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In a high-speed DI diesel engine, fuel sprays impinge surely on a wall of a piston cavity. Then the phenomenon of the heat transfer between the impinged spray and the wall appears and it has the strong effect on the combustion processes of the engine. The purpose of this study are to clarify basically the heat transfer characteristics. In the experiments, the fuel was injected into the quiescent inert atmosphere with a high temperature under high pressure field, and an evaporative single diesel spray was impinging upon a flat wall. And, the temperature distribution on the wall surface in a radial direction was detected by the Loex-Constantan thin film thermo-couples. Thus, the heat flux between the impinged spray and the wall surface was calculated from the temperature profile within the wall by Fourier's equation using the finite difference method, under the assumption of the one-dimensional heat conduction.

Stirling Thermal Motors, Inc., (STM) of Ann Arbor, Michigan, has been developing a general purpose Stirling engine designated the STM4-120.* The configuration of the STM4-120 was based on the Ford/Philips automotive Stirling engine which was successfully demonstrated in a 4500 pound Ford Torino in 1976. This engine, designated the 4-215, was a four-cycle, double-acting engine with a fixed angle swashplate drive and produced 175 horsepower (128 kW). During the Ford program, three obstacles to mass production were identified: the complexity of the mean pressure power control, the life and reliability of the rod seals, and the complex geometry and manufacturability of the heater heads. In the conceptual design phase of the STM4-120, effort was concentrated on addressing and overcoming these obstacles.

Numerical calculation based on finite element method are carried out to calculate the temperature field in an adiabatic diesel engine piston having diameter. 127 mm and made of aluminum alloy. The engine cylinder wall have the coated externally by a thin layer of very high grade ceramic insulating material. The isothermic distribution in the piston body and the heat flow rates to the cooling media at different loads have been depicted for both cases with and without insulation coating. The paper first reviews the current state of development of ‘adiabatic’ diesel engine in Europe, U.S.A and the Japan. This review section is followed by a brief description of the common element of hostile features, then comes the experimental program on thermally insulated components for single cylinder engine in the research center of Tabriz and finally by a theoretical section dealing with the performance potential of composed engine schemes based on ‘adiabatic’ engine operation.

This paper introduces the friction sphere concepts to consider the effects of friction in the spherical joint and presents a new effective numerical solution method for the analysis of multibody systems with spherical joint under Coulomb friction. Complete equations of motion and reaction forces are derived for dynamic analysis of multibody systems by using Lagrangian formulation. The numerical solutions of the new method are illustrated by its applications to the variable displacement car air conditioning compressor, which has five pistons connected to the wobble plate by five actuating rods with spherical joints at both ends. The new method successively accomplishes the solutions of the equations of motion and reaction forces of the compressor in less computing time than the conventional method.

An experimental study on emission formation processes, such as these of nitric oxide, particulate and total hydrocarbon in a small direct injection (D.I.) diesel engine was carried out by using a newly developed total in-cylinder sampling technique. The sampling method consisted of rapidly opening a blowdown valve attached to the bottom of the piston bowl, and quickly transferring most of the in-cylinder contents into a large sampling chamber below the piston. No modification of the intake and exhaust ports in a cylinder head was required for the installation of the blowdown apparatus. The sampling experiment gave a history of spatially-averaged emission concentrations in the cylinder. The effects of several engine variables, such as the length-to-diameter ratio of the nozzle hole, the ratio of the piston bowl diameter to the cylinder bore and the intake swirl ratio, on the emission formation processes were investigated.

An optically accessible, DI Diesel engine was used to investigate the effect of swirl on fuel-air mixing and flame evolution. Quiescent and swirling conditions were studied at three different fuel-air ratios at an engine speed of 900 RPM. For the mixing studies, performed with nitrogen to prevent combustion, a mirrored piston was used to permit double pass shadowgraph imaging within the combustion chamber. High speed shadowgraph cinematography, using an Argon ion laser, yielded insight into the temporal evolution of the fuel jet and permitted the calculation of penetration speeds and area of the fuel jet as a function of time. With swirl, the penetration rate of the fuel jets was reduced, and the area of the over which fuel was observed increased by 25 percent. Combustion phenomena were studied using backlighting so that the spray and visible light from combustion could be recorded on high speed video.

