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

Handle URI:
http://hdl.handle.net/10754/582676
Title:
Experimental study of the inverse diffusion flame using high repetition rate OH/acetone PLIF and PIV
Authors:
Elbaz, Ayman M.; Roberts, William L. ( 0000-0003-1999-2831 )
Abstract:
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 non-reacting 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.
KAUST Department:
Clean Combustion Research Center
Citation:
Experimental study of the inverse diffusion flame using high repetition rate OH/acetone PLIF and PIV 2016, 165:447 Fuel
Publisher:
Elsevier BV
Journal:
Fuel
Issue Date:
29-Oct-2015
DOI:
10.1016/j.fuel.2015.10.096
Type:
Article
ISSN:
00162361
Additional Links:
http://linkinghub.elsevier.com/retrieve/pii/S0016236115011102
Appears in Collections:
Articles; Clean Combustion Research Center

Full metadata record

DC FieldValue Language
dc.contributor.authorElbaz, Ayman M.en
dc.contributor.authorRoberts, William L.en
dc.date.accessioned2015-11-25T11:50:05Zen
dc.date.available2015-11-25T11:50:05Zen
dc.date.issued2015-10-29en
dc.identifier.citationExperimental study of the inverse diffusion flame using high repetition rate OH/acetone PLIF and PIV 2016, 165:447 Fuelen
dc.identifier.issn00162361en
dc.identifier.doi10.1016/j.fuel.2015.10.096en
dc.identifier.urihttp://hdl.handle.net/10754/582676en
dc.description.abstractMost 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 non-reacting 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.en
dc.language.isoenen
dc.publisherElsevier BVen
dc.relation.urlhttp://linkinghub.elsevier.com/retrieve/pii/S0016236115011102en
dc.rightsNOTICE: this is the author’s version of a work that was accepted for publication in Fuel. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Fuel, 29 October 2015. DOI: 10.1016/j.fuel.2015.10.096en
dc.subjectInverse methane diffusion flameen
dc.subjectHigh speed imagingen
dc.subjectFlame structureen
dc.titleExperimental study of the inverse diffusion flame using high repetition rate OH/acetone PLIF and PIVen
dc.typeArticleen
dc.contributor.departmentClean Combustion Research Centeren
dc.identifier.journalFuelen
dc.eprint.versionPost-printen
dc.contributor.institutionFaculty of Engineering-Mataria, Helwan University, Cairo, Egypten
dc.contributor.affiliationKing Abdullah University of Science and Technology (KAUST)en
kaust.authorElbaz, Ayman M.en
kaust.authorRoberts, William L.en
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