Numerical analysis on the cavitation characteristics of a pump with an inducer in non-uniform inflow

This study aims to investigate the mechanism of the cavitation characteristics influenced by the non-uniform inflow. A condensate pump with an inducer is investigated. The performance and the cavitation characteristics are experimentally tested. Both the cavitating and non-cavitating flow fields are carefully analyzed based on the numerical results. For a better understanding of cavitation characteristics, a comparison of the pumps with an annulus inlet casing and a straight inlet casing is conducted and analyzed. The results show that the uniformity of the inflow induced by the annulus inlet casing has little effect on the pump performance while it affects the cavitation characteristics. Under the design point, the cavitation morphology for the two different inlet casings is quite similar at the same outlet pressure. There exist three primary features at the outlet section of the annulus inlet casing: the circumferential components, the uneven axial velocity, and some typical streamwise vortex structures. Based on the secondary flow theories, it is found that the non-uniformity induced by the annulus inlet casing mainly influences the development of the secondary flow close to the hub, and the negative induced streamwise vorticity would gradually decay along the radial direction. The different inlet casings make the main contribution to the vorticity transportation around the attached cavitation region. The difference in the cavitation characteristics for the straight inlet and annulus inlet casing is mainly attributed to the different flow losses in the inlet casings and the non-uniformity of the magnitude of the relative velocity and the angle of attack due to the secondary flow.