Numerical Study on Emission Characteristics of High-Pressure Dimethyl Ether (DME) under Different Engine Ambient Conditions

Particular matter (PM) has been greatly concerned over the recent decades due to the constantly increasing restriction on its effect on environmental aspect. Oxygenated fuel such as dimethyl ether (DME) has been known to have beneficial impact on diesel engine emissions in terms of zero soot formation. In current study, under several ambient conditions including surrounding gas temperature and oxygen percentages, soot and emission formation of DME spray is investigated to provide a comparison with other diesel surrogate (n-heptane) and JP-8 surrogate fuels. One important work is to develop a number of chemical kinetic mechanisms with soot chemistry including the growth of polycyclic aromatic hydrocarbon (PAH) and nitro oxides (NO_x) formation. Using the developing detailed mechanisms, several numerical approaches were introduced to provide an integrated picture of emission formations. First, the Two-Stage Lagrangian (TSL) capable of implementing mixing effect of air/fuel mixture was used with analytical/experimental input of flame lift-off lengths. Secondly, the CFD simulation was performed to provide the information of the spray such as temperature, user-defined specie concentrations, and flame structure. From this study, DME have the lowest soot and NO_x comparing to n-heptane and JP-8 surrogate fuels. The effects of injection pressure and oxygen level were confirmed to be critical in the formation of soot and NO_x under engine conditions.