Investigating the temporal-spatial evolution mechanism of axial forces in centrifugal pump impellers under varying operating conditions using dynamic mode decomposition

The centrifugal pump is an important component of pumped storage power stations, but the axial force on the impeller significantly affects their stability. Hence, this study focuses on the IS80-65-160 centrifugal pump model and employs Dynamic Mode Decomposition (DMD) to analyze the flow field decomposition of the impeller’s axial forces at three operating points: 1.0nr–1.0Qr, 1.0nr–0.4Qr, and 0.4nr–0.4Qr. The results indicate that DMD can decouple the axial forces on the impeller and extract the temporal mono-frequency coherent structure features and their changes corresponding to the main modes of axial forces, with a nearly zero decay rate and stable periodic vibrations. The first four modes of axial force account for 99.7% of the total modal energy, with the average flow field (mode 0) containing the most flow energy and having the greatest impact on the flow field, The impeller vibrations caused by axial forces mainly occur at the impeller outlet. Modes 1 to 4 of the flow field exhibit similar periodic anti-symmetric coherent structures. At the design speed, the flow field structure is dominated by shaft frequency, but this influence significantly decreases when the speed deviates from the design speed. The findings of this study can help enhance centrifugal pump stability.