Upslope fire spread over a pine needle fuel bed in a trench associated with eruptive fire
Upslope fire spread over a pine needle fuel bed in a trench associated with eruptive fire
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上坡火势蔓延到与喷发火灾相关的沟渠内的松针燃料床上
DOI：
10.1016/j.proci.2016.07.091
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发表时间：
2017-01-01
影响因子：
3.4
通讯作者：
Li, Han
中科院分区：
文献类型：
--
作者：
Xie, Xiaodong;Liu, Naian;Li, Han
喷发性火灾是荒地燃料中典型的极端火灾行为，其特征是火势突然加速在沟槽状地形（例如在深峡谷中）的有限斜坡上蔓延。然而，沟渠结构中野火蔓延加速的研究很少。本文对倾斜沟渠中松针燃料床的火灾蔓延进行了系统的实验研究。研究了纵横比（沟槽侧壁高度与沟槽宽度之比）和坡度角度对火势蔓延行为的影响。结果表明，火焰向燃料床表面的附着是由斜坡和沟槽结构造成的空气夹带限制的综合作用引起的。火焰附着发生在具有较高纵横比的较高斜坡上，会导致火势蔓延加速，导致火势蔓延从具有较低蔓延率 (ROS) 的稳定阶段快速过渡到具有较高 ROS 的快速蔓延阶段。火焰附着引起的火势蔓延加速导致燃烧强度显着增强，火焰蔓延过程中的长火焰深度和高质量损失率证实了这一点。燃料消耗效率随着倾斜角的增加几乎呈线性下降。在较高的倾斜角（在本研究中高于 20°）下，火焰倾斜会在火焰前锋前面引起热气流，从而增强对流加热。当火焰附着发生时，对流加热的空间影响范围急剧增大。结论是，对于喷发火灾，辐射加热和对流加热在燃料预热中起着相当的作用。实验数据表明，当发生火焰附着时，对流加热大大增强，成为燃料预热的重要机制。这被推断为沟渠结构中爆发火灾的主要潜在机制。 (C) 2016 年，燃烧研究所。由爱思唯尔公司出版
Eruptive fire is a typical extreme fire behavior in wildland fuels, characterized by a sudden acceleration of fire spread over confined slopes in trench-like terrain (e.g. in a deep canyon). However, wildfire spread acceleration in trench configuration has received little study. This paper presents a systematic experimental study on the fire spread over a pine needle fuel bed in an inclined trench. The effects of aspect ratio (ratio of the trench side wall height to the trench width) and slope angle on the fire spread behaviors are investigated. It is indicated that flame attachment toward the fuel bed surface is induced by the combined effects of the slope and the air entrainment restriction due to the trench configuration. The flame attachment occurring at higher slopes with higher aspect ratios induces an acceleration of fire spread, causing the fire spread to undergo a rapid transition from a steady phase with lower rate of spread (ROS) to quick spread phase with much higher ROS. The fire spread acceleration induced by the flame attachment leads to remarkable enhancement of burning intensity, as verified by long flame depth and high mass loss rate during fire spread. The fuel consumption efficiency decreases almost linearly with increasing slope angle. Under higher slope angles (higher than 20. in this work) the flame tilting induces hot gas flow ahead of the flame front, which enhances the convective heating. When flame attachment occurs, the spatial influence range of convective heating increases sharply. It is concluded that for eruptive fire, radiative heating and convective heating play a comparable role in fuel preheating. Experimental data suggest that when flame attachment occurs the convective heating is greatly enhanced and becomes an important mechanism of fuel preheating. This is inferred to be a major potential mechanism for eruptive fire in trench configuration. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.