Study On Water Bias Problem In Outlet Passage Of The Large Pumping System With Slanting And Extensive Pump Shaft

Large low-lift pumping stations are widely used in important areas such as trans-basin water transfer,water environment improvement,agricultural irrigation and urban flood control.The inclined pump device is one of the main pump device types of large-scale low-lift pumping stations.It has been applied to many large-scale low-lift pumping stations such as Yanguan Pumping Station,Taipu River Pumping Station and Sanbao Pumping Station.In the research on the inclined pump device,it is found that the flow velocity of the two holes of the oblique water outlet channel is obviously different,and there is a serious problem of water biasIn order to solve the water bias problem of the outlet flow passage in the inclined pump unit,the paper takes a large pump station inclined pump device as the research object,uses CFD analysis method and model test method to analyze the cause of the water bias,and proposes to solve the drift problem.Thoughts and measures,the following conclusions were obtained:(1)The three-dimensional flow field numerical simulation of a pumping station using the length of the conventional length pier is carried out.The drift coefficient of the outlet channel is calculated to be 2.738,and the flow of the two-hole water outflow from the outlet channel is obviously different.One hole is large,the other one is small,and the water bias problem is serious.When viewed in the direction of the water flow,the main flow in the outlet flow channel is biased to the left side,and a large range of vortex regions exist on the right side of the flow channel.(2)The effects of the flow field on the curved flow channel and the unbent flow channel were studied under the condition that the inlet flow of the flow channel has a ring volume or not The nature of the water bias problem in the inclined water flow channel was a flow phenomenon which occurring in an oblique outflow channel with a circular flow which spirally flows into an S-shaped curved outflow channel(3)A measure to reduce the water bias problem of the inlet flow of the flow passage in the curved section of the inclined outlet passage is proposed.The numerical simulation method is used to study the influence of different elements of the deflector on the water bias in the inclined outlet channel.The results show that the longer the length of the deflector,the smaller the drift coefficient of the outlet channel and the greater the head lose;The number of baffles more,the drift coefficient smaller when only the vertical guide plate or the lateral baffle is used.The rectification effect of vertical deflector is better than that of transverse deflector.(4)The length of the pier has obvious influence on the water bias of the inclined outlet passage.The length of the conventional pier will make the main flow of the water flow to the left.The length of the long pier will make the current flow to the right.After optimization calculation,the optimal middle pier length of the outlet channel is determined to be 23.35m,and the flow rates of the two holes in the left and right flow passages are basically equal,and the drift coefficient is close to 1.(5)The optimization scheme of the length of the middle pier was adopted by a large inclined pumping station.The model test of the inclined pumping device was carried out.The test results show that the hydraulic characteristics of the inclined pumping device,such as energy performance,cavitation performance and pressure fluctuation,all meet the design requirements.The flow rate of the two outlet channels is basically the same.The numerical simulation results are in agreement with the model test results.This paper makes a thorough study on the water bias phenomenon of the outlet passage of large-scale oblique pump device,and puts forward an effective method to solve the water bias problem of the outlet passage,which improves the hydraulic performance of the outlet passage and provides an important guarantee for the safe and stable operation of the pump device.