二甲基醚/甲醇双燃料均质压燃低温氧化反应机理数值模拟

Numerical Study on the Mechanism of Low Temperature Reaction of DME/Methanol HCCI Combustion

应用零维详细化学反应动力学模型,研究了二甲基醚(DME)/甲醇双燃料均质压燃低温氧化反应机理,考察了初始温度、甲醇浓度和二甲基醚浓度对低温氧化反应的影响.结果表明,甲醇改变了二甲基醚低温反应途径,二甲基醚的低温和二次加氧过程受到抑制,CH3OCH2直接裂解(βscission)起主导作用,二甲基醚与甲醇高温反应几乎同时进行.温度升高,高温脱氢反应和βscission增强;低温脱氢反应速率增大,反应时刻提前,高温脱氢反应速率先增大后减小,加氧反应速率随着DME浓度增大而增大,βscission反应速率先增大后减小;甲醇浓度增大,DME低温脱氢反应速率降低,高温脱氢反应速率先增大后降低,βscission反应速率随甲醇浓度增大而减小,加氧反应速率则随甲醇浓度增加而升高.

The chemical reaction kinetics processes in a homogenous charge compression ignition (HCCI) engine fueled with dimethyl ether/methanol were investigated by using a zero-dimensional detailed kinetic model. The effects of initial temperature, excess air ratio of dimethyl ether (DME) and methanol on low temperature reactions (LTR) of DME were also investigated. The results show that methanol affects the DME oxidation path, and LTR of DME and the second O2 addition is inhibited. Therefore, the thermal decomposition reaction of the methoxymethyl radical (CH3OCH2) named β-scission plays a more important role in LTR of DME. Also, high temperature reactions (HTR) of DME and methanol almost occur at the same time. With increased temperature, H-abstraction reaction of high temperature and β-scission will be promoted. With the increase of DME concentration, the H-abstraction reaction of low temperature and the first O2 addition reaction will be accelerated, and HTR oxidation advances. H-abstraction reaction of high temperature and β-scission will be promoted at first and then decreased. Correspondingly, with the increasing methanol concentration, H-abstraction reaction of low temperature is inhibited, and β-scission reaction rate decreases while the first O2 addition reaction will be increased. H-abstraction reaction of high temperature will be promoted at first and then decreased.