Numerical modelling of tunnel fires and water mist suppression
Numerical modelling of tunnel fires and water mist suppression
复制标题
隧道火灾和细水雾抑制的数值模拟
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
R. Hart
中科院分区：
文献类型：
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作者：
R. Hart
矿井隧道和其他地下空间的火灾是一种严重的危害，如果不加以控制，可能导致重大的经济损失和人类悲剧。在英国，已经使用了洪水、泡沫应用和各种类型的手持灭火器等方法，但统计数据显示火灾发生率没有改善。细水雾具有成为隧道空间有效灭火系统的潜力。典型的水雾系统利用约100微米的小液滴，其具有低的终端速度和高的表面与体积比。这导致与传统洒水器不同的行为。已经确定了各种作用机制：散热;氧气耗尽;燃料冷却;辐射衰减;以及空气流动中断。每一个的相对重要性取决于情况。
目前的研究几乎完全集中在最小或没有通风的封闭空间上，并且没有与隧道中喷雾应用相关的数据。
在这篇论文中，一系列的计算流体动力学（CFD）模拟，根据已发表的实验数据，被用来间接验证一个假设的细水雾系统应用于一个真实的隧道火灾的CFD模型，并提高理解细水雾在强通风空间中的表现。水雾是由一个基于拉格朗日的粒子跟踪模型。该模型完全耦合到连续相，考虑了动量、热量和质量的传递。
首先使用一个16 m3的不通风的封闭空间来验证基于0.3 m见方的甲醇（27 kW）和己烷（115 kW）池的池火模型。热羽流的行为在隧道强制通风，然后验证，最初使用一个固定的体积热源为7.5kW的小规模的隧道，然后在一个全尺寸的3平方米的横截面隧道与3米的柴油池使用池火灾模型。
细水雾模型进行了验证与封闭火灾，和敏感性研究评估的影响，液滴直径，喷雾速度和角度，和水的流量上的系统的性能。最后将细水雾应用于隧道火灾中，在低通风量下，氧气消耗和气流中断是显著的，
而在高度通风时，薄雾的唯一作用是带走热量和降低温度。
Fires in mine tunnels and other underground space are a serious hazard, that can, if left unchecked, result in significant economic loss and human tragedy. In the UK, methods such as water deluge, foam application, and various types of handheld extinguishers have been used, but statistics show no improvement in the incidence of fire. Water mist has the potential to be an effective fire suppression system for tunnel spaces. Typical water mist systems utilise small droplets of around 100 micron that have a low terminal velocity and a high surface to volume ratio. This leads to behaviour distinct from that of traditional sprinklers. Various mechanisms of action have been identified: removal of heat; oxygen depletion; fuel cooling; attenuation of radiation; and disruption of air flow. The relative importance of each is case dependent.
Current research has focussed almost exclusively on enclosures with minimal or no ventilation, and no data relevant to the application of mist in tunnels exists.
In this thesis, a series of Computational Fluid Dynamics (CFD) simulations, based on published experimental data, are used to indirectly validate a CFD model of a hypothetical water mist system applied to a real tunnel fire, and to improve the understanding of how water mist performs in a strongly ventilated space. The water mist is represented by a Lagrangian-based particle-tracking model. This model is fully coupled to the continuous phase, accounting for transfer of momentum, heat, and mass.
A 16m3 unventilated enclosure is used first to validate a pool fire model based on 0.3m square pools of methanol (27 kW) and hexane (115 kW). The behaviour of a thermal plume in a tunnel with forced ventilation is then validated, initially using a fixed volumetric heat source of 7.5kW in a small-scale tunnel, and then on a full-scale 3m square cross-section tunnel with a 3m diesel pool using the pool fire model.
The water mist model is validated with the enclosure fire, and a sensitivity study assesses the effect of droplet diameter, spray velocity and angle, and water flow rate on the performance of the system. Finally water mist is applied to the tunnel fire At low ventilation, oxygen depletion and air-flow disruption are significant,
whereas at high ventilation the only effect of the mist is to remove heat and reduce temperature.