Numerical study of pressure fluctuation in the whole flow passage of a low specific speed mixed-flow pump

The understanding of pressure fluctuation mechanism is the basis for stability and noise analysis in pumps. In this article, numerical study was carried out for the pressure fluctuation within the impeller and the guide vane of a low specific speed mixed-flow pump. Structured mesh was adopted in the whole flow passage. The numerical approach was validated by comparing with the experimental data of external characteristics and fluctuation in the guide vane passage. Through MATLAB code and Fourier analysis, the pressure fluctuation in the whole flow passage was obtained at four flow rate conditions. It is found that pressure fluctuation due to rotor-stator interaction is first enhanced and then weakened along the stream-wise direction with the maximal value located near the guide vane inlet. As a result of the structure design of passage and secondary flow, some obvious vortexes will form at the hub region near the pressure surface at small flow rate conditions, thus aggravating pressure fluctuation therein. On the whole, pressure fluctuation at small flow rate conditions is more remarkable with the fluctuation period being more disordered; the fluctuation intensity is higher in the guide vane than the impeller, while the area of strong fluctuation is also wider.