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首页> 外文会议>International Symposium on Combustion; 20060805-11; University of Heidelberg(DE) >Molecular species adsorbed on soot particles issued from low sooting methane and acetylene laminar flames: A laser-based experiment
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Molecular species adsorbed on soot particles issued from low sooting methane and acetylene laminar flames: A laser-based experiment

机译：低烟尘甲烷和乙炔层流火焰产生的烟尘颗粒上吸附的分子种类：基于激光的实验

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Recent advances in the field of laser desorption/laser ionization mass spectrometry (LD/LI/MS) have renewed interest in these separation methods for fast analysis of chemical species adsorbed on soot particles. These techniques provide mass-separation of the desorbed phase with high selectivity and sensitivity and require very small soot samples. Combining LD/LI/MS with in situ measurements of soot and gaseous species is very promising for a better understanding of the early stage of soot growth in flames. In this work, three lightly sooting laminar jet flames (a methane diffusion flame and two premixed acetylene flames of equivalence ratio (φ) = 2.9 and 3.5) were investigated by combining prompt and 50 ns-delayed laser-induced incandescence (LII) for spatially resolved measurements of soot volume fraction (f_v) and laser-induced fluorescence (LIF) of polycyclic aromatic hydrocarbons (PAH). Soot and PAH calibration is performed by two-colour cavity ring-down spectroscopy (CRDS) at 1064 and 532 nm. Soot particles were sampled in the flames and analysed by LD/LI/Time-of-flight- MS. Soot samples are cooled to -170 ℃ to avoid adsorbed phase sublimation (under high vacuum in the TOF-MS). Our set-up is novel because of its ability to measure very low concentration of soot and PAH together with the ability to identify a large mass range of PAHs adsorbed on soot, especially volatile two-rings and three-rings PAHs. Studied flames exhibited a peak f_v ranging from 15 ppb (acetylene, φ = 2.9) to 470 ppb (acetylene, φ = 3.5). Different mass spectra were found in the three flames, each exhibiting one predominant PAH mass; 202 amu (4-rings) in methane, 178 amu (3-rings) in acetylene, φ = 2.9 and 128 amu (2-rings) in acetylene, φ = 3.5. These variations with flame condition contrasts with other recent studies and is discussed. The other PAH masses ranged from 102 (C_8H_6) to 424 amu (C_(34)H_(16)) and are well predicted by the stabilomer grid of Stein and Farr.
机译：激光解吸/激光电离质谱（LD / LI / MS）领域的最新进展已引起人们对这些分离方法的兴趣，这些分离方法用于快速分析烟灰颗粒上吸附的化学物质。这些技术提供了高选择性和灵敏度的解吸相质量分离，并且需要非常小的烟灰样品。 LD / LI / MS与烟灰和气态物质的原位测量相结合，对于更好地了解火焰中烟灰生长的早期阶段非常有希望。在这项工作中，通过组合即时和50 ns延迟的激光诱导白炽灯（LII），在空间上研究了三个轻度烟尘层流火焰（甲烷扩散火焰和两个预混乙炔火焰，当量比（φ）= 2.9和3.5）。解决了多环芳烃（PAH）的烟灰体积分数（f_v）和激光诱导荧光（LIF）的测量。烟灰和PAH的校准是通过1064和532 nm的双色腔衰荡光谱（CRDS）进行的。在火焰中对烟尘颗粒进行采样，并通过LD / LI /飞行时间MS进行分析。将烟灰样品冷却至-170℃，以避免吸附相升华（TOF-MS中在高真空下）。我们的设置新颖，因为它能够测量极低浓度的烟灰和PAH，并且能够识别吸附在烟尘上的大质量范围的PAH，尤其是挥发性的二环和三环PAH。研究火焰显示峰f_v为15 ppb（乙炔，φ= 2.9）至470 ppb（乙炔，φ= 3.5）。在三个火焰中发现了不同的质谱图，每个火焰显示出一个主要的PAH质量。甲烷中202 amu（4环），乙炔中178 amu（3环），φ= 2.9，乙炔中128 amu（2环），φ= 3.5。这些随火焰状况的变化与最近的其他研究形成对比，并进行了讨论。其他PAH的质量范围从102（C_8H_6）到424 amu（C_（34）H_（16）），并由Stein和Farr的稳定剂网格很好地预测。

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