Effect of different internal impingement structures and cratered film cooling holes on overall cooling effectiveness

The cooling performance of combined cooling depends on the cooling performance of individual structures, such as film cooling and impingement cooling, and the interaction between the two structures. This paper uses a numerical simulation method to thoroughly study a flat plate model with a combined cooling structure of impingement/film cooling, employing the Shear Stress Transport (SST) turbulence model. The aim is to reveal the impact of different impingement and film structures on the overall cooling effectiveness, providing theoretical guidance for engineering applications. At a typical blowing ratio of 1.5, various impingement cooling structures with different hole diameters, impingement distances, and hole shapes are considered, combined with two types of outer film cooling holes (simple cylindrical and cratered holes). The results indicate that the three variations in the internal cooling structure positively impact the internal heat transfer coefficient and the overall cooling effectiveness on the outer wall. Among them, the influence of the hole diameter factor is the most significant, while the impact of the impingement distance is less pronounced. Benefiting from the anti-kidney vortex pairs of the cratered film cooling holes, the cratered 2 improves the area-averaged overall cooling effectiveness by 38.69% compared with the simple cylindrical reference film cooling hole. Within the blowing ratio range of 0.5–2.5, using cratered 2 and the optimal impingement cooling structure, the overall cooling effectiveness is improved by 20.39–39.14% compared with the standard impingement structure and cylindrical film cooling hole combined structure.