -J ratio Compression-Ratio/ Plus A '"1 11 EC] 4——-—— Injector W W/// \\\\ Side View Fig. 33. Schematic of Regular CFR Diesel 595’. z \\\\\ / / Thermocouple : \ A/é Access : ___3 -e————injector Zir/ 71] //// // // W; lit Side View Fig. 3b. Schematic of modified CFR.Diesel 100. _ In order to provide a surface to which to attach the lip as shown in Figure 21(d) of Appendix B, and also to provide a means for varying the temperature of this lip, a set of stainless steel sleeves were used which would allow the use of varying means of insulation 'between themselves and the liner. Figure 35(a) shows a sleeve installed in a liner with the compression-ratio plug in place on top and the mouthpinsert necessaiy to control the gas and air inflow and outflow in its place at the bottom of the liner. This mouth-insert also serves to dissuade movement of the lip and sleeve assembly. Figure 35(b) shows a sleeve with annular grooves used as an insulating medium. It also indicates the general dimensions used on all the sleeves. A sleeve of sufficiently small outside diameter to allow installation of a 0.020" asbestos sheet between it and the liner was also used during the investigation. Figure 35(0) shows various views of the lip and its dimensions. Figure 36 is taken of one of the lip and sleeve assemblies actually used. The irregular hole in the sleeve was re- quired in order to insert the injector nozzle. The wires attached to the lip are remnants of the thennocouple which was used to measure lip temperature. The CFR engine was belted to a constant speed electric motor ‘which.could also be used as a dynamometer. The engine was held to 600 rpm plus l/2 rpm at full power to minus one rpm when motoring. No change in rotational speed was considered necessary since in diesel combustion noise is more prominent at the slower speeds. Since the electric motor served only as an absorber or driver with no method of Compression~Ratio Plug / ,. (a) Lip and Sleeve Assembly, (b) Lip and Sleeve Assembly, Including Compression—Ratio Annular Grooved Plug and Mouthrlnsert 5” Mv‘ Bottom View of Lip \.. \ 3'15 Rad. 3/4"Rad . 2, ,, l . ; rev-1 stzsf’ tszsxzsxsm A-A B-B C—C Sections (0) Dimensions of Lip Fig. 35. Dimensions of Lip and Sleeve Installation Fig. 36. Low—Temperature Lip and Sleeve Assembly 103. determing torque it was necessary to install a torque arm and scales as a measuring device. The very nature of a diesel giving heavy imp pulses to the crankshaft required the necessity of adding more damping than was available in the scales. This was successfully supplied by an aircraft-type automotive shock absorber. Noise was measured and compared in two ways. During the early part of the investigation.a direct comparative procedure consisting of a tape-recorder was used to judge the effectiveness of any changes._ This was quite successful; however, it was felt that a method should be available for presenting this information in a visual form. This was successfully done by means of a General Radio Company Sound-Level Meter. This meter measured in units of decibels. A fast and 51 w re- sponse was available and due to the large noise variation during each cycle, only the slow response was used. The B weighting scale was used only because it was recommended as a good general range. Any of the other weighting scales could have been used with the same amount of relative accuracy. A visual record of the pressure-time sequence within the cylinder is always desirable in any combustion investigation. Here an SLM Quartz Pressure pick up and a combination pre-amplifier and cali- bration unit, the Piezo-Calibrator, were used as input to a Hemlett- Packard Model 130A Oscilloscope. This pick up was installed through the cylinder-head‘water-jacket and flush with the head. It was as centrally located as possible, diametrically opposed to the mouth of 'the modified combustion chamber. This placed the pick up, the intake 1014. and exhaust valves, and the mouth of the combustion chamber in a.four- leaf clover arrangement. (See Figure 15 in Appendix B.) Horizontal external-calibration marks were obtained by a grounding circuit con- sisting of a copper'brush.mounted on a stationary bracket and two copper contacts to ground mounted on the flywheel. These marks pro- vided visual notice of 13°BTDC and 13°ATDC. They have no significance in the vertical direction. The Piezo-Calibrator is constructed in such a way that the voltage generated by the pickup can‘be applied to a resistor. The current generated will be directly proportioned to the pressure rate, 1.6., the rate of change of preSsure with respect to time, or dp/dt. The resulting voltage across the resistor is measured, itself a measure of dp/dt, and is displayed on an oscillograph. This then provides the rate-time infonnation which is