变水头装置中蝶阀流场数值模拟与实验

Numerical Simulation and Research on Flow-field of Butterfly Valve in Variable Head Device

为给变水头装置精准流量控制提供理论参考与有效方案,运用ANASIS系列软件中的CFD动网格技术使该装置普遍采用的蝶型流量调节阀恒速转动,对蝶阀流量调节过程中阀体内的流场进行三维动态数值模拟,得到了恒定水头条件下,蝶阀在10°、30°、60°和90°4个开度时,阀体内部和下游侧管路中的流场变化云图。模拟结果显示,在10°和30°开度下,阀体下游流场存在两个旋向相反的漩涡并相互影响;在60°和90°开度下,阀后流场漩涡消失,仅随阀板角度变化而发生速度方向改变,阀门开度与流量之间呈非线性函数关系。同时,运用可自定义编程功能(UDF)设置随出口流量变化的进口压力,实现变水头的边界条件以进行数值模拟,得到数值模拟结果与实体实验数值的误差在5%以内。在变水头条件下,阀门开度固定,在流量下降过程中,流量与时间呈线性变化关系,流量随时间的变化率与调节蝶阀开度引起的相对流阻变化率呈正相关。

To provide theoretical reference and effective control scheme for the accurate flow control of the variable head device.For the butterfly flow-regulating valve commonly used in the variable head device,the three-dimensional flow field in the valve body was simulated during the flow regulating process by CFD dynamic mesh technology of ANSYS series software which ensures constant rotation speed of butterfly valve.The flow field changes with cloud maps in the internal and downstream piping of the valve body under several operating conditions of 10°,30°,60°and 90°opening was proposed in the condition of constant water head.The simulation results also show that there are two opposite vortices in the flow field downstream of the valve body at 10°and 30°opening.At 60°and 90°opening,the vortices of the flow field behind the valve disappear,and the velocity direction changes only with the change of the valve plate angle and the valve opening has a nonlinear function relationship with the flow.Meanwhile,the boundary condition of variable head is realized by using the user defined functions(UDF)to program the inlet pressure with the outlet flow,the error between the numerical simulation results and the experimental values is less than 5%,Under the condition of variable water head,when the valve opening is fixed and the flow rate drops,the flow rate has a nonlinear function relationship with time and the change rate of flow rate with respect to time is positively related to the change rate of relative flow resistance of regulating butterfly valve.