Abstract In this work soot formation was studied in a series of laminar premixed flames fueled with binary heptane-toluene mixtures. The equivalence ratio (φ = 2), the cold gas velocity and the total carbon flow rate were kept constant changing accordingly the oxygen content and the diluent (N2) concentration. A very similar temperature up to 80% of toluene concentration was obtained and, hence, a direct comparison between particle formation from such different fuels. In-situ optical techniques (laser induced incandescence – LII) and ex-situ particle size distribution (PSD) measured downstream of the flame front have furnished data on the total amount and size of combustion generated particles derived from heptane/toluene combustion. LII showed an increase of total volume fraction of soot as the toluene percentage increased. PSD profiles showed that particles with sizes less than 10 nm decrease as toluene percentage in the feed mixture increases, disappearing for toluene percentages above 60%. Conversely, large aggregates grow towards sizes larger than 100 nm when toluene concentration is increased. Bulk material was also sampled thermophoretically from the flames by means of fast insertion of quartz plate. UV–Visible and Raman spectroscopy was performed in order to obtain information on the aromaticity of the particles that was found to increase with toluene percentage. These results follow what already found for other aliphatic-aromatic binary mixtures. However, the heptane/toluene mixture peculiarities different from other mixtures will have to be taken into account for the future studies on surrogates and other synthetic fuels.

中文翻译：

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预混合庚烷-甲苯火焰中的烟灰形成

摘要 在这项工作中，研究了以二元庚烷-甲苯混合物为燃料的一系列层流预混火焰中的烟灰形成。当量比 (φ = 2)、冷气速度和总碳流量保持恒定，相应地改变氧含量和稀释剂 (N2) 浓度。获得了高达 80% 甲苯浓度的非常相似的温度，因此，可以直接比较这些不同燃料的颗粒形成。原位光学技术（激光诱导白炽光 – LII）和在火焰前沿下游测量的异位粒度分布 (PSD) 提供了有关源自庚烷/甲苯燃烧的燃烧生成颗粒总量和尺寸的数据。随着甲苯百分比的增加，LII 显示烟灰的总体积分数增加。PSD 曲线显示，粒径小于 10 nm 的颗粒随着进料混合物中甲苯百分比的增加而减少，甲苯百分比高于 60% 时消失。相反，当甲苯浓度增加时，大的聚集体会朝着大于 100 nm 的尺寸生长。还通过快速插入石英板从火焰中热泳取样。进行紫外-可见光和拉曼光谱是为了获得有关颗粒芳香性的信息，发现该信息随着甲苯百分比的增加而增加。这些结果与其他脂肪族-芳香族二元混合物的结果一致。然而，在未来对替代品和其他合成燃料的研究中，必须考虑到庚烷/甲苯混合物与其他混合物不同的特性。