Effects of flow transients on the burning velocity of laminar hydrogen/air premixed flames

Im, Hong G.; Chen, Jacqueline H.

doi:10.1016/s0082-0784(00)80586-x

Cited by 76 publications

(23 citation statements)

References 25 publications

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“…Peters 2 termed this the thin reaction zones regime. In recent years, a number of two-dimensional detailed chemistry and three-dimensional simplified chemistry based direct numerical simulation ͑DNS͒ studies [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] have observed the strong curvature dependence on the local displacement speed behavior in the thin reaction zones regime as suggested by Peters. 2 Peters et al 7 and Echekki and Chen 8 suggested that it is often useful for the purpose of modeling to decompose the displacement speed into three components that originate from the reaction rate S r , flame normal diffusion rate S n , and flame curvature S t , respectively.…”

Section: Introductionmentioning

confidence: 88%

“…Therefore, most combustion DNS studies are either done in three dimensions with simplified chemistry 12,[15][16][17][18][19] or in two dimensions with detailed chemistry. [4][5][6][7][8][9][10][11]13,14 The first approach is adopted in the present study in which the chemical mechanism is simplified by a generic single-step irreversible Arrhenius-type chemical reaction given by reactants → products. ͑1͒…”

Section: Mathematical Backgroundmentioning

confidence: 99%

“…7,8 The displacement speed statistics obtained from previous threedimensional simplified chemistry-based DNS studies 12,[15][16][17][18][19] with similar assumptions regarding chemistry and transport were found to be in qualitative agreement with twodimensional detailed chemistry-based DNS data. [4][5][6][7][8][9][10][11] As turbulence decays rapidly within the burned gases, the flame-turbulence interaction is principally governed by the turbulent motion at the leading edge of the flame, which is not significantly influenced by heat release. [26][27][28][29][30][31][32][33][34][35][36] In several previous studies, [26][27][28][29][30][31][32][33][34][35][36] temperature variation of viscosity is neglected as at the small turbulent Reynolds numbers an increase in viscosity with temperature leads to a rapid decay of turbulence in the burned gases, which limits the extent and duration of the flame-turbulence interaction.…”

Section: Numerical Implementationmentioning

confidence: 99%

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Comparison of displacement speed statistics of turbulent premixed flames in the regimes representing combustion in corrugated flamelets and thin reaction zones

Chakraborty

2007

Physics of Fluids

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The curvature and strain rate dependence of local displacement speed S d is compared between two three-dimensional simplified chemistry and transport based direct numerical simulation ͑DNS͒ datasets of turbulent premixed flames with comparable turbulent Reynolds number. One of these datasets has attributes of the corrugated flamelets regime ͑Karlovitz number KaϽ 1͒, and the combustion situation in the other belongs to the thin reaction zones regime ͑KaϾ 1͒. It has been found that the probability of finding negative displacement speed increases for the flame in the thin reaction zones regime in comparison to the flame in the corrugated flamelets regime. However, the mean displacement speed remains positive throughout the flame brush in both the flames. It is shown that the curved flame contribution in displacement speed S t is principally responsible for the negative displacement speed in the flame representing the thin reaction zones regime. The alignment characteristics of scalar gradient with principal strain rates is found to be different in these two flames, which leads to significant differences in tangential strain rate and curvature dependence of the magnitude of the reaction progress variable gradient ٌ͉c͉. This difference in ٌ͉c͉ statistics leads to marked differences in the statistics of the combined reaction and normal diffusion component of displacement speed S LS = ͑S r + S n ͒, which in turn leads to significant differences in S d statistics between the corrugated flamelets and the thin reaction zones regimes. This difference has important implications in the context of flame surface density based reaction rate closure.

