气氢/气氧催化着火机理研究

Catalytic Ignition Mechanism of Gaseous Hydrogen/Gaseous Oxygen

通过实验和数值模拟对气氢/气氧在蜂窝结构陶瓷载铂催化剂中的催化着火特性开展研究,分析了反应动力学和分子扩散对催化着火特性的影响.结果表明,气流速度和混合物组分共同决定催化反应的控制机理,气流速度或当量比较大时,催化着火由反应动力学控制;气流速度和当量比较小时,催化着火由分子扩散控制;气流速度和当量比适中时,存在一个过渡区,过渡区内催化着火由分子扩散和反应动力学共同控制,反应体系既可以达到较高温度又不会发生回火.敏感性分析表明,催化反应中关键的基元反应为氢和氧的吸附反应以及氢的脱附反应,气相反应中关键的基元反应为含有自由基O、H和OH的链式反应以及HO2的生成反应.

Catalytic ignition mechanism of gaseous hydrogen/gaseous oxygen in a cylindrically shaped honeycomb ceramic coated with platinum was investigated experimentally and numerically.The effects of reaction kinet-ics and molecular diffusion on catalytic ignition characteristics were analyzed.Results show that the control mechanism of the catalytic reaction is determined jointly by the flow velocity and the composition of the mixture.When the flow velocity or equivalent ratio is relatively large,the catalytic ignition is controlled by reaction kinetics.When the flow velocity and equivalent ratio are small,the catalytic ignition is controlled by molecular diffusion.When the flow velocity and equivalent ratio are moderate,there exists a transition zone in which the catalytic ignition is controlled by both molecular diffusion and reaction kinetics,and the reaction system can reach high temperatures without tempering.Sensitivity analysis shows that the key elementary reactions in catalytic reactions are the adsorption reactions of hydrogen and oxygen and the desorption reactions of hydrogen,and that the key elementary reactions in gaseous reactions are the chain reactions containing O,H,and OH radicals and the formation reactions of HO2.