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In this study, three dimensional heat conduction analyses of piston in gasoline engine were performed by boundary element method. In order to obtain the boundary conditions for the gas temperature in cylinder and heat transfer coefficients on piston wall, diagnostic engine performance simulations were performed. In order to verify the appropriateness of boundary element method in the 3 dimensional heat conduction analysis of piston temperatures, surface temperatures of piston wall were measured. In this experiment L-link mechanism is used for leading the thermocouples from the piston to the outside of engine. Since most of the analytical results with various operating conditions agree reasonalby well with the experimental ones, appropriateness of boundary element method in the 3-dimensional heat conduction analysis was in some degree verified.

Heat Transfer experiments were carried out during the engine performance tests of a 4-cylinder 4-stroke turbo-charged gasoline engine. Diagonostic engine simulations to analyse the combustion characteristics in cylinder and heat transfer characteristics of cylinder wall were carried out employing the measured pressure variation in cylinder and cooling water temperature and flowrate. In these simulation, combustion processes were simulated by the Annand's two zone flame propagation model(1). From these simulation we can obtain not only the heat transfer coefficient of cylinder wall but also the flame speed, turbulent burning velocity and flame factor. The results are investigated with respect to engine speed and equivalence ratio. And combustion characteristics of turbocharged engine were compared with those of naturally aspirated engine.