An innovated design for low heat rejection engines (LHRE) is proposed to overcome limitations in conventional ceramic adiabatic engine designs which are the need of high temperature lubrication systems and the use of brittle ceramics. This proposed concept utilizes available materials and allows the use of the conventional lubrication techniques. In the design an extended (top) piston and cylinder approach is adopted. A high temperature resistant alloy, Haynes alloy 230, is used for the combustion chamber components instead of ceramics. The length of the top piston and the top cylinder is equal to the engine stroke. Piston rings are located on the base piston. The piston rings thus are separated from the hot combustion regions, which alleviates the need of high temperature lubrication. The thermal insulation between the top piston and the base piston is a narrow air cap. In the dissertation, (1) a LHRE engine was built and experimental investigations were conducted; (2) a dynamic model for the piston secondary motion incorporated with the hydrodynamic lubrication was developed; (3) a finite element analysis was conducted for the piston heat transfer; (4) the crevice effects on emissions were studied. Major results from the study are: (1) The proposed low temperature lubrication design for LHREs is viable. It provides a solution to the most challenging obstacle to the LHRE development based on current techniques and materials. (2) The experimental test program shows that the clearance between the top piston and top cylinder has a negligible effect on HC and CO emissions. (3) An air layer between the top piston and the base piston has a significant effect on reducing the heat transfer to the top ring groove. A 2 mm air gap is enough to maintain the low temperature lubrication for piston rings. (4) A piston of a reciprocating engine has the secondary motion. The piston-pin offset affects the piston secondary motion most. A proper offset towards the major thrust side reduces the piston slap. The piston secondary motion model developed in this study is a good design tool for unconventional pistons of LHREs.
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