NO对CH_4氧化化学影响分析

Chemical effect of NO on oxidation of CH_4

采用一个新的NO-CH4相互作用的化学动力学机理模型,在实验验证的基础上,模拟了CH4在PFR(perfectly flow reactor,充分流动反应器)和HCCI(homogeneous charge compression ignition,均质充量压缩点火)内燃机内的反应过程,改变NO初始摩尔浓度和反应温度,分析了NO对CH4氧化过程的影响,研究表明:NO主要与CH4氧化过程中产生的过氧基ROO.(过氧烷基)发生反应,将其转化成RO.(氧烷基)。低浓度NO加速了CH4的氧化,随着其浓度的升高,这种加速燃料氧化的性能逐渐被抑制;低温下,NO对CH4氧化有很好的促进作用,高温下,由于过氧基ROO.浓度很低,NO几乎失去作用;NO对CH4燃料HCCI燃烧着火延迟期的影响与其浓度密切相关,低浓度下缩短着火延迟期,而高浓度下缩短着火延迟期的趋势减缓。以上结果主要基于反应R126与R150之间的竞争。

A new chemical kinetic mechanism model of NO-CH4 interaction is adopted to simulate the reaction process of CH4 in the plug flow reactor（PRF） and HCCI engine based on the experimental verification.The initial NO mole concentration and reaction temperature are changed and the effect of NO on CH4 oxidation is analyzed.The results show that： NO mainly reacts with alkylperoxy ROO·produced in CH4 oxidative reaction,and alkylperoxy ROO · is transformed into alkoxy radicals RO ·.NO accelerates the oxidation of CH4 at low concentration.With the concentration of NO rising,its performance of speeding up fuel oxidation is inhibited.At low temperature,NO promotes oxidation of CH4.But at high temperature,due to low concentration of alkylperoxy ROO ·,NO almost loses its effects.The effect of NO on ignition delay of HCCI combustion is closely related to its concentration.The ignition delay reduces when NO is at low concentration,and the trend reducing the ignition delay slows down at high concentration.These results are mainly based on competition between R126 and R150.