Investigation of effect of unsteady interaction on turbine blade film cooling

Film cooling is extensively used to provide protection against the severe thermal environment in gas turbine engines. It is known that the cooling effectiveness of the downstream rotor is influenced by the unsteady wake of the stator. Presence of wake due to an upstream vane is studied by placing a periodic set of rods upstream of the blade in most of the investigations. In order to explore the influence of the unsteady stator wake on the cooling effectiveness of the rotor blade under real situation, the film cooling of moving turbine blades, with preceding stationary vanes, was investigated numerically, and the influence of the unsteady interaction between the rotor and the stator on the film cooling effectiveness of the flow field surrounding the cooling holes on moving blades was discussed. Results show that the unsteady interaction between the stator wake and the cooling jet flow becomes stronger for the case of larger blowing ratio under the same stator wake condition, and the fluctuation of the film cooling effectiveness is increased correspondingly. Because of the wider overlying range of the cooling jet flow at the time of the stator wake passing through the cooling holes, better film cooling effectiveness achieves downstream of the 30% arc length. Cooling jet flow can hardly reach the endwall zone due to the effect of the vortex at this zone. It is entrained downstream of the jet position, resulting in better effectiveness in this zone.