Velocity triangle oriented design of non-axisymmetric endwalls based on ridge-line method for sealing coolant flow in a high-load turbine

High-load turbines offer greater energy conversion efficiency but are subjected to elevated temperatures and mechanical loads in the field of energy. The rim seal is a critical sealing structure in gas turbines. The introduction of the sealing coolant with a significant velocity difference from the mainstream can lead to intense shear flow and mixing losses due to the abrupt momentum exchange. Therefore, a closer match between the velocity triangle of the sealing air and that of the mainstream is more desirable. To achieve this purpose, this study proposes a local non-axisymmetric endwall contouring strategy using the ridge-line method to improve the flow pattern of the sealing air. Velocity triangles of the sealing coolant are compared with the base case. The results show that non-axisymmetric endwall designs improve the alignment of the axial and circumferential velocity components of the sealing coolant with the mainstream, so flow losses are reduced. The effectiveness of the NAE is evaluated, and the maximum stage efficiency improvement reaches about 0.41%. In addition, NAE shaping changes the pressure gradient distribution along the passage. As a result, the sealing coolant redistributes earlier and in a more uniform manner, so the total pressure loss in the leading region of the passage is reduced, and the lift-up of the passage vortex at the outlet is limited. Therefore, secondary flow losses are reduced, and the overall aerodynamic performance is improved.