Study On Water Hammer Simulation And Protection Of Municipal Water Pumping Stations

As the "heart" and "blood vessel" of the city,the safety and reliability of municipal water supply pump station and pipeline system are directly related to the healthy development of the city.Pump-stopping water hammer is the most common destructive water hammer phenomenon in municipal pump station system.Once it occurs,it will lead to the paralysis of urban water supply system,which will not only cause economic losses,but also cause adverse social effects.China is one of the countries with the largest number of municipal pumping stations in the world.Therefore,it is of practical significance to study the simulation and protection of pump-stopping water hammer in municipal pumping station.In view of the difficulties in obtaining the hydraulic model parameters of municipal pump stations,the lack of reference methods for model verification and the fuzzy steps of model verification,combined with the two municipal water supply pump stations in Guizhou and Hunan,this paper studies the sensitivity and correlation of different parameters of the hydraulic model to the output results through Wanda simulation software,and uses the monitoring data and sensitivity analysis results to check and evaluate the hydraulic model of the pump station,The optimization strategy of water hammer protection under the most unfavorable pump shutdown condition is proposed.The research results are as follows:(1)The sensitivity study of hydraulic model parameters shows that the maximum water hammer pressure has the highest sensitivity to water hammer wave velocity,pipeline flow and moment of inertia;The minimum water hammer pressure at the outlet of the pump has the highest sensitivity to pipeline flow,torque and moment of inertia;The maximum reversal speed of water pump has the highest sensitivity to water hammer wave speed,pipeline flow and friction coefficient.(2)The research results on the correlation of hydraulic model parameters show that the wave velocity of water hammer,pipeline flow and friction coefficient are positively correlated with the maximum pressure of water hammer,and the moment of inertia of unit is negatively correlated with the maximum pressure of water hammer;the moment of inertia of the unit is positively correlated with the minimum water hammer pressure at the outlet of the pump,and the pipeline flow,friction coefficient and water hammer wave velocity are negatively correlated with the minimum water hammer pressure at the outlet of the pump;the water hammer wave velocity,pipeline flow and friction coefficient are positively correlated with the maximum reverse speed of the water pump,and the moment of inertia of the unit is negatively correlated with the maximum reverse speed of the water pump.(3)The research results of hydraulic model verification process show that the calibration of parameters such as pump flow,along-line resistance coefficient and local resistance coefficient in the steady-state verification can effectively reduce the simulation value error of steady-state flow and pressure and improve the accuracy of steady-state hydraulic model.The simulated value error of transient water hammer pressure change curve(maximum value,minimum value and curve trend)can be effectively reduced by the calibration of water hammer wave velocity,pipeline flow,friction coefficient,moment of inertia and other parameters in transient verification.(4)For the risk of pump-stopping water hammer in the municipal pump station system,the positive pressure of water hammer in the pipeline can be reduced by optimizing the two-stage closing law of the hydraulic control butterfly valve and increasing the moment of inertia of the pump unit.Installing an air valve at a suitable position can effectively reduce the positive and negative pressure of water hammer in the pipeline.When the total closing time and fast closing time are fixed,the maximum water hammer pressure first decreases and then increases with the decrease of fast closing angle;When the total closing time and quick closing angle are fixed,the maximum water hammer pressure of the pipeline increases with the increase of quick closing time.