Aero-thermal Performance of Coolant Released from Suction Surface in a High-Pressure Turbine Cascade

Abstract

Controlling the tip leakage flow is crucial for improving the aerodynamic and thermal performance of unshrouded highpressure turbines. The advantages of a single cooling hole to release coolant from suction surface were sought by numerical method in the cases of flat tip blade. Compared with no coolant case, the coolant cases exhibited significant differences on the intensity and evolution of tip leakage vortex and corresponding aero-thermal performance of turbine depending on locations to release coolant and blowing ratios of coolant. The impact of five axial locations to release coolant, namely 10%, 20%, 30%, 40%, and 50% axial chord of blade respectively, was studied. And the impact of three blowing ratios of coolant, namely 0.7, 1.4, and 2.1, was investigated. Within the scope of the current study, the best aerodynamic effect was achieved when the coolant was released before 30% axial chord of blade. The aerodynamic effect became worse when the coolant was released after that place. This phenomenon implied that it was a better strategy to release coolant at the initial period of evolution of tip leakage vortex. With regard to the cases with coolant released at 20% axial chord of blade, the mixed-out loss caused by tip leakage vortex reduced with the increasing of blowing ratio from 0.7 to 2.1. Last but not least, the thermal performance of suction surface of blade was improved with the increasing of blowing ratio.