Effects of compression ratio on the combustion characteristics of a homogeneous charge compression ignition engine

The effects of homogeneous charge compression ignition (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 dimethyl ether (DME) HCCI engine can work stably and can realize zero nitrogen oxides (NO^sub x^) emission and smokeless combustion under the compression ratio of both 10.7 and 14. The combustion process has obvious two stage combustion characteristics at = 10.7 ( refers to compression ratio), and the combustion beginning point is decided by the compression temperature, which varies very little with the engine load; the combustion beginning point is closely related to the engine load (concentration of mixture) with the increase in the compression temperature, and it moves forward versus crank angle with the increase in the engine load at = 14; the combustion durations are shortened with the increase in the engine load under both compression ratios.[PUBLICATION ABSTRACT]