An integrated model for negative valve overlap early injection HCCI combustion

Using exhaust top dead center injection (ETCI) mode to realize homogeneous charge compression ignition (HCCI) combustion would cause fuel wall wetting and combustion efficiency reduction, and there is no effective one-dimension simulation model to calculate and analyze the fuel wall wetting and evaporation process. In the research, a new type of integrated model is developed for the new application, HCCI combustion simulation based on ETCI mode. The model includes the following sub-models: fuel injection model, impingement model, film evaporation model, and combustion model. The improved Hiroyasu model and the Bai's model are coupled with homogenous combustion model and film evaporation model to calculate impingement fuel evaporation. The developed model is validated by experiment in a single cylinder diesel engine with ETCI combustion mode. The simulation and experimental results show that, film evaporation is mainly related to cylinder gas temperature and wall temperature, and there is an evident two stage heating process. The cumulate heat release rate is linear with exhaust valve closing (EVC) timing and wall temperature. The burned fuel fraction increases by 6 percent as the EVC timing advances by every 10 °CA, and increases by 4 percent as the wall temperature increases by every 50 K. The cumulate heat release rate decreases with the increase of boosting pressure, and the higher the boosting pressure, the smaller the decrease degree of cumulate heat release rate is.