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The characteristics of under-ventilated pool fires in both model and medium-scale tunnels

机译：模型隧道和中型隧道通风不足的池火特征

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This paper investigates the characteristics of under-ventilated fires in tunnels. This was done by using both model and medium-scale tunnels. The fuels used were heptane and xylene. The mass loss rates per unit area, ventilation rates from tunnel inlet, flame characteristics, O-2, CO and CO2 concentrations, optical densities and heat release rates were measured and recorded. Results show that the fire behaviors in under-ventilated tunnel fires are different from that in well-ventilated fires. In under-ventilated fires, the mass loss rate per unit area is found to decrease during identical periods due to the low oxygen concentration resulting from the low ventilation rate and vitiation, meanwhile the flame size dramatically reduces with a lifted and fluttering flame. This was clearly observed in model-scale tests, but due to limited optical view there was no possibility to observe this in the medium-scale tests. As a result, the ventilation rate approaches the amount required for complete combustion of vaporized fuel. This indicates that the combustion has converted from ventilation-controlled to fuel controlled. No significant increase in CO production is observed in under-ventilated fires. Besides, the equivalence ratio and combustion efficiency were analyzed in order to judge whether the combustion is fuel-controlled or ventilation-controlled. This study provides new experimental information that contributes to improving the understanding of characteristics of under-ventilated fires in tunnel and can help firefighters to make right judgements and take related protective measures during the rescue processes.
机译：本文研究了隧道通风不足的火灾的特征。这是通过使用模型隧道和中型隧道来完成的。所使用的燃料是庚烷和二甲苯。测量并记录每单位面积的质量损失率，隧道入口的通风率，火焰特性，O-2，CO和CO2浓度，光密度和放热率。结果表明，通风不良的隧道火灾的火灾行为与通风良好的火灾不同。在通风不足的火灾中，由于通风速率低和虚空产生的氧气浓度低，单位面积的质量损失率在相同时期会降低，同时，随着火焰的升起和飘动，火焰尺寸会显着降低。在模型规模的测试中可以清楚地观察到这一点，但是由于光学视野有限，因此在中等规模的测试中无法观察到这一点。结果，通风速率接近完全燃烧汽化燃料所需的量。这表明燃烧已从通风控制转换为燃料控制。在通风不足的火灾中，未观察到CO产生的显着增加。此外，还分析了当量比和燃烧效率，以判断燃烧是燃料控制还是通风控制。这项研究提供了新的实验信息，有助于增进对隧道通风不良的火灾特征的理解，并有助于消防员在救援过程中做出正确的判断并采取相关的防护措施。

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