Analysis of curvature effects on the film cooling under the rotation frame

A theoretical analysis was carried out to comprehend the mechanism of the rotation and curvature effects on the film cooling which is important in understanding the mixing process between the film coolant and the hot stream air over the high pressure turbine blade. Under the rotation frame, the effects of curvature on film cooling effectiveness can be explained by determining whether the injected fluid moves closer or further from the wall surface. The trend of jet trajectory can be determined by considering the balance of forces on the injected fluid. By the deduction, the local rotational number is used to estimate the effects of rotation. It was found that a small local rotational number results in that the jet moves away from the curved wall on the convex wall. For a large local rotational number, a high cooling effectiveness could be obtained. On the concave wall, the effects of local rotational number are the reverse of those on the convex wall. The momentum flux ratio is the key factor affecting the film departure or attachment at a small local rotational number.