Multi-dimensional Analysis on the Energy Dissipation and Flow-induced Vibration of a High-head Multi-stage Pump: The Role of Vortex Structure Evolution

Ensuring mechanical stability remains a critical challenge in high-head multi-stage centrifugal pumps, where unsteady flow phenomena induce significant structural vibrations and stress concentrations. This study systematically investigates the flow-induced excitation mechanisms and their impact on the mechanical integrity of a thirteen-stage centrifugal pump operating under small flow rate conditions. A multi-dimensional framework integrating entropy generation theory, vortex evolution analysis, pressure pulsation characteristics, and one-way fluid–structure interaction was employed to explore the coupled flow-structure dynamics. The results indicate that the impellers and guide vanes act as the principal zones of energy dissipation, with turbulent dissipation in the impeller accounting for up to 65% of the total losses. Under off-design conditions, low-frequency pressure pulsations and rotating stall phenomena severely affect the last-stage impeller, leading to nonlinear amplification of axial force and asymmetric radial excitation. Fluid–structure coupling analysis reveals that maximum equivalent stress and strain concentrate at the impeller inlet and outlet interference regions, confirming the dominant role of unsteady hydraulic loads in compromising structural stability. Overall, this work clarifies the intrinsic coupling between internal-flow instability and mechanical reliability, providing a theoretical foundation for vibration control and robust design of high-stage centrifugal pump systems.