Influence of rotor eccentricity on vibration characteristics in a five-stage centrifugal pump with vaned diffusers

To determine the effect of rotor eccentricity on the vibration of multistage pumps, a five-stage centrifugal pump with vaned diffusers was selected to experimentally measure the vibration characteristics under both stable condition and unstable condition due to the rotor eccentricity. The results show that the rotor eccentricity results in an irregular orbit of the rotor axis, which is diffused outward. As the flow rate increases, the peak amplitude of the rotor axis’ orbit first decreases and then increases, and the peak amplitude at the design flow rate is minimized. The main vibration frequencies of rotor axis’ orbit are the axis passing frequency and a secondary high frequency. After rotor eccentricity occurs, all monitoring point vibrations increase by different degrees, the increments of axial vibration are particularly obvious, and the characteristic frequencies of the pump increase.