Film cooling comparison of shaped holes among the pressure surface, the suction surface and the leading edge of turbine vane

Abstract

The present study employed commercial computational fluid dynamics software ANSYS 2019R3 to explore the adiabatic film cooling effectiveness and the net heat flux reduction (NHFR) for the comparison of the five selected shaped holes and conventional cylindrical holes between the pressure surface, the suction surface and the leading edge. Amo4ng the shape parameters of shaped holes, the lateral divergence angle (β) and the forward divergence angle (δ) were fixed as 12° and 7° in all shaped holes structures, respectively. The others varied with different regions of the turbine vane. Results showed that different holes fit different positions of vanes. On the suction surface, laidback holes performed the worst net heat flux reduction in most blowing ratios conditions, which indicated the forward divergence angle was not conducive to the flow field and heat transfer characteristics on the suction surface. Whereas, the lateral divergence angle was beneficial to the film cooling and heat transfer characteristics. Laidback fan-shaped holes performed the best adiabatic film cooling effectiveness, but once simultaneously thinking about the heat transfer, fan-shaped holes performed better in net heat flux reduction due to less vortices at holes exit. On the leading edge, the divergence angle towards the upper wall (the lateral divergence angle of spanwise expansion holes) of vanes was not conducive to steady flow. And conical holes performed best, which indicated that coolant from holes with axial divergence angles (the lateral divergence angle in axial direction of conical holes) under the influence of mainstream impact could perform higher film cooling effectiveness and more stable flow fields. On the pressure surface, holes had a lateral divergence angle in the direction of vane height, which was conducive to increasing the coolant coverage area and improving the ability to attach to the pressure surface. Additionally, the laidback hole case was observed the lowest net heat flux reduction when the blowing ratio was less than 2, which revealed that holes that expanded only in flow direction was not conducive to film cooling and heat transfer characteristics.