An experimental study on the combustion and emission characteristics of a stratified charge compression ignition (SCCI) engine

Stratified charge compression ignition (SCCI) combustion, which is developed to extend the homogeneous charge compression ignition operating range, has a good potential to improve fuel economy and reduce emissions. In this study, SCCI combustion and emissions characteristics were investigated in a single-cylinder gasoline engine with a direct-injection system. From the experimental results, we elucidated the effects of air-fuel ratio, intake temperature, and injection timing including early and late injection on the attainable SCCI combustion region. Injection timing during the intake process was found to be an important parameter that affects the extension of the SCCI operating region. The effects of stratified mixture formation can be utilized to extend the operating range for suitable SCCI combustion under different engine speeds and compression ratio conditions. In this study, we found that the higher intake temperature is very effective to evaporate the injected fuel, and this effect helps to enhance SCCI combustion. The intake temperature can be controlled by the compression ratio. Finally, the injection timing and stratified mixture formation played an important role in achieving stable combustion and extending the operating range.