典型地铁站的污染物扩散全尺寸试验研究

Full scale experimental study of pollutant diffusion in a typical subway station

为全面了解地铁站内有毒有害气体的扩散发展规律,选取北京某地铁站开展了全尺寸实地扩散试验.利用三维超声波风速仪和多通道风速仪对机械通风工况下的站内流场进行监测,并对其气流组织形式进行分析;采用六氟化硫(SF_(6))释放、时序采集和离线检测的方法,研究重气的传输速度和扩散范围等扩散与沉降规律,以期为地铁站内人员疏散路径规划提供数据支撑.结果表明:该地铁站在机械通风工况下,会形成一个较为规律的主流场,将其划分为相对独立的东、西两个区域,污染气体SF_(6)只能在释放源所处的气流顺向区域内流动,反向区域多个监测点SF_(6)均未检出;重气在扩散时会出现明显的沉降现象,SF_(6)浓度由2.5 m处的25 ppm分别升高至1.6 m处的180 ppm和0.5 m处的300ppm,且易于在楼梯、边缘等位置的地面积累从而形成局部高浓度区域,浓度可高达300 ppm以上;少量气体可以通过楼梯进入上层站厅,但浓度总体低于75 ppm,难以进一步由出入口扩散至站外地面;应急处置时,需要尽快将乘客向上层或气流反向区域疏散.

In order to fully understand the development laws of toxic and harmful gas in subway stations,full scale experiments of pollutant diffusion were carried out in an opened station in Beijing. Three-dimensional ultrasonic anemometer and multi-channels anemometer were used to analyze the flow field in the station under mechanical ventilation condition. Then the diffusion range,gas subsiding,transmission speed of heavy gas have been studied based on the methods of SF_(6)release and sampling in chronological order,which provide suggestions for emergency response. The results showed that a regular main flow field will formed under mechanical ventilation,which divided the station into two relatively independent regions,the east and the west. Because of obvious subsidence heavy gas SF_(6)tends to accumulate on the ground at stairs,edges or other locations,which concentration can be up to 300 ppm. The concentrations of SF_(6)increased from 25 ppm to 180 ppm and 300 ppm with the height decreased from 2.5 m to 1.6 m and 0.5 m,respectively. A small amount of gas can enter the hall through the stairs,however,it`s difficult to further diffuse to the outside of the station due to the low concentration(less than 75 ppm). As a result,during emergency response it is necessary to evacuate the passengers to the upper or reverse area as soon as possible.