Instability of downward flame spread over paper in an air stream
Instability of downward flame spread over paper in an air stream
复制标题
气流中向下的火焰在纸张上传播的不稳定性
DOI：
10.1016/0010-2180(76)90071-7
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发表时间：
1976
影响因子：
4.4
通讯作者：
K. Tazawa
中科院分区：
文献类型：
--
作者：
T. Hirano;Kenji Sato;K. Tazawa
对气流中火焰向下传播不稳定的机理进行了实验研究。在对不稳定火焰蔓延现象进行详细观察后，利用粒子示踪技术和细线热电偶对不稳定火焰附近的流场和预热区的温度分布进行了研究。当自由流速度超过稳定的火焰蔓延极限时，在蔓延过程中观察到一系列局部爆炸。在这种情况下，大多数前缘是倾斜或弯曲的，并且主要发生在前缘与水平面的倾斜角和前缘曲率都很小的位置。如果火焰在热电偶连接处稳定地传播，那么在给定距离的纸表面上测量到的温度-时间图几乎是相似的。在前缘为直的燃烧区，包括吹散在内的火焰传播现象可以认为主要依赖于前缘法向自由流的速度分量，而很少依赖于进近流边界层的速度剖面。
An experimental study has been conducted to elucidate the mechanism causing the instability of downward flame spread in an air stream. Following detailed observations of unstable flame spread phenomena, the flow fields near unstably spreading flames and the temperature profiles across the preheat zones were examined using particle tracer techniques and fine wire thermocouples. When the free-stream velocity was above that of the stable flame-spread limit, a series of local blow offs were observed during the spread. In this case, most leading flame edges were inclined or bended, and the blow offs occurred mainly at the locations where both inclined angle of the leading flame edge from the horizontal surface and curvature of the leading flame edge were small. Measured temperature-time diagrams at a given distance from the paper surface were almost similar if flames spread stably across the thermocouple junction. The flame spread phenomena including blow offs at the burning zone with a straight leading flame edge could be considered to depend mainly on the velocity component of the free-stream normal to the leading flame edge but scarcely on the velocity profile in the boundary layer of the approach flow.