RP-3高温氧化初始阶段反应机理的ReaxFF MD模拟

本文采用ReaxFF MD方法对一种较新的RP-3四组分替代燃料模型的高温氧化过程进行了研究。利用作者所在课题组研发的独特分析工具VARxMD，对燃烧过程中主要物种(燃料分子、O₂、C₂H₄、·CH₃)随时间和温度的演变规律及其化学反应进行了系统分析。ReaxFF MD模拟得到的燃料和氧气消耗量、乙烯和甲基自由基的生成量与相同温度和初始压力条件下CHEMKIN的计算结果处于同一量级，同时获得了详细的物质结构信息和反应列表。进一步对模拟得到的反应机理形式进行观察后发现，模拟获得的机理形式与文献中的描述一致。对燃料分子第一步反应数量的统计发现，其类型主要为攫氢反应和分子内断裂反应，且后者占主导；燃料分子第一步反应数量的统计也定性展现了不同燃烧条件下各类反应发生的可能性。对氧元素相关的反应分析发现，氧分子和C₁-C₃小分子发生的反应所占比例较大，能在一定程度上为机理简化提供有益线索。在对反应机理分析的基础上获得了RP-3四组分替代燃料体系高温氧化过程的化学反应网络。我们认为，ReaxFF MD反应分子动力学模拟、结合VARxMD对模拟结果深入分析的方法是有潜力系统认识燃料氧化反应机理的新方法，对构建燃料的燃烧反应机理库有一定的帮助。

Initial Reaction Mechanism of RP-3 High Temperature Oxidation Simulated with ReaxFF MD

The high temperature oxidative mechanism of a new four-component RP-3 surrogate fuel model was investigated using the ReaxFF MD method. The evolution of the fuel molecules, oxygen, C₂H₄, and ?CH₃, and the underlying reactions, were obtained by systematic analysis of the simulation trajectories with the aid of VARxMD, a unique tool for ReaxFF MD reaction analysis developed by the authors′ group. The simulated consumption of fuel and oxygen, as well as the amount of ethylene and methyl radicals, in RP-3 oxidation are of the same magnitude in the ReaxFF MD simulations as that predicted by CHEMKIN under the same temperature and initial pressure conditions. Based on the chemical structures of all the species and the full set of reactions obtained, the detailed mechanisms observed in the simulations broadly agree with the previous literature. The first reactions of the fuel molecules can be categorized into H-abstraction and internal scission, with the latter dominating under various temperature conditions. Observation and statistical analysis of the oxygen reactions reveal that small species of C₁-C₃ are involved in a relatively large proportion, which may allow the simplification of the reaction mechanism. A reaction network for RP-3 oxidation at high temperature is obtained through the analysis of the reaction mechanisms. This work demonstrates that the ReaxFF MD method, combined with the unique reaction analysis capability of VARxMD, provides useful insights into the mechanism of fuel combustion and should aid the construction of combustion mechanism libraries.