Three-dimensional pore-scale study of the directional heat transfer in a high thermal conductivity carbon/carbon composite protection system

High-efficiency thermal protection is becoming a critical design criterion for supersonic aircraft. Currently, there is significant research on accurately and efficiently designing heat protection systems, particularly at the high temperature stagnation point region of supersonic aircraft. In this work, a three-dimensional high thermal conductivity carbon/carbon composite thermal protection system with a directional heat transfer function is proposed to realize a high-efficiency thermal protection design in the stagnation point region. A comprehensive method that combines the lattice Boltzmann method (LBM) and finite volume method (FVM) was designed to investigate the heat transfer process in the proposed structure at the pore scale. The FVM was applied to calculate the heat radiative information, which was required to solve the energy equation with the LBM. A failure temperature is defined to quantitatively describe how well the heat transfer occurs in the designed direction in the proposed structure. The effects of the temperature of the stagnation point, thermal conductivity of the carbon fibers, carbon fiber diameters, and position of the carbon fibers on the heat transfer in the proposed structure were studied in detail. The results show that the proposed comprehensive method can predict the heat transfer in the proposed structure accurately. A competitive relationship exists between the directional heat conduction and the radiation heat transfer. The radiation heat transfer became more dominating as the temperature increased. The failure temperature for the directional heat transfer in the proposed structure increased with the thermal conductivity of the carbon fibers and the carbon fiber diameters, while it decreased as the distance between the position of the carbon fibers and the nose of the blunt structure increased. The above phenomena will be helpful for designing high-performance thermal protection systems with carbon/carbon composites.