Numerical Evaluation of the Performance of the Sister–Shaped Single–Hole Schemes on Turbine Blade Leading Edge Film Cooling

In the present study, a numerical evaluation of the performance of the sister-shaped single-hole (SSSH) schemes (downstream, upstream and up/downstream) on the leading edge of AGTB-B1 high pressure turbine blade cascade is carried out. Simulations are performed at three blowing ratios of 0.7, 1.1 and 1.5. Predicted results are compared to the single cylindrical hole and a 15° forward-diffused shaped hole. The realizable k-ε model combined with the standard wall function is used to model the flow field; wherein, the predicted pressure field was in a good agreement with the available experimental data. At the high blowing ratios of 1.1 and 1.5, a noticeable improvement in the film cooling effectiveness and the lateral spread of the cooling jet has been observed for the upstream and up/downstream SSSH schemes, in particular on the suction side. The downstream SSSH configuration provided almost similar film cooling effectiveness values to that of the forward diffused shaped hole for all blowing ratios on both the pressure and suction sides of the blade. Note that the obtained film cooling effectiveness for the downstream SSSH scheme at high blowing ratios was disappointing in comparison with other SSSH schemes where much higher film cooling effectiveness values were obtained. The mixing of the coolant with the high mainstream flow at the leading edge of the blade is considerably decreased for the upstream and up/downstream SSSH schemes and more adhered coolant to the blade’s surface is observed than with other configurations. Moreover, the jet lift-off is notably diminished for the upstream and up/downstream SSSH compared to other hole geometries.