Study On Optimizing Flow Pattern Of The Inlet And Outlet Conduit Of Postpositional Bulb Tubular Pumping System

The bulb tubular pumping system,which has the characteristics of smooth flow patterns in the inlet and outlet conduits,less hydraulic loss,large discharge capacity and high system efficiency,is especially suitable for pumping stations of the East-Route South-to-North Water Diversion Project.Consequently,it has good application value and developing potential.However,the application of large bulb tubular pumping systems is still seldom.Now,there is only some research on system performance,and few on the inlet and outlet conduits of bulb tubular pumping system.As the important part of large pumping station,inlet and outlet conduits directly affect system performance and safe and reliable operation of a pumping station.Therefore,analysis and research on optimizing flow pattern of the inlet and outlet conduits of bulb tubular pumping system is necessary for reducing hydraulic loss and increasing the efficiency of pumping systems.With the development of the theories and technique of CFD and Computer Hardware Technology,the application of numerical simulation has been more and more widely applied to study flow patterns in the pumping system.This paper uses numerical simulation of 3D turbulence flow to study the inlet and outlet conduits of bulb tubular pumping system.Taking a postpositional bulb tubular pump as an example,3D entity modeling design and unstructured mesh generation of model pumping system are completed in this paper,meanwhile,the technique of locally density mesh is adopted to achieve high accuracy and high quality mesh generation.Simulating 3D turbulent flow field in the bulb tubular pumping system by FLUENT is based on twoκ-εmodels.Comparison between numerical simulation results and model test shows that the RNGκ-εmodel is more suitable for this case.By numerical simulation,the flow field of the bulb tubular pumping system is obtained.The flow pattern in the inlet conduit is smooth,but there are vortexes and deviation flow in the outlet conduit.It is mainly affected by the bulb and circulation at the outlet of guide vane,and the affect of circulation at the outlet of guide vane is more significant.Then the flow pattern of bulb section which is the special structure of the outlet conduit is analyzed in detail.Together with the calculation of hydraulic loss for each part,it is known that the flow pattern of bulb section is not uniform,there are vortexes and deviation flow in the tail of bulb and supporting,and the main hydraulic loss is in this section.According to the characteristics of bulb section,the schemes are studied out to improve flow pattern.Taking hydraulic loss,lifting head and system efficiency as objective function,this paper analyzes the affection of the shape of the supporting and tail on flow pattern,and finally obtains the optimization scheme which can significantly increase the system efficiency.The result of numerical calculation indicates that the better the streamlined form of flow passage component,the less the hydraulic loss,the higher the system efficiency.All these research results are useful for increasing the system efficiency of postpositional bulb tubular pumps in practical project.