Research On The Protection Of Water Hammer In Long-Distance Pump Water Delivery System By Gas Injection

As the contradiction between water supply and demand continues to increase,more and more long-distance water transport projects are being constructed.In the long-distance water delivery project,the safe operation of the system is an important guarantee for the water delivery project to exert its social and economic benefits.In order to ensure the safe operation of the water delivery system,it is often necessary to choose reasonable water hammer protection measures according to the actual engineering characteristics.Aiming at the problems existing in traditional air tanks,this article proposes a new type of gas-injection water hammer protection measures,and combines the following research in a water supply project in Yulin:The article first used the characteristic line method to establish a mathematical model of the new type of gas-injection water hammer protection measures,and conducted numerical simulation calculations on the accidental pump stop water hammer without installing any water hammer protection measures,installing two-stage closing butterfly valves,air valves and new gas-injection water hammer protection devices.The calculation result was as follows,three new gas-injection water hammer protection devices were installed along the pipeline,and the maximum negative pressure of the pipeline was 0.11m.The results show that the new gas-injection water hammer protection measures can greatly reduce the negative pressure in the pipeline and avoid the occurrence of flow interruption and bridging water hammer.Compared with the installation of 24 air valves,the maximum negative pressure of the pipeline is reduced from 4.08m to 0.11m,and the peak value of the minimum pressure head is reduced.It can be seen that the new gas-injection water hammer protection measures have a better protection effect on the negative pressure of the water pipeline than the air valve,so in actual projects,the new gas-injection water hammer protection measures can be selected as the negative pressure water hammer protection measures.This article uses an inverse problem analysis method,and select the closing program parameters of the two-stage closing butterfly valve installed at the pump outlet and the control valve operating program parameters that affect the protective effect of the new gas injection water hammer protection measures.The minimum pressure head of the pipeline is used as the objective function,a numerical calculation model for parameter optimization affecting the protective effect of water hammer protective measures is set up.Due to the complex non-linear relationship between the parameters,the paper uses the improved forward and backward method to determine the initial search interval,and then uses the golden section method to find the optimal,thus obtaining the optimal solution of the protection scheme.Four different sets of initial feasible values were found in the calculation,and the optimization calculation was performed to obtain that the four sets of solutions of the water hammer protection scheme are different,indicating that the parameters of the water hammer protection scheme have optimal values,and the results are not unique.Finally,the new gasinjection water hammer protection measures were optimized,and the optimal value of each parameter was determined.Specifically,the quick closing time of the two-stage closing butterfly valve was 14.99s,and the opening degree after the quick closing was 30°.The total valve closing time is 350s,the fully open time of the controllable valve is 10.67s,the total operating time of the valve is 18.48s,the diameter of the gas injection pipe is 100mm,which provides a technically feasible,economical and reasonable water hammer protection scheme for the actual project.