Probing the smallest soot particles in low-sooting premixed flames using laser-induced incandescence

Bladh, Henrik; Olofsson, Nils-Erik; Mouton, Thomas; Simonsson, Johan; Mercier, Xavier; Faccinetto, Alessandro; Bengtsson, Per-Erik; Desgroux, Pascale

doi:10.1016/j.proci.2014.06.001

Cited by 80 publications

(51 citation statements)

References 32 publications

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“…This finding is important to refine soot formation modeling. Finally, Figure 13 confirms that there is only a very slight increase in the particle diameter with HAB in the nucleation flame (Flame1.75), supporting the conclusions of our previous studies (Mouton et al 2013;Bladh et al 2015;Faccinetto et al 2017) based only on LII measurements.…”

Section: Comparison Of Size Distributions Of Incipient Soot By Lii-hisupporting

confidence: 85%

“…In the present work we define a soot particle as a carbon-containing entity that is able to radiate continuous blackbody-type radiation and can be detected in flames in the visible spectral range without or with external radiation heating. Despite the general belief that incipient soot particles of few nanometers in diameter do not produce LII signals under the excitation of a laser pulse (Michelsen 2017), three recent experimental studies of soot formation in low-sooting burner-stabilized premixed flames (Mouton et al 2013;Bladh et al 2015;Faccinetto et al 2017) have demonstrated that LII signals can be produced by incipient soot particles and detected using LII in the so-called "nucleation flames." The equivalence ratio of those particular flames is such that the mixture is just rich enough to produce incipient soot particles and these particles undergo very minor surface growth when they are transported downstream.…”

Section: Introductionmentioning

confidence: 99%

“…The decay rate of time-resolved LII signals of incipient soot particles in these nucleation flames seems still to bear size information of such newly formed soot particles , as expected from the principle of particle sizing using LII: a smaller particle cools faster than a larger one (Will et al 1995;Schultz et al 2006). The first attempt was made by Bladh et al (2015) to use a LII model to fit the predicted time-resolved LII signal to the experimentally measured one with the aim to derive the diameter of soot particles produced in the nucleation flames. They showed that these nucleation particles are about 1 to 2 nm and thus very close to the size of soot particles detected in the nucleation region of premixed flames using HIM and SMPS (Schenk et al 2013(Schenk et al , 2015Tang et al 2017).…”

Section: Introductionmentioning

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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Section: Comparison Of Size Distributions Of Incipient Soot By Lii-hisupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

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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“…An interesting feature of the experimental results is that the soot volume fractions are considerably higher than those previously observed on McKenna burners under equivalent conditions [31,34]. The threshold equivalence ratio for soot formation in our flames is also much lower.…”

Section: Discussioncontrasting

confidence: 37%

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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“…At the time of this work the cutoff diameter of the custom‐made impactor was not known. To overcome this limitation, we sampled another flame in which the primary particle diameter was known from laser‐induced incandescence measurements and estimated to be below 4 nm . The sampling over wafers resulted in depositions that were reproducible and visible to the naked eye.…”

Section: Resultsmentioning

confidence: 99%

A comprehensive protocol for chemical analysis of flame combustion emissions by secondary ion mass spectrometry

Irimiea

Faccinetto

Carpentier

et al. 2018

Rapid Comm Mass Spectrometry

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Probing the smallest soot particles in low-sooting premixed flames using laser-induced incandescence

Cited by 80 publications

References 32 publications

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

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

A comprehensive protocol for chemical analysis of flame combustion emissions by secondary ion mass spectrometry

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