再入飞行器超高温陶瓷防热应用研究

Thermal Protection Application of Ultra High Temperature Ceramic for Reentry Vehicle

目的探索尖锥外形高超声速飞行器超高温陶瓷防热设计约束要求。方法基于计算流体力学有限体积数值求解方法研究高超声速层流状态尖锥形飞行器的气动热环境,通过不同攻角下热流及辐射平衡温度分布规律研究获得防热设计约束要求。针对典型尖锥飞行器超高温陶瓷防热设计要求开展几何尺寸、攻角范围影响研究,最后探讨超高温陶瓷高性能热导率对防热设计影响。结果尖锥飞行器高热流仅限于驻点附近很小的区域,迎风面热流随着攻角增大迅速提高。满足防热设计约束的极限飞行攻角与端头长度呈正比,端头长度增加0.1m,极限攻角增大10°。超高温陶瓷热导率对端头防热设计影响较大,随着材料热导率增大50%,驻点辐射平衡温度降低205 K,端头连接结构温度增大50 K。结论尖锥体超高温陶瓷端头防热设计的重要约束指标为端头连接结构温度限制,设计时需要合理优化飞行攻角剖面,选取热导率性能适中的材料。

Objective To explore the ultra high temperature ceramic （UHTCs） thermal protection design requirements for a sharp–edge vehicle. Methods The aerodynamic thermal environment of hypersonic velocity typical sharp edge vehicle under laminar conditions was researched through FVM based on computational fluid mechanics. The thermal protection design limits were identified through surface heat flux and radiative equilibrium temperature distribution analysis at different angles of attack. For the nose UHTCs thermal protection design of a typical sharp edge vehicle, the nose length and angle of attack effects were studied. Finally, effects of high thermal conductivity on heat protection design of UHTCs were discussed. Results The high heat flux only concentrated in a small region near the stagnation and the heat flux increased obviously with the increase of attack an-gle in the windward. Considering the thermal requirement, the maximum angle of attack was in proportion to the nose length, for example, the limited angle of attack would increase 10o when the nose length increased by 0.1m. Thermal conductivity of the UHTCs had significant influences on the temperature distribution, and the maximum tip temperature of the nose would drop by 205K while the maximum temperature of the structural material would be increased by 50K when the thermal conductivity of the UHTC was increased by 50%. Conclusion The critical limit of UHTCs sharp nose thermal protection design is the structural material temperature which is connected with the UHTCs nose. During design, the angle of attack during flight should be optimized properly and material of proper thermal conductivity should be selected.