Wavelength dependence of extinction in sooting flat premixed flames in the visible and near-infrared regimes

Simonsson, Johan; Olofsson, Nils-Erik; Török, Sandra; Bengtsson, Per-Erik; Bladh, Henrik

doi:10.1007/s00340-015-6079-z

Cited by 92 publications

(76 citation statements)

References 46 publications

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“…We observed that the measured soot volume fraction became nearly independent of λ when λ > 780 nm. We note that previous studies based on premixed or coflow diffusion flames also recommended wavelength larger than 800 nm for light extinction measurements [67][68][69][70][71].…”

Section: Methodsmentioning

confidence: 83%

Experimental and soot modeling studies of ethylene counterflow diffusion flames: Non-monotonic influence of the oxidizer composition on soot formation

Yan

Zhou

et al. 2018

Combustion and Flame

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Chung SH (2018) Experimental and soot modeling studies of ethylene counterflow diffusion flames: Non-monotonic influence of the oxidizer composition on soot formation. Combustion and Flame 197: 304-318. Available: http:// dx. AbstractPrevious soot studies in counterflow diffusion flames revealed that the sooting limit curve in regions with large oxygen mole fractions (XO) exhibited marked bending behaviors that indicated a non-monotonic variation of sooting tendency with oxygen concentration. The underlying mechanisms of this bending behavior remained unclear. In this regard, the present study systematically investigated the effect of oxygen mole fraction in the oxidizer stream on the sooting characteristics of ethylene counterflow diffusion flames. We used the near-infrared light extinction technique to measure the soot volume fractions of two types of flames that significantly differed in sooting structures: soot formation oxidation (SFO) flames with a fixed fuel mole fraction (XF) of 0.28 and varying XO between 0.5 and 1.0 and soot formation (SF) flames with pure ethylene (XF = 1.0) in the fuel stream and varied XO from 0.250.3. We also conducted detailed soot modeling studies by combining the gas-phase chemistry with a sectional soot model that accounted for soot inception, soot mass growth, particle coagulation as well as soot oxidation. Our experimental and modeling results demonstrated the non-monotonic relationship between the soot volume fractions with XO in SFO flames. A detailed analysis of the evolutionary process of soot formation revealed that the suppression of soot inception and the enhancement of the soot oxidation process with increasing XO led to a reduction of soot volume fraction. On the contrary, the surface growth rates increased with XO, resulting in an increase in soot mass concentration. These competing effects led to the nonmonotonic variation of soot volume fractions with XO for SFO flames. On the other hand, in SF flames the inception and surface growth of soot both increased as XO increased, resulting in the observed monotonic relationship between soot volume fraction and XO. We also analyzed the soot zone structures and made comparisons between SFO and SF flames.

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Section: Methodsmentioning

confidence: 83%

Experimental and soot modeling studies of ethylene counterflow diffusion flames: Non-monotonic influence of the oxidizer composition on soot formation

Yan

Zhou

et al. 2018

Combustion and Flame

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“…Additional light extinction (LE) measurements [49] with a near-infrared laser beam at the wavelength of λ = 980 nm were made to calibrate the LII signals. The choice of infrared beam was based on the fact that light in the visible spectrum is likely to be absorbed by gaseous PAH species as well as by soot particles [50][51][52]. A tomographic inversion was performed to convert the line-of-sight extinction coefficients to local values [53].…”

Section: Methodsmentioning

confidence: 99%

Chemical effects of hydrogen addition on soot formation in counterflow diffusion flames: Dependence on fuel type and oxidizer composition

Yan

Wang

et al. 2020

Combustion and Flame

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We experimentally studied and kinetically modeled the effects of hydrogen addition on soot formation in methane and ethylene counterflow diffusion flames (CDFs). To isolate the chemical effects of hydrogen in such flames, we also ran a set of experiments on flames of the same base fuels but with the addition of helium. Specifically, we measured the soot volume fractions of the flames using the planar laser-induced incandescence technique. We simulated detailed sooting structures by coupling the gas-phase chemistry with the polycyclic aromatic hydrocarbon (PAH)-based soot model, using a sectional method to resolve the soot particle dynamics. Our experimental and numerical results show that hydrogen chemically inhibits soot formation in ethylene CDFs. While in methane flames, it is interesting to observe that the difference in soot production between the hydrogen-and helium-doped cases became much smaller when the oxygen concentration in the oxidizer stream (XO) was reduced.This suggests that for methane CDFs the chemical soot-inhibiting effects of hydrogen was highly dependent on oxidizer composition (i.e., XO). Explanations are provided through detailed kinetic analysis concerning the effects of hydrogen addition on the growth of PAH, soot inception, and soot surface growth processes. Our results suggest that hydrogen's chemical role in soot formation not only depends on fuel type (ethylene or methane), it also may be sensitive to oxidizer composition.

