Research on combustion characteristics of quasi-homogeneous charge compression ignition combustion system

The quasi-homogeneous charge compression ignition (QHCCI) combustion system is an effective way to burn lean pre-mixture in diesel engine. A quasi-dimensional mathematical model is established to study the characteristics of QHCCI system in combustion. Based on the mathematical model together with the test results, the influences of pilot quantity and pilot injection timing on combustion, and the characteristic of hard combustion are investigated. The simulation results obtained by using the presented mathematical model are in good agreement with the test results. The results show that the heat release rate curve of the QHCCI system may usually have two peaks. It is also found that excessive pilot diesel and too early injection timing of pilot diesel, which result in large amount of heat release in a very short period near the top dead center, may be the main reasons for the knocking.