Numerical Analysis of Soot Emission from a Direct-injection Spark-ignition Gasoline Engine using a Compact-size Soot-formation Model (Second Report)

- Effect of coolant temperature and fuel injection timing on soot emissions -

Abstract

Direct-injection spark-ignition (DISI) engines have high thermal efficiency; however, they also show high soot emissions under cold-start conditions. It is also well known that the fuel injection timing (SOI) has a significant effect upon soot emissions. Therefore, it is important to reproduce effects of the coolant temperature and SOI on soot emissions in design calculations. In this study, numerical calculations of soot emissions from a DISI engine were performed by using a compact-size soot-formation model previously proposed by authors. We discussed the reproducibility of soot emissions by changing the coolant temperature and SOI. In addition, the experimentally observed tendency that soot emission slightly increase under fuel injection timings near the bottom dead center were discussed based on the calculated results.