Abstract: Stable homogeneous charge compression ignition (HCCI) combustion on a commercial gasoline engine was realized through the optimized kinetic process technology. Statistical analysis method was adopted to analyze the spark ignition (SI)HCCI switching process at different load point. And then the same method was used to analyze cycletocycle and cylindertocylinder variation characteristics for these two modes under the same load. Finally, the restrict conditions and solutions for HCCI load expansion were discussed. The results show that, for the switching process at low engine speed 1 400 r/min, properly increasing load can make switching process more smoothly; at the same load, each combustion parameter variation in HCCI mode is remarkably less than that of parameters in SI mode, the cycletocycle variation of indicated mean effective pressure is less than 2.5% and the cylindertocylinder variation is less than 3.0%. The statistics also show that each cylindertocylinder combustion parameter has regular difference; this trouble can be solved through the rearrangement of intake manifold and coolant circulation. Meanwhile, in order to expand the HCCI load, decreasing the inlet air temperature and exhaust gas recirculation strategies should be used to retard the beginning of combustion and slow the rate of heat release.

Key words: gasoline engine, homogeneous charge compression ignition (HCCI), cyclic variation, mode switch, indicated mean effective pressure (IMEP)