Using a seven-step quality improvement process, some of the engine build-up factors adversely influencing the severity and precision of the Sequence VI dynamometer test were examined. Insights from engineering (theory) and database (statistical) analyses enabled a 23 factorial experiment to identify oil ring tension, piston ring side clearance, and piston fit as critical parameters in a 3-oil, 9-engine, 28-test program. High ring tension was shown to emphasize the friction reducing capability of higher performing oils and the deficiency of a lower performing oil. Interactions were noted. A helpful correlation of test severity with the engine calibration indicators was shown.

The use of methanol as a fuel in transit buses is being demonstrated through the use of diesel engine retrofits and an ignition improver to methanol. This project is aimed at retrofitting the Detroit Diesel Corporation (DDC) 6V-92TAC diesel engine in a GM RTSII bus to operate on methanol. The engine is modified by installing higher compression ratio pistons, higher flowrate mechanical fuel injectors, and a different blower. The bus fuel system is also modified to accommodate the properties of methanol. New fuel lines are installed, and the diesel fuel tank is replaced with two stainless steel tanks. A high-pressure electric fuel pump and a fuel cooler are used to prevent methanol from boiling in the engine. Currently, three buses have been retrofitted. The buses operate at the Southern California Rapid Transit District (SCRTD) in Los Angeles, California.

Powder Metallurgy (P/M) renders the possibilities to tailor material properties using rapid solidification or mechanical alloying processes totally different to the options of ingot metallurgy (I/M). For demanding applications in internal combustion engines new materials have become more important because of environmental and/or performance reasons. Weight reductions to improve the performance or reduce the consumptions and consequently the amount of exhaust gases and increase of temperatures at different locations of an engine need better aluminum materials. P/M solutions are described from the point of view of material's processing and general properties. The potential for automotive pistons is discussed with several examples.

Control of turbulence during the compression stroke is suggested by both theoretical calculations and experimental results obtained with an LDV measurement in a motored engine. The authors have found experimentally that when an axial distribution of swirl intensity exists, a large-scale annular vortex is formed inside the cylinder during the compression stroke and this vortex generates and transports turbulence energy. A numerical calculation is adopted to elucidate this phenomenon. Then, an axial stratification of swirl intensity is found to generate a large-scale annular vortex during the compression stroke by an interaction between the piston motion and the axial pressure gradient. The initial swirl profile is parametrically varied to assess its effect on the turbulence parameters. Among calculated results, turbulence energy is enhanced strongest when the swirl intensity is highest at the piston top surface and lowest at the bottom surface of the cylinder head.

An experimental investigation of the effects of ceramic coatings on diesel engine performance and exhaust emissions was conducted. Tests were carried out over a range of engine speeds at full load for a standard metal piston and two pistons insulated with 0.5 mm and 1.0 mm thick ceramic coatings. The thinner (0.5 mm) ceramic coating resulted in improved performance over the baseline engine, with the gains being especially pronounced with decreasing engine speed. At 1000 rpm, the 0.5 mm ceramic coated piston produced 10% higher thermal efficiency than the metal piston. In contrast, the relatively thicker coating (1 mm), resulted in as much as 6% lower thermal efficiency compared to baseline. On the other hand, the insulated engines consistently presented an attractive picture in terms of their emissions characteristics. Due to the more complete combustion in the insulated configurations, exhaust CO levels were between 30% and 60% lower than baseline levels.

Furuhama(1)* proposed the new two ring package consist of a pressure ring and a narrow single-rail oil ring (NSOR) in 1985. Number of studies(2) have been done for the purpose of reducing the oil consumption (OC) in this ring package. However, OC reduction problem has been still remaining to solve as only one serious problem of this ring package. The reasons of a larger OC in the new ring package than the conventional three ring has been hardly understood, considering the OC control ability on second ring in three ring package will not so large since the fact that the oil film thickness is thicker than that of the oil ring. In this study, the mechanism of OC increase in new ring package was found out at last, as a result, OC of new ring package piston was improved up to the same level of conventional three ring package piston.

In recent years, demands for increased output and low fuel consumption in automobile engines have been mounting. Light weight and high performance is demanded of the main operating parts, such as pistons. In response to these demands, the crown thickness and pin boss unit thickness has been reduced by tremendous improvements in the fatigue strength, compared to strength obtained by conventional methods, by utilizing Squeeze Casting techniques. In addition, the thickness of the inside face of the pistons has been reduced by making use of a split core. Furthermore, by manufacturing a cooling gallery, the heat load has been reduced; by introduction of hollow regions, an extremely light weight and compact piston has been developed. Three new techniques are indicated here. Firstly, the technique of attaining soundness in material and excellent fatigue strength by the Squeeze Casting technique, which is superior to those attained by conventional methods.

