Study of the Effect andMechanism of the Injection Timing of a Gasoline Direct Injection Engine on Knocking and the Indicated Thermal Efficiency

Abstract

Development of knocking mitigation technology is required to improve the thermal efficiency of gasoline engines. The purpose of this study was to analyze the effect of injection timing of a direct-injection gasoline engine on knocking and thermal efficiency and its mechanism, and to contribute to injector development and reduction of control adaptation man-hours. For the knocking mechanism, the contribution of combustion speed, in-cylinder gas temperature, and air-fuel-ratio distribution to mass fraction burned 50% crank angle were considered. In the indicated thermal efficiency, in addition to the contribution of mass burned fraction 50% crank angle, the contribution of unburned fuel loss and heat loss to the total heat release were considered.