大断面瓦斯隧道风筒布置对瓦斯浓度的影响研究

Influence of Air Duct Arrangement on Gas Concentration in the Large-section Gas Tunnel

为优化超大断面瓦斯隧道掌子面的风筒布置,改善掌子面通风状况,文章以新凉风垭隧道为例,计算其需风量和选择风机型号,利用FLUENT软件建立流体力学分析模型,研究了压入式通风下超大断面隧道瓦斯浓度和风速的变化规律以及风筒位置对隧道沿程风流流场及瓦斯浓度的影响情况,最终确定了风筒最佳的安装位置。结果表明:超大断面瓦斯浓度和风速大小在同一断面分布极为不均匀;瓦斯隧道回流区影响范围与风筒到掌子面的距离呈正相关;随着风筒布置距离的增大,瓦斯浓度趋于稳定的位置随之增大;该工程隧道风筒出风口最佳布置位置距离掌子面约为2.5 S(30 m),相比其它较小断面隧道风筒距离大于15~20 m左右,瓦斯浓度最低位置在距离掌子面2 m左右区域;隧道断面的瓦斯浓度随Ly的递增呈“下降-上升-平衡”的趋势。

In order to optimize the air duct arrangement for the large-section gas tunnel to improve ventilation con? dition at tunnel face, a calculation of required air volume and selection of fan type were conducted by taking the Liangfengya tunnel as an example, then a hydrodynamic analysis model was established by FLUENT software to study the variation laws of gas concentration and air velocity of the large-section tunnel and the effect of air duct arrangement on airflow field and gas distribution in condition of forced ventilation, in consequence the optimal arrangement of air duct was determined. The results show that for the large-section gas tunnel the distributions of gas concentration and air velocity are very uneven in the same section;the influence range of recirculation zone in the large-section gas tunnel is positively related to the distance between air duct and tunnel face;the distance between the place where gas concentration is stable and tunnel face increases with an increase of the distance between air duct and tunnel face;for this tunnel the optimum distance from the outlet of air duct to the tunnel face is about 2.5 S(30 m) and it is 15-20 m longer compared with that of the small-section tunnel, the place where gas concentration is the lowest is around 2 m away from the tunnel face;The gas concentration at the tunnel section shows a tendency of‘decrease-increase-balance?? with an increasing of Ly.