Effectiveness and energy loss of film cooling in endwall with spiral-channel holes

Abstract

Spiral-channel holes are utilized on the turbine endwall to enhance cooling effectiveness. Numerical simulations and experimental verification are conducted to analyze the cooling performance and energy loss of spiral-channel holes, as well as the influence of parameters and flow field structure on the vane. Results reveal that the energy loss due to the spiral-channel hole is slightly higher than that of the cylindrical hole at low blowing ratio (M), with the opposite being true for M exceeds 1.5. Increasing M heightens the film effectiveness around the hole but reduces coolant coverage downstream of the hole. The cooling capacity of the spiral-channel hole outperforms cylindrical hole around the hole, resulting in more uniform transverse film effectiveness and greatly improved the cooling effect on the pressure section, particularly at high M. The introduction of compound angle further enhances the cooling performance of spiral-channel hole, but increases the energy loss. Upstream the hole, the laterally-averaged film effectiveness of spiral-channel hole with −28° compound angle is 16.9 % higher than that of cylindrical hole, and 20.1 % higher downstream the hole. The spiral-channel hole with −28° compound angle exhibits the best cooling performance on the pressure side, while the spiral-channel hole with 48° compound angle provides optimal cooling effect on the suction side. Moreover, the pressure section exhibits a larger vortex scale and intensity compared to the suction section. The hole with positive and negative compound angle exhibits minimal difference in the flow field structure between the pressure and suction sections, and form better protection on the endwall with a smaller zero coverage zone.

Keywords

• Spiral-channel hole
• Film cooling
• Swirling flow
• Turbine endwall