Hydraulic performance and flow in the high-flow axial-flow pump under velocity moment distribution control

Under high-flow operating conditions, axial-flow pumps often experience a pronounced efficiency deterioration caused by intensified tip leakage flow, adverse pressure gradients, and flow separation, leading to enlarged high entropy production regions. This study investigates the role of blade loading redistribution in regulating these loss-generating flow mechanisms. An inverse design method is employed to modify the blade velocity moment distribution, while a surrogate-assisted optimization framework serves as a tool to identify an improved loading configuration. The optimized model maintains a nearly identical head under high-flow conditions and improved the hydraulic efficiency. Comprehensive analyses of entropy production, pressure field, and internal flow structures reveal that the optimized blade loading effectively mitigates the adverse pressure gradient near the blade tip, suppresses tip leakage flow development, and alleviates trailing-edge separation. Consequently, the high entropy production regions contract markedly, and the trailing-edge entropy production peak is reduced. These results indicate that the efficiency improvement originates from the controlled evolution of leakage and separation losses, providing new physical insights into loss mitigation mechanisms in axial-flow pumps.