Experimental study on suction side film cooling characteristics of an adjustable turbine guide vane under different turning angles for a variable cycle engine

The suction side of adjustable turbine guide vanes in variable cycle engines experiences significant aerodynamic variations under different turning angles, which strongly influence the coolant attachment behavior. However, the adverse effects induced by turning angle variation and their underlying mechanisms have not been systematically investigated. To address this issue, this study integrates pressure-sensitive paint experiments with validated simulations to systematically investigate the suction side film cooling behavior under varying turning angles, relative mass flow ratios, and density ratios, and further evaluates structural modifications. Experimental and numerical results indicate that decreasing turning angles intensifies the suction side pressure gradient and strengthens the passage vortex, thereby affecting coolant attachment and film coverage. Specifically, reducing turning angles further deteriorates performance, with surface-averaged film cooling effectiveness reduced by 5.1–6.7% and relative standard deviation increased by 8.3–14.6% compared to the design setting. Furthermore, increasing coolant mass flow enhances near-hole cooling performance but leads to more concentrated coolant coverage. A higher density ratio is found to improve front-region attachment and increases surface-averaged film cooling effectiveness by 14.1–21.7%, though at expense of downstream uniformity. Structural modifications featuring smaller holes and staggered layouts further expand the coverage area and raise surface-averaged film cooling effectiveness by 7.0–8.7%, but still cause a deterioration in uniformity. These results provide a reference for the thermal-protection design of adjustable turbine guide vanes in next-generation variable cycle engines.