Optimization of the hump characteristics of pump-turbine based on response surface method and NSGA-III algorithm

This study optimizes the hump characteristics of a pump-turbine and explores the flow instability mechanism in the hump region. Guide vane profiles were optimized via Response Surface Method (RSM) and NSGA-III algorithm to suppress hump characteristics and investigate instability mechanisms. Optimization Scheme 1 was selected as the final design based on its superior comprehensive performance in improving hump characteristics, enhancing efficiency, and increasing head. The optimized design features slimmer geometry and improved curvature distribution. Analysis reveals that the hump formation stems from guide vane rotational separation and vortex-induced high flow energy dissipation (FED). The optimization contributed to a more stable head curve in the hump region. At the rated condition, the head and efficiency increased by 0.72 % and 0.04 %, respectively, while the shaft power rose by 0.68 %. At 0.67Qd, head and efficiency improved 3.29 %, 6.97 % with 3.44 % power reduction. The hump region peak-trough head difference decreased 64.7 %, demonstrating substantial mitigation of hump characteristics. Vortex structures at the leading and trailing edges reduced over 70 %, decreasing total FED by 39.0 %(0.62Qd), 41.3 %(0.67Qd), and 49.7 %(0.85Qd). However, local FED increases at 0.74Qd and 0.80Qd due to impeller passage vortices. The wmrDMD analysis showed optimized flow had attenuated high-frequency modes and enhanced stability. This work confirms guide vane optimization mitigates humping by reducing vortex-driven energy dissipation, highlighting collaborative impeller-guide vane optimization potential for further stability improvements.