Abstract
Homogeneous charge compression ignition (HCCI) has challenges in ignition timing control, combustion rate control, and operating range extension. In this paper, HCCI combustion was studied in a two-cylinder gasoline direct injection (GDI) engine with negative valve overlap (NVO). A two-stage gasoline direct injection strategy combined with negative valve overlap was used to control mixture formation and combustion. The gasoline engine could be operated in HCCI combustion mode at a speed range of 800-2 200 r/min and load, indicated mean effective pressure (IMEP) range of 0.1-0.53 MPa. The engine fuel consumption is below 240 g/(kW^sup -1^·h^sup -1^), and the NO^sub x^ emission is below 4 × 10^sup -5^ without soot emission. The effect of different injection strategies on HCCI combustion was studied. The experimental results indicated that the coefficient of variation of the engine cycle decreased by using NVO with two-stage direct injection; the ignition timing and combustion rate could be controlled; and the operational range of HCCI combustion could be extended.[PUBLICATION ABSTRACT]