Study On The Numerical Simulation Of The Influence Of The Outlet Circulation Of Axial Flow Pump To The Hydraulic Loss Of The Outlet Conduit

As the construction of the East Route of South-to-North Water Diversion Project, as well as the implementation of agricultural irrigation-drainage and urban flood-prevention project, our country has built or will build a large number of large-scale low-head axial flow pump stations. The outlet of the axial flow pump has circulation which leads to the additional hydraulic loss and bias flow. Therefore, studying the outlet circulation has an important practical significance in improving the pumping system efficiencyThis article is based on the CFX software and RNG-turbulent mode to simulate the whole pumping system, analyze the outlet circulation characteristics of axial flow pump under various conditions, study on the influence of outlet circulation on the hydraulic loss of outlet pipe and compare the results with the none circulation.In this paper, six different outlet conduits are analyzed and compared. Through the calculated results, we could see: (1) Under none circulation, the hydraulic loss of the outlet pipe satisfies the relation: h = SQ2, but cannot satisfy that under circulation; (2) Due to the existence of the circulation, the hydraulic loss of the outlet pipe reduces first and then increases; (3) The pressure-recovery factor under circulation increases first and then reduces with the flow increases, but under none circulation the pressure-recovery factor reduces gradually; (4) The hydraulic loss of the outlet pipe has the relation with the divergence angle of the outlet pipe, through the numerical simulation we can find the most superior angle which can make the smallest hydraulic loss; (5) The hydraulic loss in the maximum efficiency point isn't the smallest, whose flow is larger than that in the maximum efficiency point; (6) Due to the existence of the circulation, both sides'flow of the division pier of outlet pipe is different.This article has been funded by the the national"Eleventh Five-Year"science and technology project—the key technology research of the large pumping station reconstruction in the irrigation districts.