Heat transfer and ablation of carbon/carbon composites based on multi-field coupling

Abstract

With the development of hypersonic technology, the demand for thermal protection material is continuously increasing. Carbon/carbon composites are widely used as thermal protection materials in the nose and in the leading edge of hypersonic vehicles owing to their high latent heat and good resistance to high temperatures. The flow field around the aircraft affects the heat transfer and ablation of carbon/carbon composites, changing the thickness and shape of the thermal protection layer. The ablation of carbon/carbon composites alters the flow field distribution, thus conversely affecting the ablation of carbon/carbon composites. To predict the heat transfer and ablation of carbon/carbon composites, a multi-field coupling model was established to predict the transient temperature distribution, ablation rate, and ablation profile of carbon/carbon composites in hypersonic aerothermal environments. The thermochemical non-equilibrium effects of the flow field, heat transfer of the material, and ablation of the material surface were considered in the modeling. The wall temperature and heat flux in the stagnation area change significantly. The initial heat flux is higher and the stagnation heat flux at 1 s is 17.22 MW·m−2. As time passes, the wall temperature increases, the temperature gradient in the stagnation area decreases, the heat flux decreases, and the stagnation heat flux at 30 s is 10.22 MW·m−2. As the temperature of the stagnation area is high, the material at the surface reacts actively and the ablation is more serious, whereas only a small amount of ablation occurs on the side of the model. The shape of the material model changes after the ablation, the leading-edge radius increases, and the ablation depth at the material stagnation point is 17.47 mm at 30 s. The results show that, in the hypersonic aerodynamic thermal environment, the carbon/carbon composites have a certain ablation recession, which leads to change in the external flow field and thermal load. The multi-field flow-heat-ablation coupling model can be used to predict the response of thermal protection materials, which can provide some reference for the design of thermal protection systems.