不同气氛影响甲烷燃烧特性的分子动力学模拟

A Reactive Molecular Dynamics Simulation on Mechanisms of Methane Combustion Under Different Atmospheres

甲烷存在燃烧不完全的问题,可通过与其它燃料掺混以改善燃烧性能。采用反应分子动力学方法,研究了O_(2)/H_(2)与O_(2)/O_(3)不同气氛对甲烷燃烧特性的影响。结果表明,掺混氢气或臭氧均能促进甲烷燃烧,且掺混分子数增多和初始反应温度升高,促进效果均变得明显。相比于掺混氢气,一方面,O_(3)→O_(2)+O产生更多的O自由基,O会与中间产物反应生成OH自由基,另一方面,臭氧可直接和H自由基反应生成OH,因此掺混臭氧可使燃烧系统内OH数量增多。由于OH自由基的活性很强,它可以通过R2反应快速消耗CH_(4),因此,掺混臭氧比氢气更易促进甲烷的燃烧。此外,掺混氢气或臭氧可使得甲烷燃烧路径发生变化,且活化能降低。相关结果可为揭示不同掺混燃料之间的相互作用提供支撑。

The incomplete combustion problem of methane often occurs,which can be improved by adding other fuels.In this regard,the reactive molecular dynamics method(ReaxFF-MD)is adopted to study the combustion characteristics of methane in different atmospheres.The results show that,the combustion of methane can be promoted by adding hydrogen or ozone.The increase in adding the number of molecules and initial reaction temperature both can promote the combustion of methane.Compared with adding hydrogen,on the one hand,the reaction of O_(3)→O_(2)+O induces more oxygen free radicals in the system.A large amount of the oxygen free radicals reacts with other intermediate products,which can generate OH free radicals.On the other hand,ozone molecules can react with H radicals and form the OH free radicals directly.Thus,the blending of ozone molecules can raise the amount of OH free radical in the combustion system.Due to OH free radical being very active,the methane molecules can be quickly consumed by the R2 reaction.Therefore,compared with hydrogen,the ozone can better promote the combustion of methane.In addition,the combustion pathways of methane can be changed and the activation energy can be reduced by adding hydrogen or ozone.The relevant results are conducive to investigating the interaction between different mixing fuels.