Analytical Study for Heat Release Rate Prediction in Direct Injection Diesel Engine

The heat release rate patterns of direct injection diesel engine with common rail injection system were investigated and fitted by the method of approximation based on wiebe function. The approximations were divided to pilot combustion part and main combustion part, and fitted by 2 step approximations respectively. From the analytical results about heat release rates of pilot combustion part and main combustion part, ignition delays, heat release durations and total amount of heat release were quantitatively descrived as a function of engine operating conditions of engine revolution, pilot injection timing and amount, main injection timing and amount. The ignition timing was effected by the gas temperature in cylinder at injection timing and descrived as a function of injection timing, and the heat release duration was descrived as a function of ignition delay. The ignition delay and heat release duration were almost independed on the engine revolutions for the 4 valve-engine which was examined. The heat release amounts of pilot combustion were effected by pilot injection timing and that of main combustion were a function of injection amounts. The predicted results such as pressure curve of pilot and main combustion parts and dP/dθ curve by using the above relations had a good agreement to the experiments.