Search Results

The diesel engine is one of the most efficient types of heat engines and is widely used as a prime mover for many applications. In recent years, with the aid of modern computers, engine combustion modeling has made great progress. However, due to the complexities of the processes involved in the practical diesel engine, there are still too many unknowns preventing computational prediction to have the accuracy level required by industry. This book examines some basic characteristics of diesel engine combustion process, and describes the commonly used tool to analyze combustion - heat release analysis. It addition, Practical Diesel-Engine Combustion Analysis describes the performance changes that might be encountered in the engine user environment, with a goal of helping the reader analyze his own practical combustion problems.

This paper describes the development of a comprehensive simulation environment for investigations of gas-dynamic processes and combustion phenomena in rotary engines, conducted by the Austrian Institute for Powertrains and Automotive Technology of the Vienna University of Technology. In this connection, proven, commercially available engine cycle calculation Software-Tools have been used. For this, a rotary engine test bench has been established. As analysis tools, in addition to the traditional acquisition of the emitted engine torque, various pressures and temperatures, the recording of the pressure profile (combustion analysis measurement system) in the combustion chamber, as well as in the intake and exhaust ports, were used. The data of the test bench were used to develop and validate the methodology for the simulation tools. The focus in this paper is the development of a CFD (computational fluid dynamics) model with the software Converge from Convergent Science, Inc.

PISTON-ring scuffing occurs most frequently during the break-in period and has been a problem to both the automobile and ring producers, for some time. Ring coatings have been under development for several years and their general adoption by nearly all automobile companies indicates both the need for them and their effectiveness. The coatings fall into two general classes, chemical and metallic. The chemical are: Ferrox, an iron oxide; Granoseal, an iron-manganese phosphate; Graphitox and Grafotox, a zinc-iron phosphate with colloidal graphite; and Surfide, ferrous sulphide. The metallic coating is of electrolytically deposited tin. Careful tests under accelerated wear or scuffing conditions on newly finished surfaces showed that untreated rings produced twice the wear that occurred on the coated rings when only the compression rings were coated. The difference in wear was even greater when both compression and oil rings were coated properly.

Contribution to carbon neutrality is one of the most important challenges for the automotive industry. Though CO2 emission has been reduced through electrification, internal combustion engines equipped in vehicles such as Hybrid Electric Vehicle (HEV) and Plug-in Hybrid Electric Vehicle (PHEV) are still necessary for the foreseeable future, and continuous efforts to improve fuel economy are demanded. To improve powertrain thermal efficiency, direct-injection turbocharged gasoline engines have been widely utilized in recent years. Super lean-burn combustion engine has been being researched as the next generation of turbocharged gasoline engines. It is known that an increase of the boost pressure causes deposit formation, which decrease the turbocharger efficiency, in the turbocharger compressor housing. To avoid the efficiency loss due to deposit, air temperature at compressor outlet has to be limited low.

Deposits on engine parts, and in particular in combustion chambers of modern engines are causing increasing concern in the automobile industry. Highly sophisticated engine management systems make effects on emissions or performance obvious as outgassing of unburned hydrocarbons or variation of spark advance. Reduced mean heat flux away from the cylinder influences engine thermodynamics. Extreme deposits may cause noise increase by carbon rap. A special form of combustion chamber deposits, well known under the synonym spark plug fouling, is a carbon needle on spark plugs, which can cause the total damage of the catalysts (Japanese Industrial Standard D 1606: Adaptability Test Code of Spark Plug for Automobiles) The Co-ordinating European Council for the development of performance tests for transportation fuels, lubricants, and other fluids (CEC) started the development of a new performance test in 1994.

THIS paper presents numerous charts showing the wear of cylinder and piston rings. Attention is called to the fact that maximum wear usually is found in line with the top ring at the upper limit of its travel. This is attributed to the presence of dirt and to the high temperatures which make lubrication difficult in this region. Reasons are given for believing that the piston rings are more often the agent producing wear, than is the piston. Special experiments are described which illustrate the effect of insufficient oil, of abrasives, of rough surfaces and of high local temperatures. It is concluded that inadequate lubrication, but not necessarily insufficient lubricant, is the primary cause of wear.

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.

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.

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.

IN the testing method described in this paper the moment of ignition is determined by a mechanism consisting of a diaphragm in the cylinder head, a phonograph “pick-up,” a short stiff wire transmitting the motion of the diaphragm to the pick-up, a thyratron relay, and a neon lamp protractor. When ignition occurs in the cylinder the flexing velocity of the diaphragm is sufficiently high so that the voltage generated in the coil of the pick-up trips the thyratron tube and permits a high-tension condenser discharge to be sent through the neon lamp which by its flashes then indicates the time of ignition. Because of the absence of friction and arcing the action of the pick-up is more regular than that of a bouncing pin. A similar pick-up is used for indicating injection timing. Using this apparatus and the “fixed-ignition-lag method” the Diesel fuel testing in the C.F.R. engine has been so simplified that seven to eight fuels can be tested in an hour with a high degree of reproducibility.

