Research On Control Of Water Hammer From Water Pipeline Based On Valve Regulation

The industrialization and urbanization process have been accelerating and deepening of China for a long time,leading to rising demand for water resources in various regions and industries.At the same time,the shortage of water resource in many areas is still keeping large because of restriction from geographical divergence,different seasons and periods and many other factors.In order to solve the problem of water imbalance caused by geography,time domain and other factors,many long-distance water transfer projects came into being,and they have been widely applied and developed rapidly,and achieved remarkable results.It is very easy to cause the pipeline to burst or other accidents,such as damage due to internal and external pressure difference of pipeline which seriously interfere with the normal production and life order,once the water hammer problem occurs in the water transfer pipeline.The water hammer problem in the water pipeline not only seriously threaten safety of the water transfer project,but also limitand restrict the further development of the water transfer project.Therefore,it is of great significance to take reasonable and essential measures to make pressure of water hammer in the pipeline controlled which would ensure the safety and stability of the water delivery project.Based on the theoretical analysis of water hammer calculation,the water hammer calculation model was established in this paper.Then numerical simulation calculation was carry out by using the self-prograuming.The following works were completed:(1)Basic differential equations of water hammer which were solved by using the characteristic line method were showed.Combining results of water hammer's differential equations,the boundary conditions required for water hammer calculation were established,to provide theoretical support for simulation calculation.(2)The influencing factors in the continuous two-stage closing mode are studied while using one valve located in the end of the pipe as the water hammer control scheme.Results of water hammer by non-continuous two-stage closing mode are calculated and analyzed simultaneously.It is found that the maximum pressure of water hammer can be effectively reduced and the minimum pressure of water hammer can be increased effectually,reducing the negative pressure in the pipeline by extending valve operating time,adopting the "quickly closing and then slowly closing" two-stage continuous closing mode and the non-continuous two-stage closing mode with selecting a reasonable combination.The probability of water column separation also got lower.It is beneficial to exert a better control effect on the water hammer problem while closing process further decomposing the valve and increasing the number of movements.(3)The water hammer pressure in the pipeline could be controled when the pipeline is decomposed into two or more sections for segmentation management by adding valves at suitable positions in the pipeline.The influencing factors including coordination mode in two-valve,mode of action in double-valve and intermediate valve position were studied by us:ing the mode of two-valve coordinated control.The results show that the coordinated operation of the two valves played a role to the improvement of the water hammer problem in the pipeline,and the position of intermediate valve is more suitable near the middle position of the pipeline.Combined with the advantages of the two-stage continuous two-stage adjustment,the two valves are operated in two consecutive stages,which have a better control effect on the maximum and minimum pressure of the water hammer in the pipeline.When the valves are linearly closed,increasing the number of valves in the pipeline and reducing the length of the segment can further promote the control of the multi-valve coordination on the water hammer problem.(4)The water hammer control methods with different valve adjustments were used to calculate and analyze the water hammer pressure through the calculation of the example.The results showed that the single valve,double valves and three valves adjustment have excellent control on the water haumer problem in the pipeline.The effect provided a certain guiding significance for the water hammer control problem in the water transfer projects.