Large eddy simulation based analysis of the effects of cycle-to-cycle variations on air–fuel mixing in realistic DISI IC-engines

Abstract The call for environmentally compatible and economical vehicles, still satisfying demands for high performance, necessitates immense efforts to develop innovative engine concepts. Whereas direct injection gasoline engines promise considerable fuel savings, they are prone to large variations in the flow and mixing field. These fluctuations may result in combustion failures leading to a total loss of the energy stored in a full cylinder load and to the ejection of un-burnt hydrocarbons into the environment. The present work aims at investigating the impact of the phenomena of cycle-to-cycle variations on air–fuel mixing processes in a realistic IC-engine using LES. The configuration under study represents a generic four-stroke direct spray injection engine with variable charge motion system. To appraise the numerical predictions, available experimental data are first compared to LES achievements. The LES is then assessed by means of two index of quality. Finally, the impact of the cycle-to-cycle velocity fluctuations on the spray propagation and mixing processes is pointed out with emphasis on results close to the ignition point.