Research On Optimal Design And Risk Prediction Of Distributed Pressure Sewage Pipe Network System Based On Numerical Simulation

The sewage pipe network system is one of the city's important infrastructures,which is related to the city's health and future development.With the rapid development of cities,the amount of sewage water has increased and the changes in water quality have been complicated.The traditional drainage system is based on gravity flow,while the research on pressure flow drainage system is relatively small.The outdoor drainage design specification stipulates that the design of the sewage system is mainly gravity flow,and the pressure flow drainage system can be used when the terrain is restricted or gravity flow is not economical.The pressure sewage system has the advantages of small pipe diameter,shallow burial depth,large expansion flexibility,and easy to find leakage,etc.In recent years,more and more applications have been applied to the reconstruction and expansion of sewage systems in industrial parks.However,most of the research on the pressure sewage system stays at the shallow level of engineering design and construction experience,and there is a lack of deep research on the risk prediction and optimization design of the pressure sewage system.This article takes the pressure sewage system of an industrial park in Hangzhou as the background,uses Flowmaster and Fluent to simulate and analyze the hydraulic characteristics of the pressure sewage system,and predicts the overall and local water hammer risk and siltation risk,and proposes optimization measures to reduce the risk.Main conclusions as follows:(1)Drawing on the pressure water supply system,a hydraulic calculation method suitable for the pressure sewage system is proposed,and the calculation method is simulated and verified by Flowmater.The correction coefficient of the head loss along the way for the Haicheng-William formula for the pressure sewage system is 1.13;(2)Too large or too small diameter will increase the risk.If the pipe diameter is too small,the nodal pressure is 1.3bar(1bar=0.1Mpa)greater than the designed pipe diameter,which increases the risk of water hammer;when the pipe diameter is too large,the minimum flow rate is about 0.4m/s,which increases the risk of pipeline deposition;(3)Conduct risk analysis for different start-stop pump working conditions.Through correlation function analysis,the results show that the risk of water hammer is greatest when two pumps are started at the same time.Different pipe diameters correspond to different critical flow rates.When the pump is stopped,the flow rate is 0.5m/s,and siltation risk may occur;(4)Compare different types of three-way flow field to predict local riskanalysis.The hydraulic conditions of the direct tee are the best,and the risk of water hammer and siltation is the smallest.In the design,the direct tee is preferred.With the increase of the bending radius,the risk of water hammer is reduced and the risk of siltation is increased;(5)Optimize the design.Designing an air valve can reduce the risk of water hammer.The water pumps of various enterprises are linked to achieve balanced operation to ensure that the flow rate in the pipeline is greater than the critical flow rate,reducing the risk of pipeline siltation.