细水雾与排烟系统共同作用下地铁车站火灾烟气蔓延规律

Analysis of Suppression Performance of Platform Water Mist System and Exhaust System on Subway Train Fires in Stations

为研究岛式地铁车站内列车发生火灾时,站台细水雾与排烟系统对烟气蔓延的控制效果,依托西安地铁4号线岛式地铁车站,采用FDS软件建立1∶1的数值仿真模型,选择大涡模拟,研究站内列车火灾规模为5 MW时,站台细水雾与排烟系统共同作用下,火灾烟气蔓延速度、能见度与温度场的分布特征,分析了细水雾与排烟系统对烟气蔓延特性的影响规律;并通过缩尺模型试验,验证了数值模拟方法研究细水雾控制地铁火灾烟气蔓延的可靠性。研究结果表明:车门间隔开启时,烟气先向列车两侧蔓延,150 s时扩散至整个车厢并向站台层蔓延,当开启站台细水雾时,烟气温度明显下降,且随着细水雾粒径的减小与流量的增大,烟层降温效果增强;当水雾粒径为100μm,流量为8 L·min;时,距离站台中线3 m处断面平均温度为36.19℃,较未开启细水雾时温升降幅可达62.91%;同时细水雾使得烟层蔓延速度减小,在开启细水雾系统后200 s内2;楼梯口平均空气质量流速下降39.72%;当开启排烟系统时,可使列车内温度场纵向分布最大值向火源下游移动,加快站台层及列车内对流换热效率,使细水雾的气相冷却作用得到加强,二者同时作用时降温阻烟效果最佳。

To study the suppression performance of a water mist system and smoke exhaust system on the smoke spread, a full-scale model was established using Fire Dynamics Simulator(FDS) based on the island metro station of Xi’an Metro. In this paper, Large Eddy Simulation(LES) was applied to study the characteristics of fire smoke movement speed, visibility and temperature field when the heat release rate was 5 MW, and the influence law of the water mist system and smoke exhaust system on smoke movement characteristics was analyzed. The reliability of the numerical simulation method was determined by scale model(1∶10). The results show that when the door is alternately opened, the smoke spreads faster to the front and rear, and spreads to the whole train at 150 s. After the water mist system is opened, the smoke temperature decreases obviously;furthermore, the cooling effect increases with the decrease of the particle size and the increase of the water flow. For the particle size of water mist is 100 μm and the flow rate is 8 L·min;, the average temperature of the section 3 m away from the platform center line(X=3 m) is 36.19 ℃, which is 62.91% lower than that without a water mist. Meanwhile the water mist effectively slow smoke spreading speed. After opening the water mist system for 200 s, 2;stairway average air quality flow rate decreased by 39.72%. When the smoke exhaust system is turned on, the maximum longitudinal temperature in the train moves downstream of the fire source. The smoke exhaust system will accelerate the convective heat transfer efficiency between the platform layer and the train, and strengthen the gas-phase cooling effect of water mist. The fact is proved that the best effect of cooling and smoke suppression is achieved when the water mist system and smoke exhaust system work simultaneously.