Synchrotron radiation studies of additives in combustion I: Water

Mitchell, James B.; Stasio, S. di; LeGarrec, J L; Florescu-Mitchell, A. I.

doi:10.1016/j.nimb.2010.01.002

Cited by 8 publications

(16 citation statements)

References 32 publications

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“…This suggests perhaps that these are naturally formed soot primaries. The increase of the number density of aggregates ( N 2 ) with ferrocene addition may be due to the increased agglomeration induced by the presence of (very small) iron oxide nuclei (a similar effect has been seen by us when water, atomized into an ethylene flame, led to increased soot aggregation). Above z = 17 mm, the increase in the number density ( N 1 ) of primary particles in the ferrocene case also argues for oxidation-induced fragmentation of the aggregated species.…”

Section: Resultssupporting

confidence: 64%

Synchrotron Radiation Studies of Additives in Combustion, III: Ferrocene

et al. 2013

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International audienceSmall-angle X-ray scattering (SAXS) has been used to examine the growth of soot primary particles (15-20 nm) and aggregates of primaries (>30 nm) formed in an ethylene flame doped with ferrocene. It is found that, early in the flame, the size of the primary particles formed when ferrocene is added tracks that for an undoped flame. Higher up (at height z above the burner greater than 18 mm), both primary and aggregate sizes are significantly smaller with ferrocene doping compared to the undoped flame. Within experimental error, the number densities of primary (N1) particles in the ferrocene flame are about the same as for the pure ethylene flame at low heights and higher (factor of 10) at larger heights (above 18 mm). On the other hand, the number concentration of aggregate particles (N2) in the doped flame is always greater than in the pure ethylene flame regardless of the height but with drops and increases in the ferrocene-doped flame case that can be correlated with corresponding increases and decreases in aggregate size. SAXS data at sufficiently long residence times in the flame show, through the value of the Porod exponent, that the particle surfaces of primaries and aggregates are much rougher in the doped versus undoped flame, which we interpret as being the effect of iron oxide inclusion that produces enhanced oxidation inside the soot material

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Section: Resultssupporting

confidence: 64%

Synchrotron Radiation Studies of Additives in Combustion, III: Ferrocene

et al. 2013

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“…Small Angle X-ray Scattering (SAXS) is a very powerful technique that enables the size and shape at the smallest scales of nanoparticles to be characterized. This technique has been already used for the in-situ characterization of soot (Di Stasio et al 2011;Di Stasio et al 2006;Mitchell et al 2013;Mitchell et al 2006;Ossler et al 2013) but these studies were not focused on the specific study of the oxidation process. Nevertheless, most of the SAXS experiments do not allow information concerning primary particle diameter and aggregate size to be obtained at the same time, when one exceeds 100 nm.…”

Section: Introductionmentioning

confidence: 99%

Investigation of soot oxidation by coupling LII, SAXS and scattering measurements

Yon

Ouf

Hébert

et al. 2018

Combustion and Flame

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“…The burner assembly was mounted on a movable stage that allowed horizontal and vertical scanning of the flame with high precision. The details of the SAXS setup are reported in previous work, 13 where the effect of plain water droplet addition was studied. 11 The flame under investigation was obtained by a Bunsen burner, 10 mm in diameter, which is the same as that which we used for all previous SAXS experiments.…”

Section: ' Experimental Methodsmentioning

confidence: 99%

“…In both cases, a system was used to aspirate liquid droplets into the air stream before mixing it with the fuel gas. In our previous work, we demonstrated, using small-angle X-ray scattering (SAXS) , and transmission electron microscopy (TEM) studies, that aggregation occurring in a flame is a hierarchical process, in that the so-called “primary particles” (20−50 nm), which are the bricks of fractal soot aggregates (typically about a few hundred nanometers in size), are in themselves constituted by the clustering of smaller units (<15 nm in size), which we called “subprimary particles” . Evidence of the contemporaneous decrease of subprimary particles and buildup of primary modes in the particle size distribution has been demonstrated using SAXS .…”

Section: Introductionmentioning

confidence: 99%

Synchrotron Radiation Studies of Additives in Combustion, II: Soot Agglomerate Microstructure Change by Alkali and Alkaline-Earth Metal Addition to a Partially Premixed Flame

2011

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International audienceSmall-angle X-ray scattering (SAXS) has been used in a comparative study to characterize soot particle formation in a partially premixed ethylene−air flame into which plain water, and 0.1 mol/L solutions of potassium chloride, cesium chloride, barium chloride, and calcium chloride were aspirated. The plain water results are assumed to be the reference in this study. On the basis of previous findings, a two-level universal fitting function for the scattering intensity I(q), 0.04 nm−1 < q < 0.5 nm−1, is used to retrieve the size and concentration of both primary particles, which are the subunits of relatively large (100 nm) fractal aggregates, and smaller subprimary particles, which aggregate in turn to form primaries. It is found that CsCl addition produces 40% smaller primary particles at larger residence times, compared to plain water addition. CaCl2, BaCl2, and KCl addition have almost no effect on primary and subprimary sizes. Cesium chloride addition produces a dramatic reduction of the subprimary particle dimension, up to a factor of 2.2, while the concentration of primaries and subprimaries is increased by factors of up to 5 and 2, respectively, with respect to plain water. The contribution to the soot volume fraction (fv) from primary and subprimary particles is separately estimated for all the additives, with respect to the standard plain water addition. At larger residence times, CsCl addition leads to a reduction of the fv contribution from primaries, with larger rates compared to KCl. On the other hand, the effect of suppression by CsCl at smaller heights can be weaker than pure water, contrary to KCl, which is a better fv suppressor than water at all heights, even if a smaller rate than that for CsCl is in operation. The effect of CsCl and KCl is the same for the subprimary fv contribution. BaCl2 has the effect of yielding a primary fv contribution, which is a factor of 2 smaller than that for plain water, almost independently of the height in the flame and, moreover, it yields a large decrease (up to a factor of 4 at a height above the burner (HAB) of 28 mm) in the subprimary fv contribution, compared to plain water. CaCl2 addition has a negligible effect on both the primary and subprimary fv contribution, with respect to water

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Synchrotron radiation studies of additives in combustion I: Water

Cited by 8 publications

References 32 publications

Synchrotron Radiation Studies of Additives in Combustion, III: Ferrocene

Synchrotron Radiation Studies of Additives in Combustion, III: Ferrocene

Investigation of soot oxidation by coupling LII, SAXS and scattering measurements

Synchrotron Radiation Studies of Additives in Combustion, II: Soot Agglomerate Microstructure Change by Alkali and Alkaline-Earth Metal Addition to a Partially Premixed Flame

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