Lewis number effect on the propagation of premixed laminar flames in narrow open ducts

Kurdyumov, Vadim N.; Fernández-Tarrazo, Eduardo

doi:10.1016/s0010-2180(01)00358-3

Cited by 80 publications

(81 citation statements)

References 18 publications

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“…Heat loss is found to amplify the diffusive-thermal instability for Le F < 1, as demonstrated in a Hele-Shaw configuration [13,14], for example, can also drive the flame to oscillate [15,16]. These unsteady solutions were found when increasing the duct size in the case of isothermal walls for Le F < 1 [8]; however, they only appear in the adiabatic-wall cases for Le F > 1, as shown later in the present work. Following a subcritical Hopf bifurcation, two stable combustion modes, that is, a steady weak flame (also called mild combustion) and an ignition-extinction oscillating flame, can coexist when the wall temperature is sufficiently close to the quenching extinction limit.…”

Section: Introductionsupporting

confidence: 70%

“…As done before in [6,8], a reference frame attached to the flame front at a point (x * , y * ) is used to describe the flame propagation. Consider a line parallel to the wall located at a distance y = y * , as sketched in Figure 1.…”

Section: Formulation Of the Problemmentioning

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%

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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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Section: Introductionsupporting

confidence: 70%

Section: Formulation Of the Problemmentioning

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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“…A pioneering paper by Lee & T'ien (1982) reports a two-dimensional numerical simulation of laminar flame flashback in a sidewall quenching (SWQ) configuration and suggests that a pressure-based interaction between the premixed flame and the boundary layer flow is the reason behind a larger computed laminar flame speed in the two-dimensional configuration compared with the one-dimensional case. Subsequent studies by Kurdyumov, Fernandez & Linan (2000) and Kurdyumov et al (2007) and Kurdyumov & Fernandez-Tarrazo (2002) on the boundary layer flashback of laminar two-dimensional flames added more realistic features to the model, such as effects of the fuel species Lewis number, but are still limited to one-step chemical kinetics and to the interpretation that boundary layer flashback is governed by physical processes whose main characteristics are two dimensional. Poinsot, Haworth & Bruneaux (1993) performed a DNS of HOQ in a two-dimensional, pseudo-turbulent reactive boundary layer while Bruneaux et al (1996) studied three-dimensional HOQ of a back-to-back, premixed flame propagating in constant-density turbulent channel flow.…”

Section: Previous Workmentioning

confidence: 99%

Direct numerical simulation of premixed flame boundary layer flashback in turbulent channel flow

et al. 2012

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Direct numerical simulations are performed to investigate the transient upstream propagation (flashback) of premixed hydrogen–air flames in the boundary layer of a fully developed turbulent channel flow. Results show that the well-known near-wall velocity fluctuations pattern found in turbulent boundary layers triggers wrinkling of the initially flat flame sheet as it starts propagating against the main flow direction, and that the structure of the characteristic streaks of the turbulent boundary layer ultimately has an important impact on the resulting flame shape and on its propagation mechanism. It is observed that the leading edges of the upstream-propagating premixed flame are always located in the near-wall region of the channel and assume the shape of several smooth, curved bulges propagating upstream side by side in the spanwise direction and convex towards the reactant side of the flame. These leading-edge flame bulges are separated by thin regions of spiky flame cusps pointing towards the product side at the trailing edges of the flame. Analysis of the instantaneous velocity fields clearly reveals the existence, on the reactant side of the flame sheet, of backflow pockets that extend well above the wall-quenching distance. There is a strong correspondence between each of the backflow pockets and a leading edge convex flame bulge. Likewise, high-speed streaks of fast flowing fluid are found to be always colocated with the spiky flame cusps pointing towards the product side of the flame. It is suggested that the origin of the formation of the backflow pockets, along with the subsequent mutual feedback mechanism, is due to the interaction of the approaching streaky turbulent flow pattern with the Darrieus–Landau hydrodynamic instability and pressure fluctuations triggered by the flame sheet. Moreover, the presence of the backflow pockets, coupled with the associated hydrodynamic instability and pressure–flow field interaction, greatly facilitate flame propagation in turbulent boundary layers and ultimately results in high flashback velocities that increase proportionately with pressure.

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“…For the eigenvalue calculation, the algorithm described in Kurdyumov et al [17] and in Kurdyumov and Fernández-Tarrazo [18] has been used.…”

Section: Results Of the Numerical Analysismentioning

confidence: 99%

Flame spread over solid fuels in opposite natural convection

Fernández-Tarrazo

Liñán

2002

Proceedings of the Combustion Institute

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The downward spread of a flame along the surface of a thermally thick solid fuel inclined at an angle to the vertical is investigated. The flow and the heat transfer in the flame front region that controls the spread rate are described numerically using a single-step Arrhenius model for the gas-phase reaction. The effect of the finite rate kinetics is discussed in terms of a Damkö hler number defined as the square of the ratio of the speed of the planar stoichiometric flame of the fuel vapor to the characteristic speed induced by buoyancy in the flame front region. The computed spread rate is lower when the burning surface faces downward than when it faces upward due to the influence of the pressure gradient parallel to the surface.

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Lewis number effect on the propagation of premixed laminar flames in narrow open ducts

Cited by 80 publications

References 18 publications

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

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

Direct numerical simulation of premixed flame boundary layer flashback in turbulent channel flow

Flame spread over solid fuels in opposite natural convection

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