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.