Study On Characteristics Of Pump Station Intake And Sewage Intake

The sewage in the river flows to the pumping station with the water flow.The pumping station is generally equipped with a trash rack to intercept the dirt,and the larger dirt can be intercepted.However,due to the spacing of the trash grid,the smaller dirt enters the pump through the trash rack and enters.The dirt which enters the pump is easy to cause entanglement and affect the safe operation of the pump unit.In this paper,based on the problems above in the pumping station,the combination of numerical simulation,experiment and theoretical analysis is used to study the characteristics of pumping station inlet and sewage pumping,analyzing the influence of factors such as type of dirt and the position of the dirt when it cross the trash rack on the position of the dirt reaching the inlet section of the pump impeller and entanglement.The main research contents and results are as follows:(1)Numerical simulation of the internal flow of the experimental axial flow pump device and the large axial flow pump device from the inlet flow passage to the outlet section of the pump is carried out,The internal flow field of the inflow runner is studied under the different working conditions,such as no clogging of the trash rack in front of the inlet flow passage,blockage of the upper and lower part.Analyze the influence of the starting position of the streamline,the blockage of the trash rack and the pump operating conditions on the flow path and the position of the inlet section of the impeller and the internal flow of the inlet runner.Among them,the streamline in the saddle area is very chaotic,indicating that reflow has occurred.The flow velocity distribution of the inlet section of the large axial flow pump device is consistent with the field measurement results.It is uneven and asymmetrical in the overall distribution,and the flow velocity on the right side is significantly larger than the left side.(2)The original test bench was reconstructed,and the inflow channel and the impeller chamber were made of transparent plexiglass for observing the traveling posture and movement law of the dirt in the inlet flow passage and the impeller chamber;A filter screen is installed on the inlet section of the impeller to record the position of the dirt when it reaches the inlet section of the pump impeller,and the position where the impeller chamber is likely to form a blockage is analyzed.Several typical monomer contaminants were tested to determine the main physical properties of the contaminants and to release contaminants at different starting points of the fouling section cross-section streamline used in the corresponding numerical simulations.Photographing from the side and the top of the elbow inlet flow passage records the progress of the dirt in the inlet passage and the circumferential and radial positions of the annular screen reaching the inlet section of the impeller.(3)The results show that when the pump is running in the saddle area,the phenomenon of reflow in the pump mainly comes from the water flow in the middle of the flow channel and the bottom of the flow channel.The actual movement law of the dirt behind the trash rack and the inlet flow passage and its position to the impeller inlet section are the result of the combined influence of the gravity of the dirt and the buoyancy of the water on the basis of the streamline trajectory.The numerical simulation and theoretical analysis results of the dirt movement are consistent with the experimental results.That is,in the direction of the water outlet,the dirt released on the left/right side of the inlet section of the inlet runner is also substantially left/right when it reaches the inlet face of the impeller;Thick cotton cloth,denim,etc.,which are denser than water,are more likely to be clogged on the water outlet side of the impeller.Plastic bags,textile bags,etc.,which are denser than water,are more likely to clog on the left side of the impeller inlet side.Wherein,the dirt whose density larger than water has a critical value passing through the depth of the trash rack.When the depth is less than the critical depth,the dirt passes through the trash rack and rises,and cannot enter the inlet runner due to the blockage of the inlet wall of the pump station.