Optical soot characterization using two-color laser-induced incandescence (2C-LII) in the soot growth region of a premixed flat flame

Bladh, Henrik; Johnsson, Jonathan; Olofsson, Nils-Erik; Bohlin, Alexis; Bengtsson, Per-Erik

doi:10.1016/j.proci.2010.06.166

Cited by 111 publications

(116 citation statements)

References 36 publications

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“…The E(m) values at 1064 nm at different HABs are also reported in Table 1. It shows an increase in E(m) at 1064 nm with increasing HAB in accordance with the results of an earlier study conducted by Bladh et al [11]. It is worth pointing out these E(m) values at 1064 nm should not be considered as accurate due to the use of density and heat capacity for mature soot, due to the unavailability of such thermal properties for young and immature soot, used in the determination of E(m) values in the growth region of the flat rich premixed methane flame.…”

Section: Evaluation Of Absolute Absorption Function At 1064 Nmsupporting

confidence: 92%

“…There seems a consensus in the literature that this value falls in the range of about 0.2-0.4, i.e., with a uncertainty of about a factor of 2. Nevertheless, investigations conducted so far tend to support that E(m) seems dependent on the type of fuel and the maturation of the soot particle [11][12][13]. It is well known that the soot absorption function is difficult to determine accurately and many methods have been proposed [12,[14][15][16][17][18][19][20][21][22].…”

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confidence: 99%

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Influence of soot aggregate size and internal multiple scattering on LII signal and the absorption function variation with wavelength determined by the TEW-LII method

Yon

Therssen

Liu³

et al. 2015

Appl. Phys. B

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Section: Evaluation Of Absolute Absorption Function At 1064 Nmsupporting

confidence: 92%

mentioning

confidence: 99%

Influence of soot aggregate size and internal multiple scattering on LII signal and the absorption function variation with wavelength determined by the TEW-LII method

Yon

Therssen

Liu³

et al. 2015

Appl. Phys. B

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“…The value of absorption function E(m) for mature soot in the visible and near-infrared is about 0.3 to 0.4 (Snelling et al 2004;Bladh et al 2011;Bejaoui et al 2015). 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.…”

Section: Modelmentioning

confidence: 95%

“…Second, the TEM images of these nascent particles have poor contrast and the particle structure is prone to be damaged by the electron beam Schenk et al 2013). Due to these limitations, the smallest soot particles measured by the TEM approach are typically about 10 nm Bladh et al 2011). Only a few studies using TEM have reported particles as small as 5 nm (Simonsson et al 2017;Zhang et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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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“…Additionally, the particle size and physical properties of soot may change as a function of height above burner. In particular, a variation of E(m) with vertical position has been noted in ethylene-air flat flames by other authors [32,33]. Since both the prompt LII and the photoacoustic measurement generate a signal that is dependent on the absorption of laser light by soot, such variation in E(m) may introduce experimental errors in each technique.…”

Section: Discussionmentioning

confidence: 89%

A simple photoacoustic method for the in situ study of soot distribution in flames

et al. 2015

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of soot formation during combustion is a key step in developing soot reduction strategies [3,4].Optical measurement techniques are ideally suited for combustion environments because they generally cause negligible perturbation to the combustion process. One of the most widely used optical techniques for the study of particulate matter in flames is laser-induced incandescence (LII). Typical LII experimental schemes use a high-power pulsed laser source (such as a solid-state Nd:YAG laser) [5] to heat the soot particles. The resulting thermal emission is then detected, usually over a narrow range of wavelengths selected using either a system of optical filters [6] or a monochromator [7]. The peak signal level provides a measure of the relative soot volume fraction. The absolute soot volume fraction is found either by calibration based on optical extinction measurements [8,9] or by a two-colour approach in which a second filtered detector collects light from the same measurement volume, and the ratio of signals is used to determine the peak particle temperature [10,11]. A feature of this type of experimental set-up is that a high-power pulsed laser source and relatively fast photodetectors or intensified cameras are required.Photoacoustic (PA) detection has been used to make highly sensitive laser absorption measurements in a number of applications, such as IR spectroscopy [12]. The principle of photoacoustic detection of particles is that absorption of the incident laser energy leads to an increase in the temperature of the particle. Heat is transferred from the particles to the surrounding gas, resulting in the expansion of the gas [13]. A change in laser intensity leads to a change in the rate of heat transfer, and an acoustic pressure wave can therefore be established by modulating the intensity of the laser [14]. The pressure wave can be detected using a microphone, and its amplitude measured using a lock-in amplifier. This method of detection has a further advantage Abstract This paper presents a simple photoacoustic technique capable of quantifying soot volume fraction across a range of flame conditions. The output of a highpower (30 W) 808-nm cw-diode laser was modulated in order to generate an acoustic pressure wave via laser heating of soot within the flame. The generated pressure wave was detected using a micro-electro-mechanical microphone mounted close to a porous-plug flat-flame burner. Measurements were taken using the photoacoustic technique in flames of three different equivalence ratios and were compared to laser-induced incandescence. The results presented here show good agreement between the two techniques and show the potential of the photoacoustic method as a way to measure soot volume fraction profiles in this type of flame. We discuss the potential to implement this technique with much lower laser power than was used in the experiments presented here.

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Optical soot characterization using two-color laser-induced incandescence (2C-LII) in the soot growth region of a premixed flat flame

Cited by 111 publications

References 36 publications

Influence of soot aggregate size and internal multiple scattering on LII signal and the absorption function variation with wavelength determined by the TEW-LII method

Influence of soot aggregate size and internal multiple scattering on LII signal and the absorption function variation with wavelength determined by the TEW-LII method

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

A simple photoacoustic method for the in situ study of soot distribution in flames

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