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Viewing 43621 to 43650 of 44126
1936-01-01
Technical Paper
360101
P. M. Heldt
ROUGHNESS in the operation of engines has increased in seriousness with increase in the compression ratio and in the provisions for inducing turbulence in the combustion chamber, both of which factors tend to increase the rate of pressure rise in the engine. In this paper the thesis is maintained that this roughness consists of synchronous transverse vibration of the crankcase, due to variations in gas pressure and inertia forces. By synchronous vibration is meant a vibration which passes through a cycle in exactly the same time as the periodic force which produces it, so that the amplitude of the vibration builds up from cycle to cycle until the damping forces become equal to the exciting force. Owing to the angularity of the connecting rod in all except the dead-center positions, the gas pressure produces an alternating horizontal force on the crankcase at the main bearings.
1936-01-01
Technical Paper
360103
Alex Taub
THE fuel consumption prevailing today is no better than it was five years ago. Higher road speeds are responsible. Cars in the hands of owners today are below potential economy between 10 and 15 per cent. Minor adjustments can correct this. Phasing of the burn with valve and piston movement is necessary for economy. Spark-plug position relative to the whole chamber is important. Spark-plug points position inward is important. The spark-plug gap width must be worked out. Mixture “fish hooks” to determine leanest mixture that will burn without raggedness, are the yardstick. Mixture distribution is important. The attitude of today is that a specific type of manifold does not exist. The manifold must be “tailored” to fit individual conditions. Offside mixtures out of the carburetor is real problem of distribution. Exhaust dilution of the mixture is the handicap to clean operation with lean mixtures. Timing is the most important avenue of progress.
1936-01-01
Technical Paper
360132
P. A. Anderson
THIS paper deals with air-cooled aircraft-engine installations and covers such units as cowling, engine mounts, exhaust systems, carburetor-ice eliminators, oil systems, fuel systems, controls, accessories, and so on. No attempt is made to describe any particularly new ideas in engine-installation design, but rather the paper explains the fundamental requirements for satisfactory operation of Wright air-cooled aircraft engines.
1936-01-01
Technical Paper
360127
F. D. Klein
INCLUDED in this paper are: Comparative performance of various types of fuels in high-output, single-cylinder liquid-cooled engine, and comparative performance of 100-octane toluene blend and iso-octane blend relative to 92-octane Army method regular gasoline in full-scale engine with two-speed supercharger and normal compression ratio. Endurance tests scheduled in Cyclone and two-row Wasp with 8:1 compression ratio and very low specific fuel consumption. Military present and contemplated future use of this fuel and its commercial possibilities. Possible means for increasing available supply. Availability of unleaded high-antiknock fuels and leaded fuels superior to 100-octane fuel.
1936-01-01
Technical Paper
360121
Raymond W. Young
DURING the past decade the general trend of aircraft-engine design has continued toward increased piston displacement, higher crankshaft speed, higher brake mean effective pressure, and improved materials. These changes have had a marked influence on increasing the overall performance of the airplane by improving take-off, bettering climb, permitting higher cruising speeds at greater altitude, increasing periods between overhaul, and improving the reliability of the powerplant. Although of secondary importance until quite recently, today fuel economy has become a major objective in both military and commercial operation. Fuel consumption is a function, generally speaking, of engine design, of the properties of the fuel itself, and of the procedure for introducing and regulating the fuel-air mixture in the operation of the powerplant.
1936-01-01
Technical Paper
360122
F. C. Mock
THERE are two main requirements as to proper preparation of the fuel charge for rapid combustion in our present engines: (1) The fuel must be vaporized, or in a similarly small order of subdivision, before ignition. (2) The fuel and air must be intimately mixed. Light fuels, such as our present aviation gasoline, may be vaporized in the carburetor and supercharger to quite a satisfactory degree, providing that the intake air is heated when flying at low temperatures. With this system, as we know, the air and fuel mixing is quite thorough. Heavier fuels, if released in the carburetor, may not vaporize in the intake-air flow, but instead may puddle and trickle on the side walls. Under such conditions, not only does the fuel fail to reach the cylinders in metered charges but also, if and when it should do so and if it vaporizes in the cylinder rather than getting on the cylinder wall, there is usually inadequate means for mixing the vapor with the air charge.
