Investigation of the internal flow characteristics of a mixed-flow pump in the hump region

Global energy shortage has increasingly become a major issue of global concern. Since the pump is the largest component in the energy conversion device, it is very important to improve the energy characteristics. The existence of tip clearance leads to the formation of leakage vortices, which causes flow instability and performance degradation, especially in the hump region. This paper investigates the internal flow characteristics of a mixed-flow pump in the hump performance region. The boundary vorticity flow (BVF) diagnosis theory and the vorticity transport equation are utilized to analyze the influence of complex vortex structures on pressure pulsation and flow patterns. It can be found the vortex structure in the impeller is divided into primary tip leakage vortex (PTLV) and secondary tip leakage vortex (STLV) under the hump condition (0.7Q_dm). The vortex structure near the leading edge (LE) of the blade have a tendency to move to the next blade, and the scale increases first and then decreases. On the contrary, the vortex structure near the trailing edge (TE) does not change significantly with time. In the spectrum analysis of the leakage vortex and pressure pulsation, the complete evolution frequency of the leakage vortex is 1.1f_n, while the pressure pulsation is 1.0f_n. This study provides a theoretical basis and technical support for the design of the mixed-flow pump.