Hydrodynamic optimization of the impeller and diffuser vane of an axial-flow pump

Enhancing the hydraulic performance of an axial-flow pump is necessary for increasing the working efficiency and reducing the costs of the pump. In the present study, the impeller and diffuser vane geometry of an axial flow pump are optimized to improve the total efficiency and total head. The internal flow field was obtained by solving the steady-state Reynolds-averaged Navier-Stokes equations in the k-ω shear stress transport reattachment modification turbulence model. The structure was modeled on a hexahedral mesh with a small y+ value at all walls. The total efficiency and total head were chosen as the objective functions in two multi-objective optimizations: one for the impeller with four design variables (shroud chord length, hub chord length, inlet blade angle at mid span, and stagger angle at mid span), the other for the diffuser vane with four design variables (hub radius at the trailing edge, hub position at the leading edge, hub blade angle at the leading edge and middle blade angle at the leading edge). These design variables were selected because they sensitively affect the objective functions, as confirmed using the screening technique based on the 2k factorial method. The blades were optimized by an approximation function based on the following surrogate models: response surface approximation, kriging meta, and a radial basis neural network. After optimizing the impeller, the total efficiency and total head were 0.974 % and 21.028 % higher respectively, than those of the reference impeller, and after optimizing the diffuser vane, the total efficiency and total head were 3.097 % and 10.205 % higher, respectively, than those of the reference model.