Edges of flames that do not exist: flame-edge dynamics in a non-premixed counterflow

Thatcher, R. W.; Dold, J. W.

doi:10.1088/1364-7830/4/4/304

Cited by 43 publications

(50 citation statements)

References 12 publications

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“…Detailed numerical studies have also been carried out for freely propagating edge-flames without the effects of heat release by Kioni et al (1993) and with the effects of heat release by Ruetsch, Vervisch & Liñán (1995) and Echekki & Chen (1998). In the interest of understanding the interaction of the flame edges in more complex flows, some studies have considered the interaction of the edge-flame with a counterflow that is perpendicular to the plane of the flame, also called a strained mixing layer (Daou & Liñán 1998;Vedarajan & Buckmaster 1998;Buckmaster & Short 1999;Thatcher & Dold 2000;Short, Buckmaster & Kochevets 2001). Experiments have also been performed.…”

Section: Introductionmentioning

confidence: 99%

Direct simulation of non-premixed flame extinction in a methane–air jet with reduced chemistry

Pantano¹

2004

J. Fluid Mech.

110

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A three-dimensional direct numerical simulation (DNS) study of a spatially evolving planar turbulent reacting jet is reported. Combustion of methane with air is modelled using a four-step reduced mechanism in the non-premixed regime. A total of eight chemical species are integrated in time along with the fluid mechanical fields. The solution of the compressible Navier-Stokes equations is obtained numerically for moderately low Mach number. A large computational grid, with 100 million grid points, is required in order to resolve the flame. The cold flow Reynolds number is 3000. The focus of the study is to investigate the dynamics of extinction fronts in threedimensional turbulent flows. A novel data reduction and identification algorithm was developed to postprocess the large DNS database and extract the shape of the evolving flame surface including its edges and their propagation velocity. The joint probability density function (p.d.f.) of edge velocity and scalar dissipation was obtained and the results indicate that the three-dimensional flame edges propagate with a velocity that is largely controlled by the local rate of scalar dissipation, or equivalently in terms of the local Damköhler number at the flame edge, as predicted by theory. Naturally, the effects of unsteadiness in this flow produce a broad joint p.d.f. The statistics collected also suggest that the mean value of the hydrogen radical reaction rate are very small in the turbulent regions of the flow owing to the functional form of the hydrogen radical reaction rate itself. The consequence of these results in the context of turbulent combustion modelling is discussed. Additional statistical and morphological information of the flame is provided.

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Section: Introductionmentioning

confidence: 99%

Direct simulation of non-premixed flame extinction in a methane–air jet with reduced chemistry

Pantano¹

2004

J. Fluid Mech.

110

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“…This happens when the Lewis number is low enough (Le < Le 0 ) for the edge of the diffusion flame (a triple flame [1,3]) to have a positive speed of propagation at the quenching Damköhler number [2,4]. Solutions of this type, propagating in an oscillatory way, are illustrated at different times in figure 2.…”

mentioning

confidence: 99%

“…A characteristic feature of the oscillatory mode of propagation is that the leading flame tube repeatedly elongates and splits, as seen in figure 2, thereby creating new flame tubes as its leading edge advances. The speed of propagation of the leading edge becomes periodic in time, reaching its maximum value shortly after each splitting of the flame tube behind it [2].…”

mentioning

confidence: 99%

Oscillatory flame edge propagation, isolated flame tubes and stability in a non-premixed counterflow

Thatcher

Omon-Arancibia

Dold

2002

Combustion Theory and Modelling

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An investigation is carried out into the ranges of Damköhler number and Lewis number, less than unity, in which different forms of combustion phenomena arise within a non-premixed counterflow; cases that are symmetrical across the counterflow are chosen for study. These link oscillatory and steady propagation of flame edges, zero propagation speeds, isolated flame tubes, quenching and marginal stability of planar diffusion flames. Over a range of Lewis numbers, the transition between steady and oscillatory propagation of a flame edge has characteristics that are consistent with a subcritical Hopf bifurcation. Isolated flame tubes are found to persist up to a Lewis number that is very close to unity.

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“…The existence of multiple and isolated, stationary flame tubes in a counterflow for certain fuel mixtures was shown numerically for non-premixed combustion [5] and was observed for premixed combustion [3]. The experiments also showed that flame tubes may drift in the combustion chamber.…”

Section: Introductionmentioning

confidence: 76%

“…in which the Lewis number Le = D T /D F , α h has been approximated by 1 and exp (β(T − 1)) by T β [5]. Dirichlet, cold boundary conditions, namely T = 0 and F = 1 , are imposed at y = ±Y m and Neumann, independent of x boundary conditions These equations have the cold solution F = 1 , T = 0 for all time but for certain combinations of Le and δ they also have a stationary solution independent of x, namely the one dimensional flame in the burner described above.…”

Section: C622mentioning

confidence: 99%

Numerical modelling of drifting flame tubes

Thatcher¹,

Weber²

2007

ANZIAMJ

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Stationary, isolated flame tube and stationary, multiple flame tubes are found both experimentally and numerically in a counterflow burner. For some flames established experimentally, moving multiple flame tubes are observed. We examine numerically the effect of placing two isolated flame tubes in close proximity to each other. We find that the influence of one flame tube on the other is to cause the tubes to move and drift apart.

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Edges of flames that do not exist: flame-edge dynamics in a non-premixed counterflow

Cited by 43 publications

References 12 publications

Direct simulation of non-premixed flame extinction in a methane–air jet with reduced chemistry

Direct simulation of non-premixed flame extinction in a methane–air jet with reduced chemistry

Oscillatory flame edge propagation, isolated flame tubes and stability in a non-premixed counterflow

Numerical modelling of drifting flame tubes

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