A modified quasi-dimensional multi-zone combustion model for direct injection diesels

A quasi-dimensional multi-zone combustion model for direct injection diesel engines has been developed and subsequently evaluated using test results from a PA6 engine. In the new model, fuel spray is divided into a number of zones, which are treated as open thermodynamic systems exchanging mass and energy with the surrounding air. This paper pays particular attention to the fuel evaporation process whereby a detailed evaporation model is developed to predict the fuel evaporation rate. The effects of both collision and aggregation of fuel droplets have been included in the fuel evaporation mechanism. The theory of grouping of fuel droplets and interference areas among droplets is used to gain more accurate fuel evaporating and burning rates for the engine. The results from the simulation studies have shown good agreement with the measurements from the experimental engine. In-cylinder pressure and temperature are given particular attention in this study. The developments reported in this paper lead to a better understanding of the underlying physical mechanisms and the effects of various parameters on engine combustion. This work also presents a methodology for the development of a reliable but simple multi-zone model. Conclusions have been reached that the developed model is able to predict the rate of heat release and engine performance with a high accuracy.