Influence of Trenched Shaped Holes on Turbine Blade Leading Edge Film Cooling

Computational results are presented for a row of coolant injection holes on each side of a high-pressure turbine blade near the leading edge. Seven hole configurations have been used to show the effect of various diffusion shaped holes and their trenching on film cooling effectiveness: (1) cylindrical film hole; (2) forward diffused film hole; (3) trenched forward diffused film hole; (4) conically flared film hole; (5) trenched conically flared film hole; (6) laterally diffused film hole; and (7) trenched laterally diffused film hole. Computational solutions of the steady, Reynolds-averaged Navier-Stokes equations are obtained using a finite-volume method. Results show that the main effect of trenching is the reduction of jet lifting off from the blade surface and so the prevention of sudden lowering of cooling effectiveness after the injection location. Moreover, hole trenching has more effect on film cooling flow on the suction side than on the pressure side. Also, the trenched laterally diffused shaped hole has the highest laterally averaged effectiveness on both the suction side and the pressure side of the blade.