Abstract An experimental work is carried out to investigate the influence of pressure on morphological parameters of soot in counterflow flames of N2-diluted methane and air. Flames are stabilized at 3, 5, 7 and 10 atm in a pressure vessel and a global strain rate of 30 s−1 is maintained at all pressures by adjusting the inlet mass flux. The mole fraction of methane is maintained at 0.7. The entire soot zone of the counterflow flames are sampled using a thermophoretic sampling device attached to the pressure vessel. Our sampling method minimizes the flow disturbances to a level that they are visually negligible during the sampling process. Collected samples are analyzed under a transmission electron microscope and information about mean primary particle diameter, fractal dimension (Df), fractal prefactor (kf) and aggregate size distribution is inferred at different pressures. To investigate the effects of carbon flux on primary particle size, fuel mole fraction is decreased to 0.5 and primary particle size is investigated at 5, 7 and 10 atm. Mean primary particle size increases by 70% when pressure is changed from 5 to 10 atm and remains independent of fuel mole fractions. Geometric mean and geometric width of aggregate size distributions also increase by increasing the pressure. Fractal properties of soot aggregates are found to be insensitive to the pressure. Fractal dimension varies between 1.56 and 1.65 while fractal prefactor values range between 1.96 and 2.1.

中文翻译：

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通过 TEM 成像在高压下从 N2 稀释的甲烷/空气逆流火焰中取样的烟灰形态

摘要 通过实验研究了压力对N2稀释甲烷和空气逆流火焰中烟尘形态参数的影响。火焰在压力容器中稳定在 3、5、7 和 10 个大气压，并且通过调节入口质量通量在所有压力下保持 30 s-1 的全局应变率。甲烷的摩尔分数保持在 0.7。使用连接到压力容器的热泳采样装置对逆流火焰的整个烟灰区进行采样。我们的采样方法最大限度地减少了流动干扰，使其在采样过程中可以忽略不计。收集的样品在透射电子显微镜下进行分析，并获得有关平均初级粒径、分形维数 (Df)、分形前因数 (kf) 和骨料尺寸分布是在不同压力下推断出来的。为了研究碳通量对初级粒径的影响，燃料摩尔分数降低到 0.5，初级粒径在 5、7 和 10 个大气压下进行研究。当压力从 5 个大气压变为 10 个大气压时，平均初级粒径增加了 70%，并且不受燃料摩尔分数的影响。聚集体尺寸分布的几何平均值和几何宽度也随着压力的增加而增加。发现烟灰聚集体的分形特性对压力不敏感。分形维数在 1.56 和 1.65 之间变化，而分形前因子值的范围在 1.96 和 2.1 之间。5 和初级粒径在 5、7 和 10 个大气压下进行研究。当压力从 5 个大气压变为 10 个大气压时，平均初级粒径增加了 70%，并且不受燃料摩尔分数的影响。聚集体尺寸分布的几何平均值和几何宽度也随着压力的增加而增加。发现烟灰聚集体的分形特性对压力不敏感。分形维数在 1.56 和 1.65 之间变化，而分形前因子值的范围在 1.96 和 2.1 之间。5 和初级粒径在 5、7 和 10 个大气压下进行研究。当压力从 5 个大气压变为 10 个大气压时，平均初级粒径增加了 70%，并且不受燃料摩尔分数的影响。聚集体尺寸分布的几何平均值和几何宽度也随着压力的增加而增加。发现烟灰聚集体的分形特性对压力不敏感。分形维数在 1.56 和 1.65 之间变化，而分形前因子值的范围在 1.96 和 2.1 之间。