The Effect of Operating Parameters on Soot Emissions in GDI Engines

Due to the upcoming regulations for particulate matter (PM) emissions from GDI engines, a computational fluid dynamic (CFD) modeling study to predict soot emissions (both mass and solid particle number) from gasoline direct injection (GDI) engines was undertaken to provide insights on how and why soot emissions are formed from GDI engines. In this way, better methods may be developed to control or reduce PM emissions from GDI engines. In this paper, the influence of engine operating parameters was examined for a side-mounted fuel injector configuration in a direct-injection spark-ignition (DISI) engine. The present models are able to reasonably predict the influences of the variables of interest compared to available experimental data or literature. For a late injection strategy, effects of the fuel composition, and spray cone angle were investigated with a single-hole injector. For an early injection strategy, the effects of multi-component fuel surrogates for gasoline, SOI timings and wall temperatures were studied with a six-hole injector. The investigations confirmed the necessity to consider the multi-component fuel composition and also demonstrate how and why wall films significantly contribute to soot emissions from DISI engines.