Analysis of the effect of charge inhomogeneity of fuel distribution on the ignition and combustion in HCCI Engine by chemiluminescence measurement

In HCCI Engine, inhomogeneity of fuel distribution and temperature in pre-mixture microscopically exists and has possibility to affect the ignition and combustion process. In this study, the effect of charge inhomogeneity of fuel distribution on the HCCI combustion process was investigated. Pressure profiles were measured and two dimensional chemiluminescence images were captured by using a framing camera with a 4-stroke optical access engine. DME was used as the test fuel. Changing the way of mixing air and fuel in the intake manifold, inhomogeneity of fuel distribution in the pre-mixture was varied. The result showed that luminescence started and stopped at the same instant in whole the combustion chamber on the homogeneous condition. On the other hand, on the inhomogeneous condition luminescence started with a spatial variation in the combustion chamber. However local luminescence duration was almost the same on both conditions. It is clarified that a time lag appears spatially in combustion in the chamber on the inhomogeneous condition.