1936-01-01
Technical Paper
360124
D. J. Vail
DEVELOPMENT of cast camshafts at the Campbell, Wyant & Cannon Foundry Co., starting in 1924, proceeded slowly until a material was developed that met all requirements from metallurgical, engineering, and manufacturing standpoints. “Proferall,” the name given this material, means processed-ferrous-alloyed iron made by the duplexed-electric-furnace process. Camshafts of this material have a Brinell hardness of 262-293, as cast. A series of tests, equivalent to runs of 46,560 miles, showed that both chemical analysis and hardness affect camshaft-gear wear. Comparative wear tests on bearings showed more than three times as much wear on steel camshafts as cast ones. Other tests showed the cast shafts expanded less than those of steel. After describing foundry processes the paper concludes by summing up the advantages of cast camshafts, such as the smaller cost of patterns as compared with forging dies and the elimination of heat-treating, copper plating, carburizing, and hardening.
1936-01-01
Technical Paper
360133
E. M. Barber, B. A. Kulason
IT is the purpose of this paper to present a chart by means of which the vapor-locking characteristics of a gasoline (represented by a curve showing the quantity of vapor formed as a function of the temperature) can be estimated with moderate accuracy for gasolines in the current commercial distillation ranges from the conventional Reid vapor pressure and A.S.T.M. distillation tests on the gasoline. Interpretation and consolidation of car data are facilitated by means of the chart and, in this respect, vapor-lock test data are given for eight 1934, eleven 1935, and several 1936 model cars. The use of the chart and car data is illustrated by a group of sample problems which are specially designed to show the degree of assurance that may be placed on the use of either Reid vapor pressure or A.S.T.M. 10 per cent point alone as a criterion of vapor lock. The problem of evaporation losses from the fuel system, which can be roughly treated by means of the chart, is also discussed briefly.
1936-01-01
Technical Paper
360140
R. L. Hershey, J. E. Eberhardt, H. C. Hottel
THE thermodynamic analysis of an internal-combustion engine, even in the idealized case, is in general more complex than a similar analysis of an engine cycle in which the fluid undergoes no chemical change. It is the purpose of this paper to show that, despite the inherent complexity of the problem, an exact solution by graphical methods is possible, and the method is very similar in nature to those used in connection with the Mollier diagram for steam. Two types of charts are presented, one descriptive of the thermodynamic properties of the airfuel mixture (and residual products of combustion) before combustion, the other descriptive of the properties of the equilibrium mixture after combustion. Full allowance is made for the variation of specific heats with temperature and for the complex dissociation at the high temperatures attained after combustion. All calculations are based on the most recent basic thermodynamic data available in the literature.
1936-01-01
Technical Paper
360117
Morris P. Taylor
THE effect of gas pressure on piston friction was investigated, in the laboratory of the Massachusetts Institute of Technology, by driving with an electrical dynamometer a six-cylinder engine with the valves removed and the valve-stem bushings plugged. Air under pressure was admitted to the closed space made up of the cylinders, valve passages, and manifolds, and a constant air pressure was maintained on the pistons. Under these conditions, it was found that the friction increased approximately as a linear function of the pressure and the running speed. The effect of jacket-water temperature on piston friction was marked, but it could not be directly connected with the absolute viscosity of the oil at the temperature of the jacket water. Tests run with gas pressure relieved from behind the piston rings indicated that about a fourth of the rate of increase in friction with pressure is due to gas pressure behind the rings.
1935-01-01
Technical Paper
350099
E. S. Dennison
THE paper describes a procedure for analyzing the performance of an internal-combustion engine. It is first shown that the characteristics of ideal cycles can be conveniently represented with the help of a fictitious “fuel mean pressure” which is proportional to the useful heat input. The diagram so obtained is used to represent certain ideal Otto and Diesel cycles. It is pointed out that actual performance can be similarly expressed. A simple correction for the variation of atmospheric conditions is then introduced. Examples from tests are used to show that this correction is in accordance with actual experience. The final form of the proposed diagram embodies the correction. It is then shown that the performance of a cylinder as it appears in this diagram is a measure of the success of the designer in dealing with factors lying within his control, as distinguished from those arising from the conditions of operation.
1935-01-01
Technical Paper
350097
S. D. Heron
OIL cooling of aircraft powerplants is increasingly difficult. The weight and drag of the oil coolers necessary with the present maximum “Oil-in” temperature of 185 deg. fahr. (85 deg. cent.) are both decidedly objectionable. It appears possible to increase the “oil-in” temperature to about 220 deg. fahr. (104 deg. cent.) with oils which can be produced by the newer refining methods. The use of an “oil-in” temperature of 220 deg. fahr. would render possible a material reduction in weight, size and drag of oil coolers in comparison with present practice. Oils suitable for use at 220 deg. fahr. “oil-in” temperature would not be likely to cause a material increase of engine-starting difficulty, as they would only be used in summer when the shearing resistance of the oil has slight influence on engine starting. The approximate temperature cycle encountered by the oil in its passage through a modern aircraft-engine is discussed.
