Numerical Optimization For Curve Flared Two-way Outlet Conduit Of Vertical Axial Flow Pump

In China, the tank two-way passage vertical pumping device is applied to most of the large-scale pumping stations with tasks of both irrigation and drainage in order to draw and discharge water as well as pump water in and out. This device has quite a few advantages. It occupies smaller space; its production technology is mature; it is easy to install and its maintenance is convenient. However, in order to reduce the pump station excavation depth so as to reduce the construction cost, this device is designed to have the shorter vertical height, which leads to the difficulty of designing the pump outlet structure and results in the hydraulic loss in the outlet conduit and its low efficiency. Considering its design difficulty and, the numerical optimization based on CFD technology will hopefully improve its efficiency, which is of great theoretical and practical significance.The Reynolds-averaged N-S equations and the standard k-sturbulent flow model are adopted in this paper to numerically simulate one typical tank two-way pumping station so as to uncover the internal flow conditions, and the simulation results are used for external characteristics comparison and analysis, thus to check the reliability of CFD calculation. By comparison of the hydraulic loss and the flow of outlet conduit in the situations with and without impellers, the influence of the pump on the hydraulic loss and the flow conditions should be considered during the two-way passage optimization process, in which the pumping device is calculated in an integrated way.The orthogonal test of three factors and five levels is made. Three factors are the height from the center of the impeller to the top plate H, the height of the bell-mouth below the top plate h, and the diameter of the outlet of the bell-mouth Do. The25programs are calculated under8operating conditions, and the influence of the factors on outlet conduit are observed and analyzed. Based on the optimized size of the outlet conduit, the effects of the different conditions with the straight guide vane and the diffusion guide vane on the device efficiency are analyzed.Research shows that the optimal value of the height from the center of the impeller to the top plate is1.9D, that the optimal value of the height of the bell-mouth below the top plate is0.5D, and that the optimal value of the diameter of the outlet of the bell-mouth is1.6D. Using the diffusion guide vanes can further improve the efficiency of the pump device.