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Spray propagation and mixture formation in an air guided direct injection gasoline engine

Abstract Numerical analysis is used to gain information on the spray propagation and mixture formation in tumble guided gasoline direct injection (DI) engines. In order to achieve reliable predictions an atomization model for high-pressure swirl injectors is described and verified by comparison to experimental data. The approach is capable of adequately predicting the most important effects, such as nozzle orifice diameter, cone angle or injection pressure on spray development. Furthermore, it is found that the pre-jet generated at the beginning of the injection strongly affects the overall spray development. The temporal development of the pre-jet is described empirically. The in-cylinder computational fluid dynamics (CFD) analysis reveals that the tumble charge motion strongly affects spray propagation and mixture formation in the stratified operation mode, as it transports the fuel vapour cloud towards the spark plug. The CFD simulation improves understanding of the interaction between the flow field, spray propagation and evaporation and enables guidance of the optimization of the flow control and of the injection parameters for tumble guided gasoline DI engines.