C/C复合材料喷管烧蚀壁面退移流固耦合仿真研究

Fluid-Solid Coupling Simulation of Ablation Wall Recession of C/C Composite Nozzle

关键词:  C/C复合材料  烧蚀  数值模拟  流固耦合  固体火箭发动机

Key words:  C/C composites  Ablation  Numerical simulation  Fluid-solid coupling  Solid rocket motor

摘要:

为了保障固体火箭发动机C/C喷管的可靠性，建立了一套正确反映发动机喷管烧蚀过程的流固耦合计算模型，以实现对喷管烧蚀率的高精度预估。依据热化学烧蚀理论以及喷管内燃气与喷管结构体界面的质量平衡和能量平衡关系，建立并验证了考虑壁面退移的C/C喷管流固耦合方法，实现了燃气流动、异相化学反应、结构体传热三者间的耦合。通过实验发动机喷管的烧蚀计算，论证了模型的正确性，并分析了不同金属铝含量对烧蚀率的影响，计算所得的烧蚀率与实验值最大相对误差为4.3%，与不考虑壁面退移的耦合算法计算结果对比，计算精度最高可提升46%。计算结果表明：C/C喷管在喉部附近烧蚀最为严重；推进剂中Al含量的增加导致燃气中氧化组分浓度降低，进而减少了烧蚀速率，这些结论与C/C喷管烧蚀相关研究结果一致。

Abstract:

In order to ensure the reliability of solid rocket motor C/C composites nozzle， a fluid structure coupling calculation model was established to accurately reflect the ablation process of solid rocket motor nozzle， so as to achieve high precision prediction of nozzle ablation rate. Based on the thermochemical ablation theory and the mass balance and energy balance relationship between the gas and the nozzle structure， a fluid structure coupling method for C/C composites nozzle considering wall retrogression is established and verified. The coupling among gas flow， heterogeneous chemical reaction and structure heat transfer is realized. The correctness of the model is verified by the calculation of nozzle ablation and the effects of aluminum content on the ablation rate are analyzed. The maximum relative error between the ablation rate of numerical simulation and the experimental value is 4.3%. Compared with the results of the coupling algorithm without considering the wall retrogression， the calculation accuracy can increase by 46%. The calculation results show that the ablation of C/C nozzle is the most serious near the throat. The increase of Al content in the propellant leads to the decrease of the concentration of oxidation components in the gas， thus reducing the ablation rate. These conclusions are consistent with the relevant research results of C/C nozzle ablation.