Abstract In this study, the effect of sodium chloride (NaCl) on the evolution of size, mixing state, and optical properties of particle emissions was investigated. A smoking laminar diffusion flame of methane with flame length of ~100 mm was used, with and without NaCl particles introduced into the fuel stream. Extractive probe sampling with high dilution was used to sample particles and characterize their size and mixing state. Particle size distribution results showed that for the methane-only flame, the soot particles underwent typical processes of formation and coagulation in the flame, partial oxidation near the flame tip, and further coagulation in the post-flame region. In the case of the methane–NaCl flame, the coagulation rate between soot particles decreased in the agglomeration region of the flame, resulting in smaller soot particles with higher number concentration. Near the open tip of the flame, the NaCl inhibited soot oxidation, leading to larger particles compared to the methane-only flame due to continued coagulation and reduced oxidation of soot particles. In the post-flame region, where the temperature was sufficiently low, NaCl particles nucleated from its vapour phase, which was a distinct mode from that of soot in the particle size distributions. Electron microscopy images showed that these nucleated NaCl particles were mostly externally mixed and occasionally internally mixed with soot particles. Thermal-optical analysis of emissions sampled from post-flame region showed that the mass concentration of elemental carbon increased by a factor of ~3 when NaCl was added to the flame. However, addition of NaCl did not affect the mass-specific absorption coefficient of particle emissions, which was within previously reported values in the literature.

中文翻译：

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氯化钠对来自吸烟层流扩散火焰的烟灰颗粒尺寸、混合状态和光吸收的影响

摘要 在这项研究中，研究了氯化钠 (NaCl) 对粒子发射的大小、混合状态和光学性质演变的影响。使用火焰长度约为 100 毫米的甲烷冒烟层流扩散火焰，在燃料流中引入和不引入 NaCl 颗粒。使用高稀释度的萃取探针取样对颗粒进行取样并表征它们的大小和混合状态。粒径分布结果表明，对于纯甲烷火焰，烟尘颗粒在火焰中经历了典型的形成和凝聚过程，在火焰尖端附近部分氧化，并在火焰后区域进一步凝聚。在甲烷-NaCl 火焰的情况下，在火焰的团聚区域，烟尘颗粒之间的凝聚率降低，导致具有更高数量浓度的更小的烟灰颗粒。在火焰的开放尖端附近，NaCl 抑制了烟灰氧化，由于持续的凝结和烟灰颗粒的氧化减少，与仅含甲烷的火焰相比，会产生更大的颗粒。在火焰后区域，温度足够低，NaCl 颗粒从其气相成核，这与颗粒尺寸分布中的烟灰模式截然不同。电子显微镜图像显示，这些成核的 NaCl 颗粒大多在外部混合，偶尔在内部与烟尘颗粒混合。从火焰后区域采样的排放物的热光学分析表明，当将 NaCl 添加到火焰中时，元素碳的质量浓度增加了约 3 倍。然而，