An Investigation of Effects of Fuel Stratification and Cooled EGR on DME HCCI Engine's Operating Ranges by Numerical Analysis

ABSTRACT Homogeneous charge compression ignition (HCCI) engines have the potential to provide both diesel-like efficiency and very low emissions of nitrogen oxide (NOx) and particulate matter(PM). However, several technical issues still must be resolved before HCCI can see application. Among these, steep pressure-rise rate which leads to narrow operating range of HCCI engine continues to be a major issue. This work investigates the combination of two methods to mitigate the excessive pressure-rise rates at high power output, namely fuel stratification and Cooled exhaust-gas recirculation (Cooled EGR), after identifying the each effects to pressure-rise rate. When applying the fuel stratification to simulation, total fuelling width of 0.15 at BDC is set as a equivalent ratio difference based on the previous research. In order to simulate the effects of cooled EGR, CO 2 mole fraction in pre-mixture is changed ranging from 0 to 30%. DME which has a characteristic of two-stage ignition is used as a fuel.KEY WORDS : HCCI(예혼합자기착화), Fuel stratification(농도성층화), EGR(배기가스환원장치). Pressure-rise rate(압력상승률), DME(디메틸에테르)