A DISTINCTION is to be made between non-continuous-wear and continuous-wear measurements. To the former class belong measurements where the piston-rings are weighed or the cylinders and piston diameters are measured. Such a method takes a great deal of time, not only because of the long duration of the test itself but also because of the time necessary for the removal of the pistons, weighing, measuring, and re-assembling the engine. In the latter method, cylinder wear is measured by determining the ash content of oil dripping from the piston while the engine is running. A standard fuel and lubricating oil is used, and wear is expressed as a “wear factor”-the ratio between the weight of ash collected on the sample used and the weight of ash collected from the standard sample. This factor correlates well with actual wear measurements. Wear decreases with decreasing load, but increases again with very light loads within specified limits.

CYLINDER temperature is definitely one of the many important factors affecting the efficiency and life of an internal-combustion engine. Experience has indicated that cylinder temperature can be too low or too high. Each temperature extreme produces its own particular set of evils, but the high temperatures are the most destructive and the most difficult to control. Cooling-water or fin temperature is only slightly indicative of the cylinder-surface temperatures. Since we are most vitally interested in the temperature of the working surfaces, research on the subject must start on the inside. The evils of thermal distortion are well known but probably not fully appreciated. Practically every factor of engine performance is dependent upon lubrication. Excessive cylinder temperature destroys lubrication which, in turn, eventually shortens the life and decreases the efficiency of an engine.

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.

THIS paper gives a brief resumé of the development of the Rolls-Royce Kestrel engine and then analyzes the requirements of the high-performance engine of the future, developing at least 1500 b.hp. and operating on fuels of high knock ratings. The problems investigated include those of engine form, fuels, detonation, waste-heat disposal, cooling drag, cooling medium, and the mechanical and operational features. Conclusions deduced from the arguments are: (a) Compression ratios, charge density, and rotational speeds will need to increase and, therefore, cylinder bores and strokes will decrease; it may be necessary to adopt the sleeve-valve type. (b) The arrangement of the engine will tend to multithrow crankshafts with more than two pistons per crankpin.

MUCH remains to be desired in the vibration characteristics of present crankshaft-propeller systems, in the opinion of the author. Discrepancies between torque-stand and flight measurements of torsional vibration on the same engine may explain propeller fractures due to the vibration of flexure. Recent fatigue fractures of crankshafts, differing from those due to torsional vibration, must be attributed to longitudinal vibration. Degrees of freedom are discussed with a graphical summary of vibration frequencies. Vibration forms, sources, stresses, and resonances are subjected to mathematical analysis. Three roads open to effective measures against vibration are given as: direct elimination of sources; subsequent destruction or damping of existing vibrations; and changing the pitch of the vibrating system, or displacing the resonance points to fields outside of the operating range. Of these methods the last is believed to be the most promising.

EVOLUTION of automobile radiators is recounted step by step from the primitive water-pipe types to those in use today. Pertinent heat-transfer principles are given to show cause for various changes. The effects of larger engines, higher speeds, quieter operation, are discussed fully. Poor water-jacket design is blamed for a multitude of cooling-system troubles, such as warped valves, valve seats, and cylinder bores, and it is believed that these troubles could be eliminated largely on the drawing board by the water-jacket designer. A special test apparatus, called a “dissipator” and built expressly for testing radiators, is described. Considerable space is devoted to test procedure and discussion of test results on hexagon-core, fin-and-tube core, double-center core, and a new vee-type radiator for different depths, air speeds, and frontal areas. In addition, tests made on a full-sized wind tunnel are discussed and interpreted.

THIS paper describes a number of applications of the cathode-ray tube to the solution of engine problems, such as indication of pressures in the cylinder and in Diesel fuel lines; mechanical vibration of moving parts; torsional oscillations of shafts; whip of shafts; and time of arrival and duration of flame at any point in the cylinder-head. The different technique involved when hard-vacuum cathode-ray tubes are used instead of the gas-filled variety, is also indicated. An outline is given of some of the work rendered possible by its aid. This includes observations on the nature of the octane scale in so far as its relation to combustion pressure is concerned. A contribution is made to the theory of the mechanism of Diesel knock intensity together with some information on improving the power output and cleanliness of running of a C.F.R.-Pope Diesel engine.

Abstract Demonstrating ring pack operation in an operating engine is very difficult, yet it is essential to optimize engine performance parameters such as blow-by, oil consumption, emissions, and wear. A significant amount of power is lost in friction between piston ring–cylinder liner interfaces if ring pack parameters are not optimized properly. Thus, along with these parameters, it is also necessary to reduce friction power loss in modern internal combustion engines as the oil film thickness formed between the piston ring and liner is vital for power loss reduction due to friction. Hence, it has also been a topic of research interest for decades. Piston and ring dynamics simulation software are used extensively for a better ring pack design. In this research work, a similar software for piston ring dynamics simulation reviews the ring pack performance of a four-cylinder diesel engine.