Transonic Turbine Vane Suction Side Film Cooling With Showerhead Effect Using PSP Measurement Technique

This work focuses on the parametric experimental study of film cooling effectiveness on the suction side of a scaled turbine vane under transonic flow condition. The experiments were performed in a five-vane annular sector cascade blowdown facility. The controlled exit Mach numbers were 0.7, 0.9, and 1.1, from high subsonic to transonic conditions. N₂, CO₂, and Argon/SF₆ mixture were used to investigate the effects of coolant-to-mainstream density ratios, ranging from 1.0, 1.5 to 2.0. Three row-averaged coolant-to-mainstream blowing ratios in the range 0.7, 1.0, and 1.6 are studied. The test vane includes three rows of radial-angle cylindrical holes around the leading edge and two rows of compound-angle shaped holes on the suction side. All the cooling holes are active in order to study the resultant film cooling on suction side as well as from leading edge. Pressure sensitive paint (PSP) technique was used to obtain the film cooling effectiveness distributions from suction side holes and the contribution from leading edge showerhead holes. This work shows the effects of coolant-to-mainstream blowing ratio, density ratio, and exit Mach number on the film cooling effectiveness as well as its interaction with a potential shock wave. The results indicate that when the cooling holes are located in a critical region on the vane suction surface, the parametric effect on film cooling performance will significantly deviate from the common trend for a typical hole geometry.