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“…For incipient soot, however, the value of E(m) is likely somewhat lower based on recent studies (Bladh et al 2011;Bejaoui et al 2015) and likely dependent on the degree of soot maturity (L opez-Yglesias et al 2014;Simonsson et al 2015), which cannot be easily quantified. Nevertheless, there are considerable uncertainties in the thermal (density, specific heat, vapor pressure, enthalpy of vaporization/sublimation) and optical (refractive index, or the absorption function in the context of LII) properties of incipient soot particles.…”

Section: Modelmentioning

confidence: 99%

“…Several efforts have been made to investigate the absorption function E(m) of aging soot in the visible and near infrared as a function of HAB in flat premixed flames (Bladh et al 2011;Bejaoui et al 2015;Maffi et al 2011) and its wavelength dependence (L opez-Yglesias et al 2014; Simonsson et al 2015;Cl eon et al 2011;Migliorini et al 2011). These studies have shown that the soot absorption increases with increasing HAB from about 0.2 to 0.4 as soot particles evolve from young to more mature state.…”

Section: Thermal and Optical Properties Of Incipient Sootmentioning

confidence: 99%

“…These studies have shown that the soot absorption increases with increasing HAB from about 0.2 to 0.4 as soot particles evolve from young to more mature state. In addition, E(m) of young soot low in the flames displays a strong wavelength dependence and it increases with decreasing wavelength (L opez-Yglesias et al 2014; Simonsson et al 2015;Migliorini et al 2011). The spectral dependence of E(m) has a strong implication for the soot temperature inferred from 2C-LII: assuming a wavelength-independent E(m) in the visible leads to a higher soot temperature than assuming an increasing E(m) with decreasing wavelength.…”

Section: Thermal and Optical Properties Of Incipient Sootmentioning

confidence: 99%

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Investigation of the size of the incandescent incipient soot particles in premixed sooting and nucleation flames of n-butane using LII, HIM, and 1 nm-SMPS

Betrancourt

Liu

Desgroux

et al. 2017

Aerosol Science and Technology

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(2017) Investigation of the size of the incandescent incipient soot particles in premixed sooting and nucleation flames of nbutane using LII, HIM, and 1 nm-SMPS, Aerosol Science and Technology, 51:8, 916-935, DOI: 10.1080/02786826.2017 Laser-induced incandescence (LII) measurements were conducted to explore the ability of LII to detect small soot particles of less than 10 nm in two sooting flat premixed flames of n-butane: a socalled nucleation flame obtained at a threshold equivalence ratio F D 1.75, in which the incipient soot particles undergo only minor soot surface growth along the flame, and a more sooting flame at F D 1.95. Size measurements were obtained by modeling the time-resolved LII signals detected using 1064 nm laser excitation. Spectrally-resolved LII signals collected in the nucleation flame display a similar blackbody-like behavior as mature soot. Soot particle temperature was determined from spectrally-resolved detection. LII modeling was conducted using parameters either relevant to those of mature soot or derived from fitting the modeled results to the experimental LII data. Particle size measurements were also carried out using (1) ex situ analysis by helium-ion microscopy (HIM) of particles sampled thermophoretically and (2) online size distribution analysis of microprobe-sampled particles using a 1 nm-SMPS. The size distributions of the incipient soot particles, found in the nucleation flame and in the early soot region of the F D 1.95 flame, derived from time-resolved LII signals are in good agreement with HIM and 1 nm-SMPS measurements and are in the range of 2-4 nm. The thermal and optical properties of incipient soot were found to be not radically different from those of mature soot commonly used in LII modeling. This explains the ability of incipient soot particles to produce continuous thermal emissions in the visible spectrum. This study demonstrates that LII is a promising in situ optical particle sizing technique that is capable of detecting incipient soot as small as about 2.5 nm and potentially 2 nm and resolving small changes in soot sizes below 10 nm.

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Wavelength dependence of extinction in sooting flat premixed flames in the visible and near-infrared regimes

Cited by 92 publications

References 46 publications

Experimental and soot modeling studies of ethylene counterflow diffusion flames: Non-monotonic influence of the oxidizer composition on soot formation

Experimental and soot modeling studies of ethylene counterflow diffusion flames: Non-monotonic influence of the oxidizer composition on soot formation

Chemical effects of hydrogen addition on soot formation in counterflow diffusion flames: Dependence on fuel type and oxidizer composition

Investigation of the size of the incandescent incipient soot particles in premixed sooting and nucleation flames of n-butane using LII, HIM, and 1 nm-SMPS

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