二甲醚HCCI燃烧高温反应动力学分析

应用单区燃烧模型对二甲醚均质压燃燃烧的化学反应动力学过程进行了数值模拟研究。通过分析在内燃机压燃燃烧边界条件下二甲醚高温氧化反应过程中的关键基元反应速度、关键中间产物以及自由基的浓度随曲轴转角的变化,得到了二甲醚燃烧氧化的高温反应途经。结果表明,二甲醚均质压燃燃烧具有明显的两阶段放热特性,即低温反应放热和高温反应放热。高温反应阶段又可分为蓝焰反应阶段和热焰反应阶段,其中蓝焰反应阶段是甲醛氧化成CO的过程,热焰反应主要是CO氧化成CO2的过程。二甲醚氧化产物之一甲酸(HOCHO)在蓝焰反应阶段分解生成CO2。

ANALYSIS OF CHEMICAL KINETICS MECHANISM AT HIGH TEMPERATURE IN HCCI COMBUSTION WITH DIMETHYL ETHER

A numerical simulation study on chemical kinetics process of homogeneous charge compression ignition (HCCI) combustion fueled with dimethyl ether (DME) was performed by using single-zone model coupled with a detailed kinetic model. The chemical kinetics process of dimethyl ether oxidation at high temperature was obtained by analyzing the reaction rates of the key elementary reactions, the key intermediate species and radicals. The results indicate that the HCCI combustion fueled with DME consists of a low temperature reaction (LTR) heat release period and a high temperature reaction (HTR) heat release period. The HTR period includes blue-flame reaction and hot flame reaction. In the blue-flame reaction stage, OH abstracts H-atom from CH2O to generate HCO, and then HCO oxidation to CO. Hot-flame reaction is dominated by the oxidation of CO to CO2. Formic acid (HOCHO), one of the intermediate productions of DME oxidation, is decomposed to CO2 during the blue-flame reaction stage.