长隧道内利用分段水雾进行阻火隔烟的性能研究

Due to the relatively limited cross-sectional area in tunnels, hot smoke can spread rapidly, e.g., downstream with the traffic flow or due to longitudinal ventilation. Consequently, people downstream of the fire may be exposed to high temperatures and toxic gases, especially in case of traffic congestion. In order to prevent smoke spreading to downstream, a new method which by using water mist segment as a partition in tunnel was proposed. Similar method, water curtain, was investigated a few years ago. However, because of its low capability of smoke blocking, it is not applicable at present. In this research project, theoretical analysis and experimental, numerical study will be used to investigate the process of interaction between smoke layer and water mist. Considering the effect of heat transfer, adsorption and collision by water mist, the smoke movement inside the water mist segment will be studied. Meanwhile, a mathematical model which presents to describe the temperature, velocity and concentration of smoke which have already passed the water mist segment will also be developed. Small-scale model will be used to study how different heat release rates, longitudinal ventilation velocities impact on the effectiveness of smoke and heat blocking. Numerical study is going to optimize the operating parameters of water mist segment, which corresponding to different heat release rate and tunnel geometry. All this work will contribute to give a guidance to engineering application and the completeness of basic theory of fire mitigation and smoke reduction by water mist.

在纵向通风的隧道中由于烟气是从隧道下游排出，一旦下游发生拥堵，其车辆和人员均无法安全疏散，本研究提出利用分段水喷雾的方式将长隧道划分成若干区段，通过水雾段阻止火灾烟气向下游蔓延，虽然有类似概念的隧道水幕曾被提出，但因其隔烟效果差，故一直未能在实际工程中应用。本项目通过理论分析和模型试验方法研究水雾与火灾烟气层相互作用过程，探讨烟气通过水喷雾段时烟颗粒与液滴的碰撞、吸附以及热交换机理，揭示烟气在水雾作用下的运动规律；利用小尺寸试验模型研究不同火灾功率下，纵向风压对隧道水喷雾段隔热、隔烟效率的影响；建立描述烟气层穿越水雾段后速度、温度及浓度变化的数学模型，同时结合数值模拟方法找出不同火灾功率、隧道断面几何尺寸下最佳水喷雾工作参数，为其工程应用提供理论指导，也对水喷雾灭火减烟等相关基础理论的完善具有重要的科学价值。

在纵向通风的隧道中由于烟气是从隧道下游排出，一旦下游发生拥堵，其车辆和人员均无法安全疏散，本研究提出利用分段水喷雾的方式将长隧道划分成若干区段，通过水雾段阻止火灾烟气向下游蔓延，从而为人员疏散提供良好条件。本项目建立了1:3隧道模型，通过理论分析和模型试验方法相结合研究了水雾与火灾烟气层相互作用过程，探讨烟气通过水喷雾段时烟颗粒与液滴热交换机理，并结合数值模拟方法找出不同火灾功率下阻止烟气蔓延的水喷雾系统工作参数、设置要求，建立了喷头作用下细水雾颗粒与烟气作用的数学模型以及半横向排烟系统隧道火灾回流烟气长度预测模型，找出了不同液滴分布及通量与烟气运动速度、扩散距离、隔热效率的关系，其研究成果可以为其工程应用提供理论指导。