An advanced low heat rejection engine concept has been selected based on a trade-off between thermal insulating performance and available technology. The engine concept heat rejection performance is limited by available ring-liner tribology and requires cylinder liner cooling to control the piston top ring reversal temperature. This engine concept is composed of a titanium piston, headface plate and cylinder liner insert with thermal barrier coatings. Monolithic zirconia valve seat inserts, and thermal barrier coated valves and intake-exhaust ports complete the insulation package. The tribological system is composed of chrome oxide coated cylinder, M2 steel top piston ring, M2 steel valve guides, and an advanced polyol ester class lubricant.

The next decade will show a change in all motor fuels used in public transportation. As of this writing, methanol is viewed as one of the most promising of the new “clean air fuels.” Florida Institute of Technology, in competition with 13 other Universities, designed and completed modification on a 1988 Chevrolet Corsica supplied by General Motors. These modifications included high compression ceramic coated pistons in conjunction with turbochargin. Further research included camshaft testing, ignition and fuel curve changes, and a unique 6/3 cylinder cut-out scheme during low engine load conditions. The Corsica was then entered in the 1990 Methanol Challenge.

Light-load unburned hydrocarbon emissions were studied experimentally in a spark-ignited direct-injection engine burning gasoline where the piston temperature was varied. The test engine was a single-cylinder Direct Injection Stratified-Charge (DISC) engine incorporating a combustion process similar to the Texaco Controlled Combustion System. At a single low load operating condition, the piston temperature was varied by 50 K by controlling the cooling water and oil temperature. The effect of this change on unburned hydrocarbon emissions and heat release profiles was studied. It was found that by carefully controlling the intake air temperature and pressure to maintain constant in-cylinder conditions at the time of injection, the change in piston temperature did not have a significant effect on the unburned hydrocarbon emissions from the engine.

A telemetry linkage system has been developed for piston temperature measurements in a direct-injection diesel engine. In parallel with the development of the telemetry linkage system, fast response thermocouples were installed at three piston locations - two on the bowl surface and one on the crown surface. A novel design was used to achieve electrical continuity between the piston and the connecting rod by means of a flexible steel strap pivoted on the piston skirt. The telemetry linkage system was then used to transport the electrical wires from the thermocouples to the external data acquisition system. A series of tests was run to determine the effects of location and load on piston surface temperatures. Surface temperature profiles varied substantially among the three locations, reflecting the differences in the combustion and heat flow characteristics of their surrounding regions.

The mechanical properties of an aluminum silicon alloy reinforced with ceramic fibers has been investigated as part of a much larger program to develop metal matrix composite Pistons for diesel engine applications. Tensile and fatigue tests were carried out over a range of temperatures typical of those experienced during engine operation. The influence on the properties of non-fibrous extrinsic particles, which originate from the fiber manufacturing process, are considered in detail. These data show that the tensile and fatigue characteristics are much improved over those of unreinforced materials at temperatures in the range of the maximum engine operating temperature. The presence of extrinsic defects has little effect on the tensile properties but causes a reduction in the fatigue life, which may be greater than one order of magnitude at a given load.

Semi-active suspension is one of many effective devices to improve vehicle stability, controllability and riding comfort. A practical means to realize semi-active suspension is to vary the damping force of the shock absorber. In this paper, we propose a new type of shock absorber using a piezoelectric sensor and actuator. The piezoelectric sensor and actuator are built into the piston rod which is a part of the shock absorber. The piezoelectric element provides a fast response and a high actuation force. We used the piezoelectric element in shock absorbers in order to take advantage of these two features. High level compatibility between stability, controllability and riding comfort is expected, since damping force changes very quickly using this new type of shock absorber. In this paper, several topics are discussed. First, a general description of the damping force control system with simple configuration is explained.

A new practical concept for piston compounding engines is described. The calculated thermal efficiency of a fully insulated, piston compounded, overcharged diesel engine can exceed 60%. The design considerations for construction of such an engine from controlled expansion superalloys is also described.