Computational Study of Homogeneous and Stratified Combustion in a Compressed Natural Gas Direct Injection Engine

In recent years, the type of combustion occurred within engine cylinder plays an important role determining the performance and emissions. In the present study, the computational investigation was performed in order to compare characteristics of homogeneous and stratified combustion in a compressed natural gas direct injection engine. The numerical simulation was performed for single cylinder of the 1.6-liter engine running at wide open throttle at 2000 rpm and 4000 rpm, accounting for medium and high loads for light-duty vehicle. The results of Computational Fluid Dynamic (CFD) shows that calculated data of homogeneous combustion are in good agreement with the experiment data obtained from previous work single-cylinder engine. Parametric studies are then conducted to address effect of some parameters on engine performance. Important parameters analysed include cylinder pressure, engine power, mass fraction burned, CO, CO, and NO emissions. It is found that homogeneous combustion has an advantage in producing more performance compared to the stratified condition With drawback on higher emissions level, while stratified combustion has ability in reducing the exhaust emissions with less performance.