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

应用零维详细化学反应动力学模型对二甲基醚均质压燃燃烧反应机理进行了数值模拟研究。结果表明二甲基醚放热反应为典型的双阶段放热反应，经历低温反应、负温度系数区域和高温反应三个过程．高温反应又分为蓝焰和热焰两个阶段。二甲基醚自燃着火由过氧化氢(H2O2)分解所控制，甲醛(CH2O)是过氧化氢的主要来源。基于化学敏感性分析．得到了均质压燃二甲基醚反应的主要途径：首先是二甲基醚脱氢，经过两次加氧后得到甲醛基；然后生成甲酸基(HCO)；最后生成一氧化碳(CO)。在二甲基醚的氧化反应过程中，氢氧根(OH)发挥着重要的作用，它是二甲基醚脱氢反应和CO氧化过程中的主要自由基。

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

The auto-ignition and combustion mechanisms of dimethyl ether (DME) in a four-stroke HCCI engine were investigated by using a zero-dimensional thermodynamic model coupled with a detailed chemical kinetics model. The results indicated that DME indicates two-stage combustion, heat release with low temperature reaction (LTR) and high temperature reaction (HTR), and heat release with HTR can be separated into two stages: blue flame and hot flame. HCCI ignition is controlled by hydrogen peroxide (H_(2)O_(2)) decomposition. Formaldehyde (CH_(2)O) is the main source of H_(2)O_(2) and CH_(2)O is formed by reaction 332. Based on the sensitivity analysis of chemical reactions, the major paths of the DME reaction occurring in the engine cylinder are clarified. The major paths of the DME reaction is abstract H from DME, followed by first addition O_(2 )and second addition O_(2), then oxidation to formaldehyde (CH_(2)O), the formyl radical (HCO), and finally CO. OH plays a very important role in DME oxidation and it is the essential radical in the H-atom abstraction from DME and CO oxidation. CO oxidation occurs at hot flame by the reaction: CO+OH=CO_(2)+H.