PIV Measurement And Numerical Simulation Of Flow Field In The Outlet Of Campaniform Inlet Conduit

As an important part of the large and middle size pumping station projects, the inlet conduit is the intake structure of providing good flow pattern for the pump that can divert the water in forebay smoothly into the impeller room of the pump, of which flow pattern can affect the pump performance and security operation greatly.Campaniform inlet conduit is one of large scale intake conduit forms, in abroad; especially in Japan already has a large application, but less domestic application for the lack of designing experience. At present, the experimental researching methods have been mostly confined to the outside characteristics of pump device; no further researches have been done to the internal water flow movement. With the development of computer technology and the wide application of CFD fluid calculation software, although through the method of numerical simulation of water flow, we can achieve all-round flow distribution of the passageway, but the reliability of numerical simulation of internal complex flow of pumping system still needs further textual researching. Therefore, the researching result doesn’t really reflect the internal water flow movement situation. However, only clearly find out internal water flow movement state, can we deeply analyze the hydraulic characteristics and provide the basis for the optimization design of passageways.The author set up a test rig for a set of vertical axial-flow pump device with transparent inlet conduit and analyzed the difference between the performance curve of the pump device acquired on the test rig and that obtained by numerical simulation with FLUENT. For the first time, this thesis adopted advanced, non-contact flow field measurement technique with PIV (Particle Image Velocimetry) to measure the flow pattern distribution of outlet area of campaniform inlet conduit with2D and3D technique and compared with the result by numerical simulation. At the same time, the thesis analyzed three different flow conditions(small flow condition, optimal flow condition and large flow condition),which showed axial velocity along the axial and radial distribution relatively matched but through PIV measured data in the small flow condition summed up the flow pattern distribution of outlet area of campaniform inlet conduit, near the inlet of blade appeared rotational flow with impeller, but in optimal flow and large flow conditions showed the flow was impacted by the coming flow inertia caused by90°diversion and wasn’t influenced by rotational impeller and also showed that the flow prewhirl area caused by rotating impeller was very tiny. So there will be some velocity component along the coming flow direction in the outlet area of the intake conduit, which can cause the uneven distribution in the outlet section of the intake conduit. The designers should fully considered the impact when designing the campaniform intake conduit, but the numerical simulation results in simulating of three conditions have no obvious differences, there is velocity component of flow direction on the sections of the passageway export, this shows that the using of turbulence model of numerical simulation needs improvement to simulate the complex internal flow at the small flow condition. And further illustrate the rotation of the impeller caused more prewhirl area in the outlet area at the small flow condition.