Effects of injection timing on fuel-air interaction in a direct injection gasoline engine

Effects of injection timing on the process of mixture preparation in a direct injection gasoline engine are investigated by employing full-scale multidimensional numerical simulations. The flow characteristics are predicted for both early and late injection conditions. The numerical results show that the gas temperature inside the cylinder of both early and late injection schemes is relatively lower than that without spray injection. The early injection scheme generally degenerates the gas flow motion, while the late injection scheme promotes the tumble motion and enhances the turbulence intensity. Wall wetting phenomena are shown unavoidable in all of the investigated cases. It is, however, more severe for the cases of late injection scheme.