EFFECTS OF AIR COOLANT INJECTION ON CASCADE SURFACE PRESSURE DISTRIBUTION

The effects on turbine blade surface pressure distribution were investigated experimentally with air coolant discharge from each of nine individual rows of coolant holes on the blade surface in a rectilinear cascade with typical turbine guide van profile.Mass flow ratios of air coolant to mainstream were 0,0.6,and 1.2 percent,respectively.The experimental results showed that the variations of the surface pressure distribution were dependent chiefly on the amount of air coolant and the location of injecting holes.Injection from the blade leading edge right against the mainstream altered the surface pressure distribution slightly,and the pressure surface injection did not change the surface pressure distribution so obviously as the suction surface injection due to the difference of mainstream pressure gradients and mainstream velocity.In general,the surface pressure decrease caused by kidney-shaped vortex was more significant than the pressure increase due to the mainstream stagnation resulted from air coolant injection.