Flame Spread Mechanisms over PMMA Surfaces
Flame Spread Mechanisms over PMMA Surfaces
复制标题
PMMA 表面的火焰传播机制
DOI：
10.11196/kasai.27.2_33
复制
发表时间：
1977
期刊：
影响因子：
--
通讯作者：
K. Akita
中科院分区：
文献类型：
--
作者：
T. Hirano;T. Koshida;K. Akita
研究了火焰在有机玻璃（PMMA）平面上的传播机理。采用粒子示踪技术、细丝热电偶和马赫-曾德尔干涉仪测量了垂直向下和水平向蔓延火焰的蔓延速率，并研究了蔓延火焰附近的气体速度和温度分布。对于厚度小于0.2 cm的PMMA板，蔓延速率与厚度成反比;对于厚度大于2.0 cm的PMMA板，蔓延速率与厚度无关。在预热区前面的速度分布类似于均匀温度壁附近的边界层上的速度分布，而预热区和热解区的温度分布则类似于边界层上的扩散火焰分布，温度分布表明，随着离热解前沿距离的减小，表面热流量增加。当燃烧片较薄时，预热区气相进入固相的热通量远大于热解区气相进入固相的热通量，而当燃烧片较厚时，热通量之间的关系变得相反。如果前一种情况和后一种情况可以分别被分类为热薄的和厚的板燃烧，则当PMMA板的厚度分别小于0.2cm或大于2.0cm时，可以认为PMMA板是热薄的或热厚的。
The mechanisms by which flames spread over flat surfaces of polymethylmethacrylate (PMMA) have been studied. Spread rates of vertically downward and hrizontally spreading flames were measured, and the gas velocity and temperature profiles near the spreading flames were examined using particle tracer techniques, fine wire thermocouples, and a Mach-Zender interferometer.For PMMA sheets thinner than 0.2 cm, the spread rate was inversely proportional to the thickness, and for those thicker than 2.0 cm, it was independent of the thickness. The velocity profiles in front of the preheat zone resembled those across the boundary layer near a uniform temperature wall, while those in the preheat zone and pyrolysis zone resembled those across the boundary layer with a diffusion flame.The temperature profiles indicated that the heat flux to the surface increased with the decrease of the distance from the pyrolysis front.A brief theoretical analysis based on the experimental results indicated that when a buring sheet was thin, the heat flux through the gas phase into the solid phase in the preheat zone was much larger than that into the solid phase in the pyrolysis zone, while when a buring sheet was thick, this relation between the heat fluxes became reverse. If the former and latter cases can be classified as thermally thin and thick sheet burings, respectively, a PMMA sheet can be considered to be thermally thin or thick when its thickness is smaller than 0.2 cm or larger than 2.0 cm, respectively.