Film cooling and stress concentration properties of the backward-diffusion elliptical hole

Abstract

Film cooling is a commonly used cooling technology in gas turbines. However, it faces the problem of stress concentration. The present work proposes a low-stress film cooling hole with good cooling performance, namely the backward-diffusion elliptical hole. The Pressure Sensitive Paint experiments compare the film effectiveness of the backward-diffusion elliptical hole and the 7–7–7 fan-shaped hole. The film effectiveness of the backward-diffusion elliptical hole is higher than that of the 7–7–7 fan-shaped hole, especially at high blowing ratios. The structure of the jet vortex system of the backward-diffusion elliptical hole is analyzed by large eddy simulation. The results show that the backward-diffusion elliptical hole induces a stronger anti-counter-rotating vortex pair than the elliptical hole. The anti-counter-rotating vortex pair weakens the harmful effects of the counter-rotating vortex pair on the film effectiveness. The stress concentration factor of the backward-diffusion elliptical hole is obtained by finite element analysis. The backward-diffusion elliptical hole’s stress concentration factor is about 2.85, similar to the elliptical hole (2.84). However, the stress concentration factor of the 7–7–7 fan-shaped hole is 6.58. Therefore, the stress concentration factor for the backward-diffusion elliptical hole is only 43.3% of that for the 7–7–7 fan-shaped hole. The backward-diffusion elliptical hole is a more promising low-stress, high-cooling-efficiency film hole.