不同通风模式下地铁站毒气扩散的实地试验

为全面了解通风系统对地铁站内有毒气体扩散的影响，以北京某地铁站为研究对象，开展了全尺寸实地扩散试验.采用三维超声波风速仪对机械通风和应急通风下的站内流场进行监测，分析其气流组织形式；采用六氟化硫（SF₆）释放，时序采集和离线检测的方法，研究重气的扩散与沉降，为疏散路径规划提供建议.结果表明，应急模式下各监测点的风速更大，是机械通风的1.2~2倍；SF₆在机械通风工况下扩散，会出现明显的沉降现象，易于在楼梯和边缘等位置的地面积累从而形成局部高浓度区域，且长时间高于50×10^-6；应急通风系统开启后，沉降的SF₆加速向上传输，且会快速充满整个站台，东西站台浓度最高均达到200×10^-6以上；应急处置时，需要尽快将乘客向上层或反向区域疏散，严禁开启应急通风设备，避免地面气体向呼吸区扩散.

In-situ experimental study on poison gas diffusion in subway station under different ventilation modes

To fully understand the influence of ventilation system on poison gas diffusion in subway station, full scale experiments were carried out in a subway station in Beijing. Three-dimensional ultrasonic anemometer was used to analyze the flow field in the station under mechanical ventilation and emergency ventilation. Then the gas diffusion and subsiding of heavy gas were studied based on the methods of SF₆ release and sampling in chronological order, which provide suggestions for emergency response. The results showed that in emergency ventilation, the wind speed was greater, which was 1.2~2 times that of mechanical ventilation.When SF₆ diffused under mechanical ventilation, obvious settlement was observed, and SF₆ was accumulated on the ground to form an area, concentration of which was higher than 50×10^-6 for a long time. After the emergency ventilation was turned on, the settled SF₆ accelerated upward transmission and quickly filled the whole station hall and the maximum concentration was more than 200×10^-6. During emergency disposal, it was necessary to evacuate passengers to the upper or reverse area as soon as possible. It is strictly prohibited to open the emergency ventilation to avoid the diffusion of ground gas to the breathing area.