In this study, the effects of impingement with various configurations at different aerothermal conditions on film cooling are investigated. The detailed adiabatic film cooling effectiveness distributions are obtained by solving steady three dimensional Reynolds-averaged Navier-Stokes equations with SST k-ω turbulence model closure. The influence of impingement on film cooling effectiveness is revealed by comparing the results from two cases: one where coolant is directly fed from a plenum (baseline case) and the other where the film coolant is extracted from the post-impingement flow on spherical dimples. For the latter case with post-impingement flow, the variations of the jet impingement configurations are considered at separation distances (H/Dj) from jet plate to target surface of 1, 2, 4 and 6, and eccentricities (F/Dj) between dimple center and film hole center of 0, 2, and 4. Besides, the effects of target wall heating the post-impingement flow on the external adiabatic film cooling performance are examined. The temperature ratios of the target surface to main flow at the inlet are set at 0.6, 0.7 and 0.8. The results are presented for four various averaged jet Reynolds numbers, which correspond to blowing ratios ranging from 0.5 to 2.0. It is observed that the impingement through the jet plate brings out pressure re-distributions on the target plate with film holes, and the dominant effect is on the flow structures in the supply chamber and near the entrance of the film hole. At the lowest blowing ratio of 0.5, film cooling with post-impingement air on dimples is reduced in comparison with the baseline case, while at higher blowing ratios, the effect of the impingement configuration on film cooling all depends on the flow conditions. In addition, the heating effect of target wall on the post-impingement flow could lower the coolant-to-mainstream density ratio, and then reduces the adiabatic film cooling performance.

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