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首页> 外文期刊>International Journal of Heat and Mass Transfer >Soot graphitic order in laminar diffusion flames and a large-scale JP-8 pool fire
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Soot graphitic order in laminar diffusion flames and a large-scale JP-8 pool fire

机译：层流扩散火焰和大型JP-8池火中的碳黑石墨顺序

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High-resolution transmission electron microscopy (HRTEM) has been performed on soot samples collected from two smoking laminar ethylene diffusion flames (one steady and one unsteady) and from the active-flaming region of a 5-m diameter JP-8 pool fire. The motivation for this study is to improve the understanding of the influence of soot microstructure on its optical properties. The soot sampling positions in the steady ethylene flame correspond to locations of maximum soot mass growth, partial soot oxidation, and quenched oxidation along a common streamline. Visual examination of the HRTEM images suggests that the graphitic crystalline layers of soot undergo increased den-sification along the sampled streamline in the steady laminar flame. Quantitative image analysis reveals a small decrease in the mean graphitic interlayer spacing (d_(002)) with increasing residence time in the high-temperature region. However, the differences in the mean interlayer spacing are far smaller than the spread of interlayer spacings measured for any given soot sample. Post-flame samples from the unsteady ethylene flame show interlayer spacing distributions similar to the lower region of the steady flame. The soot samples from the pool fire show little evidence of oxidized soot and have interlayer spacings similar to the unsteady ethylene flame. Previous research in the carbon black field has demonstrated a direct relation between the graphitic interlayer spacing and the optical absorptivity of the carbon. Consequently, the current HRTEM results offer support to recent measurements of the dimensionless extinction coefficient of soot that suggest that the optical absorptivity of agglomerating soot shows only minor variations for different fuels and flame types.
机译：对从两个吸烟的层状乙烯扩散火焰（一个稳定的和一个不稳定的）以及从直径为5 m的JP-8池火的主动燃烧区域收集的烟尘样品进行了高分辨率透射电子显微镜（HRTEM）。这项研究的动机是增进对烟灰微结构对其光学性能的影响的理解。稳定乙烯火焰中的烟灰采样位置对应于沿着共同流线的最大烟灰质量增长，部分烟灰氧化和淬火氧化的位置。 HRTEM图像的目测表明，在稳定的层流火焰中，烟灰的石墨结晶层沿采样流线经历了增加的致密化。定量图像分析表明，平均石墨层间间距（d_（002））随高温区域中停留时间的增加而略有下降。但是，平均层间间距的差异远小于对于任何给定的煤烟样品测得的层间间距的差异。来自不稳定乙烯火焰的火焰后样品显示出与稳定火焰下部区域相似的层间间距分布。池火中的烟灰样品几乎没有氧化烟灰的迹象，并且层间间距与不稳定的乙烯火焰相似。炭黑领域的先前研究表明，石墨层间间距与碳的吸光度之间存在直接关系。因此，当前的HRTEM结果为烟灰的无量纲消光系数的最新测量提供了支持，这表明团聚的烟灰的光学吸收率对于不同的燃料和火焰类型仅显示出很小的变化。

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