基于改进空气阀模型的输水系统支管放空过程分析

为了分析复杂管道系统支管上游阀门关闭所诱发的水力过渡过程现象,采用进气量由空气阀安装处逐步向下游推进的方法,建立改进的空气阀计算模型,并以某输水系统为例,分别采用2种空气阀模型开展相应的水锤计算.研究结果表明:采用经典空气阀计算模型时,受支管上游高程较大的影响,支管产生了“虚假”流量,导致仿真结果与工程实际偏离较大;而采用改进的空气阀计算模型时,支管流量逐步减小为0,汇流点主线上游流量逐步增大,下游流量逐步减小,过渡过程中主线各调压井水位有所下降,但并未出现漏空现象;各调压井水位及汇流点稳定压力与恒定流计算(主线流量为121.5 m³/s,支线流量为0)结果最大偏差仅0.16 m.计算结果证明了该改进空气阀计算模型的适用性,并为复杂输水系统的放空及充水过程研究提供了一种新的方法.

Analysis of branch vent draining process in complex pipeline system based on improved air valve model

In order to analyze the hydraulic transition process induced by the closure of upstream valve of branch pipe in the complex pipeline system, an improved air valve calculation model was established by using the method of gradually advancing the air volume from air valve to the downstream. Taking a diversion project as an example, two air valve models were used to calculate the corresponding water hammer. The results show that when the classical air valve calculation model is adopted, the ″simulated″ flow is caused by the large upstream elevation, and the simulation results deviate greatly from the engineering practice. The branch pipe flow gradually decreases to 0 based on the improved air valve calculation model, and the upstream flow of the main line at the meeting point gradually increases, the downstream flow gradually decreases, and the main line flow finally reaches 121.5 m³/s. In the transition process, the water level of each surge tank of the main line decreases, but there is no leakage. Water level of each surge tank and meeting point pressure are similar to the steady-state calculated values(main line flow 121.5 m³/s), and the maximum deviation is only 0.16 m, which proves the accuracy of the improved air valve calculation model. It provides a new method for the study of filling and draining of complex water conveyance system.