航空煤油热氧化结焦与流动换热耦合机理研究

Flow, heat transfer and thermal oxidation coking of supercritical pressure aviation kerosene are key problems among high performance aero-engine thermal protection research in the future. Combined with previous research results, the main difficulties in this study are listed. 1) The chemical mechanism of thermal oxidation in aviation kerosene is not comprehensive and the physical process of coking migration is obscured. Moreover, it lacks of complete mechanism description and mathematical modeling about wall and liquid-space coking. 2) With the influence of thermal coking, the law of heat transfer of aviation kerosene caused by drastic variations of physical properties is still not clear and no broad consensus has been reached. In response to these two types of problems, this project will focus on exploring a simplified predictive model for the thermal oxidation coking reaction kinetics of domestic aviation kerosene RP-3. Based on the computational fluid dynamics ALE program and the dynamic grid adaptive method, a universal coking model including wall deposition and liquid-space suspension will be created. The turbulence model based on physical pulsation correlation will be adopted, coupled coking chemical reaction mechanism and physical migration process. And then the high-precision temperature, velocity and pressure field will be obtained using numerical simulation and coking thermal resistance prediction technology. Several experimental measurements on flow and heat transfer of supercritical pressure aviation kerosene will be conducted to comparing the numerical results. The key parameters and the variation rule can be summarized. Finally, mechanism of thermal oxidation coking coupling convective heat transfer of supercritical pressure aviation kerosene will be achieved.

超临界压力航空煤油流动换热及热氧化结焦问题是未来高性能航空发动机热防护研究所必须面对的难题。结合前期研究成果分析，该研究难点主要在于：1）航空煤油热氧化结焦化学机理尚不全面，且焦炭迁移的物理过程规律模糊，壁面及液体空间结焦问题缺乏完整系统的机理描述及数学建模。2）考虑结焦因素影响下，物性剧烈变化引起的航空煤油流动换热规律仍不清晰。针对以上两类问题，本项申请将聚焦于探究国产航空煤油RP-3热氧化结焦反应动力学简化预测模型，基于计算流体力学ALE算法程序及动态网格自适应方法，建立普适的结焦沉积及液体空间悬浮的物理模型；基于物性脉动关联项的湍流模型，耦合结焦化学反应机理及物理迁移过程，采用数值模拟及结焦热阻预测技术获取高精度的温度、速度及压力场；通过实验测量得到超临界压力航空煤油流动换热数据，对比数值计算结果，提炼关键参数总结变化规律，最终获得超临界压力航空煤油热氧化结焦与流动换热耦合机理。

冷却通道中的热氧化结焦问题影响整个发动机工作的安全性和稳定性，本课题基于航空发动机热防护及CCA技术中基础科学问题的研究需求，以国产航空煤油RP-3为研究对象，采用数值计算结合实验的研究手段，对超临界压力航空煤油热氧化结焦与流动换热耦合机理开展研究。.在数值计算方面，构建“流-固-热-化”多场耦合模型，探究验证了适用于RP-3的34步拟详细结焦反应动力学模型，结焦量预测结果与实验值偏差10.2%。重点讨论了典型工况下和300~500K进口温度、0.5~12.5g/s宽范围质量流量、1.1~3.8s驻留时间、3~5MPa系统压力等参数对航空煤油热氧化结焦及流动换热特性的影响。而后基于耦合机制进一步开展了结焦层耦合流动换热数值模拟研究，一方面，在光管模型基础上引入不同厚度结焦层开展计算；另一方面，探究弹簧光顺法和局部重构法相结合的动网格算法，动态模拟流固边界随壁面结焦规律移动及流/固体域变形引起流场压力场变化的非稳态过程。.在实验方面，设计搭建了航空煤油RP-3热氧化结焦实验系统，开展了超临界压力微细管内RP-3热氧化结焦特性实验，对热氧化结焦产物表观形貌进行分析，测得250~400℃结焦温度下的密度和导热系数，填补了国产航空煤油RP-3热氧化结焦导热系数实验测量的空白。