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Detection of nanostructures and soot in laminar premixed flames

机译：检测层状预混火焰中的纳米结构和烟尘

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This paper presents both in-situ and ex-situ measurements of nanostructures (also loosely referred to as nanoparticles) in laminar flames with the purpose of providing an understanding of their evolution to soot. Two laminar flame burners are studied covering a range of C/0 ratios and hence different sooting propensities. Ex-situ measurements, utilizing soot sampling and analysis using differential mobility analyzers, are performed to yield information on the particle size distribution (PSD). A broad range of in-situ measurement techniques are employed including laser-induced fluorescence (LIF), laser-induced incandescence (LII), and elastic laser scattering. In-situ measurements completed at the University of Sydney, utilise fast response photomultiplier tubes to monitor time-resolved emission signals simultaneously in four different spectral regions, whilst measurements performed at the University of Naples Federico II are spectrally resolved. The temporal lifetimes of the LIF signals are found to be much longer than that expected for molecules at the same temperature, yet much shorter and spectrally different than that of soot particles. The laser based measurements, combined with the PSD results, suggest that LIF is able to track nanostructures as condensed phase matter with sizes in the order of few nanometers and with internal structures exhibiting the spectroscopic behavior of small PAHs. Conversely, LII is more suited for the detection of solid state particles which are larger in size and have a more aromatic character. It is found that close to the burner exit plane in the early regions of the flames LIF is measured both in the visible and ultraviolet (UV) bands, but not LII, implying the existence of nanostructures rather than soot. Further downstream, these nanostructures continue to exist but now in the presence of soot as is evident by the persistence of the LIF-UV and LIF-visible in conjunction with LII and laser scattering. Collectively, these findings confirm the hybrid nature of nanostructures that dominate the early evolution of soot. (C) 2016 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
机译：本文介绍了层流火焰中纳米结构（也称为纳米颗粒）的原位和异位测量，目的是了解它们向烟ot的演变。研究了两个层流火焰燃烧器，覆盖范围为C / 0的范围，因此具有不同的烟ot倾向。使用烟灰采样和使用差分迁移率分析仪进行分析进行异地测量，以得出有关粒度分布（PSD）的信息。采用了广泛的原位测量技术，包括激光诱导荧光（LIF），激光诱导白炽度（LII）和弹性激光散射。在悉尼大学完成的现场测量，利用快速响应光电倍增管在四个不同的光谱区域中同时监测时间分辨的发射信号，而那不勒斯费德里科二世大学进行的测量则进行了光谱分辨。发现LIF信号的时间寿命比在相同温度下分子的预期寿命长得多，但比烟灰颗粒的寿命短得多，并且在光谱上也不同。基于激光的测量结果与PSD结果相结合，表明LIF能够跟踪纳米结构为凝聚相物质，其大小约为几纳米，内部结构表现出小PAH的光谱行为。相反，LII更适合于检测尺寸较大且具有更多芳香特性的固态颗粒。发现在火焰的早期区域中，靠近燃烧器出口平面的LIF在可见和紫外（UV）波段均被测量，而LII未被测量，这意味着存在纳米结构而不是烟灰。在更下游，这些纳米结构继续存在，但是现在存在烟灰，这可以通过LIF-UV和LIF-visible与LII和激光散射的持久性来证明。总而言之，这些发现证实了主导烟灰早期发展的纳米结构的混杂性质。 （C）2016年燃烧研究所。由Elsevier Inc.出版。保留所有权利。

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