Modelling of a hollow-cone spray at different ambient pressures

Abstract

Prediction of the mixture formation processes inside a gasoline direct injection (DI) engine is strongly required in order to improve both the fuel consumption and exhaust gas emissions. Swirl-type injectors, widely used for gasoline DI engines, are characterized by the fact that the spray cone angle drastically changes with ambient pressure. The present study is intended to describe the effect of ambient pressure on the characteristics of a free hollow-cone spray formed by a swirl-type injector using a numerical simulation that is based on a discrete droplet model (DDM) method. In this model, the droplet deformation is calculated for determining droplet break-up and the drag force variation of droplet due to the droplet deformation is taken into account. The simulation result was compared with an experiment focusing on the effect of ambient pressure on the spray shape. It was shown that the characteristics of a spray formed by a swirl-type injector are predicted very well by introducing a selected break-up model and a drag force model with appropriate initial conditions. The drag force of droplets affected by the droplet deformation was found to be a crucial factor in determining the spray shape at various ambient pressures.