固体火箭发动机3D C/C材料喉衬热结构模拟与烧蚀行为

Thermo-structural Simulation and Ablation Behavior of 3D C/C Composites Throat in Solid Rocket Motor

摘要:

以高氯酸铵/端羟基聚丁二烯/Al三组元为推进剂，在压强6.5 MPa、工作时间20、60、95 s的烧蚀条件下，进行长时间的固体火箭发动机烧蚀，模拟计算了喷管3D C/C材料喉衬热平衡状态下的对流换热系数、温度场和应力场，结合计算结果分析了喉衬各区的烧蚀特征与机理。结果表明：喉衬收敛段温度最高，烧蚀为氧化组分（H₂O、CO₂、H₂）与表面碳发生的热化学烧蚀；喉径区换热系数最大，温度较高，内表面在应力作用下，烧蚀最为严重，为燃气热化学烧蚀、高速气流机械剥蚀及粒子冲刷的共同作用，表面呈现出微小的沟槽或裂纹，应力与氧化使喉衬在低于材料极限应力下发生分解破坏；出口段应力降低，温度明显下降，烧蚀率显著降低。喉衬烧蚀机理为温度、应力影响下燃气氧化组分与碳的热化学烧蚀、气流机械剥蚀和Al₂O₃颗粒侵蚀的联合作用。

Abstract:

The heat transfer coefficient, temperature distribution, and stress distribution of 3D carbon/carbon (C/C) composite solid rocket motor (SRM) throat at the thermal equilibrium state were calculated through the comprehensive thermo-structural simulation, and SRM used the tri-component propellant of ammonium perchlorate/hydroxyl-terminated polybutadiene/Al under the condition of 6.5 MPa for long run of 20, 60, and 95 s. The analysis of ablation behavior and mechanism of different throat regions was also conducted according to the simulation results. The results show that the temperature at throat convergent zone is the highest due to the thermochemical ablation between the oxidation components (H₂O, CO₂, H₂) and the surface carbon. The central throat zone has the maximum heat transfer coefficient with relatively high temperature. The ablation in the central throat zone is the most severe due to the stress of inner surface, including the gas thermochemical ablation, high-speed-flow mechanical denudation, and particle erosion. The central throat surface has small grooves or cracks, and the throat tends to decompose due to the stress and oxidation. The stress and temperature of throat exit zone are decreased, and the ablation rate is obviously reduced. The throat ablation mechanism is the combination effect of thermochemical ablation of oxidation components and the carbon influenced by the stress and temperature, flow mechanical denudation, and Al₂O₃ particle erosion.