Study On The Comprehensive Protection Of Water Hammer In The Long-Distance Water-Transmission Line

In recent years,due to the shortage of water resources and the waste of water resources,more and more long-distance water supply projects appear in people's vision.In the long-distance water supply project,due to the long distance of the water pipelines and the changes in elevation,if water hammer happens,there will be serious consequences.At the same time,the occurrence of water hammer phenomenon is also becoming more and more frequent.This problem need to be solved urgently.Therefore,the positive study of water hammer has an important actul meaning and the prediction and the protection of the phenomenon of water hammer can ensure the security,reliability of water supply projects.This thesis studies on the water hammer calculation model of long-distance water-transmission line and the measures of comprehensive protection.The basic model of the water hammer and the method of characteristics in hydraulic transient's analysis is described.The characteristics of long-distance water pipeline and water hammer are analysed.The basic structures,principles,advantages and disadvantages of water hammer protection devices(such as the surge tank,air valves,check valve,butterfly valve)are briefly introduced.The mathematical models and computing methods arre established.Because Matlab has powerful capabilities of processing data and graphical output,so we can program water hammer using Matlab,combined with a variety of boundary conditions of the pipeline and the method of characteristics.The result of water hammer and the protection can be clearly observed.The water hammer is simulated In Matlab with programming the boundary conditions of the various types of equipment,using the method of characteristics.Combined with some examples of calculation by the computer numerical simulation,the following conclusions are given.Because the pipeline is long and the elevation changes,negative pressure and water column separation can occur frequently in the long-distance water pipeline.Negative pressure changes widly and the result of water column separation is serious.It is complex to calculate the water hammer and protect the pipeline.So Preventing the occurrence of negative pressure,water hammer of cavities collapsing especially,is emphasis.The Calculate of water hammer and the protection of the pipeline rely on the principles of reliability,effectiveness and economic.The locations and parameters of surge tank,air valves are adjusted gradually according to the principles and the characteristics of long distance pipeline.We need to take comprehensive and effective measures to improve the safety and reliability of the protection.Check valves are Installed in the pump outlet.The surge tank must be Installed in the start of pipeline if there is high negative pressure.According to the elevation of the pipeline and the optimization calculation of water hammer,surge tanks can be installed appropriately in the pipeline.Compound air valves are installed in the pipeline reasonably and overpressure relief valves are installed between surge tank and air valves.the comprehensive protection of water hammer can Improve reliability highly and it is the most effective measure of solving the problem of water hammer of cavities collapsing and the cavity in the long pipeline.The improved design method of the water injection pipes in surge tank is proposed.It is suggested that the simulation experiment should be done in the site to make sure of the reliability and validity of the protection.