Research On Influencing Factors And Regulation Measures Of Outlet Pipeline Deposition In Water Intake Pump Station

Under the increasingly prominent contradiction between supply and demand of water resources in China,the construction of water transmission and diversion project to solve the problem of water quality shortage has gradually become a main way of water supply.If there is a large amount of sediment in the pipeline in the water transmission project,it will seriously affect the safety and economy of the normal operation of the pipeline.In this paper,based on the research background of the water transmission and diversion project in a city,the sediment distribution law of the outlet pipeline of the water intake pump station under the design operation mode and different operation conditions is studied by CFD numerical simulation technology.(1)Using software ansys 14.5,the mixture model of Euler-Euler model is selected for multiphase flow model,and the standard k-? model is selected for steady simulation of turbulence model.Through the analysis of grid independence,the total number of grid is 3.3 million.(2)Under the design operation mode,the distribution law of sediment in the water delivery pipeline in the water source area.The sediment deposition is more near the bottom of the pipeline,and the sediment content in the gradually expanding section is reduced,and the overall trend from the inlet pipe to the outlet pipe is gradually reduced.There is a vortex in the middle and rear part of the diffuser,where the sediment is not easy to deposit.(3)Under the design operation mode,the sediment characteristics have a certain influence on the sediment deposition in the outlet pipeline of the water intake pump station.The sediment deposition in the pipeline is directly proportional to the sediment size and content of the incoming flow.The larger the sediment size is,the larger the sediment content is,and the easier it is to deposit in the water transmission pipeline.Therefore,in the water transmission and diversion project in the water source area,it is necessary to pay attention to the sedimentation efficiency of the pre sedimentation aeration tank.(4)The influence of the structural parameters of the pipeline on the sediment distribution in the water transmission and diversion project under the design operation mode.The geometric parameters of the outlet pipeline structure of the pumping station have a certain influence on the sediment deposition in the pipeline.The diameter of the water pipe has a certain influence on the velocity of non scouring and non silting in the pipeline.When the diameter of the water pipe is 2.4m and the velocity is 2.77m/s,the sediment stratification in the water pipe is the most obvious and the sediment distribution is relatively uniform.Different pipeline gradients also make the distribution of sediment content in the pipeline different.When the pipeline gradient is negative and reaches 0.02.the sediment distribution in the sediment laden flow reaching the second half of the pipeline is more uniform,and the sediment is easy to flow out of the pipeline with the flow,so the gradient is more favorable for the pipeline to transport sediment laden flow.The angle change of the bend also has a certain influence on the sediment deposition in the pipeline.When the bend degree is 45°,the pipeline is most favorable to transport sediment laden flow.The larger the angle of the bend is,the more sediment is deposited in the water pipe of the pump station,and the smaller the degree of the bend is,the sediment in the water flow is easier to enter the main water pipe.Therefore,under the design operation condition,the pipe structure adopts the water pipe diameter of 2.4m,the gradient of-0.02,and the elbow angle of 45°.it is the most favorable for the regional water transfer of the water transmission and diversion project in the water source area.(5)This paper studies the influence of different operation modes on the sediment distribution in the pipeline of water transmission and diversion project in the water source area and explores the regulation measures.Under four different flow conditions with different number of pump units,the sediment deposition rules under different operation modes are analyzed.When there are more units in operation,that is,when four or five pump units are running at the same time,it is not easy to deposit in the pipeline.Under the operation condition of four pump units running at the same time,the influence of different pump opening modes on the sediment deposition in the pipeline is studied.The results show that the height of the high sediment concentration area at the bottom of the outlet pipe is relatively small,the sediment layer of the outlet pipe is obvious,the sediment distribution is relatively uniform,and there is no vortex in the gradually expanding pipe section,which is a better operation scheme when the 1#?2#?3#and 5#pump units are running at the same time under different pump on conditions.