Multi-objective optimization of thermal protection / drag reduction under the synergistic effect of multiple factors in transpiration cooling

Transpiration cooling, which is regarded as a highly prospective active thermal protection approach, has seen its structural optimization design become a research focus. This study employs Taguchi-ANOVA to analyze the effect degree of various factors (directional angle, porosity, and segment length) on evaluation parameters (average temperature, maximum temperature, and friction coefficient), thereby investigating the heat transfer mechanism and structural optimization design of segmented directional transpiration cooling. Furthermore, a multi-objective optimization of the segmented directional transpiration structure is conducted based on entropy weight method-TOPSIS approach. Results indicate that an increase in porosity of the front section generates a pressure gradient due to the differential flow resistance between the anterior and posterior sections of the porous plate. This pressure gradient induces mass transport of the coolant within the cavity towards the initial transpiration position. Simultaneously, the directional angle ensures effective cooling maintenance in the rear section. A comprehensive performance comparison between the optimized structure and the conventional segmented transpiration configuration, the optimized design demonstrates a substantial reduction in the maximum surface temperature by 141 K, accompanied by a 6.6 % decrease in the average friction coefficient.