Soot zone structure and sooting limit in diffusion flames: Comparison of counterflow and co-flow flames

Kang, Kyung‐Tae; Hwang, Jeongjae; Chung, Suk Ho; Lee, W.

doi:10.1016/s0010-2180(96)00163-0

Cited by 158 publications

(98 citation statements)

References 17 publications

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“…Because changes may be made before formal publication, this is made available with the understanding that it will not be cited or reproduced without the permission of the author. The potential differencesbetweenthe laminar smoke propertiesof buoyant and nonbuoyant flamescanbeattributedmainlyto thedifferenthydrodynamicpropertiesof these flames [24][25][26][27]. In particular,sootparticlesaretoo largeto diffuse like gasmoleculessothat they areconvectedby gasvelocitiesasidefrom minor effectsof thermophoresis [24].…”

Section: Wordsmentioning

confidence: 99%

Smoke-point properties of non-buoyant round laminar jet diffusion flames

Urban

Zhuang

Sunderland

et al. 2000

Proceedings of the Combustion Institute

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Section: Wordsmentioning

confidence: 99%

Smoke-point properties of non-buoyant round laminar jet diffusion flames

Urban

Zhuang

Sunderland

et al. 2000

Proceedings of the Combustion Institute

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“…Experimental study of the inverse diffusion flame using high repetition rate OH characteristics, the feasibility of using IDFs in industrial and domestic heating processes has 41 motivated a number of experimental and numerical studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”

mentioning

confidence: 99%

“…Wu and Essenhigh's [1] where the soot forms on the outside of the flame [8,10]. Soot collected from IDFs is observed 60 to be tar-like with a high hydrogen content [11,12].…”

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confidence: 99%

Experimental study of the inverse diffusion flame using high repetition rate OH/acetone PLIF and PIV

Elbaz

Roberts

2016

Fuel

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Most previous work on inverse diffusion flames (IDFs) has focused on laminar IDF emissions and the soot formation characteristics. Here, we investigate the characteristics and structure of methane IDFs using high speed planar laser-induced fluorescence (PLIF) images of OH, particle image velocimetry (PIV), and acetone PLIF imaging for nonreacting cases. First, the flame appearance was investigated with fixed methane loading (mass flux) but with varying airflow rates, yielding a central air jet Reynolds number (Re) of 1,000 to 6,000 (when blow-off occurs). Next, it was investigated a fixed central air jet Re of 4500, but with varied methane mass flux such that the global equivalence ratio spanned 0.5 to 4.It was observed that at Re smaller than 2000, the inner air jet promotes the establishment of an inverse diffusion flame surrounded by a normal diffusion flame. However, when the Re was increased to 2500, two distinct zones became apparent in the flame, a lower entrainment zone and an upper mixing and combustion zone. 10 KHz OH-PLIF images, and 2D PIV allow the identification of the fate and spatial flame structure. Many flame features were identified and further analyzed using simple but effective image processing methods, where three types of structure in all the flames investigated here: flame holes or breaks; closures; and growing kernels. Insights about the rate of evolution of these features, the dynamics of local extinction, and the sequence of events that lead to re-ignition are reported here. In the lower entrainment zone, the occurrence of the flame break events is counterbalanced by closure events, and the edge propagation appears to control the rate at which the flame holes and closures propagate. The rate of propagation of holes was found to be statistically faster than the rate of closure. As the flames approach blow-off, flame kernels become the main mechanism for flame re-ignition further downstream. The simultaneous OH-PLIF/Stereo PIV measurements indicate that the individual breaks events could be correlated to local vortical flow structure and strain rates fields. The detailed measurements provide a more complete understanding of IDF flame characteristics and structure than was previously possible. Dear Prof.I am enclosing here with a manuscript entitled "High-speed imaging of OH and acetone PLIF reveals the structure of methane inverse diffusion flames" for evaluation. With the submission of this manuscript, I would like to undertake that the above mentioned manuscript has not been published elsewhere, accepted for publication elsewhere or under editorial review for publication elsewhere. Thank you for accepting revising our paper and we appreciate the efforts of the reviewers. They have carefully critiqued our manuscript and provided important comments to improve the work. We have considered all their comments and responded by modifying the manuscript. We believe the revised manuscripts is a considerable improvement and suitable for publication in FUEL. Sincerely yours, Ayman elbaz...

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“…Due to the oxidizer surrounded by fuel in an inverse diffusion flame (IDF) and counter-flow flame, the formed soot was readily conveyed away from the main reaction region in the flame front by thermophoretic forces avoiding significant oxidation and carbonization by oxygen [14]. Therefore, IDF is widely utilized which is basically designed by exchanging oxidizer and fuel positions relative to a normal diffusion flame (NDF) configuration to obtain large samples of nascent soot particles.…”

Section: Introductionmentioning

confidence: 99%

Nanoscale Characteristics and Reactivity of Nascent Soot from n-Heptane/2,5-Dimethylfuran Inverse Diffusion Flames with/without Magnetic Fields

et al. 2018

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Abstract:In this study, the differences of nanostructure and oxidation reactivity of the nascent soot formed in n-heptane/2,5-dimethylfuran (DMF) inverse diffusion flames (IDF) with/without influence of magnetic fields were studied, and the effects of DMF-doped and magnetic fields were discussed. Morphology and nanostructures of the soot samples were investigated using high-resolution transmission electron spectroscopy and X-ray diffraction, and the oxidation reactivity characteristics were analyzed by thermogravimetric analyzer. Results demonstrated that both additions of DMF-doped and magnetic fields could promote soot production and modify the soot nanostructure and oxidation reactivity in IDF. Soot production increased along with the increase of DMF-doped. With DMF blends, more clustered soot particles and typical core-shell structures with well-organized fringes were exhibited compared with that formed from the pure n-heptane IDF. With effects of magnetic fields, the precursor formation and the oxidization of soot were promoted, soot production was enhanced. Soot particles became relatively more mature with typical core-shell structure, thicker shell, longer fringe lengths, smaller fringe tortuosity, higher graphitization degree and lower oxidation reactivity. With magnetic force pointed to the central line and the inner direction of IDF under the conditions of N pole and S pole of the magnet facing the flame, oxygen was trapped, having an increased residence time to get more chance to react with the fuel molecules to cause more soot to be yielded and oxidized. That resulted in the soot precursor promotion, soot production enhancement, and soot part-oxidization and graphitization.

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Soot zone structure and sooting limit in diffusion flames: Comparison of counterflow and co-flow flames

Cited by 158 publications

References 17 publications

Smoke-point properties of non-buoyant round laminar jet diffusion flames

Smoke-point properties of non-buoyant round laminar jet diffusion flames

Experimental study of the inverse diffusion flame using high repetition rate OH/acetone PLIF and PIV

Nanoscale Characteristics and Reactivity of Nascent Soot from n-Heptane/2,5-Dimethylfuran Inverse Diffusion Flames with/without Magnetic Fields

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