风机横向布置间距对公路隧道污染物分布的影响研究

Study on influence of horizontal fans spacing on distribution of pollutants in highway tunnels

隧道内风机布置方式对通风效率和汽车尾气净化有显著影响,为了优化隧道顶部风机横向布置,提高隧道通风效率,改善隧道内的环境质量,有效节约隧道运营通风能耗,利用计算流体软件Fluent,建立公路隧道射流通风模型,开展不同风机横向布置间距隧道内流场和污染物分布的三维数值模拟,分析隧道内流场分布、纵向CO质量分数分布和不同截面CO质量分数分布特征及规律。结果表明:风机横向布置间距对隧道内的通风和净化除尘效果都有一定的影响,流场分布与污染物分布规律相似;在风机横向布置间距为3倍风机直径时,升压折减系数为0.6154,达到最大值,此时隧道内的流场分布和污染物控制效果较好;因此,在进行风机布置时,建议将风机横向布置间距确定为3倍风机直径。

The present paper intends to conduct a 3D numerical simulation of the impacts of the different horizontal fans layout interspace according to the space distribution of the tunnel pollutants. As is known,highway tunnels have to be laid out as a preferably closed underground space for the railway or automobile cars to pass through,for,in so doing,it would be possible to reduce naturally large amounts of pollutants produced by the computer software. However,in this paper,we have to adopt a fan diameter D as the benchmark,with a fan system horizontally installed as 1D,2D,3D and 4D,accordingly andrespectively. In addition,large amounts of interactive software has to be arranged to account the numerical simulation time in a steady-state algorithm. Besides,the tunnel entrance can also be defined as the boundary condition of the velocity entrance,with the velocity being set as 4 m/s. And,oppositely,the tunnel exit can be defined as the boundary condition of the pressure outlet,whereas the tunnel wall surface can be taken as the wall surface of the corresponding roughness. Therefore,seeing that a section of negative pressure area is likely to be formulated before the fan inlet,the inlet has to be defined as the velocity inlet boundary,with the velocity size being-33. 8 m/s,so as to guarantee the regularity of the mass conservation. On the contrary,if the fan outlet is defined as the velocity inlet boundary condition,the velocity size can also be defined as the fan wind-velocity outlet,with its size being 33. 8 m/s. At the same time,the fan’s wall has to be laid out in a form of a smooth wall surface,thus,the results of the above study should imply that the horizontal spacing of the fan may have a similar effect on the distribution of the flow field and the distribution of the pollutants in the tunnel,signifying that the distribution law of the pollutants turns to be similar to the flow field. Thus,when the horizontal spacing of the fan is measured as 1D,2D,3D and 4D,respectively,the boost reduction coefficients should be made equal to 0. 597 6,0. 613 4,0. 615 4 and 0. 605 2,accordingly. Nevertheless,if the horizontal spacing of the fan is equal to 3D,the boost reduction coefficient ought to reach the maximum limit. Therefore,when the fans are needed to be properly assembled,the horizontal spacing of the fans should be recommended to 3D.