Synergistic effects of micro-hole injection and film cooling for increasing the cooling effectiveness: A numerical investigation

The continuous drive to improve the efficiency and power output of gas turbines has led to the need for advanced cooling strategies that can effectively dissipate high thermal loads. This study presents a comparative analysis of the thermal performance of various micro-hole configurations integrated with a main cooling hole, highlighting their synergistic effects on film-cooling effectiveness and flow behavior. Five distinct configurations were evaluated at three different blowing ratios of 0.25, 0.5, and 1.0. The SST k-ω turbulence model is employed to simulate the turbulent flow. Outcomes reveal that regardless of the configuration of micro-holes, their combination with the main hole of film cooling could increase the cooling effectiveness. Also, the comparison of different configurations demonstrates that the Quad-type (QT) configuration consistently outperformed the other designs at all tested blowing ratios. At a blowing ratio of 0.5, the QT configuration exhibited the highest centerline cooling effectiveness, with a value of 0.44 compared to 0.37 for the Step-type (ST) configuration at the X/D = 30 location. Additionally, the QT configuration had the highest spanwise-averaged cooling effectiveness, with a value of 0.3170 at X/R = 20, representing a 54.9% improvement over the previously proposed design. Furthermore, the QT configuration demonstrated the best cooling uniformity, as indicated by the lowest CUC among the investigated configurations.