地铁站厅至站台楼梯口风速对火灾烟气运动的影响

地铁车站站台发生火灾,连接站厅与站台的楼梯口保持一定风速,可阻挡烟气向站厅蔓延并为人员疏散提供诱导气流.为研究楼梯口风速对车站火灾烟气运动的影响,试验对不同排烟模式下楼梯口风速进行测量,建立数值计算模型进行模拟.结果表明:火灾场景下楼梯口风速大于无火源场景下风速,因此常规楼梯口风速校核设计方法由于没考虑真实火灾情况下各种因素的复杂作用,需进一步改进；楼梯口附近起火,烟气易从挡烟垂壁溢出向站厅层蔓延,站台火灾时站厅层为送风状态,存在溢出烟气时站厅层烟浓度可增至大于站台层；站台公共区着火,增开隧道风机,能够增加楼梯口风速,但由于对流场的扰动,破坏了烟气分层,使烟气充填区域增大,因此,防排烟系统设计中科学组织烟气流动、合理控制烟气运动路径与控制排烟量同等重要.

Analysis of Fire Smoke Movement with Different Air Velocity at the Stair head to the Hall of a Metro Station

When a fire happens at the subway platform,the downward ventilation at the staircase which connects the hall and platform can prevent smoke spreading into the hall and provides guiding air for evacuation people.To investigate the influence of the ventilation rate on the smoke movement,the air velocity at the staircase was measured under three ventilation modes.Numerical model was established to simulate the real fire scenario.It is shown that the downward air velocity under fire is greater than that without fire,and the traditional design procedure without considering complex factors interaction in real fire scenario should be improved;when fire is near the staircase,smoke easily spills from the smoke screen to the concourse.And smoke concentration of concourse is even higher than that of platform because the hall is under air supply mode;when the fire locates at the public area of the platform,turning on the tunnel fans can increase the downside flow at the staircase.However exceeding high flow can produce disturbance and destroy the smoke stratification,so more area will be filled with smoke.Therefore,reasonable smoke management scheme is as important as smoke exhausting system capability.