Influences of low atmospheric pressure on downward flame spread over thick PMMA slabs at different altitudes
Influences of low atmospheric pressure on downward flame spread over thick PMMA slabs at different altitudes
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DOI：
10.1016/j.ijheatmasstransfer.2013.01.066
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发表时间：
2013-06
影响因子：
5.2
通讯作者：
Junhui Gong;Xiaodong Zhou;Zhihua Deng;Lizhong Yang
中科院分区：
文献类型：
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作者：
Junhui Gong;Xiaodong Zhou;Zhihua Deng;Lizhong Yang
研究了低气压对静止空气中向下火焰在PMMA厚平板上传播过程的影响。在合肥（1.0atm）、西宁（0.77atm）和拉萨（0.67atm）三个海拔高度进行了一系列实验。本文研究了燃烧速率（质量损失速率）、火焰传播速率和火焰高度。根据减压下的实验结果，燃烧速率由以下表达式关联：m温度P1.8。在较低压力下，发现火焰熄灭低于一个临界达姆科勒数，这是由于化学动力学变化和减少总热量反馈从火焰到固体燃料。对于有限宽度的试样，由实验得到的火焰传播速率随试样厚度的增加而增加，这与以往基于无限宽度假设的结论不同。火焰传播速率和火焰高度与压力的幂律关系，以及指数与样品厚度之间的线性关系。
This study addresses the influences of low atmospheric pressure on heat and mass transfer process of downward flame spread over thick PMMA (polymethyl methacrylate) slabs in quiescent air. Series of experiments were conducted at three altitudes: Hefei (1.0atm), Xining (0.77atm) and Lhasa (0.67atm). Burning rate (mass loss rate), flame spread rate and flame height were investigated in this paper. From experimental results in reduced pressure, burning rates are correlated by the expression: m˙∝P1.8. At lower pressure, it was found that flames go quenching below a critical Damkohler number, which is caused by chemical kinetic change and reduction of total heat feedback from flame to solid fuel. For finite width samples, the flame spread rate derived from experiments increased with the sample thickness, which is different from the previous conclusions based on an assumption of infinite width. Power-law progressions of flame spread rate and flame height to pressure were produced, and linear relationships between the index and thickness of samples were obtained.