Secondary Loss Reduction via Integrated Endwall and Blade Profiling in Turbine Stage

Improving turbine performance requires both the mitigation of secondary flows and effective blade row matching. In this study, integrated endwall contouring and blade shaping were applied to a 1.5-stage axial turbine to suppress secondary flow development while maintaining favorable stator/rotor matching. The stator endwall contouring, developed using a B-spline surface parameterization based on a validated aft-loaded cascade, reduced endwall losses but induced stator/rotor mismatch in the lower passage. Positive bowing was therefore introduced to enhance upper passage flow control in synergy with the endwall contouring while independently regulating the lower passage flow. These modifications altered the stator exit flow angle, increasing mass flow and impacting blade loading; section profiling was applied to readjust the exit angle and maintain the operating point within an acceptable range. The rotor endwall contouring was designed using the same parameterization method. The final integrated profiling configuration achieved a 0.62% efficiency improvement at the design point and demonstrated robust performance over a wide operating range, as confirmed by steady simulations. Subsequent unsteady simulations further revealed its effectiveness in mitigating flowfield oscillations. This work provides practical design insights into the coupling effects of endwall and blade flow-control strategies at the stage level and their implications for stator/rotor matching.