公路隧道通风系统局部结构阻力研究

Study on Local Structural Resistance of Ventilation System in Highway Tunnels

公路隧道通风系统中存在着大量的局部三通、变径及弯道结构。为了研究公路隧道通风管段在三通、变径及弯道结构处的通风风流的运动形式及局部阻力损失系数,文章采用Fluent计算软件,考虑不同影响因素,对公路隧道通风系统的三通结构(斜向合流、直向及斜向合流、斜向分流、直向及斜向分流)、变径结构(突扩、突缩、渐扩、渐缩)、弯曲风道等工况进行了研究。结果表明:(1)在斜向合流时,支、主流面积比A3/A1和夹角θ对局部阻力损失系数ζ的影响较大,断面形状和支、主流流量比Q1/Q3对ζ的影响较小;(2)对于斜向分流,支、主流夹角θ、面积比A3/A1和流量比Q1/Q3对局部阻力损失系数ζ的影响较大,断面形状对ζ的影响较小;(3)对于突扩、突缩风道,两段截面的比值对局部阻力损失的影响系数均非常明显,断面均宜设计为圆形;(4)对于弯曲风道,局部阻力损失系数ζ将随着弯曲半径r的增大而减小,同时弯曲半径r不宜小于弯道直径D。另外局部阻力损失系数ζ将随着弯曲角度γ的增大而增大,且宜为圆形。

In the ventilation system of highway tunnels,there are a large number of structures of local three-way,variable diameter and bending.In order to study the movement pattern of air flow and loss coefficient of local resistance in this context,the software named Fluent was adopted to analyze the cases of three-way structure(oblique confluence,straight and oblique confluence,oblique shunting,straight and oblique shunting),variable diameter structure(sudden enlargement,sudden downsizing,gradual enlargement and gradual downsizing) and curved air duct and so on.The results show that:for the oblique confluence structure,the area ratio of branch and trunk duct A3/A1 and angle θ between the branch and trunk duct have significant influence on loss coefficient ζ of local resistance,but the section form and flow ratio Q1/Q3 of branch and trunk duct have little influence on ζ;for the oblique shunting structure,the angel θ between branch and trunk duct,the area ratio A3/A1 and flow ratio Q1/Q3 have significant influence on loss coefficient ζ of local resistance while the section form has little influence on loss coefficient ξ of local resistance;for the sudden enlargement and downsizing of ventilation duct,the ratio of two different sections has obvious influence on loss coefficient ζ of local resistance,and all the section should be designed as round form;for the curved duct,the loss coefficient ζ of local resistance will decrease with an increase of bending radius r which should not be smaller than the bending diameter D,and the loss coefficient ζ of local resistance will increase with an increase of bending angle y and the section should be designed as round form.