A Study of a Gasoline-fueled Compression Ignition Engine ∼ Expansion of HCCI Operation Range Using SI Combustion as a Trigger of Compression Ignition ∼

A new combustion concept, called spark-ignited compression ignition (SI-CI) combustion, is proposed for expanding the operation range of homogeneous charge compression ignition (HCCI) combustion. The authors previously showed that raising the mixture temperature before compression so as to induce auto-ignition near top dead center reduces the quantity of trapped gas, resulting in a lower maximum indicated mean effective pressure (IMEP). With the newly proposed combustion concept, auto-ignition of a homogeneous lean mixture is accomplished by the additional compression resulting from SI combustion of a small quantity of stratified mixture instead of raising the intake air temperature.

This SI-CI combustion process reduced the necessary increase in intake air temperature compared with conventional HCCI combustion. A higher maximum IMEP was achieved with SI-CI combustion than with conventional HCCI combustion, as was planned. However, nitrogen oxide (NOx) emissions increased due to the SI portion of the combustion process. Reducing NOx emissions through the application of exhaust gas recirculation is an issue of SI-CI combustion for future research.