Technical Paper
Expansion of HCCI Operating Region by the Combination of Direct Fuel Injection, Negative Valve Overlap and Internal Fuel Reformation
2003-03-03
2003-01-0749
A gasoline-fueled homogeneous charge compression ignition (HCCI) engine with both direct fuel injection and negative valve overlap for exhaust gas retention was examined. The fuel was injected directly into the residual in-cylinder gas during the negative valve overlap interval for the purpose of reforming it by using the high temperature resulting from exhaust gas recompression. With this injection strategy, the HCCI combustion region was expanded dramatically without any increase in NOx emissions which were seen in the case of compression stroke injection. Injection timing during the negative valve overlap was found to be an important parameter that affects the HCCI region width. The injection timing also had the most suitable value in each engine load for the best fuel consumption. From this result, A new injection strategy in which only a portion of the fuel was injected during the negative valve overlap interval, while the rest of fuel was injected in intake stroke, was proposed.