a visual indication of the combustion process. The calibration marks at 13°BTDC and 13°ATDC appear on this diagram also. A Polaroid Land Camera has been adapted to the oscilloscope to record the traces aforementioned. In this paper these traces are ar- ranged such.that the firing, or combustion, pressure-time diagram is on top, its rate-time diagram on the bottom, the motoring pressure— time diagram is second from the top and its rate-time diagram second from the bottom. Two horizontal lines also show up, and these are described in the explanation which follows. Although the oscilloscope traces from left to right, the photographic equipment reverses this, and the trace in all oscilloscope pictures is from right to left. It 105‘. should also be noted that occasionally, as in the combustion rate-time curve in Figure 1 in Presentation and Discussion of Data, one of the calibration marks fails to register. Calibration of the SLM pickup consisted of using a.dead-weight tester to impose a specific pressure on the pickup. It was found, using the oscilloscope settings necessary to produce appropriate diagrams, that one cm. corresponded to 305 psi. Calibration lines at 578 psi and 1157 psi were superimposed on the diagrams and these will be seen at approximately two and four centimeters up from the center horizontal axis. In order to determine the rate of pressure rise, dp/dt, it was first necessary to determine a pressure calibration factor. This is obatined from the following:7 where 2.7 is potentiometer voltage x 10 R is range setting (capacitance) DV is dial setting (or potentiometer percentage) P is pressure applied so K = 2.7 xglogggs’é) = 2.h6 )1/M Cb/psi The rate of change calibration factor is then Kr . K x Resistance = volts/psi/sec 1012 “where Resistance is the resistance across which potential is applied = 2.h6 x 105 1012 = 2.h6 x 10"7 volts/psi/sec. 105 onus. So Kr = 106. The oscilloscope vertical scale was 0.05 volts per centimeter so each centimeter variations of the dp/dt trace represented 203,000 psi per second. . The relative measure of smoke density was obtained by means of a General Electric exposure meter intended for use with a Polaroid Land camera. This light-meter was inserted into a downstream pro- jection of an elbow in the exhauster system connected to the engine. Approximately eight feet above, also in the exhauster system, and in another projection at an elbow, a Ken-rad 150 watt, 130 volt Par 38 Projection Spot-Flight provided the intensity for measurement. (See Figures 37 and 38.) The exhauster system provided sufficient suction under maximum power output, 0.1; inches of water at the upper elbow, to keep both the exposure meter and the spotlight swept clean by air entering small holes appropriately placed. These holes were shielded to preclude entrance of any appreciable amount of external light. The readings on a General Electric exposure meter such as this increase as the intensity of the light reaching it increases. As used here these readings would be somewhat inversely proportional to the density of the smoke between it and the source of light. It was, therefore, decided to use as an indication of the density of smoke produced by the engine and measured by the light-meter the amount (8 - x) where x is the light-meter reading. This is the number entered under the heading of moke Density in the -Tables and Graphs. A clear exhaust would therefore give a Smoke Density in the order of 1.3 while an exhaust darkened by the recommended fuel rate for the CFR at inter- mediate compression ratios would show a Smoke Density of 6.0 or more. 10? . .4——— Light Source 0 . 33°“: 3%? 1/ L 11 II —-—>- To Exhauster 19" r” """' 9" Conduit I I l 4—*————-h" Conduit M / Opening, Both Sides (1 3/810 x 1» x in) \ V.V\X\\\\\\ \\ A 7/8" Ligl eter We 7 ////x [fl/ll y. \ \\\\\\\\ / 1L l/h" W I l %% ‘Jiew A-A ' __J 1 3/8" 3'. .d . Flexible Exhaust Conduit to Engine Flange, 23" S Fig. 38. Schematic of Smoke—meter Fig. 3?. Schematic of Smoke-Meter 109 . It was found that Chromel-Alumel thermocouples were necessary to withstand the high temperatures and other abuses of this investi- gation. No commercial thermocouples were immediately available which could be easily installed in a.combustion chamber so hand fabrication was resorted to. The thermocouple wires were led through rifle—drilled holes in the liner to the appropriate recording places. A pressure tight seal was obtained as shown in Figure 39 in which a thermocouple is shown attached to the sleeve. The thermocouple was silver soldered to the place for which the temperature was desired. Liner T*—-Sleeve To . . Steel Po tentiometerfi Block We -<—-Silver Solder Soft Gasket Material Fig. 39. Installation of Thermocouple An L and N No. 8657-C portable, double range, Potentiometer