Comparison of thermal protection performance of active and passive cooled struts in a hypersonic air-breathing engine

Struts are commonly used in airbreathing engines to ensure effective mixing, ignition, and stable combustion of the fuel. As the flight Mach number and engine operation time increase, the injection strut requires adequate thermal protection. This paper proposed three kinds of cooling schemes for injection strut, including high-temperature alloy (GH3625) active cooling, TA-10 W leading edge active–passive cooling, and composite material leading edge passive cooling. Their cooling characteristics under engine operating conditions were investigated numerically and experimentally. The coupling strategy was adopted to handle the combustion and heat transfer for accurate prediction of the thermal environment. The supercritical-pressure flow, heat transfer with endothermic pyrolysis in the cooling channel were calculated using SST k-ω model and the three-step quasi-global chemical kinetic model. The results reveal significant uneven heat load distribution exists on the injection struts, influenced by circumferential wall injection and combustion heat release. Under the same thermal environment, the high-temperature alloy active cooling strut and the novel TA-10 W leading edge active–passive cooling strut can withstand the prolonged high-temperature gas scouring. In contrast, the composite passive cooling strut exhibits the highest wall temperature and significant ablation, negatively impacting flow field uniformity and the efficient mixing of kerosene. Compared to the high-temperature alloy active cooling scheme, the TA-10 W leading edge active–passive cooling scheme reduces the heat input into the strut by 8.5 % and decreases the consumed fuel heat sink by 8 %, despite having a relatively higher wall temperature. Therefore, the selection of the strut scheme must consider the engine application conditions. When sufficient coolant heat sink is available, the high-temperature alloy actively cooled strut is optimal; however, if the coolant heat sink is inadequate to provide an additional cold source for active cooling, the TA-10 W leading edge active–passive cooled strut scheme is more appropriate. The findings and experimental data from this study provide practical implications for the design of engine cooling structures.