Unsteady flow and pressure pulsation characteristics in centrifugal pump based on dynamic mode decomposition method

Considering the computing accuracy and resources of numerical calculation, a hybrid Reynolds-averaged Navier–Stokes/large-eddy simulations method based on the von Kármán scale and the corrected eddy viscosity has been used to study the unsteady flow structure and pressure pulsation characteristics in a centrifugal pump. The unsteady flow characteristics of the vertical two-stage marine centrifugal pumps with complex structure have been studied. The dynamic mode decomposition method is used to study the internal unsteady flow structure and analyze the mechanism of pressure pulsation in the centrifugal pump. The results show that the unstable flow in impeller is mainly affected by the inflow state, system rotation, and the structure of the impeller. Different inflow states lead to obvious differences of the internal flow states and unsteady flow structures between the first-stage and second-stage impellers. There are complex pressure pulsation characteristics dominated by different frequencies in different parts of a two-stage centrifugal pump. The impeller blade main pass frequency has different causes at different locations in the downstream flow passages. The mutual matching of different numbers of impeller blades and guide vane blades will result in a kind of impeller guide vane blade interaction frequency in guide vane and volute, which will excite higher harmonics of the impeller blade frequency. Other important characteristic frequencies in centrifugal pumps had been analyzed. The pressure pulsation mechanism analysis of the centrifugal pump will help researchers to optimize the design of the centrifugal pump and improve the operation stability of the centrifugal pump. Some possible improvement measures for typical frequency pressure pulsation are recommended.