Experimental and numerical analysis of hydraulic performance in an axial-flow pump under diverse inflow conditions

Axial-flow pumps have complex hydraulic performance under diverse conditions, especially under low-flow conditions, which may occur rotational stall and brings serious system vibration. By combining experiments and numerical simulation analysis, the fine features of the local internal flow field in multi-flow rate conditions are accurately reflected, revealing the mechanism of changes in the internal flow field and hydraulic performance of axial-flow pumps under different flow conditions, especially at low-flow conditions. As the flow rate decreased, the backflow velocity in near wall area of the inlet pipe and circumferential swirl velocity increased gradually, and the tip leakage vortex (TLV) and pressure surface vortex also increased gradually. Based on the average axial velocity V0 under the design flow rate, the axial backflow velocity was −1.18 V0 and the circumferential velocity was −3.53 V0 under the deep stall condition. The maximum vorticity of TLV, secondary vortex and pressure surface vortex was 5 × 106 S−2, and the area of maximum intensity was the largest. The interaction between the secondary vortices and the mainstream intensifies the formation and development of passage vortex and blocks the inlet pipe. Under the influence of comprehensive factors, the entropy production in the inlet channel and impeller region reached the maximum under the deep stall condition, both of which were above 22 × 10−2 kg m2 s−3 K−1, more than twice that outside the saddle zone. This study analyzed the flow instability under biased conditions from multiple levels and perspectives, providing a basis for improving the hydraulic performance under diverse flow conditions in the future.