Designing an accurate and efficient heat protection system for the area around the high-temperature stagnation point on supersonic aircraft is still an important topic of research. In the present study, a three-dimensional high thermal conductivity carbon/carbon (C/C) composite thermal protection system embedded with L-shaped carbon fiber bundles for directional heat transfer is proposed as a high-efficiency thermal protection design. A multi-scale method, which couples the finite volume method (FVM) and lattice Boltzmann method (LBM), is developed to investigate the directional heat transfer in the proposed structure. The FVM is used to calculate the heat radiation information, which is needed to solve the energy equation with the LBM. Further, the failure temperature of the proposed thermal protection structure is defined. The effects of the porosity, carbon fiber bundle and pore diameter on the directional heat transfer of the L-shaped C/C composite thermal protection system are investigated in detail. The results show that the effective thermal conductivity of the proposed thermal protection system increases with increasing temperature and carbon fiber bundle diameter. It decreases with increasing porosity when the temperature is below 1000 °C. There exists the competitive relationship between the pore heat radiation and carbon fiber bundle thermal conductivity. An increased porosity results in a decrease in the failure temperature of the proposed thermal protection structure, while increasing the carbon fiber bundle diameter can increase the failure temperature. These findings can provide some new insights for designing a high-performance C/C composite thermal protection system.

为超音速飞机高温停滞点附近的区域设计一种准确有效的热保护系统仍然是研究的重要课题。在本研究中，提出了一种三维高导热率碳/碳（C / C）复合热保护系统，该系统内嵌L形碳纤维束以进行定向传热，是一种高效的热保护设计。开发了一种多尺度方法，将有限体积方法（FVM）和晶格玻尔兹曼方法（LBM）结合在一起，以研究所提出结构中的定向传热。FVM用于计算热辐射信息，这是使用LBM求解能量方程所需要的。此外，定义了所提出的热保护结构的故障温度。详细研究了孔隙率，碳纤维束和孔径对L形C / C复合热保护系统定向传热的影响。结果表明，所提出的热保护系统的有效导热系数随温度和碳纤维束直径的增加而增加。当温度低于1000°C时，它会随着孔隙率的增加而降低。孔隙热辐射与碳纤维束的导热系数之间存在竞争关系。孔隙率的增加导致所提出的热保护结构的失效温度降低，而碳纤维束直径的增加会升高失效温度。