Effect of circumferential spokes on the rotating stall flow field of mixed-flow pump

Mixed-flow pumps are highly susceptible to experiencing rotational stall and generating vortices, as well as unstable pressure fluctuations when operating at low flow rates. These issues lead to a decline in the stability and efficiency of pump systems. To address this challenge, this paper introduces a circumferential spoke structure as an alternative to the traditional “J-Groove” to delay the onset of rotational stall in mixed-flow pumps. Using numerical simulations and experimental measurements, the study compares the external and internal flow characteristics of conventional mixed-flow pumps with those equipped with circumferential spoke structures of varying depths. The research findings demonstrate the significant effectiveness of circumferential spoke structures in enhancing the stall performance of mixed-flow pumps. Notably, when a 5 mm-depth circumferential spoke structure is employed, it leads to a 1.27 % improvement in efficiency and a 2.18 % increase in head at 1.0Qdes. Furthermore, at 0.54Qdes and 0.62Qdes, there are efficiency enhancements of 3.96 % and 0.59 %, along with head improvements of 3.62 % and 0.67 %, respectively. Additionally, the 5 mm-depth circumferential spoke structure helps mitigate rim leakage flow and stall vortex development within the mixed-flow pump impeller. This research outcome provides valuable theoretical insights for the optimization and efficient, stable operation of large-scale hydraulic machinery.