Modeling of Spark Ignition and Aftertreatment Systems for SI Combustion Engines

点击翻译按钮获取中文摘要

Developing engines with better fuel economy has become the main focus for the automotive industry to counter global warming and meet government regulations. Lean/diluted spark ignition engines have been proven to improve fuel economy and reduce pollutant emissions, but the unfavorable air/fuel stoichiometry results in more prominent cycle-to-cycle variation which limits the extension of lean-burn and EGR-diluted high efficiency operations. A critical part to optimize the lean/diluted gasoline engines is to improve the spark ignition and flame kernel development processes, especially for the engines that utilize strong cylinder flow to accelerate the combustion for better efficiency. Spark initiated flame propagation involves complex phenomena such as plasma channel stretching as well as multiple restrikes in a strong cross flow field. Energy transfer from the spark plasma to the combustible gas is a key factor to enable stable flame kernel formation thereby reducing the cycle-to-cycle variation of high efficiency diluted gasoline engines. Currently, there is still a lack of accuracy in combustion modeling to predict the spark plasma channel because of the complex phenomenon of spark stretching and restrike under strong turbulent flow. As for the lean/diluted operation of gasoline engines, the nitrogen oxides aftertreatment is challenging due to the lower exhaust temperature and the oxygen abundance in the exhaust stream. Thus, the low temperature light-off characteristics and oxygen storage capability of the three-way-catalyst (TWC) are of critical importance in TWC modeling for lean/diluted SI engines for industrial needs. The proposed research will focus on: 1) building an empirical spark ignition model which can better predict the spark stretching and the restrike phenomenon; 2) quantitatively determining the energy distribution of the spark channel and the spark-to-gas energy transfer; 3) investigating the low temperature light-off of TWC for lean/diluted SI engines. The proposed research will utilize the established expertise and advantages in measurement and control resources at the Clean Combustion Engine Laboratory (CCEL), directed by Dr. Zheng with supports from FCA.