Influence of outlet edge position of guide vane on performance of well submersible pump

Abstract: The well submersible pumps have a large number of stages and complex structures. The inflow conditions of the secondary impeller are quite different from its first stage. Provided that the inflow conditions of the remaining secondary impeller inlets cannot be guaranteed, the efficiency will be significantly reduced as compared with the first stage impeller, which will result in a decrease of the overall efficiency of entire pump and uncontrollability of the pump design. Therefore, in order to study how the space guide vane ensures the inflow conditions of the secondary impeller, especially the influence of the outlet position of the space guide vane on the inflow conditions of secondary impeller, the 250QJ125 five-stage well submersible pump was studied as a model in this paper. Under the given conditions that other geometric parameters were fixed, the position of the outlet edge of the original guide vanes was changed along axial direction to make it both perfectly perpendicular to the rotation axis and coincide with the radius line, and 6 schemes were designed, including 1 original scheme and 5 improved schemes. Based on Reynolds time-averaged Navier-Stokes equations and RNG(re-normalization group) k-ε model, the SIMPLE algorithm was used to perform the three-dimensional numerical simulation of the entire flow path. The head and efficiency of the schemes were obtained. It was found that the scheme in which guide vane outlet position extended 30 mm along the axial direction had an increase of hydraulic efficiency of 1.2% compared with the original scheme, and the head increased by 6.8 m, and it was the best scheme. At the same time, according to the calculation results of the external characteristics under the design conditions of each scheme, the impeller data from the first to fifth stage of each scheme were extracted, and it was found that the hydraulic efficiency and head of the first stage impeller were basically the same with the best improved scheme. The remaining secondary impeller efficiency and head were quite different from those of the first stage. The remaining secondary impeller efficiency of the best improved scheme was basically the same as that of the first stage impeller, and the head reduced by 1 m; however, its head was approximately increased by 2.2 m compared with the heads of the other stages of the original scheme. Finally, the internal flow field of each scheme on the outlet section of the vanes was analyzed. The results showed that the vanes' outlet edge position along the axial direction can change the flow state of the water flow at the vanes' outlet, and make it a dispersed rotating flow. The number of dispersed vortices is as same as the number of blades of the guide vane. When the outlet edge of the guide vane extends to an appropriate position, the inlet ring volume and impact loss of the following stage impeller can be reduced. The matching relationship between the guide vanes and the following stage impeller can be improved.