Opposed flame spread over folded PMMA plate with various internal angles
Opposed flame spread over folded PMMA plate with various internal angles
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DOI：
10.1016/j.proci.2022.07.153
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发表时间：
2022-09
影响因子：
3.4
通讯作者：
T. Matsuoka;Y. Chiba;Shinnosuke Okuno;H. Torikai;S. Bhattacharjee;T. Yamazaki;Yuji Nakamura
中科院分区：
文献类型：
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作者：
T. Matsuoka;Y. Chiba;Shinnosuke Okuno;H. Torikai;S. Bhattacharjee;T. Yamazaki;Yuji Nakamura
实验研究了内倾角对厚折板上向下火焰传播的影响。将热塑性板的侧面以所需角度切割，并将这些板中的两个焊接以形成单个折叠样品。除了前面和前面每侧的两个5 mm区域之外的所有面都被涂覆以抑制燃烧。对60°、90°、120°、180°等不同角度的折板进行了实验。在样品的上边缘点燃后，观察到正面上的相反火焰蔓延，并通过图像分析量化各个位置处的火焰蔓延速率。火焰在折叠边缘处传播得更快，而其他部分随后加速以赶上拐角传播，并且最终，整个宽度上的所有部分实现与折叠边缘相同的火焰传播速率。这一结果表明，在折叠边缘处的火焰传播速率是代表感兴趣的系统的稳态的特征值。一个简单的模型，考虑到对火焰的加热体积的变化和变化的诱导流速，由于几何形状。前一种效果是从边缘附近的几何考虑制定的，而后者是根据火焰高度与内角成反比的实验事实制定的。通过对传统的平板火焰传播速率预测公式的修正，建立了折边火焰传播速率的预测公式。计算的火焰传播速率与实验数据相当吻合。该研究有助于从根本上了解实际可燃物（如具有各种横截面形状的柱或杆）的火焰传播行为。
The effect of the internal angle on downward flame spread over a thick folded plate is experimentally investigated in this study. The lateral side of a thermoplastic plate is cut at desired angles and two of these plates are welded to form a single folded sample. All the faces other than the front and two 5-mm areas of the front face from each side were coated to inhibit the combustion. Experiments are conducted for various folded plates of different angles, 60°, 90°, 120°, and 180°. Following ignition at the upper edge of the sample, the opposed flame spread on the front face is observed and the flame spread rate at various positions is quantified by image analysis. The flame spreads more rapidly at the folding edge, while the other parts then accelerate to catch up with the corner spread and, eventually, all the parts across the width achieve the same flame spread rate as the folding edge. This result indicates that the flame spread rate at the folding edge is the characteristic value which represents the steady-state of the system of interest. A simple model is developed considering change of heated volume against the flame and change of the induced flow velocity due to the geometry. The former effect is formulated from geometrical consideration in the vicinity of the edge, while the latter is formulated based on an experimental fact that the flame height is inversely proportional to the internal angle. A prediction formula of the flame spread rate at the folding edge is established by modifying the conventional one for the flat plate. The calculated flame spread rate shows reasonably good agreement with the experimental data. This study helps fundamental understanding of the flame spread behavior of practical combustibles such as pillars or rods with various cross-sectional shapes.