二甲基醚/天然气双燃料均质压燃详细化学反应动力学数值模拟研究(Ⅱ)--二甲基醚/天然气反应机理研究

应用零维详细化学反应动力学模型研究了二甲基醚／天然气双燃料均质压燃燃烧反应机理。结果表明由于两种燃料相互作用，DME低温反应进行程度很小，没有第二次加氧过程，β-scission起主导作用，大部分甲醛由CH3O生成，而不是DME的低温反应；H2O2主要由DME控制，H2O2浓度升高促进了天然气的低温反应进行；另一方面，天然气低温反应放热也促进了DME的氧化反应，OH浓度升高，使CO能够全部氧化。计算结果表明，在压缩比较高的条件下，天然气浓度变化对DME稀燃极限几乎没有影响，但压缩比较低时，随着天然气浓度升高，DME稀燃极限浓度升高。

Numerical Study on the Mechanism of Dimethyl Ether and Natural Gas Dual-Fuel HCCI Combustion with a Detailed Kinetic Model (Ⅱ)-- The Reaction Kinetic of Dimethyl Ether/ Natural Gas

The auto-ignition and combustion mechanisms of dimethyl ether (DME)/natural gas in a four-stroke HCCI engine were investigated by using a zero-dimensional thermodynamic model coupled with a detailed chemical kinetics model. The results indicate that the low temperature reactions (LTR) of DME proceed slowly and the second O_2 addition process is not presented in the dual fuels' model. Most of the formaldehyde (CH_2O) is produced from methoxy (CH_3O) rather than through the LTR of DME and hydrogen peroxide (H_2O_2) is mainly controlled by DME. Increasing in H_2O_2 concentration promotes the LTR of natural gas and heat release from LTR of natural gas LTR accelerate the DME reactions, bringing high concentration of OH and causing to completely oxidize CO. The simulation results show that natural gas concentration has little effect on the DME ignition limit under the high compression ratio, however, under the low compression ratio, DME ignition limit will extend with the increase of natural gas concentration.