Optimization and performance analysis of mixed-flow pump impeller under different blade inclination angles

To investigate the influence of blade inclination angle on the performance of mixed-flow pumps, this study takes a blade-adjustable mixed-flow pump with a specific speed of 748 as the reference model. Under the constraints of keeping the impeller head basically unchanged and the cavitation performance not deteriorating under the design condition, the parameters of mixed-flow pump blades with blade inclination angles of 50°, 55°, 60°, 65°, and 70° are optimized. We compared the performance of the pump under different blade inclination angles and analyzed the reasons for the performance differences based on entropy production theory. The research results show that for the scheme with a blade inclination angle of 70°, there is an obvious saddle region in the head curve, while for the other schemes, although there are inflection points in the head curve, no obvious saddle region appears. As the blade inclination angle increases, the high-efficiency region of the blade work generally shows a decreasing trend, and the efficiency under the design flow condition gradually increases. When the blade inclination angle is small, there is an obvious secondary flow at the hub of the guide vane inlet, resulting in an increase in entropy production in the outlet section. Under the large flow condition, with the increase in blade inclination angle, pump section efficiency first increases and then decreases. Under unstable flow conditions, there is a strong secondary flow from the impeller to the inlet section, leading to an increase in entropy generation at the inlet section. This research reveals the influence of blade inclination angle on the performance of mixed-flow pumps, and the results can provide a reference for the optimal design of rotating machinery.