Numerical investigation of flow distribution and heat transfer behaviors of hydrocarbon fuel in porous media with hybrid TPMS structures

Transpiration cooling using endothermic hydrocarbon fuels has attracted increasing attention due to its high cooling capability for hypersonic vehicles under extremely high heat flux. However, the sweeping effect of the mainstream leads to maldistribution of the coolant, resulting in insufficient coolant supply in upstream high-heat-flux regions and nonuniform wall temperature distribution. In this study, a hybrid Gyroid-Diamond (G_D) TPMS structure is proposed to improve coolant distribution along the mainstream direction by regulating topological connectivity and local flow resistance. A three-dimensional pore-scale numerical model coupled with conjugate heat transfer and cracking reactions of n-Decane is established in this study. Compared with single G- and D-type structures, the hybrid G_D structure significantly improves the uniformity of coolant distribution along the mainstream direction. With the hybrid angle of 158.20°, the coolant proportion in the first half of the G_D IV structure reaches 40.6%, which increases by 26.1% and 14.0% compared with the pure G-type and D-type configurations, respectively. Furthermore, increasing the G-section porosity reduces upstream flow resistance and enhances coolant supply. When the G-section porosity increases to 0.5, the coolant proportion in the first half exceeds 50% while the corresponding coolant proportion in the conventional graded G-type structure is only 36% with the same average porosity. Compared with the G-type structure, the selected G_D IV-0.5 configuration reduces the maximum wall heat flux and maximum wall temperature by 32% and 12.2%, respectively, while the non-uniformity of wall temperature and cooling efficiency are greatly reduced by 71.9% and 73.4%, respectively. These results identify the performance limit of the hybrid G/D topological structures and render an effective strategy to improve coolant re-distribution toward high-heat-flux regions. This study provides better insight into the coupling mechanism between local flow distribution, endothermic reactions and heat transfer in TPMS structures.