NH_(3)/O_(2)/H_(2)O混合物着火特性的动力学分析

Kinetic Analysis of the Ignition Characteristics of NH_(3)/O_(2)/H_(2)O Mixtures

为了探讨NH_(3)在O_(2)/H_(2)O氛围下的着火行为与NOx分布,利用Chemkin-Pro动力学软件对NH_(3)在不同氧气体积分数(21%~30%)和掺水率(0~30%)下的着火延迟时间进行了计算。结果表明,随着氧气体积分数增加,着火过程的H、O和OH活性自由基浓度和NOx生成量单调递增,NH_(3)的着火延迟时间单调递减。H_(2)O对NH_(3)的着火呈现低温抑制和高温促进的作用,同时在全温度范围降低活性自由基和NOx的生成。随着温度升高,NH_(2)基的加氧反应(NH_(2)+O_(2)=H_(2)NO+O)对着火的促进作用超过H_(2)NO(H_(2)NO+O_(2)=HNO+HO_(2))成为最显著的。链终止反应NH_(2)+NO=N2+H_(2)O、NH_(2)+NO_(2)=N2O+H_(2)O抑制反应活性,不利于OH池的建立。第三体基元反应NO+H(M)=HNO(+M)和NO+OH(+M)=HONO(M)主要贡献NO的形成。NO的消耗主要通过反应NO+HO_(2)=NO_(2)+OH、NH_(2)+NO=NNH+OH和NH+NO=N2O+H。

In order to investigate the ignition behavior and NOx distribution of NH_(3)in an O_(2)/H_(2)O atmosphere,the ignition delay time of NH_(3)was calculated at different oxygen volume fractions(21%-30%)and water contents(0-30%)using Chemkin-Pro kinetic software.The results showed that with the increase of oxygen volume fraction,the concentration of H,O and OH reactive radicals and NOx generation of the ignition process monotonically increased,and the ignition delay time of NH_(3)monotonically decreased.H_(2)O showed low-temperature inhibition and high-temperature facilitation of the ignition of NH_(3),while decreasing the generation of reactive radicals and NOx.With increasing temperature,the promotion of ignition by the oxygenation reaction of NH_(2)radicals(NH_(2)+O_(2)=H_(2)NO+O)over H_(2)NO(H_(2)NO+O_(2)=HNO+HO_(2))becomes the most significant.The chain termination reactions NH_(2)+NO=N2+H_(2)O and NH_(2)+NO_(2)=N2O+H_(2)O inhibit the reactivity and are detrimental to the establishment of the OH pool.The third-body motif reactions NO+H(M)=HNO(+M)and NO+OH(+M)=HONO(M)contribute mainly to the formation of NO.NO is consumed mainly through the reactions NO+HO_(2)=NO_(2)+OH,NH_(2)+NO=NNH+OH,and NH+NO=N2O+H.The reactions NH_(2)+NO=N2+H_(2)O and NH+NO=N2O+H are the most significant.