Experimental Study of the Effect of Swirling Inflow on Full-Film Cooling of Turbine Guide Vane

Abstract The use of compact engines reduces the distance between the combustor and the turbine, leading to the interaction of the remaining inhomogeneous swirling flow at the combustor outlet with the mainstream of the turbine vane cascade. Consequently, previous turbine vane cooling designs may struggle to meet the cooling requirements for swirling inflow conditions. This study aims to investigate the impact of swirling inflow on the full-film cooling of turbine guide vanes. The film cooling effectiveness (η) of the turbine vanes under two inflow conditions and three mass flow ratios was measured using the pressure-sensitive paint technique. The cylindrical film holes on the suction and pressure surfaces of the vane were replaced with different types of laid-back fan-shaped holes (LBFS), and the cylindrical holes at the leading edge were replaced with droplet holes. The results revealed that swirling flow alters the coolant outlet flow from the film holes on the vane surface, causing deflection of the film. Droplet holes at the leading edge were found to reduce the coolant outlet momentum and improve η, in comparison to cylindrical holes. Furthermore, LBFS demonstrated a significant advantage in mitigating the negative effects of swirling flow. Specifically, LBFS with wider outlet width were found to be more suitable for the pressure side, while no additional outlet width of the air film holes was required for the suction side.