Lewis number effect on the propagation of premixed flames in narrow adiabatic channels: Symmetric and non-symmetric flames and their linear stability analysis

Kurdyumov, Vadim N.

doi:10.1016/j.combustflame.2010.11.011

Cited by 67 publications

(107 citation statements)

References 21 publications

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“…In both cases, the steady-state solution remains unique and symmetric S ¼ 0 for all the mass fractions considered. A similar behavior has been reported before by Kurdyumov in [21], where very lean flames propagating in an adiabatic channel were studied.…”

Section: The Stationary Solutionsupporting

confidence: 62%

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Effect of the equivalence ratio, Damköhler number, Lewis number and heat release on the stability of laminar premixed flames in microchannels

Sánchez–Sanz

Fernández-Galisteo

Kurdyumov

2014

Combustion and Flame

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This is a postprint version of the following published document:Sánchez-Sanz, M. ; Fernández-Galisteo, D. ; Kurdyumov, V. N. Effect of the equivalence ratio, Damköhler number, Lewis number and heat release on the stability of laminar premixed flames in microchannels. Combustion and Flame, 2014, 161 (5) The effect of the equivalence ratio on the stability and dynamics of a premixed flame in a planar microchannel with a step-wise wall temperature profile is numerically investigated using the thermo-diffusive approximation. To characterize the stability behavior of the flame, we construct the stability maps delineating the regions with different flame dynamics in the inlet mass flow rate m vs. the equivalence ratio / parametric space. The flame stability is analyzed for fuels with different diffusivity by changing the Lewis numbers in the range 0:3 6 Le F 6 1:4. On the other hand, the Lewis number of the oxidizer is kept constant and equal to unity Le O ¼ 1. Our results show that, for very diffusive fuels, the stability of the flame varies significantly with the equivalence ratio, transitioning from stable flames for lean mixtures to highly unstable flames when / > 1. As the fuel Lewis number approaches unity, the stability behavior of the flame for lean and rich mixtures becomes more similar to give, in the equidiffusional case Le F ¼ 1, a symmetric stability map around the stoichiometric mixture / ¼ 1. In all cases considered, the most stable flames are always found around the stoichiometric mixtures / ¼ 1, when the flame instabilities are completely suppressed for very diffusive fuels Le F < 1, or are reduced to a narrow range of inflow velocities for fuel Lewis numbers equal or greater than unity.The ratio between the size of the channel and the flame thickness d turns out to be of great importance in the stability behavior of the flame. Keeping the rest of parameters constant, an increase in d for lean flames makes the flame considerably more unstable, confirming the findings of previous works. Nevertheless, as the stoichiometric ratio approaches / ¼ 1, that trend is reversed to give flames that become more stable as the size of the channel is increased.

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Section: The Stationary Solutionsupporting

confidence: 62%

“…For the reasons exposed above, we used the method developed by Kurdyumov in [21] to compute the eigenvalue with the largest real part. To study the emergence of the symmetric and asymmetric modes, we solved the above set of equations in the half-height domain 0 6 y 6 1=2 with boundary conditions…”

Section: Stability Analysismentioning

confidence: 99%

Effect of the equivalence ratio, Damköhler number, Lewis number and heat release on the stability of laminar premixed flames in microchannels

Sánchez–Sanz

Fernández-Galisteo

Kurdyumov

2014

Combustion and Flame

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“…On the other hand, for Le F > 1, in cases where the planar flame suffers from oscillatory instabilities [12], the Poiseuille flow stabilises the flame and oscillatory solutions vanish. The effect of the differential diffusion between heat and mass in the symmetry-breaking or oscillatory instability occurrence is seen to decrease in importance as the width of the channel is reduced [6,7]. All the work cited above made use of the thermo-diffusive approximation, also called the constant density approximation, to eliminate the flame-fluid interaction due to thermal expansion and viscous effects and therefore to concentrate on the preferential diffusion effect of the fuel.…”

Section: Introductionmentioning

confidence: 99%

“…Although this simple kinetic model does not consider intermediate species, it has demonstrated an acceptable success in clarifying the role of the complex physical phenomena involved in flame dynamics in channels [4][5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…Le F = 1 flames were further studied in [6], also in adiabatic channels and with the use of a one-step kinetic model. There, it was demonstrated that for Le F < 1 the differential diffusion effect destabilises the steady symmetric solutions to non-symmetric ones, this effect being amplified due to flame curvature when the flow rate in the channel is increased.…”

Section: Introductionmentioning

confidence: 99%

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The differential diffusion effect of the intermediate species on the stability of premixed flames propagating in microchannels

Fernández-Galisteo

Jiménez

Sánchez–Sanz

et al. 2014

Combustion Theory and Modelling

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The propagation of premixed flames in adiabatic and non-catalytic planar microchannels subject to an assisted or opposed Poiseuille flow is considered. The diffusive-thermal model and the well-known two-step chain-branching kinetics are used in order to investigate the role of the differential diffusion of the intermediate species on the spatial and temporal flame stability. This numerical study successfully compares steady-state and time-dependent computations to the linear stability analysis of the problem. Results show that for fuel Lewis numbers less than unity, Le F < 1, and at sufficiently large values of the opposed Poiseuille flow rate, symmetry-breaking bifurcation arises. It is seen that small values of the radical Lewis number, Le Z , stabilise the flame to symmetric shape solutions, but result in earlier flashback. For very lean flames, the effect of the radical on the flame stabilisation becomes less important due to the small radical concentration typically found in the reaction zone. Cellular flame structures were also identified in this regime. For Le F > 1, flames propagating in adiabatic channels suffer from oscillatory instabilities. The Poiseuille flow stabilises the flame and the effect of Le Z is opposite to that found for Le F < 1. Small values of Le Z further destabilise the flame to oscillating or pulsating instabilities.

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A Versatile Numerical Tool for Simulating Combustion Features at Small-Scales

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Lewis number effect on the propagation of premixed flames in narrow adiabatic channels: Symmetric and non-symmetric flames and their linear stability analysis

Cited by 67 publications

References 21 publications

Effect of the equivalence ratio, Damköhler number, Lewis number and heat release on the stability of laminar premixed flames in microchannels

Effect of the equivalence ratio, Damköhler number, Lewis number and heat release on the stability of laminar premixed flames in microchannels

The differential diffusion effect of the intermediate species on the stability of premixed flames propagating in microchannels

A Versatile Numerical Tool for Simulating Combustion Features at Small-Scales

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