Design Optimization of Mixed-flow Pump Impellers and Diffusers in a Fixed Meridional Shape

In this paper, design optimization for mixed-flow pump impellers and diffusers has been studied by using a commercial CFD code and DOE(design of experiments). We also discussed how to improve the performance of the mixed-flow pump by designing the impeller and diffuser in the mixed-flow pump. Geometric design variables were defined by the vane plane development which indicates the blade-angle distributions and length of the impeller and the diffusers. The vane plane development was controlled by using blade-angle in a fixed meridional shape. First the design optimization of the defined impeller geometric variables was done, and then the flow characteristics were analyzed in the point of incidence angle at the diffuser leading edge for the optimized impeller. Then design optimizations of the defined diffuser shape variables were performed. The importance of the geometric design variables was analyzed by using 2(k) factorial designs, and the design optimization of the geometric variables were determined using the response surface method. The objective functions are defined as the total head and the total efficiency at the design flow-rate. From the comparison of CFD results between optimized pump and base design model, the reason for the performance improvement was discussed.