The blow-off mechanism of a bluff-body stabilized laminar premixed flame

Handle URI:
http://hdl.handle.net/10754/599880
Title:
The blow-off mechanism of a bluff-body stabilized laminar premixed flame
Authors:
Kedia, Kushal S.; Ghoniem, Ahmed F.
Abstract:
© 2014 The Combustion Institute. The objective of this work is to investigate the dynamics leading to blow-off of a laminar premixed flame stabilized on a confined bluff-body using high fidelity numerical simulations. We used unsteady, fully resolved, two-dimensional simulations with detailed chemical kinetics and species transport for methane-air combustion. The flame-wall interaction between the hot reactants and the heat conducting bluff-body was accurately captured by incorporating the conjugate heat exchange between them. Simulations showed a shear-layer stabilized flame just downstream of the bluff-body, with a recirculation zone formed by the products of combustion. The flame was negatively stretched along its entire length, primarily dominated by the normal component of the strain. Blow-off was approached by decreasing the mixture equivalence ratio, at a fixed Reynolds number, of the incoming flow. A flame is stable (does not undergo blow-off) when (1) flame displacement speed is equal to the flow speed and (2) the gradient of the flame displacement speed normal to its surface is higher than the gradient of the flow speed along the same direction. As the equivalence ratio is reduced, the difference between the former and the latter shrinks until the dynamic stability condition (2) is violated, leading to blow-off. Blow-off initiates at a location where this is first violated along the flame. Our results showed that this location was far downstream from the flame anchoring zone, near the end of the recirculation zone. Blow-off started by flame pinching separating the flame into an upstream moving (carried within the recirculation zone) and a downstream convecting (detached from the recirculation zone) flame piece. Within the range of operating conditions investigated, the conjugate heat exchange with the bluff-body had no impact on the flame blow-off.
Citation:
Kedia KS, Ghoniem AF (2015) The blow-off mechanism of a bluff-body stabilized laminar premixed flame. Combustion and Flame 162: 1304–1315. Available: http://dx.doi.org/10.1016/j.combustflame.2014.10.017.
Publisher:
Elsevier BV
Journal:
Combustion and Flame
KAUST Grant Number:
KUS-11-010-01
Issue Date:
Apr-2015
DOI:
10.1016/j.combustflame.2014.10.017
Type:
Article
ISSN:
0010-2180
Sponsors:
This work was supported by King Abdullah University of Science and Technology (KAUST) Award Number KUS-11-010-01. We would like to acknowledge Dr. Habib Najm, Dr. Cosmin Safta and Dr. Jaideep Ray (Combustion Research Facility, Sandia National Laboratories, Livermore, CA, USA) for their major contribution towards the SAMR tool development. Special thanks to Dr. Santosh Shanbhogue (Research Scientist, Reacting Gas Dynamics Laboratory, MIT, Cambridge, MA, USA) for his invaluable inputs and suggestions.
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Full metadata record

DC FieldValue Language
dc.contributor.authorKedia, Kushal S.en
dc.contributor.authorGhoniem, Ahmed F.en
dc.date.accessioned2016-02-28T06:31:34Zen
dc.date.available2016-02-28T06:31:34Zen
dc.date.issued2015-04en
dc.identifier.citationKedia KS, Ghoniem AF (2015) The blow-off mechanism of a bluff-body stabilized laminar premixed flame. Combustion and Flame 162: 1304–1315. Available: http://dx.doi.org/10.1016/j.combustflame.2014.10.017.en
dc.identifier.issn0010-2180en
dc.identifier.doi10.1016/j.combustflame.2014.10.017en
dc.identifier.urihttp://hdl.handle.net/10754/599880en
dc.description.abstract© 2014 The Combustion Institute. The objective of this work is to investigate the dynamics leading to blow-off of a laminar premixed flame stabilized on a confined bluff-body using high fidelity numerical simulations. We used unsteady, fully resolved, two-dimensional simulations with detailed chemical kinetics and species transport for methane-air combustion. The flame-wall interaction between the hot reactants and the heat conducting bluff-body was accurately captured by incorporating the conjugate heat exchange between them. Simulations showed a shear-layer stabilized flame just downstream of the bluff-body, with a recirculation zone formed by the products of combustion. The flame was negatively stretched along its entire length, primarily dominated by the normal component of the strain. Blow-off was approached by decreasing the mixture equivalence ratio, at a fixed Reynolds number, of the incoming flow. A flame is stable (does not undergo blow-off) when (1) flame displacement speed is equal to the flow speed and (2) the gradient of the flame displacement speed normal to its surface is higher than the gradient of the flow speed along the same direction. As the equivalence ratio is reduced, the difference between the former and the latter shrinks until the dynamic stability condition (2) is violated, leading to blow-off. Blow-off initiates at a location where this is first violated along the flame. Our results showed that this location was far downstream from the flame anchoring zone, near the end of the recirculation zone. Blow-off started by flame pinching separating the flame into an upstream moving (carried within the recirculation zone) and a downstream convecting (detached from the recirculation zone) flame piece. Within the range of operating conditions investigated, the conjugate heat exchange with the bluff-body had no impact on the flame blow-off.en
dc.description.sponsorshipThis work was supported by King Abdullah University of Science and Technology (KAUST) Award Number KUS-11-010-01. We would like to acknowledge Dr. Habib Najm, Dr. Cosmin Safta and Dr. Jaideep Ray (Combustion Research Facility, Sandia National Laboratories, Livermore, CA, USA) for their major contribution towards the SAMR tool development. Special thanks to Dr. Santosh Shanbhogue (Research Scientist, Reacting Gas Dynamics Laboratory, MIT, Cambridge, MA, USA) for his invaluable inputs and suggestions.en
dc.publisherElsevier BVen
dc.subjectBlow-off mechanismen
dc.subjectBluff-bodyen
dc.subjectConjugate heat exchangeen
dc.subjectLaminaren
dc.subjectPremixed flameen
dc.titleThe blow-off mechanism of a bluff-body stabilized laminar premixed flameen
dc.typeArticleen
dc.identifier.journalCombustion and Flameen
dc.contributor.institutionMassachusetts Institute of Technology, Cambridge, United Statesen
kaust.grant.numberKUS-11-010-01en
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