Experimental investigation of pressure fluctuation in a mixed-flow pump under gas-liquid two-phase flow conditions

The flow in mixed-flow pumps under gas-liquid operating conditions is complex, involving special phenomena such as secondary flow and bubble breakup and coalescence. As a result, its pressure fluctuation characteristic is far different from that under pure water conditions. In this work, the energy performance, pressure fluctuation characteristics, and flow pattern under different inlet gas volume fractions (IGVFs) are studied through a visualization test in a mixed-flow pump. The air pocket forms easily close to the suction side of diffuser vanes, where two pressure fluctuation monitoring points are set up. The pressure increment decreases continuously when the IGVF increases, and the flow pattern shows a transition from bubble, condensed bubble, and air pocket to separated flow. Moreover, the pressure fluctuation amplitude and peak-to-peak values increase. The main frequency under different IGVFs is maintained as the blade passing frequency. When the IGVF increases to 15%, the peak-to-peak amplitude at P1 reaches the maximum, which is 2.24 times that of the pure water condition. Some amplitudes at one frequency fluctuate at different times when the IGVF is higher than 10%. The findings contribute theoretical support in improving the stability of multiphase pumps.