LES Simulation of Direct Injection SI-Engine In-Cylinder Flow

The present paper deals with the application of the LES approach to in-cylinder flow modeling. The main target is to study cycle-to-cycle variability (CCV) using 3D-CFD simulation. The engine model is based on a spark-ignited single-cylinder research engine. The results presented in this paper cover the motored regime aiming at analysis of the cycle-resolved local flow properties at the spark plug close to firing top dead center. The results presented in this paper suggest that the LES approach adopted in the present study is working well and that it predicts CCV and that the qualitative trends are in-line with established knowledge of internal combustion engine (ICE) in-cylinder flow. The results are evaluated from a statistical point of view based on calculations of many consecutive cycles (at least 10). Special attention is paid to local properties at the spark plug as these local conditions are supposed to strongly influence early phase of combustion process (early flame kernel development). Important conclusion is that the cold-flow local properties at the spark-plug (motored regime) is the source of significant CCV, which is supposed to be amplified when combustion is considered.