一端开敞的地铁区间隧道烟气流动特性及其烟气控制研究

Study on fire smoke flow and smoke control in underground metro tunnel with one end to outside

以重庆某一段349 m长的一端连接地下车站另外一端和室外相通的地铁区间隧道为例,开展全尺寸的火灾实验和数值模拟分析,研究一端开敞的地铁区间隧道烟气流动特性。分析火源在隧道中心位置、不同热释放速率条件下隧道内火灾烟气蔓延速率、隧道内烟气最高温度以及烟气温度在隧道纵向分布的特征,并对比分析利用区间隧道事故风口进行机械排烟和机械送风的烟气控制模式效果,提出描述区间隧道断面形状对烟气流动特性影响的参数。研究结果表明:烟气蔓延速率受纵向风速和车站烟囱效应作用影响,火源上游区域烟气蔓延速率较小,烟气回流距离比两端开敞的公路隧道经验公式计算值小,隧道内烟气最高温度比Kurioka预测模型计算值小,隧道顶部上游的烟气温度纵向分布服从指数衰减规律;将隧道烟气最高温升预测模型应用于形状系数小于1的区间隧道需要进一步修正;区间隧道内靠近地下车站的事故风口,采用机械排烟或机械送风模式,可以有效排除着火区间隧道内的烟气;事故风口机械通风量及其运行模式的选择需综合考虑隧道地理形式、火源功率、疏散方式等因素。

Fire smoke flow characteristics in an underground metro tunnel were researched by full-scale experiments and numerical simulation in program FDS （fire dynamic simulation）, and the tunnel is 349 m in length with one end connected to an underground metro station and the other end opened to outside in Chongqing, China. Smoke spread velocity, maximal smoke temperature and smoke temperature distribution in the longitudinal direction of the metro tunnel were analyzed on the conditions of different heat release rates with the combustion source in the middle of the tunnel, effects of mechanical smoke exhaust mode and air supply mode through the emergency vent were compared, and the sectional shape factor of a tunnel was introduced. The results show that smoke spread rate is affected by longitudinal air velocity and chimney effect, smoke spread rate is small in the upstream area of combustion source, backflow distance is shorter than calculated by the empirical equations acquired from the tunnel with two open ends, the excess maximal temperature rise in tunnel is lower than that predicted by Kurioka, smoke temperature distribution in the longitudinal direction on the top area of the metro tunnel obeys exponential decay laws, and further correction can be added to Kurioka model when the sectional shape factor of tunnel is less than 1. In case of a fire breakout in the metro tunnel, mechanical smoke exhaust mode or air supply mode through the emergency vent is working, and smoke in the tunnel can be exhausted effectively. Mechanical ventilation volume and mode are related to factors including geography information of the tunnel, fire heat release, evacuation route and etc.