TY - JOUR
T1 - Simultaneous laser-induced emission of soot and polycyclic aromatic hydrocarbons within a gas-jet diffusion flame
AU - Vander Wal, Randall L.
AU - Jensen, Kirk A.
AU - Choi, Mun Y.
N1 - Funding Information:
RVW acknowledges support through NASA contract NAS3-27186. MYC and KAJ gratefully acknowledge support from The Ohio Aerospace Institute through the NASA-ASEE Summer Fac-ul~ Fellow and Accompanying Student Program. The authors gratefully acknowledge the TEM work performed by Mr. Zhi-Qiang Zhou of UIC.
PY - 1997/5
Y1 - 1997/5
N2 - Simultaneous images of laser-induced fluorescence (LIF) due to polycyclic aromatic hydrocarbons (PAHs) and laser-induced incandescence (LII) visualization of soot concentrations are presented for laminar gas- jet diffusion flames. Spatially integrated measurements reveal similar spectral emission for LIF and LII, but vastly different time scales associated with radiative decay. Comparison of spatially resolved images using either 266-nm or 1064-nm excitation light reveals distinct regions of molecular fluorescence and soot incandescence. Consideration of photophysical properties of PAHs suggests that the fluorescence wavelength distribution is dependent on the size of the PAH. Using different detection spectral bands, spatially resolved regions attributed to different-sized PAHs are presented. The spatial distribution of PAll size is consistent with the putative growth mechanism of PAHs. In the region between the LIF due to PAHs and LII due to soot, a dark zone is observed that is attributed to the presence of soot precursor particles. Current understanding of soot formation indicates that through both physical and/or chemical condensation, large PAHs react first to form soot precursor particles prior to the formation of soot particles. Transmission electron microscopy analysis of thermophoretically collected material from within this dark region confirmed the presence of soot precursor particles 2 to 5 nm in diameter.
AB - Simultaneous images of laser-induced fluorescence (LIF) due to polycyclic aromatic hydrocarbons (PAHs) and laser-induced incandescence (LII) visualization of soot concentrations are presented for laminar gas- jet diffusion flames. Spatially integrated measurements reveal similar spectral emission for LIF and LII, but vastly different time scales associated with radiative decay. Comparison of spatially resolved images using either 266-nm or 1064-nm excitation light reveals distinct regions of molecular fluorescence and soot incandescence. Consideration of photophysical properties of PAHs suggests that the fluorescence wavelength distribution is dependent on the size of the PAH. Using different detection spectral bands, spatially resolved regions attributed to different-sized PAHs are presented. The spatial distribution of PAll size is consistent with the putative growth mechanism of PAHs. In the region between the LIF due to PAHs and LII due to soot, a dark zone is observed that is attributed to the presence of soot precursor particles. Current understanding of soot formation indicates that through both physical and/or chemical condensation, large PAHs react first to form soot precursor particles prior to the formation of soot particles. Transmission electron microscopy analysis of thermophoretically collected material from within this dark region confirmed the presence of soot precursor particles 2 to 5 nm in diameter.
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U2 - 10.1016/S0010-2180(96)00189-7
DO - 10.1016/S0010-2180(96)00189-7
M3 - Article
AN - SCOPUS:0030936882
SN - 0010-2180
VL - 109
SP - 399
EP - 414
JO - Combustion and Flame
JF - Combustion and Flame
IS - 3
ER -