输水管线空气阀进排气孔径的合理选择

Reasonable selection of intake and exhaust diameters for air valve in water pipelines

输水管线空气阀进排气孔径的选择,包括防水锤型空气阀低压进排气孔、缓冲板小排气孔和高压微量排气孔,不仅影响输水的安全性,而且严重影响工程投资。为了合理选择各种类型空气阀进排气孔径,本文首先提出了气体流量与流量系数、孔径、气压的函数关系,以及输水管液柱弥合水击压力与输水管直径、水击波速和空气阀流量改变量的函数关系;然后,建立了空气阀进排气孔径与输水管线充水和排水流速、负压控制要求及水击压力之间的函数关系,同时考虑了管材刚度和位置高程的影响。最后,分别以重力流输水管线和泵站加压输水管线为例,应用所得理论公式分别计算确定了复合式空气阀和防水锤型空气阀进排气孔孔径,结果表明按照本文公式确定的空气阀进排气孔径,不仅比按照常规经验确定的空气阀孔径小得多,而且可以有效削减输水管的液柱弥合水击压力。

The selection of inlet and outlet diameters for air valves in water pipelines,including low-pressure intake and exhaust diameters for waterproof hammer type air valve,small exhaust diameter for buffer plate,and high-pressure micro exhaust diameter,not only affects the safety of water diversion project,but also seriously affects engineering investment.In order to reasonably select various types of air valve intake and exhaust diameters,this article first provides the functional relationship between the air volume flow rate and the flow coefficient,diameter,and air pressure,as well as the functional relationship between the water hammer pressure of the liquid column bridging and the pipe diameter,the water hammer wave velocity,and the volume flow rate increment of the air valve.Then,the functional relationship between the air valve intake and exhaust diameters and the water filling and drainage flow rates,negative pressure control requirements and water hammer pressure are established,taking into account the influence of pipe stiffness and position elevation.Finally,taking the gravity flow water pipeline and the pump station pressurized water diversion pipeline as examples,the theoretical formulas obtained were applied to calculate and determine the intake and exhaust diameters of the composite air valve and the waterproof hammer type air valve,respectively.The results show that the intake and exhaust diameters of the air valves determined according to the formula in this article are not only much smaller than those determined by conventional experience,but can also effectively reduce the liquid column bridging water hammer pressure in the water pipeline.