Indicator, with manual reference junction (cold junction) compensation was used to determine thenmocouple potential. The thermocouple was i 110. connected directly to the potentiometer without use of extension leads. A general view of this equipment, taken while in operation, is shown in Figure hO. The scales can be seen in the upper left back- center foreground and the CFR console is on the left. The oscilloscope, calibrator, and camera are on the right. The ladder was used for access to the smoke~meter spot-light. At the very bottom, between the potentiometer and the oscilloscope table, is the sound-meter. The highsspeed still~photographs were taken with the aid of a General Radio Company Strobotac, Type 6h8~A, and Strobolux Type 631931. These were connected to the pressure-operated switch on the fuel in- jector of the engine. The fuel injector was mounted on a table next to a small hot-plate and a fuel line was run to it. (See Figure bl.) By varying the spring rate on the switch, the stroboscopic light was made to flash at the desired time within the fuel delivery cycle. This explains how the still-pictures presented in Appendix C were obtained. Moving pictures were taken by means of a 16 mm. 100"Wollensok Fastax camera at 6000 to 7500 frames per second. .fimflgfl 80.3834 and .383 $6 confine: «o For, assume .3 .mg .oowgm u so eOHpOOnoH Hose mo £33305 Boewuemdi .Se manta 03 oMHh BIBLIOGRAPHY BIBLIOGRAPHY ‘ SELECTED REFERENCES l. Landen, E.‘W., "Combustion Studies of the Diesel Engine," SAE Journal, June l9h6. 2. Elliot, M. A., "Combustion of Diesel Fuel,“ SAE Quarterly Trans- actions, July l9h7. 3. Schweitzer, P. H., "Must Diesel Engines Smoke?", SAE Quarterly ; Transactions, July l9h7. , h. Meurer, J. 5., "Evaluation of Reaction Kinetics Eliminates Diesel ' Knock," SAE Transactions, Vol. 6h, 1956. S. Dicksee, C. B., The High-Speed Compression-I nition En ine, Blackie and Sam, Limited, London and Glasgow, I9h5. 6. Lee, D. W., "A Study of Air Flow in an Engine Cylinder," NACA . Report gig, 1939. 7. Anonymous, Maintenance Manual, SLM Pressure Indicator, Kistler ' Instrument Company, North Tonawanda, New York. GENERAL REFERENCES "ASTM Manual of Engine Test Methods for Rating Fuels," American Society for Testing_Materials, Philadelphia, Pennsylvania, I952. Belles, F. 3., "A Preliminary Investigation of Wall Effects on Pressure- Inflammability Limits of Propanquir Mixtures," NACA RE E50J10a. Bogen, J. S. and G. C. Wilson, "Ignition Accelerators for Compression- Ignition Engine Fuels," Petroleum Hefiner, July l9hh. Frank, C. E., et al, "Investigation of Spontaneous Ignition Tempera- tures of Organic Compounds with Particular Emphasis on Lubricants," NACA Technical Note 28h8, December 1952. Frank, C. W} and A. U. Blackham, "heaction Processes Leading to _ Spontaneous Ignition of Hydrocarbons," NACA Tech. Note 2955, June 1953. 115. Green, W. P., "Optimum Compression Ratios for a HighsSpeed Diesel 0 Engine," ASME Transactions, Vol. 67, 19h5. Hockel, H. L., "The MWM Balanced-Pressure Pre-combustion Chamber System for HighFSpeed Diesel Engines," SAE Transactions, Vol. 66, 1958. Hunter, H. 0., Diesel Smoke Measurement, SAE Transactions, Vol. 6h, 0 1956. Jackson, J. L., "Spontaneous Ignition Temperatures of Pure Hydro- carbons and Commercials and Commercial Fluids," NACA RE E50J10, December 1950. Jalcob, M., Heat Transfer, John Wiley and Sons, Inc., New York, 19h9. Lang, Y. S., et a1, "Heat and Momentum Transfer between Spherical Particle and Air Streams," NACA Tech. Note 2867, March 1953. .Lewis, B., R. N. Pease, and H. S. Taylor,_gombustion Processes, ~ Princeton University Press, Princeton, New Jersey, 1956. Lewis, B. and G. von Elbe, Combustion, Flames and Explosions of Gases, Academic Press, Inc., New York, 1951. Lichty, L. C., Internal-Combustion Engines, MoGrawaHill Book Co., 1951. Loeffler, B., "Development of an Improved Automotive Diesel Combustion 9 System," SAE Preprint #188, November 1953. Obert, E. F., Internal Combustion En ines, International Textbook ' Co., Scranton, Pennsylvania, 9 0. O'Neal, 0., "Effect of Pressure on the Spontaneous Ignition Temperature . of Liquid Fuels," NACA Tech. Note 3829, October 1956. SAE Special Publication, "Diesel Engine Exhaust Smoke," SAE Papers 121, ~ 122, 123, 12b, and 125, January 1958. SAE Special Publication, "multifuel Engine Symposium," SAE Paper 158, October 1958. Spalding D. B. Some Fundamentals of Combustion Academic Press Inc. 3 .9 __ 3 a New York, 1955. Taylor, C. F., et a1, "Ignition of Fuels by hapid Compression," SAE Quarterly Transactions, April 1950. Yu, 0. A., et al, "Physical and Chemical Ignition Delay in an Operating Diesel USing the Hothotored Technique, SAE Transactions, Vol. 6h, 1956. ROOM USE ONLY W OGLW n ”9721 1950 n "9”" USE wa 1|IllllllllmllllfllllllllIIIIHHIIWIHIIUIWlHNlWHl