Study On Pump Shutdown And Terminal Control Water Hammer In Branch Water Supply Network With Single Pump And Multiple Tanks

Due to the uneven spatial and temporal distribution of water resources in China and the influence of topography,long-distance branch water transmission and distribution system has been an important way of regional control of water resources in China.During the operation of the water distribution system,if the valve or pump state changes for a short period of time,the violent water pressure fluctuation caused by it will pose a greater threat to the safe operation of the pipeline,and in serious cases,the pipeline can be broken,affecting the normal water consumption of residents.Therefore,in order to ensure the safe and stable operation of the water distribution system,this paper investigates the water hammer of single-pump multi-pool branch water supply pipeline network stopping and end-regulating valve shutdown through experimental and numerical simulation methods,and proposes corresponding protective measures based on the simulation results.Firstly,through the test pipeline system,the valve action test of three kinds of flow and pressure control valves and butterfly valves is carried out.The results show that the rapid closing of hydraulic water level control valve and butterfly valve causes large water hammer pressure rise in the pipeline system,and it is positively correlated with pipeline flow velocity and valve closing time.Two kinds of flow and pressure control valves,i.e.,the jet hole opposed flow type high proportion pressure reducing control valve and the frequency-free dynamic hammer elimination control valve,have no sudden pressure increase during the closing process.Through analysis,the jet hole opposed flow type high proportion pressure reducing control valve is suitable for the branch pipe connection or the front of the end pool,and the frequencyfree dynamic hammer elimination control valve is suitable for the water inlet of the pool with regulating storage volume.Secondly,combined with the case analysis of the impact of water hammer in the stop pump after the pump check valve closure mode and different operating conditions of the system on the pipeline pressure.The results show that the maximum water hammer pressure is reduced by the way of closing the check valve after the pump,but there is no significant effect on improving the negative pressure of the pipeline;when the branch pipe is in stop operation,the water hammer phenomenon is more obvious than the normal water flow,the maximum water hammer pressure of each branch pipe increased by 19%,40%,10%.Thirdly,the influence of different valve closing laws and different operating conditions on the water hammer characteristics and pressure of the system valve closure is analyzed.The results show that the valve closing method of fast first and then slow is better overall,but there is an optimal solution in the fast-closing time and angle,the water hammer boost is not positively correlated with it,and the pressure fluctuation characteristics at the valve are related to the valve and system characteristics and the valve closing method.The water hammer wave of the branch pipe closing valve was mainly concentrated in the branch pipe,and the water hammer pressure of the other pipelines was positively correlated with the pipe diameter of the branch pipe and the number of valve closures.The water hammer phenomenon of the system is obvious when the main pipe closes the valve,and if the branch pipe is in the stopped state,the water hammer pressure change is more obvious than when the normal water is connected;The pipe pressure change is most obvious when the system valve is closed at the same time,and the maximum pressure is 308.43 m.Finally,the case of water hammer protection design,in the main pipe at the designated location of the installation of box-type two-way surge tank,can effectively alleviate the pipeline pump water hammer pressure.The end of the pipeline is provided with a jet hole opposed highproportion pressure-reducing flow control valve or a frequency-free dynamic anti-hammer flow control position control valve for valve closing water hammer protection,so as to eliminate water hammer pressure rise from the source.The combined protection can effectively ensure the safe and stable operation of pressure flow branch pipeline system.