Mapping and structure of inverse diffusion flames of methane

Wu, Kuang-Tsai; Essenhigh, Robert H.

doi:10.1016/s0082-0784(85)80691-3

Cited by 75 publications

(40 citation statements)

References 9 publications

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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].…”

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

Elbaz

Roberts

2016

Fuel

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“…Whilst some studies of laminar air flames have found that inverse and normal diffusion flames are similar in structure [4,8], other authors have observed differences in the measured temperature in air combustion [7] and in the OH* chemiluminescence fields in oxy-fuel combustion [9]. To our knowledge, a similar comparison of turbulent normal and inverse diffusion flames has not been published.…”

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confidence: 86%

“…In the present investigation, we focus on analyzing the differences between non-piloted IDFs and NDFs, extending previous laminar studies [4,[7][8][9] towards turbulent oxy-fuel flames. The influence of turbulence on flame structure in both configurations is studied using experimental and numerical data.…”

Section: Introductionmentioning

confidence: 98%