隧道通风系统90°弯折处导流板设置研究

Study of a Tunnel Ventilation System Having Guide Plates in the 90° Bend of the Air Duct

为了研究隧道通风系统的局部阻力损失,针对风道90°弯折处,利用计算流体力学软件Fluent建立1∶1的数值仿真模型,选择k-ε计算模型,研究不同r/D(r为风道内壁弯折处半径,D为风道宽度)与导流板数目n条件下,拱形断面风道90°弯折处风速场分布规律与局部阻力损失系数ζ_(90°);分析了90°弯折处的减阻措施的减阻效果,并采用物理模型试验,验证了采用数值仿真方法研究风道90°弯折处阻力特性的可靠性。研究结果表明:在风道弯折处内壁设置曲线,或在弯折处设置导流板,均可有效减小90°弯折处及其下游段的涡流区,使风速场分布更加均匀,减小因流体微团相互碰撞而引起的局部阻力损失,使得局部阻力损失系数ζ_(90°)减小;导流板占用90°弯折处有效流动空间,在实现其导流作用的同时也存在阻力作用,因此,当r/D较小时,ζ_(90°)随着导流板数目n的增加,呈先减小后增加的趋势;随着r/D增加,风流经过导流板时受到的阻力作用大于其导流作用,使得ζ_(90°)随着导流板数目n的增加而增加;风道90°弯折处数值模拟结果显示,当r/D分别为0.2与0.3时,使得ζ_(90°)最小的导流板数目n分别为2和1;当r/D分别为0.4,0.5,0.6时,未设置导流板时的ζ_(90°)最小。

To study the local resistance loss of a tunnel ventilation system,a numerical simulation model was developed for the 90°bend of the air duct of the ventilation system.The standard k-εturbulence model was used for the computational fluid dynamic（CFD）analysis to simulate the airflow in the duct with the 90°bend.The local resistance loss of the 90°bend（ζ90°）and the velocity field were analyzed under conditions of varying dimension parameters（r/D）.After setting the number of guide plates to investigate the effect of different drag reduction measures,a model test of the 90°bend of the air duct was conducted,and the reliability of the numerical simulation model was validated by analyzing the correlation result between the CFD model andfield measurement.The results show that by increasing the radius of the inner wall of the bent duct and by setting guide plates in the 90°bend,the vortex formed by the rapid changes in the flow direction in the 90°bend and the local resistance loss coefficient can be effectively reduced.However,the guide plates occupy apart of the flow space in the duct and exhibit a diversion effect as well as resistance effect simultaneously.Therefore,when the value of r/Dis small,theζ90°reduces first and then increases with increasing number of guide plates.When the value of r/Dis relatively high,the resistance effect of the guide plates is greater than the diversion effect,and the value ofζ90°increases with increasing number of guide plates.In the numerical simulation model,when the value of r/Dis 0.2 and 0.3,the number of guide plates with the least resistance loss is 2 and 1,respectively;when the value of r/Dis 0.4,0.5,and 0.6,the resistance loss is the least with no guide plates.