Numerical study on discrete film cooling performance of non-axisymmetric endwall

The non-axisymmetric endwall can effectively reduce the circumferential pressure difference and control the complex secondary flow inside the passage. Consequently, this enhanced the aerodynamic performance of the airfoil. The non-axisymmetric endwall significantly impacted the outlet area of the film holes and the trajectory of the coolant. The concave-convex changes along the circumferential and axial directions on a flat plate were studied to explore the effects of different shaping positions on the film cooling characteristics. A row of discrete film holes at positions of 10%C_ax, 40%C_ax, and 70%C_ax inside the non-axisymmetric vane cascade were positioned. The numerical method of solving the time-averaged Reynolds equations was used to investigate the influence of the endwall shape on the cooling characteristics of the film holes. The results were as follows. Only when there were concave-convex changes along the circumferential direction on the flat plate, excluding the most concave and convex points, could other positions effectively reduce the blow-off of the coolant jet at a high blowing ratio. In the case of concave or convex changes along the axial direction, the exit area of the holes significantly increased behind the most concave point and in front of the most convex point. Compared with the flat plate, the maximum outlet area of the holes can increase by 51.4%, resulting in a substantial expansion of the high adiabatic effectiveness region. The non-axisymmetric endwall profiling based on passage pressure difference method can reduce the circumferential pressure gradient and the intensity of the horse-shoe vortex, improving aerodynamic performance. The endwall shaping in the film hole arrangement can improve the coolant attachment. The overall cooling performance was better under a higher blowing ratio. When M=1.0 and M=1.5, the area of high adiabatic effectiveness region with η>0.2 can be increased by 5.58% and 5.51%, respectively, compared with the flat endwall.