Probing structures of soot formed in premixed flames of methane, ethylene and benzene

Russo, Carmela; Alfè, Michela; Rouzaud, Jean-Noël; Stanzione, Fernando; Tregrossi, A.; Ciajolo, A.

doi:10.1016/j.proci.2012.06.127

Cited by 85 publications

(51 citation statements)

References 26 publications

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“…[44][45][46] In the mid-1990's, D'Alessio [47][48][49] showed that absorption spectra collected at locations throughout sooting, premixed flames showed an evolution in OBG attributed to the chemical growth of soot precursors based on the relationship proposed by Robertson and Ferrari. [50][51][52][53][54][55][56] Most recently, our group presented Tauc analysis for soot particulate in the inception region (2 cm above the burner surface) of a 60%-C 2 H 4 /40%-N 2 non premixed flame. [50][51][52][53][54][55][56] Most recently, our group presented Tauc analysis for soot particulate in the inception region (2 cm above the burner surface) of a 60%-C 2 H 4 /40%-N 2 non premixed flame.…”

Section: Extinction Measurements and Tauc Analysismentioning

confidence: 99%

Extinction measurements for optical band gap determination of soot in a series of nitrogen-diluted ethylene/air non-premixed flames

Adkins

Miller

2015

Phys. Chem. Chem. Phys.

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Visible light extinction was measured in a series of nitrogen-diluted, ethylene/air, non-premixed flames and this data was used to determine the optical band gap, OBG, as a function of flame position. Collimated light from a supercontinuum source is telescopically expanded and refocused to match the f- number of a dispersing monochromator. The dispersed light is split into a power metering channel and a channel that is periscoped and focused into the flame. The transmitted light is then recollimated and focussed onto a silicon photodiode detector. After tomographic reconstruction of the radial extinction field, the OBG was derived from the near-edge absorption feature using Tauc/Davis-Mott analysis. A slight evolution in OBG was observed throughout all flame systems with a consistent range of OBG observed between approximately 1.85 eV and 2.35 eV. Averaging over all positions the mean OBG was approximately 2.09 eV for all flame systems. Comparing these results to previously published computational results relating calculated HOMO-LUMO gaps for a variety of D2h PAH molecules to the number of aromatic rings in the structure, showed that the observed optical band gap is consistent with a PAH of about 14 rings or a conjugation length of 0.97 nm. This work provides experimental support to the model of soot formation where the transition from chemical to physical growth starts at a modest molecular size; about the size of circumpyrene.

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Section: Extinction Measurements and Tauc Analysismentioning

confidence: 99%

Extinction measurements for optical band gap determination of soot in a series of nitrogen-diluted ethylene/air non-premixed flames

Adkins

Miller

2015

Phys. Chem. Chem. Phys.

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“…Keeping in mind that recent advances in combustion chemistry modeling have led to a detailed understanding of the small molecule chemistry in flames of these C 4 fuels [10,[14][15][16], we have shifted the focus of this work on the larger molecular species containing up to four condensed aromatic rings (pyrene). We also discuss the impact of the fuel structures on the morphology of the nascent soot [13,[17][18][19].…”

Section: Introductionmentioning

confidence: 99%

PAH formation and soot morphology in flames of C4 fuels

Schenk

Hansen

Vieker

et al. 2015

Proceedings of the Combustion Institute

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In this work, we describe experimental studies on the formation of polycyclic aromatic hydrocarbons (PAH's) in opposed-flow atmospheric-pressure flames of n-butane, i-butane, i-butene, and i-butanol and on the morphology of nascent soot particles sampled from premixed atmospheric-pressure flames of the same fuels. To identify the major contributors to the molecular growth mechanism in opposed-flow flames, we employed flame-sampling molecular-beam mass spectrometry with electron ionization (EI) and in situ gas-chromatography (GC) with mass spectrometric detection. The EI and GC-EI mass spectra indicate that several pathways with different building blocks can contribute to molecular growth. Besides the commonly accepted hydrogen-abstraction-C 2 H 2 -addition steps, we found reactions of the methyl radical to be important steps. This observation is also supported by the complexity of the mass spectra which indicates that at least one of the building blocks is rather small. The importance of phenyl radicals as building blocks seems to be limited. We also sampled nascent soot particles from premixed atmospheric-pressure flames of the above mentioned fuels and used helium-ion microscopy to unravel the influence of the fuel structure on the morphology of the sampled particles. While differences in flame temperatures and residence times are known to influence the particle sizes, the observed different morphologies are likely due to slightly different C/O ratios and potentially the chemical nature of the fuel.

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“…A dehydrogenation process has been observed in combustion with soot formation. As time progresses, or as the soot matures, the H/C ratio of soot decreases [47,48]. This type of phenomena should affect the carbon char as well, and may help explain the discrepancies observed in experimentally measured char compositions.…”

Section: Iic Expected Char Compositionmentioning

confidence: 95%

“…A slight variant of this model is also proposed such that any hydrogen content from coronene is added back into the overall gaseous species composition. This accounts for the dehydrogenation effect previously mentioned [47,48]. This method is referred to as Model #1, and is outlined by the following equations:…”

Section: Va Model #1mentioning

confidence: 99%

Pyrolysis Gas Composition for a Phenolic Impregnated Carbon Ablator Heatshield

Rabinovitch

Marx

Blanquart

2014

11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference

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Published physical properties of phenolic impregnated carbon ablator (PICA) are compiled, and the composition of the pyrolysis gases that form at high temperatures internal to a heatshield is investigated. A link between the composition of the solid resin, and the composition of the pyrolysis gases created is provided. This link, combined with a detailed investigation into a reacting pyrolysis gas mixture, allows a consistent, and thorough description of many of the physical phenomena occurring in a PICA heatshield, and their implications, to be presented.

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Probing structures of soot formed in premixed flames of methane, ethylene and benzene

Cited by 85 publications

References 26 publications

Extinction measurements for optical band gap determination of soot in a series of nitrogen-diluted ethylene/air non-premixed flames

Extinction measurements for optical band gap determination of soot in a series of nitrogen-diluted ethylene/air non-premixed flames

PAH formation and soot morphology in flames of C4 fuels

Pyrolysis Gas Composition for a Phenolic Impregnated Carbon Ablator Heatshield

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