Effects of Tunnel Length on Combustion Efficiency in Tunnel Fires
Effects of Tunnel Length on Combustion Efficiency in Tunnel Fires
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DOI：
10.1007/978-981-32-9139-3_77
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发表时间：
2018-10
期刊：
影响因子：
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通讯作者：
Tasuku Ishikawa;Keita Kasumi;Futoshi Tanaka
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文献类型：
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作者：
Tasuku Ishikawa;Keita Kasumi;Futoshi Tanaka
采用1:20比例、0.25 m高H的模型隧道，改变模型隧道长度L作为实验参数，测量隧道火灾燃烧效率。进行了一系列的燃烧实验，以确定燃烧效率是否受到隧道长度，L。选取定义为asL*=L/ h的无量纲隧道长度asL*= 8、16、24、32、40、48，对应满尺40 ~ 240m。结果表明：无因次隧道长度在ml *= 8 ~ 32范围内，燃烧效率不受影响，其平均值为90%；然而，当无因次隧道长度为l *= 40及以上时，在模型隧道顶棚下流动的部分烟雾下降到地板上，烟雾下降现象极大地改变了烟雾的流动动力学。结果，燃气燃烧器上的火焰变得不稳定，最终在火源附近观察到重影火焰现象。除了燃烧效率外，我们还定性地讨论了重影火焰现象的原因。
Combustion efficiency in tunnel fires was measured using a 1:20 scale model tunnel with a 0.25-m height,H, while varying the length of the model tunnel,L, as the experimental parameter. A series of fire experiments was conducted to confirm whether combustion efficiency was affected by the tunnel length,L. A dimensionless tunnel length defined asL*=L/Hwas selected asL*= 8, 16, 24, 32, 40, and 48, corresponding 40–240 m in full scale. The results showed that combustion efficiency was not affected by the dimensionless tunnel length ranging fromL*= 8–32, and its average value was 90%. However, when the dimensionless tunnel length wasL*= 40 or more, part of the smoke flowing under the ceiling of the model tunnel descended to the floor, and the smoke descent phenomenon dramatically changed the flow dynamics of the smoke. As a result, the flame on the gas burner became unstable, and ultimately the ghosting flame phenomenon was observed close to the fire source. We qualitatively discussed the cause of the ghosting flame phenomenon, in addition to combustion efficiency.