1935-01-01
Technical Paper
350111
Ernest G. Whitney
MIXING of the fuel and air presents the major problem in maintaining high efficiency at low excess-air percentages in the high-speed compression-ignition engine. The outputs obtained from a single-cylinder 5 by 7-in. test-engine with three types of combustion chamber are compared and their respective characteristics discussed. Airflow is depended upon for mixing the fuel and air in the pre-chamber engine. Performance is shown to be influenced by clearance distribution, connecting-passage size, pre-chamber shape, location of the fuel spray, and boosting. The integral, or quiescent combustion chamber depends upon multiple sprays properly proportioned and directed to reach the available air. Results of an extensive series of injection-nozzle variations are shown in tabular form. The effects of scavenging and boosting and of high coolant-temperatures are discussed. Optimum performance showed either type to be inadequate for use as an aircraft powerplant.
1935-01-01
Technical Paper
350112
Kenneth A. Browne
THE need for improvement of fuel consumption in modern aircraft is stressed. The basic economy of oil engines for airline service is briefly summarized, together with the effect of lower fuel consumption on the range and payload of airplanes. The theoretical efficiencies of the Otto and Diesel cycles are compared with the efficiency actually obtained on present aircraft engines. The data are presented in condensed graphic form for easy comparison. A prediction is made of the fuel economy that may be expected from the gasoline aircraft-engine in the near future, together with a summary of the means required to obtain it. The prospective place of the compression-ignition engine in commercial and military service is briefly outlined. An analysis of the weight possibilities of compression-ignition engines as compared to present gasoline engines is made.
1935-01-01
Technical Paper
350108
John M. Campbell, Wheeler G. Lovell, T. A. Boyd
SINCE the design of the automobile engine depends largely upon the volatility and knock rating of the gasoline fuel it uses, a major problem is the fitting of the engine to these two fuel-characteristics. Regarding volatility, the engine must take the best advantage of the present available fuels; its design cannot be entirely made to suit an average gasoline; and, once an engine has been built, it must operate and give satisfactory service over a considerable period of years. Recent trends in important items of design are noted, as well as the trends to automatic chokes and warm-up controls. The author states that a system of classifying gasolines in terms of volatility is needed, and discusses various aspects of the starting problem. Other features include comments upon the trends in mixture temperatures, acceleration, crankcase dilution, and vapor lock.
1935-01-01
Technical Paper
350107
Guy E. Beardsley
THE basic idea of accomplishing both a power limitation and a control of the mixture with one unit was evolved by the late Thorp Hiscock. He proposed, by throttling the air entering the carburetor, to maintain the density of air entering the venturis equivalent to that at an altitude of 7000 ft. Thus the carburetor would virtually be held at 7000 ft. and would deliver, even though the airplane might be at sea level, a mixture of the same fuel-air ratio that it would normally deliver at 7000 ft. Details of the development of the automatic power and mixture-control unit are given, together with descriptions of tests made and statements of results obtained. In conclusion, it is stated that, from the reports available on general fuel consumptions, it is apparent that some method of control is desirable.
1935-01-01
Technical Paper
350086
J. F. Campbell
THIS paper covers in a general way the development of a complete fuel injection system, including fuel injector, discharge nozzle, control system, fuel system, etc., and the application of the system to Pratt and Whitney Wasp engines, Wright Aeronautical Cyclone, Curtiss Conqueror and Allison V-1710 engines, also the installation of the Pratt and Whitney Wasp engine in service airplanes and the performance obtained with the system.
1935-01-01
Technical Paper
350087
Clarke C. Minter
COMBUSTION roughness is defined as the ratio of the rise in pressure to the time required for the burning. It is pointed out that evidence shows that the time required to burn a charge in an engine is directly proportional to the volume of the charge. A measure of the “natural roughness” of a combustion chamber is given by the ratio of the compression pressure to the clearance volume. The question of how flame speed varies during the burning is taken up and it is brought out that flame speed goes through a maximum when half the volume of the charge is burned. In designing a combustion chamber for smoothness of burning, it is necessary to consider the variations in the speed of flame propagation, and to attempt to bring the maximum speed early in the burning so as to get the flame off to a good start. In this manner it is possible to avoid unduly rapid increases in pressure at a late stage of the burning.
