氧浓度对微通道内甲烷均相/非均相耦合反应特性的影响

Effect of oxygen concentration on homogeneous/heterogeneous coupled reaction characteristics of methane in microchannel

基于详细的甲烷均相与非均相反应机理,对平板微通道内甲烷催化燃烧反应过程模拟,探究入口氧浓度变化对耦合反应特性的影响与调控机制。结果表明,氧浓度升高导致甲烷均相与非均相反应放热位置向入口侧移动,缩短均相着火距离,拓宽稳燃范围。固定入口甲烷浓度,氧浓度升高导致化学当量比降低,同时也改变了均相/非均相反应对反应物O_(2)的竞争机制;氧浓度与化学当量比共同作用改变了气相自由基的吸附与脱附行为。增加O_(2)浓度促进CH_(4)和H自由基的均相反应消耗同时抑制CH_(4)和H的非均相反应速率。随着O_(2)浓度的升高,O_(2)以及中间产物CO和H_(2)参与非均相反应速率先升高后降低。

Based on the detailed homogeneous and heterogeneous reaction mechanisms of methane,the catalytic combustion process of methane in a planar microchannel was simulated,and the effect of inlet oxygen concentration on the coupled reaction characteristics and its regulation mechanism were analyzed.The results show that the increase of oxygen concentration causes the exothermic position of the homogeneous and heterogeneous reactions of methane to move to the inlet side,shortening the homogeneous ignition distance and broadening the stable combustion range.At a fixed methane concentration at the inlet,increasing O_(2)concentration lowers the equivalence ratio of mixture and changes the competition mechanism between homogeneous and heterogeneous reactions for reactant O_(2);the combined effect of O_(2)concentration and equivalence ratio changes the adsorption and desorption behavior of gas radicals.The increase of O_(2)concentration promotes the homogeneous reaction consumption of CH_(4)and H radicals and also inhibits the heterogeneous reaction rate of CH_(4)and H on the catalytic surface.With the increase of O_(2)concentration,the rates of O_(2),and intermediate gas phase products CO and H_(2)participating in the heterogeneous reaction first increase and then decrease.