Numerical Study on the Chemical Reaction Kinetics of DME/Methanol for HCCI Combustion Process

A numerical study was carried out to investigate the chemical reaction mechanism encountered in the homogenous charge compression ignition (HCCI) process of dimethyl ether (DME) and methanol dual fuel mixture by using a zero-dimensional thermodynamic model coupled with a detailed chemical kinetic model. The results show that methanol affects the DME oxidation path, low temperature reaction (LTR) of DME is inhibited and the heat release shape of dual-fuel only shows a one-stage heat release, owning to the heat released by high temperature reaction (HTR) of DME and methanol, including blue-flame and hot-flame reactions. In dual fuel reaction, the second molecular oxygen addition of DME is restrained, and the thermal decomposition reaction of the methoxymethyl radical (CH₃OCH₂) named β -scission plays a more important role in DME oxidation. Also, HTR of DME and methanol, including blue-flame and hot-flame reactions, almost occur at the same time. Based on the detailed analysis of chemical kinetics, the major paths of the DME/methanol HCCI reaction occurring in the engine cylinder were clarified.