Improved Film Cooling Effectiveness With a Round Film Cooling Hole Embedded in a Contoured Crater

Studies of film cooling holes embedded in craters and trenches have shown significant improvements in the film cooling performance. In this paper a new design of a round film cooling hole embedded in a contoured crater is proposed for improved film cooling effectiveness over existing crater designs. The proposed design of the contour aims to generate a pair of vortices that counter and diminish the near-field development of the main kidney-pair vortex generated by the flm cooling jet. With a weakened kidney-pair vortex, the coolant jet is expected to stay closer to the wall, reduce mixing, and therefore increase cooling effectiveness. In the present study, the performance of the proposed contoured crater design is evaluated for depth between 0.2D and 0.75D. A round film cooling hole with a 35° inclined short delivery tube (l/D = 1.75), free stream Reynolds number Re_D = 16000 and density ratio of coolant to free stream fluid ρ_j/ρ_∞ = 2.0 is used as the baseline case. Hydrodynamic and thermal fields for all cases are investigated numerically using large eddy simulation technique. The baseline case results are validated with published experimental data. The performance of the new crater design for various crater depths and blowing ratios are compared with the baseline case. Results are also compared with other reported crater designs with similar flow conditions and crater depth. Performance improvement in cooling effectiveness of over 100% of the corresponding baseline case is observed for the contoured crater.