Film cooling performance comparison at different positions on blade suction side

Film cooling performances of two fan shaped film holes at different positions on blade suction side were experimentally studied in a linear transonic cascade. The film cooling effectiveness of the fan shaped film holes on blade suction side was measured at mainstream inlet Reynolds number of 3.7×10⁵, different mainstream exit Mach number of 0.81, 0.91, 1.01, and different blowing ratio of 0.6-2.1. Results shows the film hole 2 is at the position with higher curvature, where the mainstream forces the coolant to better flow along the surface, however, this has both advantages and disadvantages. At smaller blowing ratio, the jet of film hole can flow close to the wall itself, so the advantage of the mainstream isn't obvious, but the mainstream forces the coolant to flow downstream and the coolant will be difficult for spanwise flow, bringing about lower film cooling effectiveness. At higher blowing ratio, the jet of film hole has large vertical velocity component, the coolant can be easily lifted off, then coolant of the film hole 2 can be forced to get close to the wall, so the film cooling effectiveness is increased substantially.