The soot formation process has been investigated at pressures up to 16 bar using a non-premixed laminar coflow flame with nitrogen-diluted ethylene. 2D diffuse line-of-sight attenuation (2D LOSA) and planar laser-induced incandescence (PLII) were used to measure soot volume fraction (SVF). The peak SVF increased exponentially with increasing pressure, and the spatial distribution of soot volume fraction changed substantially. At pressures below 6 bar, the two techniques agreed well. At pressures above 6 bar, the techniques began to disagree, with 2D LOSA showing higher peak SVF values at a location lower in the wings of the flame compared to PLII. Errors in the LOSA measurements due to the molecular absorption of PAHs were assessed by performing measurements with bandpass filters centered at 435 nm and at 647 nm. Furthermore, the evolution of polycyclic aromatic hydrocarbons (PAH) in the flame was studied using planar laser-induced fluorescence (PLIF) with the excitation laser set at 282.85 nm and compared to LOSA measurements. Fluorescence signals were captured using bandpass filters (350, 400, 450, and 510 nm) corresponding to increasing PAH size. The peak concentration of PAHs moved closer to the burner nozzle as pressure increased. Absorption by PAH was unable to explain discrepancies between LOSA measurements and PLII measurements. Using the Rayleigh–Debye–Gans approximation for polydisperse fractal aggregates (RDG-PFA), the differences between LOSA and PLII measurements were analyzed, and it was found that LOSA is more sensitive to the soot primary particle diameter due to changes in the scattering-to-absorption ratio (ρ_sa). The effect of gate duration on SVF imaging with PLII is also reported.

中文翻译：

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层流非预混同流火焰中压力对PAH分布的影响和二维烟灰体积分数诊断的测量

已经使用非预混合层流同流火焰和氮气稀释的乙烯在高达16 bar的压力下研究了烟灰的形成过程。使用二维漫射视线衰减（2D LOSA）和平面激光诱导的白炽度（PLII）来测量烟灰体积分数（SVF）。SVF峰值随压力的增加呈指数增长，烟灰体积分数的空间分布发生了显着变化。在低于6 bar的压力下，两种技术非常吻合。在高于6 bar的压力下，该技术开始出现分歧，与PLII相比，二维LOSA在火焰翼部较低的位置显示出较高的SVF峰值。通过用中心在435 nm和647 nm处的带通滤光片进行测量，可以评估由于PAH分子吸收而导致的LOSA测量误差。此外，使用平面激光诱导的荧光（PLIF）和激发激光设置在282.85 nm上，研究了火焰中多环芳烃（PAH）的释放，并与LOSA测量结果进行了比较。使用带通滤光片（350、400、450和510 nm）捕获荧光信号，对应于增加的PAH尺寸。随着压力的升高，PAHs的峰值浓度移近燃烧器喷嘴。PAH的吸收无法解释LOSA测量值和PLII测量值之间的差异。使用Rayleigh-Debye-Gans近似的多分散形分形聚集体（RDG-PFA），分析了LOSA和PLII测量值之间的差异，发现由于散射的变化，LOSA对烟尘一次粒径更敏感。吸收比（ρ_sa）。还报道了门限持续时间对使用PLII进行SVF成像的影响。