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Section: Introductionmentioning

confidence: 88%

Section: Mathematical Backgroundmentioning

confidence: 99%

Section: Numerical Implementationmentioning

confidence: 99%

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Comparison of displacement speed statistics of turbulent premixed flames in the regimes representing combustion in corrugated flamelets and thin reaction zones

Chakraborty

2007

Physics of Fluids

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“…Following [3], it is emphasized that different definitions of S T may be useful in different contexts. In the present simulations, the consumption speed S c is defined following [40] and computed as the volume integrated overall rate of fuel combustion per unit flame area (assuming complete fuel consumption on the burned gas side), in a similar manner as employed, for instance, in [41,42]:…”

Section: Turbulent Burning Velocitymentioning

confidence: 99%

Impact of Turbulence Intensity and Equivalence Ratio on the Burning Rate of Premixed Methane–Air Flames

Fru¹,

Thévenin²,

Janiga³

2011

Energies

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Direct Numerical Simulations (DNS) have been conducted to study the response of initially laminar spherical premixed methane-air flame kernels to successively higher turbulence intensities at five different equivalence ratios. The numerical experiments include a 16-species/25-step skeletal mechanism for methane oxidation and a multicomponent molecular transport model. Highly turbulent conditions (with integral Reynolds numbers up to 4 513) have been accessed. The effect of turbulence on the physical properties of the flame, in particular its consumption speed S c , which is an interesting measure of the turbulent flame speed S T has been investigated. Local quenching events are increasingly observed for highly turbulent conditions, particularly for lean mixtures. The obtained results qualitatively confirm the expected trend regarding correlations between u ′ /S L and the consumption speed: S c first increases, roughly linearly, with u ′ /S L (low turbulence zone), then levels off (bending zone) before decreasing again (quenching limit) for too intense turbulence. For a fixed value of u ′ /S L , S c /S L varies with the mixture equivalence ratio, showing that additional parameters should probably enter phenomenological expressions relating these two quantities.

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“…The consumption speed depends on the rate at which the flame consumes the reactants and is defined as (1) where ρ u , Y F andω are the unburnt mixture density, the mass fraction of reactants and the mass burning rate per unit volume, respectively [6]. Previous studies found that the consumption speed can give a more consistent and physically intuitive representation of the flame response to strain [6,20]. As suggested in Fig.…”

Section: Introductionmentioning

confidence: 99%

Combined Influence of Strain and Heat Loss on Turbulent Premixed Flame Stabilization

Tay-Wo-Chong

Zellhuber

Komarek

et al. 2015

Flow Turbulence Combust

Self Cite

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The present paper argues that the prediction of turbulent premixed flames under non-adiabatic conditions can be improved by considering the combined effects of strain and heat loss on reaction rates. The effect of strain in the presence of heat loss on the consumption speed of laminar premixed flames was quantified by calculations of asymmetric counterflow configurations ("fresh-to-burnt") with detailed chemistry. Heat losses were introduced by setting the temperature of the incoming stream of products on the "burnt" side to values below those corresponding to adiabatic conditions. The consumption speed decreased in a roughly exponential manner with increasing strain rate, and this tendency became more pronounced in the presence of heat losses. An empirical relation in terms of Markstein number, Karlovitz Number and a non-dimensional heat loss parameter was proposed for the combined influence of strain and heat losses on the consumption speed. Combining this empirical relation with a presumed probability density function for strain in turbulent flows, an attenuation factor that accounts for the effect of strain and heat loss on the reaction rate in turbulent flows was deduced and implemented into a turbulent combustion model. URANS simulations of a premixed swirl burner were carried out and validated against flow field and OH chemiluminescence measurements. Introducing the effects of Wolfgang Polifke Flow Turbulence Combust strain and heat loss into the combustion model, the flame topology observed experimentally was correctly reproduced, with good agreement between experiment and simulation for flow field and flame length.

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Effects of flow transients on the burning velocity of laminar hydrogen/air premixed flames

Cited by 76 publications

References 25 publications

Comparison of displacement speed statistics of turbulent premixed flames in the regimes representing combustion in corrugated flamelets and thin reaction zones

Comparison of displacement speed statistics of turbulent premixed flames in the regimes representing combustion in corrugated flamelets and thin reaction zones

Impact of Turbulence Intensity and Equivalence Ratio on the Burning Rate of Premixed Methane–Air Flames

Combined Influence of Strain and Heat Loss on Turbulent Premixed Flame Stabilization

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