U型隧道火灾烟气运动机制研究

发布时间：2018-03-31 04:17

本文选题：U型隧道　切入点：隧道火灾　出处：《西南科技大学》2017年硕士论文

【摘要】：通过对比小尺寸试验平台的试验值与FDS的模拟值,验证FDS在火灾模拟中可行性。为了研究U型隧道的火灾烟气运动机制,基于火灾烟气流动理论的重要性,采用FDS模拟火灾场景,研究在不同自然通风速率、不同坡度、不同火源功率的工况下,隧道内生成的烟气温度、烟气蔓延速度和方向、烟气层高度及CO浓度,并得到以下结论:(1)U型隧道火灾烟气逆流现象较另外两种隧道模型更为严重。U型隧道中,自然通风速率的改变引起四个现象:一为能使烟气蔓延至下游出口但最终烟气依旧完全逆流;二为能使烟气最终从下游出口排出,但初期烟气能蔓延至上游入口;三为能使烟气出现逆流现象,但无法从上游入口排出;四为能使烟气不出现逆流。(2)火源熄灭后,U型隧道比水平隧道能更快排出火灾烟气、降低温度,烟气排出方向与火源功率稳定阶段烟气最终排出方向一致。(3)在火源功率稳定阶段,U型隧道中,坡度α=45°对于上游测点数据为一个临界值,坡度的增加影响升温的时间、烟气层厚度、CO浓度变化。坡度增加引起的测点最高温度的变化,与坡度变化引起的温度初次升高时间变化观察规律不一致。(4)在两端下行与上行隧道坡度一样的U型隧道中,其是关于中心对称的,若烟气必须从下游出口排出,火源位置对于烟气的蔓延、通风排烟方式的选择有着决定性的影响。
[Abstract]:The feasibility of FDS in fire simulation was verified by comparing the test value of small scale test platform with the simulated value of FDS.In order to study the mechanism of fire smoke movement in U-type tunnel, based on the importance of fire smoke flow theory, FDS was used to simulate the fire scene.The flue gas temperature, the velocity and direction of flue gas propagation, the height of flue gas layer and the concentration of CO are generated in the tunnel. The following conclusions are obtained: the reverse flow phenomenon of smoke from the fire in the U type tunnel is more serious than that in the other two tunnel models.The change of natural ventilation rate leads to four phenomena: one is that the flue gas can spread to the downstream outlet but the final flue gas is still completely countercurrent, the other is that the flue gas can eventually be discharged from the downstream outlet, but the initial flue gas can spread to the upstream inlet.Third, it can cause the smoke to appear countercurrent, but it can not be discharged from the upstream entrance; fourth, it can make the smoke do not appear countercurrent. (2) after the fire source is extinguished, the U-type tunnel can discharge the fire smoke faster and lower the temperature than the horizontal tunnel.The direction of flue gas emission is the same as that of the final discharge direction of flue gas at the stage of power stabilization of fire source.) in the U-type tunnel with stable power of fire source, the slope of 45 掳is a critical value for the data of upstream measurement point, and the increase of slope affects the time of heating up.Change of CO concentration in flue gas layer thickness.The change of the maximum temperature of the measuring point caused by the increase of the slope is inconsistent with the observation rule of the time change of the initial rise of the temperature caused by the change of the slope. (4) in the U type tunnel with the same slope at both ends of the downlink and the upstream tunnel, it is about centrosymmetric.If the flue gas must be discharged from the downstream outlet, the location of the fire source has a decisive effect on the smoke spread and the choice of ventilation and exhaust mode.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U458

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