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Lubrication of advanced high temperature engines has been one of the greatest obstacles in the development of the Adiabatic engine. Liquid lubricants which gave lubricating properties as well as heat removal function can no longer carry out this duty when piston ring top ring reversal temperatures approach 540°C. Solid lubricants offer some hope. Since solid lubricants cannot perform the heat removal function, its coefficient of friction must be very low, at least <0.10, in order to prevent heat build up and subsequent destruction to the piston rings and cylinder liners. The Hybrid Piston concept developed in the U.S. Army Advanced Tribology program offers some hope, since the top solid lubricant ring slides over the bottom hydrodynamic lubricant film section during each stroke. This paper presents the progress made with the solid lubricant top ring in the Hybrid Piston. Four materials have shown promise in the laboratory to fullfil its mission.

A long-distance microscope with pulse-laser as optical shutter up to 25kHz was used to magnify the diesel spray at the nozzle hole vicinity onto 35-mm photographic film through a still or a high-speed drum camera. The injectors examined are high-pressure valve-covered-orifice (VCO) nozzles, from unit injector and common rail injection systems. For comparison, a mini-sac injector from a hydraulic unit injector is also investigated. A phase-Doppler particle analyzer (PDPA) system with an external digital clock was also used to measure the droplet size, velocity and time of arrival relative to the start of the injection event. The visualization results provide very interesting and dynamic information on spray structure, showing spray angle variations, primary breakup processes, and spray asymmetry not observed using conventional macroscopic visualization techniques.

The successful design of engine components for high temperature applications is very dependent on the use of advanced finite element methods. Without the use of thermal and structural modeling techniques it is virtually impossible to establish the reliable design specifications to meet the application requirements. Advanced modeling and design of two key engine components, the cylinder head thermal insulating headface plate and the capped air gap insulated piston, are presented. Prior engine test experience contributes to further understanding of the important factors in recognizing successful design solutions. It has been found that the modeling results are only as good as the modeling assumptions and that all modeling boundary conditions and constraints must be reviewed carefully.