Influence of Fan-shaped Outlet of Film Holes on Gas Turbine Blades

Numerical simulation method was used to transform the outlet of cylindrical holes (CH), double-jet holes (DJH) and big-small holes (BSH) into fan-shaped holes, and different hole types were compared with the original structures under different blowing ratios (M) with the cooling fluid of air and droplet/air mixture, respectively. Results show that transforming the outlet of CH and BSH into fan shape causes an apparent decrease in the film cooling effectiveness (FCE). Transforming the outlet of DJH into fan shape is advantageous when M=0.50 and 0.75, but it reduces the FCE when M=1.25 and 1.50. Compared to the original structures, fan-shaped outlet produces a stronger rotating kidney vortex pair, making it easier for the cooling film to detach from the cooled surface. Meanwhile, fan-shaped outlet contributes to the spanwise expansion of cooling fluid under low blowing ratio condition. Injecting droplet into cooling air can evidently improve the FCE. On real blades, the BSH achieve the best FCE at all three positions.