Numerical study on the flow and heat transfer of an integrated transpiration cooling structure composed by octet-truss micro-element-various porosity and multi-arrangement

To address the thermal protection challenges in the high-heat-load environment of afterburners, this research proposes a novel thermal protection structure based on an octet truss microlattice array. The impact mechanisms of key geometric parameters such as porosity, pore size and structural thickness on the overall cooling effectiveness, effective gas film degree and the overall thermal protection performance of transpiration structures are systematically researched. In response to the non-uniform outflow characteristics of the coolant, two design strategies with variable porosity layouts are designed. The research results show that when the porosity is reduced from 58.4% to 47.6%, the overall cooling effectiveness of the wall surface is increased by 2.75%. The effective film cooling effectiveness is primarily impacted by the parameters of the front-section transpiration structure. For transpiration structures of the same size, a higher overall cooling effectiveness in the front section leads to a lower effective film cooling effectiveness in the downstream extended region. When the thickness of the transpiration cooling structure is increased by 50%, the extended effective film cooling effectiveness improves by 28.7%. Furthermore, the strut type of the octet truss significantly affects the thermal protection performance. Under conditions where the cooling air is not extremely abundant, the quadrangular prism strut type demonstrates the best thermal protection performance, albeit with the highest flow resistance. The intermittent transpiration structure can reduce the coolant flow rate by 28.6% while achieving the same cooling effect. This research provides important theoretical support for the design of efficient thermal protection structures.