Research On The Flow Pattern Improvement Of The Aeration Tank And Forebay By CFD

The water intake punp station of water source includes three main parts:settling tank,aeration tank and forebay.The flow velocity in water intake pump station is slow,the water level changing between a large range,and the internal flow pattern is disorder.When there is no hydraulic optimization measures for the water intake pump station,the internal flow pattern of the settling tank is disorder,the backflow zone,the velocity pole area and vortex appear in the aeration tank and forebay.The adverse flow pattern inside of the water intake pump station can result in local sediment precipitation in aeration tank and forebay,and uneven distribution of flow velocity into the pump.Based on the CFD technology,rectifying measures of the water intake pump station is on research,the study focus on the uniformity of water distribution of perforated tracery wall and hydraulic optimization measures of the whole water intake pump station,as well as the flow characteristics of forebay and the difference of pump suction uniformity under multiple pump running mode.The research results have certain guiding significance to further improving the flow pattern of the water intake pump station,preventing sediment deposition,improving the operation safety and efficiency of water pump,and the reference for choose way can be provided when referring to multiple pump running conditions.(1)Commercial software ANSYS 14.5 was used to simulate the flow pattern of the water intake pump station.The total mesh nodes'number was 1.756 million,which was chose by mesh independence experiment.Compared with different turbulence models,standard k-?turbulence model was slected to do numerical simulation.(2)The perforated tracery wall's hydraulic optimization of settling tank was on research.Under different water level,the water distribution uniformity is different when using different forms(rectangle,circle,diamond)perforated tracery wall;Using diamond perforation tracery wall,water in settling tank distributing more uniform,the flow pattern is relatively smooth,and it is conducive to the settlement of sediment and other solid particles.(3)The flow characteristics of the water pump station was on research.For slope brake hole inflow water intake pump station and slope diffusion free inflow water intake pump station,when there are no measures were taken,the water flow pattern is disorder,the backflow zone,the velocity pole area and vortex appear in the the corner of aeration tank and the slope,and there are serious deviation problem in the forebay.The slope segment of the ramp brake hole inflow water intake pump station exists a large backflow zone,it is difficult to spread evenly in the form of jet flow into the forebay;it is easy to form large area of backflow region in front of the forebay and the slope when it is concerned to the slope diffusion free inflow water intake pump station.(4)The flow pattern improvement of the aeration tank was on research.Filletting the corner of aeration tank and setting up the U-shaped wall and 1/4 arc guide wall at the corridor corner can eliminate the flow separation and dead water zones existing at the corridor effectively;Setting up the double U-shaped wall and double uniform isolation pier on the slope section can improve the apparent drift problem and weaken the backflow whirlpool effectively,which makes the water flow into the forebay relative smoothly.(5)The flow pattern improvement of the ramp brake hole inflow water intake pump station was on research.Without the rectification measures,water flow through the lock hole in jet form and hit back wall directly,which results the formation of large area backflow on both sides of the forebay.The velocity uniformity of the water pump unit has big difference,and each bell mouth section presented inverted V-shape,the velocity uniformity of the intermediate pump unit is the highest,the both sides is poor.By setting up diversion pier in eight shape,partition pier and changing the forebay's rectangular wing wall shape,the flow pattern of the forebay and the flow velocity distribution have improved a lot,especially the bottom water spread evenly,there is no obvious vortex,and the backflow on surface has been controlled.The uniformity of the pump unit are improved,and the difference of the pump unit's uniformity has reduced markedly.(6)The flow pattern improvement of the slope diffusion free inflow water intake pump station was on research.Without the rectification measures,water flow into the forebay through the diffuser,and it forms the backflow zone on either side of the forebay,at the same time the local vortex occurring near the forebay's back wall;Meanwhile,the suction uniformity is high on both sides of pump unit,and the intermediate pump unit is low.By setting up diversion pier in eight shape,partition pier and 45° inclined baffle,the flow pattern of the forebay and the flow velocity distribution have improved a lot,the suction uniformity of the pump unit are improved.Increasing the height of partition pier is benefit to improve the surface flow pattern of the forebay,and weaken the underlying mutual interference between the each pump unit.The position of the diversion pier in eight shape should be set at the diffuser,if it is too close to the back and sides,the vortex and backflow on the surface of pump unit become more serious;The angle of the diversion pier in eight shape is suitable for taking 18 ° or so,if the spread angle is too small,the suction uniformity will reduce on both sides of the pump unit,on the contrary,the local vortex in the forebay will increase;It is remarkable for the improvement of the flow pattern within using 45° inclined baffle,with inclined baffle's position away from the wall direction,the velocity distribution at bottom is more uniform,and the uniformity of the suction pump unit is the better.(7)The research on hydraulic characteristics of slope gate inflow within different opening pump ways.Under the condition of no measures in the water pump station,different ways to open pump have less effect on the flow pattern in the forebay.NO.1,NO.2,NO.3,NO.4 pump units is run at the same time,each unit pump suction has better uniformity and less difference.That is the optimal solution under the condition of no measures.After water intake pumping station optimization measures,under the different ways of opening pump,the parties state pool at the bottom of the streamline distribution is relatively uniform,no obvious return.In the middle of former pool,there are different level partial backflow whirlpool;In the former pool surface streamline distributes more uniform,and the difference is not obvious.There is local vortex occurred in two side inclined wall;In the ways of opening pump in scheme 4 and 3,uniformity of operation of pump unit water absorption is higher,the velocity uniformity of the exit section in the fallopian tube in scheme 4 is over 72%,so the scheme 4 should be application to run water intake pumping station which is adopted by improvement measures.