Non-Axisymmetric stator Hub Endwall Contouring for Tandem Bladed Axial Compressor stage

Secondary flow within the compressor stator passage induces 3D flow separation and reduces the flow passage which in turn decreases the efficiency, operating range and pressure rise capacity of the compressor stage. The aim of this study is to reduce the effects of secondary flow losses near the lower span region by implementing a NonAxisymmetric Hub Endwall contour. The linear stator hub cascade is used by utilizing point displacement m e t h o d in con jun c t ion with optimization. The numerical simulation was performed using ANSYS CFX (R) to solve steady state 3D-RANS equation with SST K-. turbulence model for a single blade passage with translational periodicity, Parameterization of Hub endwall was done using commercial software CAESES (R) using control points based NURBS curves. The optimization for the NAEW was performed using ANSYS Direct optimization by availing the ASO (Adaptive Single Objective) optimization method, which is the combination of optimal space filling, kriging response surfaces and MISQP (Mixed-integer sequential quadratic programming). The optimization has been done for the design incidence case, which resulted in the reduction of total pressure loss coefficient of maximum 1.2%. The same optimized endwall contour has been numerically s tu d i ed for the different incidence angles of -4 degree and +4 degree. It was found at the -4 degree incidence angle, the blade stall has been removed completely. The change in the endwall pressure gradient and thereby spanwise pressure gradient bring the change in the flow structure. Reduction of total pressure loss coefficient increases with the increase in the positive incidence angle which is due to the reduction of loss coefficient along the spanwise direction increases. The endwall contour of Design A found to be more favorable compared to other profiles.