The existing research on improving the hydraulic performance of centrifugal pumps mainly focuses on the design method and the parameter optimization. The traditional design method for centrifugal impellers relies more on experience of engineers that typically only satisfies the continuity equation of the fluid. In this study, on the basis of the direct and inverse iteration design method which simultaneously solves the continuity and motion equations of the fluid and shapes the blade geometry by controlling the wrap angle, three centrifugal pump impellers are designed by altering blade wrap angles while keeping other parameters constant. The three-dimensional flow fields in three centrifugal pumps are numerically simulated, and the simulation results illustrate that the blade with larger wrap angle has more powerful control ability on the flow pattern in impeller. The three pumps have nearly the same pressure distributions at the small flow rate, but the pressure gradient increase in the pump with the largest wrap angle is smoother than the other two pumps at the design and large flow rates. The pump head and efficiency are also influenced by the blade wrap angle. The highest head and efficiency are also observed for the largest angle. An experiment rig is designed and built to test the performance of the pump with the largest wrap angle. The test results show that the wide space of its efficiency area and the stability of its operation ensure the excellent performance of the design method and verify the numerical analysis. The analysis on influence of the blade wrap angle for centrifugal pump performance in this paper can be beneficial to the optimization design of the centrifugal pump.
The valuation of the hydraulic performance of a centrifugal pump with pre-whirl regulation of the inlet guide vanes was studied experimentally by varying the pre-whirl angle from -60° to 60° with distances between the inlet guide vanes and the impeller inlet of 280 mm, 380 mm and 460 mm. The efficiency-flow curves and the characteristic curves were obtained for the pump for various operation conditions. The experiment results demonstrated that the pre-whirl regulation widened the high efficiency zone and improved the hydraulic performance for off-design conditions with the proper pre-whirl angle. The axial distance between the inlet guide vanes and the impeller inlet influenced the pre-whirl regulation effect of the inlet guide vanes with the best pre-whirl regulation effect obtained for an axial distance of 380 mm. These results showed that an appropriate axial distance between the inlet guide vanes and the impeller inlet can improve the fluid flow at the impeller entrance with pre-whirl regulation for centrifugal pumps.
