Previous studies have shown that addition of potassium chloride (KCl) reduces soot concentration and primary particle size. To improve the understanding of this phenomenon, this work focuses on investigating the influence of KCl addition on formation of polycyclic aromatic hydrocarbons (PAHs), assumed to be precursors of soot. The method used is laser-induced fluorescence (LIF), for which different size classes of PAHs can be probed using selected combinations of excitation and detection wavelengths. KCl solutions of different concentrations were aspirated into premixed ethylene-air flames, and spectral and 2D imaging PAH-LIF measurements were performed using laser excitation at 266 nm and 532 nm. PAH-LIF spectra using 266 nm excitation showed a peak in the UV region at around 350 nm and a peak at around 550 nm in visible region, where the latter peak intensity increased strongly with flame height. The normalised PAH-LIF spectra obtained using 532 nm excitation showed no spectral change with flame height. The main results from this study showed that KCl addition, firstly, had negligible influence on the formation of smaller PAHs (measured using excitation at 266 nm and detection at ∼ 320 nm), and secondly, decreased the formation of larger PAHs at increasing flame heights (measured using excitation at 532 nm and detection in the visible region).

先前的研究表明，添加氯化钾 (KCl) 会降低烟尘浓度和初级粒径。为了加深对这种现象的理解，这项工作的重点是研究 KCl 添加对多环芳烃 (PAH) 形成的影响，多环芳烃 (PAH) 被认为是烟尘的前体。使用的方法是激光诱导荧光 (LIF)，可以使用选定的激发和检测波长组合来探测不同大小类别的 PAH。将不同浓度的 KCl 溶液吸入预混合的乙烯-空气火焰中，并使用 266 nm 和 532 nm 的激光激发进行光谱和二维成像 PAH-LIF 测量。使用 266 nm 激发的 PAH-LIF 光谱在紫外区 350 nm 附近有一个峰，在可见区 550 nm 附近有一个峰，其中后者的峰值强度随着火焰高度的增加而显着增加。使用 532 nm 激发获得的归一化 PAH-LIF 光谱没有显示光谱随火焰高度的变化。该研究的主要结果表明，首先，添加 KCl 对较小多环芳烃的形成的影响可以忽略不计（使用 266 nm 激发测量和 ~ 320 nm 检测），其次，在增加火焰高度时减少了较大多环芳烃的形成（使用 532 nm 激发和可见光区检测测量）。