Cooling Injection Effect on the Suction Side Near-Tip Region of Turbine Blade With High-Speed Relative Casing Motion

Abstract The high-speed relative casing motion between the casing and the turbine blade tip introduces significant complexities to the flow field near the tip, resulting in alterations to the heat transfer distribution on the suction surface of the blade near the tip, and further influences the arrangement of film cooling arrangements. However, due to the challenges associated with measuring heat transfer, the influence of cooling injection on the near-tip region of the suction side under high-speed relative casing motion still remains uncertain. This study aims to address this knowledge gap by conducting experiments on a high-speed disk rotor experimental rig. The heat transfer coefficient and cooling effectiveness are investigated for different cooling hole arrangements. Additionally, based on the computational fluid dynamic (CFD) method, the interaction mechanism of cooling injections under high-speed relative casing movement is comprehensively discussed. It is observed that the cooling effect, which would be effective under stationary conditions, is greatly diminished or even rendered ineffective when subjected to high-speed relative casing conditions. Furthermore, arranging the cooling holes at the location where the interaction between the over-tip-leakage flow and the passage flow occurs would be an effective approach to enhance the cooling performance on the blade near-tip suction side. The effect of different relative casing speeds on suction side near-tip region cooling injection performances is also numerically investigated. These findings contribute to a better understanding of the considerations involved in the film cooling design of turbine blades.