Investigation of optical properties of aging soot

Migliorini, Francesca; Thomson, Kevin A.; Smallwood, Gregory J.

doi:10.1007/s00340-011-4396-4

Cited by 107 publications

(90 citation statements)

References 77 publications

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“…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%

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: Thermal and Optical Properties Of Incipient Sootmentioning

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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show abstract

“…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: 86%

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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“…They also reviewed several scattering models used to calculate the spectrally-dependant E(m) and suggested that those models should be used with care because they assumed the same optical properties between soot particles and carbon, and this has yet to be verified by experiments. Migliorini et al [13] investigated the optical properties of soot by using the line-of-sight-attenuation (LOSA) method in different regions of the flame and they reported that E(m) is sensitive to both wavelength and location in the flame for wavelengths less than 700 nm. They attribute the difference in light attenuation to the absorbance of large PAH (Polycyclic Aromatic Hydrocarbon) molecules, condensed species and nanoparticles.…”

Section: The Complex Refractive Index Of Soot Particlesmentioning

confidence: 99%

“…complex, branched, chain-like structures) consisting of different sizes of spherical primary particles [12,13,15]. A review on the scattering properties of soot aggregates has been made by Sorensen [15].…”

Section: Non-spherical Particles and Particle Aggregatesmentioning

confidence: 99%

Measurement of the spatially distributed temperature and soot loadings in a laminar diffusion flame using a Cone-Beam Tomography technique

Zhao¹,

Williams²,

Stone³

2014

Journal of Quantitative Spectroscopy and Radiative Transfer

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Investigation of optical properties of aging soot

Cited by 107 publications

References 77 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

Measurement of the spatially distributed temperature and soot loadings in a laminar diffusion flame using a Cone-Beam Tomography technique

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