Investigation of Effects of Compression Ratio on the Combustion Characteristics of a Homogeneous Charge Compression Ignition Engine

The effects of HCCI engine compression ratio on its combustion characteristics were studied experimentally on a modified TY1100 single cylinder engine fueled with dimethyl ether.The results show that DME HCCI engine can work stably and nearly realize zero NO_x emission and smokeless combustion un- der both the compression ratio of 10.7 and 14.The combustion process has obvious two stage combustion characteristics ateof 10.7,and the combustion beginning point is decided by the compression temperature, which varies little with the engine load.With the increase of compression temperature,the combustion be- ginning point is tightly related to the engine load (concentration of mixture) and the combustion beginning point moves advance versus crank angle with the increase of engine load ateof 14.The combustion durations are shortened with the increase of engine load under both the compression ratios.