Effect of boost pressure on thermal stratification in HCCI engine using the multi-zone model

The homogeneous charge compression ignition (HCCI) engine is a next-generation engine offering high efficiency and low emissions. However, the rate of pressure rise is a major limitation for a high load range. Recently, the rate of pressure rise was reduced using thermal stratification. Nevertheless, this was insufficient to produce high power. In the absence of a higher equivalent ratio, one way to improve power is to increase intake boost pressure. The rate of pressure rise is suggested to be reduced by thermal stratification, and power is increased by boost pressure at the same time. The objective of this work is to understand the characteristics of combustion, knock, and emissions for utilizing both thermal stratification and boost pressure. Calculations are performed by CHEMKIN and modified SENKIN. As a result of increasing boost pressure, a higher indicated mean effective pressure (IMEP) was attained, while the rate of pressure rise increased only slightly in HCCI with thermal stratification.