1935-01-01
Technical Paper
350083
R. F. Gagg
AN outline of some current problems in aircraft engines with particular reference to the types used for main-line scheduled-transport operations is presented, it being limited so far as possible to a consideration of the conventional four-stroke gasoline-engine. Types of airline service are considered and, as regards engine sizes, it is remarked that airline service demands engines in a range of sizes from the maximum available to about 250 hp. as a minimum. Statistics of the present performance of airline engines are given, and it is stated that the horsepower output required to meet the contemplated schedule with the most adverse wind normally expected on the route is a nearly correct measure of the true effective size of the airline engine; further, that its durability and performance should, in general, be judged on that basis. The importance of fuel consumption is stressed.
1935-01-01
Technical Paper
350092
Alan Ferrier
THE author describes the conditions of aircraft operation in Canada during the winter and after outlining the laborious technique pursued for several years emphasizes the need for improvement in lubrication and starting technique in order that commercial undertakings may make full use of the short northern day. Elimination of cold weather lubrication difficulties is based on the proposition that oil temperature is in itself immaterial and that its only real importance is the effect on viscosity which is regarded as a state rather than as a property. In consequence a variation of oil grade and a premeditated variation of oil operating temperature under adequate control is advanced as the solution and the results of two years practical trial are offered as proof. A brief specification of a desirable oil system is given, together with a forecast of possible developments in the near future to deal with existing lubricants.
1935-01-01
Technical Paper
350072
F. M. YOUNG
1935-01-01
Technical Paper
350079
N. Mitchell
OF the 455,000 trucks or passenger-carrying motor-vehicles in the United Kingdom at least 5500 are now fitted with compression-ignition engines, 57 per cent of these being fitted to passenger-carrying vehicles. The engines are of the direct-injection and of the separate-chamber types. This paper does not discuss the merits of one system as compared with another, but merely the findings as regards costs and general service as derived from data supplied by the manufacturers and users. By courtesy of the London Passenger Transport Board, data are presented on compression-ignition engines as compared with gasoline engines operating in the London area and the experiences regarding the adoption of the former are related. Another operating company has in service 50 vehicles equipped with Gardner direct-injection engines. Several direct-injection systems are illustrated, and curves for comparative fuel-consumptions of the Leyland engine, using gasoline and using gas oil, are presented.
1935-01-01
Technical Paper
350074
Louis A. Graham
1935-01-01
Technical Paper
350075
W. J. Cumming
1935-01-01
Technical Paper
350076
W. B. GOODMAN
1935-01-01
Technical Paper
350118
Kenneth Campbell
TO convert cooling results observed under one set of conditions to equivalent values for other conditions, a better understanding of some of the many variables involved is needed. The progress of experiments being conducted along several lines with this objective in view is reported. Published data on heat-transfer research have been examined and, from these, a working approximation relating air temperature and mass flow has been set up. Single-cylinder engine and full-scale testing have been conducted to evaluate this equation as applied to modern baffling conditions. Tests to observe directly the effect of cooling-air temperature-variation on cylinder-wall temperatures under specified conditions have been made. The effect of carburetor-air temperature on cylinder-wall temperatures at constant manifold pressure has been experimentally determined.
1935-01-01
Technical Paper
350119
C. Fayette Taylor
ABSTRACT
1935-01-01
Technical Paper
350116
O. D. Treiber
THREE sizes of six-cylinder Diesel-engines for automotive service have been developed by this company and are now in production, these being interchangeable in mounting dimensions with its six-cylinder series of gasoline engines. These modern Diesels develop power which equals, or exceeds, that of a gasoline engine of corresponding displacement. Subjects treated include noise, smoke, installation, performance, power output and maintenance, together with fuel and lubricating-oil costs. A feature of these Diesels is a spherical combustion chamber located at the side of the cylinder with a spray of fuel entering at the side, below the center of the sphere but injecting across its center. Comparisons between Diesel and gasoline-engine performance in similar service are made.
1935-01-01
Technical Paper
350115
D. D. Robertson
THIS paper points out how the problems of decreasing oil-consumption and blow-by and preventing piston-slap are affected by different piston and piston-ring characteristics, and some of the things that can be done toward solving them. Improvements made in pistons-as to design, materials and construction-are cited. Problems concerning oil-control are stated, and means for solving them are set forth. Interesting figures on piston-ring-wear tests are presented and the conclusion regarding them is that the wear of pistons, piston-rings and cylinders, is due almost entirely to factors which, though usually present, are outside influences. These include abrasive material entering with the intake air, crankcase sludge, excessive choking, cold starting, and blow-by. Wear inside the cylinders cannot be eliminated without the use of improved air-filters and oil-filters, and by improved cold-starting conditions.