Study on Fingering Pattern of Spreading Flame Over Non-charring Solid in a Narrow Space
Study on Fingering Pattern of Spreading Flame Over Non-charring Solid in a Narrow Space
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DOI：
10.1007/s10694-019-00865-1
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发表时间：
2020-01
期刊：
影响因子：
3.4
通讯作者：
T. Matsuoka;Akihiro Yoshimasa;M. Masuda;Y. Nakamura
中科院分区：
文献类型：
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作者：
T. Matsuoka;Akihiro Yoshimasa;M. Masuda;Y. Nakamura
最近观察到火焰在厚固体上传播的指状图案形成。由于微重力下的富氧大气会促进指状现象的发生，从而导致太空火灾，因此了解其机制非常重要。受此启发，之前的一项研究试图验证与阴燃指法的相似性。然而，它仍然存在争议，因为由于实验设计，指法的定量评估并不令人满意：固体的边缘对该现象有影响。在这项研究中，开发了一种新的风洞，可以在人工边界影响最小的情况下进行实验并评估模式。使用厚的热塑性塑料和氧气作为燃料和氧化剂，并在不同的通道高度和氧化剂速度下进行了一系列实验。然后对指状件的数量、平均指状件宽度和平均火焰蔓延速率进行量化，以估计表征指状件图案的缩放波长。讨论了火焰存在和固体厚度的影响，并对阴燃燃烧理论进行了相应修改，以检查与控制参数（即修改后的有效路易斯数）的相关性。结果表明，缩放后的波长与修改后的有效路易斯数得到了很好的总结。另一方面，当参数变大时，数据偏离直线，表明与阴燃指法存在差异。获得的知识将有助于对太空火灾进行更严格的风险评估。
Fingering pattern formation of flame spread over a thick solid has been observed recently. Since the oxygen-enriched atmosphere in microgravity promotes the occurrence of fingering and thus it leads to a fire in space, it is important to understand the mechanism. Motivated by this, a previous study attempted to validate a similarity to smoldering fingering. However, it remains controversial because the quantitative evaluation of the fingering pattern was not satisfactory done due to the experimental design: edges of the solid have an influence on the phenomenon. In this study, a new wind tunnel was developed, enabling experiments under the least effects of the artificial boundaries and evaluation of the pattern. A thick thermoplastic and oxygen were used as fuel and oxidizer, and a series of experiments were conducted under various channel heights and oxidizer velocities. A number of fingers, average finger width and, average flame spread rate were then quantified to estimate the scaled wavelength which characterizes the fingering pattern. The effects of the existence of flame and solid thickness are discussed and the theory for smoldering combustion was then modified accordingly to examine a correlation with the governing parameter, i.e., the modified effective Lewis number. The result shows the scaled wavelengths are well-summarized against the modified effective Lewis number. On the other hand, the data deviates from the line when the parameter becomes large, indicating a difference from the smoldering fingering. The obtained knowledge will help to develop a more rigorous risk assessment for the fire in space.