Effect of Mainstream Attack Angle on Film Cooling Effectiveness of Aero-engine Fully Shielded Strut

Infrared stealth capability is critical for advanced aero-engines. To reduce rear-body infrared radiation, the fully shielded strut is used to shield the turbine blades. However, due to its unique structure, airflow is prone to separation from the strut under off-design conditions, exerting nonnegligible effects on film coverage. This study investigates the film cooling characteristics of a fully shielded strut under different mainstream attack angles. Using a validated numerical model, the flow field of an uncooled strut is first analyzed under various mainstream attack angles (- 15°, -8°, 0°, 8°, and 15°). Subsequently, the cooling effectiveness of film holes located in separated and unseparated regions is evaluated. The results indicate that in the infrared-visible region, flow separation occurs at positive attack angles. Film coverage in the separated and unseparated regions responds differently to varying attack angles. In the unseparated region, laterally averaged film cooling effectiveness is not sensitive to the mainstream attack angle. In the separated region, laterally averaged film cooling effectiveness increases significantly. The study reveals the mechanism behind this enhancement is that the separation vortex strengthens the lateral diffusion of cooling air. This effect is more pronounced at larger positive attack angles with stronger separation vortices. These findings may provide new insights into fully shielded strut cooling and aero-engine infrared stealth design.