Mechanisms of stabilization and blowoff of a premixed flame downstream of a heat-conducting perforated plate

Handle URI:
http://hdl.handle.net/10754/598792
Title:
Mechanisms of stabilization and blowoff of a premixed flame downstream of a heat-conducting perforated plate
Authors:
Kedia, Kushal S.; Ghoniem, Ahmed F.
Abstract:
The objective of this work is to investigate the flame stabilization mechanism and the conditions leading to the blowoff of a laminar premixed flame anchored downstream of a heat-conducting perforated-plate/multi-hole burner, with overall nearly adiabatic conditions. We use unsteady, fully resolved, two-dimensional simulations with detailed chemical kinetics and species transport for methane-air combustion. Results show a bell-shaped flame stabilizing above the burner plate hole, with a U-shaped section anchored between neighboring holes. The base of the positively curved U-shaped section of the flame is positioned near the stagnation point, at a location where the flame displacement speed is equal to the flow speed. This location is determined by the combined effect of heat loss and flame stretch on the flame displacement speed. As the mass flow rate of the reactants is increased, the flame displacement speed at this location varies non-monotonically. As the inlet velocity is increased, the recirculation zone grows slowly, the flame moves downstream, and the heat loss to the burner decreases, strengthening the flame and increasing its displacement speed. As the inlet velocity is raised, the stagnation point moves downstream, and the flame length grows to accommodate the reactants mass flow. Concomitantly, the radius of curvature of the flame base decreases until it reaches an almost constant value, comparable to the flame thickness. While the heat loss decreases, the higher flame curvature dominates thereby reducing the displacement speed of the flame base. For a stable flame, the gradient of the flame base displacement speed normal to the flame is higher than the gradient of the flow speed along the same direction, leading to dynamic stability. As inlet velocity is raised further, the former decreases while the latter increases until the stability condition is violated, leading to blowoff. The flame speed during blow off is determined by the feedback between the growing recirculation zone and the cooling burner plate. © 2011 The Combustion Institute.
Citation:
Kedia KS, Ghoniem AF (2012) Mechanisms of stabilization and blowoff of a premixed flame downstream of a heat-conducting perforated plate. Combustion and Flame 159: 1055–1069. Available: http://dx.doi.org/10.1016/j.combustflame.2011.10.014.
Publisher:
Elsevier BV
Journal:
Combustion and Flame
Issue Date:
Mar-2012
DOI:
10.1016/j.combustflame.2011.10.014
Type:
Article
ISSN:
0010-2180
Sponsors:
This work was supported by King Abdullah University of Science and Technology (KAUST).
Appears in Collections:
Publications Acknowledging KAUST Support

Full metadata record

DC FieldValue Language
dc.contributor.authorKedia, Kushal S.en
dc.contributor.authorGhoniem, Ahmed F.en
dc.date.accessioned2016-02-25T13:41:19Zen
dc.date.available2016-02-25T13:41:19Zen
dc.date.issued2012-03en
dc.identifier.citationKedia KS, Ghoniem AF (2012) Mechanisms of stabilization and blowoff of a premixed flame downstream of a heat-conducting perforated plate. Combustion and Flame 159: 1055–1069. Available: http://dx.doi.org/10.1016/j.combustflame.2011.10.014.en
dc.identifier.issn0010-2180en
dc.identifier.doi10.1016/j.combustflame.2011.10.014en
dc.identifier.urihttp://hdl.handle.net/10754/598792en
dc.description.abstractThe objective of this work is to investigate the flame stabilization mechanism and the conditions leading to the blowoff of a laminar premixed flame anchored downstream of a heat-conducting perforated-plate/multi-hole burner, with overall nearly adiabatic conditions. We use unsteady, fully resolved, two-dimensional simulations with detailed chemical kinetics and species transport for methane-air combustion. Results show a bell-shaped flame stabilizing above the burner plate hole, with a U-shaped section anchored between neighboring holes. The base of the positively curved U-shaped section of the flame is positioned near the stagnation point, at a location where the flame displacement speed is equal to the flow speed. This location is determined by the combined effect of heat loss and flame stretch on the flame displacement speed. As the mass flow rate of the reactants is increased, the flame displacement speed at this location varies non-monotonically. As the inlet velocity is increased, the recirculation zone grows slowly, the flame moves downstream, and the heat loss to the burner decreases, strengthening the flame and increasing its displacement speed. As the inlet velocity is raised, the stagnation point moves downstream, and the flame length grows to accommodate the reactants mass flow. Concomitantly, the radius of curvature of the flame base decreases until it reaches an almost constant value, comparable to the flame thickness. While the heat loss decreases, the higher flame curvature dominates thereby reducing the displacement speed of the flame base. For a stable flame, the gradient of the flame base displacement speed normal to the flame is higher than the gradient of the flow speed along the same direction, leading to dynamic stability. As inlet velocity is raised further, the former decreases while the latter increases until the stability condition is violated, leading to blowoff. The flame speed during blow off is determined by the feedback between the growing recirculation zone and the cooling burner plate. © 2011 The Combustion Institute.en
dc.description.sponsorshipThis work was supported by King Abdullah University of Science and Technology (KAUST).en
dc.publisherElsevier BVen
dc.subjectBlowoffen
dc.subjectBurner heat lossen
dc.subjectCurvatureen
dc.subjectFlame stabilizationen
dc.subjectPerforated plateen
dc.subjectPremixeden
dc.titleMechanisms of stabilization and blowoff of a premixed flame downstream of a heat-conducting perforated plateen
dc.typeArticleen
dc.identifier.journalCombustion and Flameen
dc.contributor.institutionMassachusetts Institute of Technology, Cambridge, United Statesen
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