Effect of equivalence ratio on premixed flame response to unsteady strain-rate and curvature

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The detailed dynamical response of flames in turbulent reacting flow involves a complex interaction between unsteady flow structures and flame chemistry. Two essential features of this interaction are the unsteady strain-rate and curvature disturbances to the reaction zone. In this work, the authors focus on a single flow length/time scale feature in two dimensions (2D), and its effect on a premixed flame for a range of mixture conditions. In particular, they study the interaction of a premixed freely propagating methane-air flame with a 2D counter-rotating vortex pair in an unbounded domain. In earlier work, they studied this flow using C{sub ... continued below

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5 p.

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Najm, H.N.; Wyckoff, P.S. & Knio, O.M. November 1, 1997.

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  • Najm, H.N.
  • Wyckoff, P.S. Sandia National Labs., Livermore, CA (United States)
  • Knio, O.M. Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Mechanical Engineering

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Description

The detailed dynamical response of flames in turbulent reacting flow involves a complex interaction between unsteady flow structures and flame chemistry. Two essential features of this interaction are the unsteady strain-rate and curvature disturbances to the reaction zone. In this work, the authors focus on a single flow length/time scale feature in two dimensions (2D), and its effect on a premixed flame for a range of mixture conditions. In particular, they study the interaction of a premixed freely propagating methane-air flame with a 2D counter-rotating vortex pair in an unbounded domain. In earlier work, they studied this flow using C{sub 1} kinetics, at stoichiometric conditions. Notable observations include the shift of the reaction zone into the products on the vortex-pair centerline, leading to depletion of H, O and OH, and the consequent general drop in reaction rates on the centerline flame segment. Curvature-induced focusing/defocusing effects were observed at the positively curved flame cusp, leading to modifications in internal transport fluxes of various species and radicals in the flame, and associated effects on H production and fuel consumption rates. These results were extended to more detailed kinetics, using other C{sub 1} and C{sub 2} mechanisms, which demonstrated the effect of choice of chemical mechanism on the observed transient flame response. The present study focuses on the dependence of the transient flame response on reactants mixture equivalence ratio. Two reactants mixture conditions are studied: case 1 is a stoichiometric conditions - equivalence ratio {Phi} = 1.0, and case 2 is rich at {Phi} = 1.2. In both cases, the reactants are 20% N{sub 2}-diluted.

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5 p.

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OSTI as DE97054451

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  • 1997 fall technical meeting of the Eastern State Section of the Combustion Institute: chemical physical processes in combustion, Hartford, CT (United States), 27-28 Oct 1997

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  • Other: DE97054451
  • Report No.: SAND--97-8672C
  • Report No.: CONF-9710112--
  • Grant Number: AC04-94AL85000
  • Office of Scientific & Technical Information Report Number: 555225
  • Archival Resource Key: ark:/67531/metadc699260

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  • November 1, 1997

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  • Aug. 14, 2015, 8:43 a.m.

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  • Nov. 19, 2015, 10:10 p.m.

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Najm, H.N.; Wyckoff, P.S. & Knio, O.M. Effect of equivalence ratio on premixed flame response to unsteady strain-rate and curvature, article, November 1, 1997; United States. (digital.library.unt.edu/ark:/67531/metadc699260/: accessed August 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.