Combustion efficiency during fires in tunnels with natural ventilation by vitiated air including descending smoke
Combustion efficiency during fires in tunnels with natural ventilation by vitiated air including descending smoke
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DOI：
10.1016/j.firesaf.2020.103093
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发表时间：
2021-04-12
影响因子：
3.1
通讯作者：
Moinuddin, Khalid A. M.
中科院分区：
文献类型：
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作者：
Ishikawa, Tasuku;Kasumi, Keita;Moinuddin, Khalid A. M.
利用1：20的隧道模型对隧道火灾的燃烧效率进行了测量。对丙烷和庚烷火灾进行了一系列模型实验，以确定隧道长度是否影响燃烧效率。结果表明，隧道长度对燃烧效率影响不大，丙烷火灾燃烧效率平均值为89%，庚烷火灾燃烧效率平均值为80%。在长隧道的情况下，由于新鲜空气和下降的烟雾混合，产生了下降的烟雾和空气的回流，火灾完全被污染的空气包围。在这种污染的火灾条件下，在靠近火的地方观察到幽灵火焰，最终由于缺氧而使火自行熄灭。针对传统的量热方法难以应用于有毒火灾条件下的问题，提出了一种基于质量反应速率估算有毒火灾条件下的热释放速率的量热方法。利用该方法，估算了污染火灾条件下的化学反应比和燃烧效率。在污染火中，火的化学HRR降至正常火的一半或更低，但庚烷火的燃烧效率为94%。
Combustion efficiency in tunnel fires is measured using a 1:20 scale model tunnel. A series of model experiments with propane and heptane fires is conducted to confirm whether combustion efficiency is affected by tunnel length. The results show that combustion efficiency is little affected by tunnel length, and its average value is 89% for propane fires and 80% for heptane fires. In the case of a long tunnel, descending smoke and backflow of air vitiated by mixing fresh air with descended smoke occurs, and the fire is completely surrounded by vitiated air. In this vitiated fire condition, a ghosting flame is observed close to the fire, and ultimately the fire selfextinguishes due to lack of oxygen. A calorimetry method of estimating the heat release rate (HRR) under the vitiated fire condition based on the mass reaction rate is developed as a traditional calorimetry method is difficult to apply to the vitiated fire condition. Using the method, the chemical HRR and combustion efficiency are estimated under the vitiated fire condition. In the vitiated fire, the chemical HRR of the fire decreases to half or less that in the normal fire, but combustion efficiency is 94% for heptane fires.