Numberical Study On HCCI Combustion Of DME/MEOH Dual Fuels

Homogeneous Charge Combustion Ignition (HCCI) is an attractive advancedcombustion process that offers the potential for substantial reductions in both NOx andPM, while providing high efficiencies. Controlling of the auto-ignition timing andreaction rate of combustion expanding of engine loads are the keys and difficulties toput HCCI engines into practical use. A new combustion technique of methanol which enables high efficiency andlow emission has been developed in this paper. DME is to be produced from methanol,the HCCI engine is fueled with DME/methanol dual fuels, and controlling ofauto-ignition timing and reaction rate of combustion expanding of HCCI combustionto a wide operable range through adjusting the proportion of two fuels. DME can bereformed from methanol in endothermic reactions by using the heat from the exhaustgases. The chemical reaction kinetics processes in a HCCI engine fueled withDimethyl Ether / Methanol were investigated by using a zero-dimensional detailedkinetic model. The HCCI operating range of DME/methanol dual fuels is computedand the result is consistent with the experiments. The effects of initial temperature,excess air ratio of dimethyl ether (DME) and methanol on oxidation methanism ofDME/methanol were investigated also. The results show that methanol affects theDME oxidation path, LTR of DME and the second O2 addition is inhabited. Therefore,the thermal decomposition reaction of the methoxymethyl radical (CH3OCH2) namedβ-scission plays a more important role in LTR of DME. Also, high temperaturereactions (HTR) of DME and methanol almost occur at the same time. A reducedmodel of dymethyl ether (DME)/methanol has been developed on the basic of detailedkinetics model through analysis of reaction paths of combustion of DME/methanoland sensitivity analysis . It consists of 35 reactions for 27 species. The developedreduced model of DME/methanol agreed well with the detailed model in ignitiontiming temperature and pressure in cylinder. The reduced model also can predict wellwith various of initial temperature and concentration. It can well predict theauto-ignition timing and peak temperature and peak pressure. This reduced model canbe used to simulate HCCI combustion of DME/methanol.