Investigation of swirl-induced film cooling deterioration and mechanism-based layout optimization for pressure side in variable geometry turbines

Variable cycle engines face thermal management challenges due to non-uniform thermal loads from swirl inflow and adjustable turbine guide vanes (ATGV). These complex inflow conditions significantly impair pressure side film cooling. Pressure-sensitive paint (PSP) measurements and validated computational fluid dynamics (CFD) simulations were employed in first attempt to quantify swirl-induced film cooling deterioration in variable geometry turbines. Results reveal that swirl-induced radial momentum negates the beneficial streamwise pressure gradient of smaller vane openings, eliminating expected cooling gains. Swirl inflow causes regional cooling deterioration: mid-to-upper span regions suffer coolant detachment and lateral drift, while the lower span shows minimal improvement. Additionally, leading edge showerhead jets deflect the coolant from pressure side film holes downstream, increasing radial misalignment and spanwise non-uniformity, with the relative standard deviation (RSD) of cooling effectiveness rising by up to 35.09 %. To counter this, a novel mechanism-informed layout optimization strategy is proposed, which first applies particle swarm optimization (PSO) guided by local cooling demand fields to mitigate swirl-induced non-uniformities. The optimized layout reduces RSD by 11.85 %, enhancing thermal protection under swirl-distorted conditions. Distinct from traditional or empirically tuned layouts, this study establishes a robust mechanism-informed optimization algorithm framework that enhances thermal protection in next-generation variable geometry turbines.