Investigation Into In-cylinder Gas Movement And Combustion Of DME Engine

To meet increasingly stringent emission regulations and solve the world's energy problem,automobile engines need to be cleaner and more efficient.DME has similar physical properties as diesel,but produces very few particles and less NO_X emission.DME is a very attractive alternative fuel for compression ignition engine which receive increasing attention in recent years.This thesis includes simulation of electronically controlled DME engine in-cylinder gas flow and combustion;analyzes combustion and emission at speeds,inlet pressures,loads and EGR rates.The results show that as speed increases,in-cylinder flow velocity increases,fuel and air mix better.Inlet pressure affects spray penetration and in-cylinder flow during spraying.As load increases,NO_X significantly increases,CO decreases and then increases.As EGR rate increases,NO_X decreases and CO increases.Experimental studies on heat release and emissions at speeds,loads and EGR rates show that as speed increases,maximum pressure,heat release and NO_X decrease.As load increases,cylinder pressure,exhaust temperature and NO_X increase.As EGR rate increases,cylinder pressure,in-cylinder temperature decrease while exhaust temperature increases and max heat release rate increases;NO_X decreases but HC increases.To compromise between HC and NO_X emissions,there exists an optimum EGR rate.