Study On Transient Pressure Variation In Leaky Pipe Network

Urban water supply pipe network is one of the most important basic facilities in the city and plays a positive role in ensuring the steady development of society and the normal healthy life of residents.Losses of pipe network are a common problem in domestic and foreign water supply industries.The problem of pipeline leakage not only leads to wasting water resources,but also causes huge economic losses to water utilities and society.When the actual water supply pipe network is in operation,the transient pressure in the pipe will be caused due to problems such as valve closing,accidental pump shutdown,and sudden change of water consumption.Foreign pollutants will enter water supply system through leak points when the pressure in pipes is negative,which affecting drinking water safety and residents' health problems.When positive transient pressure is generated in pipe,a sharp rise in pressure can damage the pipeline and affect the normal operation of the pipeline network.It has practical significance to study the transient pressure changes in the leaky pipeline network.This paper designs a leaky pipe network experimental platform based on the physical model principle.The transient pressure in the pipe is generated by sudden self-produced ball valve closing in upstream of the pipe.The branch pipe is replaced in order to simulate various pipe types in the test.Different areas of circular leaks are set to simulate different leaky pipe network.The valve and the upstream equipment are workable to control the flow rate,pressure and other working conditions in pipes.The pressure measurement and acquisition system installed on the platform can record the information of the pressure change in the pipe,and on this basis,the amplitude value and attenuation law of the transient pressure transmitted in the pipe is studied.The experiment mainly focuses on the analysis of transient hydrodynamic phenomena in the pipe and the theoretical calculation.The regularity of the transient pressure at each position of the pipe network are studied.The content is as follows:(1)Through the monitoring of the transient pressure of each position in the pipeline,the influence of the influencing factors on the transient pressure at the boundary is based on the results of the data.The law of the superimposed and reduction of the transient pressure in the pipes of different layouts and the changes of propagation along the leaky pipeline are also analyzed in this paper.(2)Two characteristic values of transient pressure are proposed in this paper: maximum pressure drop,the difference between maximum negative pressure and maximum positive pressure,in order to analyze the influencing factors such as the initial flow rate in the tube,the diameter of the leaky hole,the form of the pipeline,and the valve closing time.(3)The coupling relationship between the influencing factors and the transient pressure at the leaky point is summarized.Based on the transient flow theory,an empirical formula is deduced,combining software to optimize the maximum pressure drop of transient pressure at leaky points.Through the analysis of the test results,the main conclusions can be obtained as follows:(1)With the increase of the initial flow velocity and the decrease of the valve closing time,and the fluctuation at the leaks is more severe.(2)The transient pressure in the pipe is regulated by the leakage point.Under the same working condition,the transient pressure gradually decreases with the increase of the leakage diameter.(3)The change of transient pressure is related to the form of the pipeline,especially the location and quantity of branch pipes.