甲基肼/四氧化二氮反应化学动力学模型构建及分析

Construction and Analysis of a Chemical Kinetic Model for Monomethylhydrazine/Nitrogen Tetroxide Reactions

甲基肼(MMH)和四氧化二氮(NTO)是常用的液体火箭发动机推进剂,但目前对其反应机理的研究还十分有限.本文首先构建了一个包含23种组分和20个基元反应的MMH/NTO反应动力学模型;对MMH/NTO自燃着火过程进行的验证计算表明,该机理能够合理地描述MMH/NTO的自燃温升过程,准确预测反应物系统的着火延迟时间及平衡温度,并能合理地反映MMH/NTO反应物系统着火延迟时间对反应初始压力以及氧燃比的依赖关系;通过灵敏度分析方法指出了影响MMH/NTO着火过程的关键反应.模拟分析了在不同压力和氧燃比条件下MMH/NTO系统的自燃温升过程,结果表明,随着压力的升高,系统着火延迟时间变短,平衡温度升高;在一定范围内增大氧燃比,着火延迟时间变长,平衡温度先升高后减小.

A reduced chemical kinetic model including 20 reactions and 23 species devoted to the gas-phase reaction of monomethylhydrazine/nitrogen tetroxide （MMH/NTO） mixtures is presented in this study. It was constructed strictly through the extension of the chemical kinetic and thermochemical parameters used to describe major reactions between MMH and NTO. This mechanism is capable of representing the low temperature auto-ignition and high-temperature combustion of a MMH/NTO bipropellant system. The constructed model was verified using computational and theoretical data from the literature. The good agreement shows that the reduced mechanism can give an accurate prediction of the ignition delay time and the equilibrium temperature of MMH/NTO mixtures over a broad range of initial temperatures and pressures. The mechanism can also reasonably describe the dependence of the MMH/NTO mixture ignition delay time on the initial pressure and the oxygen/fuel ratio. Additionally, important reactions for ignition have been identified through a sensitivity analysis. The influence of different initial pressures and NTO/MMH ratios on the auto-ignition and combustion of MMH/NTO mixtures was investigated. Results show that with an increase in initial pressure, the MMH/NTO ignition delay time decreases while the equilibrium temperature increases. When the NTO/MMH ratio increases within a certain range, the computational ignition delay time increases while the equilibrium temperature increases initial y and then decreases.