Research on the spatiotemporal evolution of pressure pulsations during part-load operation of pump-turbine under power generation conditions

Abstract

Pressure pulsation of pump-turbines under part-load operation exhibits pronounced multi-scale and strongly coupled characteristics, which are closely related to the hydraulic stability and vibration safety of pumped storage units. In this study, the part-load operation of a pump-turbine under turbine-mode conditions is investigated, and the spatiotemporal evolution characteristics of pressure pulsation in the vaneless region are analyzed. Based on unsteady CFD simulation results, an adaptive variational mode decomposition method is introduced to decompose pressure signals at different scales. Combined with the responses of blade radial force and runner radial force, the frequency-domain characteristics of pressure pulsation at different monitoring points, the decomposition results of representative signals, and the temporal evolution of pressure, velocity, vortex structure, and turbulence kinetic energy, the pressure-pulsation behaviour under different load conditions is systematically examined. The results show that the pressure pulsation characteristics in the vaneless region vary significantly with load. At 85%Pr, the pulsation field remains relatively regular and is mainly governed by rotor-stator interaction, with dominant energy concentrated near blade-passing-related components. At 40%Pr, low-frequency pulsation is markedly enhanced, circumferential non-uniformity becomes more obvious, and flow separation, local stall, and vortex development intensify the unsteady flow. The evolution of pressure pulsation is governed by the coupling between temporal characteristics and spatial flow structures. These findings provide a theoretical basis for hydraulic stability evaluation and vibration-risk identification of pump-turbines under flexible operation.