A tip region film cooling study of the fan-shaped hole using PSP

Abstract

Suction side tip region film cooling of fan-shaped hole was investigated experimentally. In the experiments, the cylindrical hole film cooling performance is also studied for comparison. The experiments were completed in a cascade, which is constituted by five rotor blades with the tip clearance of 1.0 mm. The film hole was located at 7/8 height of the total blade. The adiabatic film cooling effectiveness contours were obtained by the pressure sensitive paint (PSP) technology. Inlet velocity was controlled by the inlet and outlet valves. Simultaneously, the averaged pressure at the outlet was measured. The mainstream turbulence intensity was controlled within 3.2%–5.6%. In this paper, the blowing ratio effects, the density ratio effects, the tip structure effects and the Reynolds number effects were studied. The results showed the fan-shaped hole film cooling performance is worse than that of the cylindrical hole. As the blowing ratio increases the fan-shaped hole film coverage area increases while that of the cylindrical hole decreases gradually. Finally, for the results of M = 2.0, they both decreases greatly. The film deflection angle of the fan-shaped hole is much higher. The density ratio experiments show the low density ratio jet has bigger momentum to resist the passage vortex. High Reynolds number weakens influences of leakage flow and passage vortex on the film. At last, the single squealer tip reduces the pressure gradient near the film, promoting the jet-off.