Secondary Flow Losses Mitigation for Low-Pressure Turbine Cascade Using Response Surface Optimization

Abstract The increasing demand for highly loaded cascades in modern gas turbines and jet engines has led to a rise in endwall secondary losses within the flow passage. Non-axisymmetric endwall contouring is a promising technique for reducing these losses and enhancing the aerodynamic performance of turbine cascades. This paper presents a CFD-based shape optimization of non-axisymmetric endwall contouring for a highly loaded low-pressure linear turbine cascade vane at design inflow condition. Based on planar endwall secondary flow investigations, the parameterization of the design space for non-axisymmetric endwall contouring was determined. The novelty in shape optimization focused on understanding the impact of upstream platform leading-edge (PLE) extension in non-axisymmetric endwall contouring, with the goal of minimizing the total pressure loss coefficient. The results of planar cascade simulations align well with experimental data. The optimized non-axisymmetric endwall (NAEW) contouring demonstrated a reduction in endwall non-uniformities, cross-passage flow, and the span-wise extension of the passage vortex. The ideal design configuration places the platform leading edge at 20% Cax upstream and 70% Cax downstream of the blade leading edge. The study revealed that the optimized endwall contouring reduces the total pressure loss coefficient by 11.8% under design inflow conditions.