A numerical study of intake valve jet flapping in a GDI engine

This paper presents findings from a numerical study of intake valve jet flapping within a gasoline direct injection engine, using a large eddy simulation turbulence modelling approach. The experimental test case and computational setup, including choice of sub-grid scale turbulence model, are presented and discussed. An example cycle where intake valve jet flapping is seen to be prominent is discussed in detail. It was found to be initiated as a consequence of turbulent fluctuations in the intake valve curtains. Cycle-by-cycle variations in valve curtain flux and subsequent jet flapping events are investigated and significant cyclic variability is found. Finally, it was observed that due to the highly transient nature of this flow phenomenon, the typical ensemble-averaging procedure used in LES simulations causes most information related to this process to be lost.