Analysis of axial force and pressure pulsation of centrifugal pump as turbine impeller based on dynamic mode decomposition

To investigate the spatiotemporal evolution mechanism of the axial force on a centrifugal pump acting as a turbine, this study focuses on a single-stage single-suction centrifugal pump and applies dynamic mode decomposition (DMD) to decompose the flow field of the turbine impeller's axial force. The axial force of the impeller under three flow conditions, namely, 1.0Qd, 1.3Qd, and 1.6Qd, is extracted and analyzed. Results show that the DMD method can accurately extract the spatiotemporal coherent structural characteristics of the main modes of axial force, with the first five modes accounting for more than 99.97% of the total mode energy. Under the 1.3Qd condition, the flow field is stable, and the axial force remains constant over time with a very small degree of pressure pulsation. However, under the 1.6Qd condition, the flow field inside the pump becomes complex and unstable, leading to larger changes in axial force compared to the 1.0Qd condition, with an increase in 2.13 times. The amplitude of the pressure pulsation gradually decreases from the impeller inlet to the outlet under both 1.0Qd and 1.6Qd conditions, with vibration caused by the axial force mainly occurring at the impeller inlet. These findings provide a reference basis for improving the stability of centrifugal pumps acting as turbines.