Synergistic interactions of thermodiffusive instabilities and turbulence in lean hydrogen flames

Berger, Lukas; Attili, Antonio; Pitsch, Heinz

doi:10.1016/j.combustflame.2022.112254

Cited by 77 publications

(36 citation statements)

References 61 publications

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“…1(a). Note that the critical Karlovitz number is substantially less for DL instability, Since development of TD instability is commonly associated with growth of flame surface area, the present results indicating weak contributions of TD instability to U T in flames T/U and T/UM are in line with earlier DNS [37,72,83] and experimental [29] data, which showed significant (weak) influence of differential diffusion on turbulent burning velocity (flame surface area, respectively). Moreover, the present results are in line with (i) DNS data by Day et al [84], which indicate that both magnitudes and length scales of fuel consumption rate perturbations differ significantly in unstable laminar and turbulent lean hydrogen-air flames, cf.…”

Section: Resultssupporting

confidence: 91%

“…Figs. 6a and 6b in the cited paper, and (ii) DNS data by Berger et al [37], which show significantly different mean local flame characteristics in unstable laminar and moderately turbulent lean H 2 -air flames, see Figs. 13,17,[19][20][21][23][24][25] in the cited paper.…”

Section: Resultsmentioning

confidence: 78%

“…This fundamental challenge has also been attracting rapidly growing interest in applied Computational Fluid Dynamics (CFD) research aiming at developing zero-emission technologies for power generation by utilizing chemical energy bound in renewable carbon-free fuels such as hydrogen. The point is that (i) since pioneering experiments by Karpov et al [17,18], significant differences between molecular diffusivities of H 2 , O 2 , and heat were well known to result in strongly increasing turbulent burning velocities U T in sufficiently lean hydrogen-air mixtures, as reviewed elsewhere [8,16,19], see also recent experimental studies [20,21,22], (ii) a similar phenomenon was recently documented in experiments with fuel blends that contain H 2 , e.g., lean syngas/air mixtures [23,24,25,26] or lean ammonia/hydrogen/air mixtures [27,28,29,30,31], (iii) a widely established predictive model of this important effect has yet to be developed, while (iv) the effect is often discussed [16,21,27,30,32,33,34,35,36,37] in terms of TD instability of laminar premixed flames.…”

Section: Introductionmentioning

confidence: 91%

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Turbulent burning velocity and thermo-diffusive instability of premixed flames

Lee¹,

Wu²,

Dai³

et al. 2023

Preprint

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Reported in the paper are results of unsteady three-dimensional direct numerical simulations of laminar and turbulent, lean hydrogen-air, complex-chemistry flames propagating in forced turbulence in a box. To explore the eventual influence of thermo-diffusive instability of laminar flames on turbulent burning velocity, (i) a critical length scale Λn that bounds regimes of unstable and stable laminar combustion is numerically determined by gradually decreasing the width Λ of computational domain until a stable laminar flame is obtained and (ii) simulations of turbulent flames are performed by varying the width from Λ < Λn (in this case, the instability is suppressed) to Λ > Λn (in this case, the instability may grow). Moreover, simulations are performed either using mixtureaveraged transport properties (low Lewis number flames) or setting diffusivities of all species equal to heat diffusivity of the mixture (equidiffusive flames), with all other things being equal. Obtained results show a significant increase in turbulent burning velocity UT when the boundary Λ = Λn is crossed in weak turbulence, but almost equal values of UT are computed at Λ < Λn and Λ > Λn in moderately turbulent flames characterized by Karlovitz number equal to 3.4 or larger. These results imply that thermo-diffusive instability of laminar premixed flames substantially affects burning velocity in weak turbulence only, in line with a simple criterion proposed by Chomiak and Lipatnikov (Phys. Rev. E 107, 015102, 2023).

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Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 91%

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Turbulent burning velocity and thermo-diffusive instability of premixed flames

Lee¹,

Wu²,

Dai³

et al. 2023

Preprint

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“…Finally, it is worth noting that the presented simulations feature two dimensional flows and quantitative comparisons among the different cases may change in three dimensions. Recently, a DNS of case Ref with a lateral domain width of 35lF has been performed in three dimensions [26]. In this simulation, the consumption speed and the formation of the large-scale flame fingers are still affected by the moderate domain size, but the lateral domain width is sufficient to allow for a domain-independent behavior of the local flame state and the stretch factor I0.…”

Section: Three-dimensional Flame Configurationsmentioning

confidence: 99%

Flame fingers and interactions of hydrodynamic and thermodiffusive instabilities in laminar lean hydrogen flames

Berger

Grinberg

Jurgens

et al. 2023

Proceedings of the Combustion Institute

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“…2019; Yu & Lipatnikov 2019; Song et al. 2021; Berger, Attili & Pitsch 2022). In addition, can tend to infinity in the vicinity of so-called ‘zero gradient points’ (Gibson 1968), e.g.…”

Section: Background and Research Goalsmentioning

confidence: 99%

Displacement speed, flame surface density and burning rate in highly turbulent premixed flames characterized by low Lewis numbers

et al. 2023

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Direct numerical simulation data obtained from four pairs of turbulent, lean hydrogen–air, complex-chemistry flames are analysed to explore the influence of molecular diffusion on flame surface density, displacement speed $S_d$ and the flame surface density transport equation terms. Each pair involves (i) a flame where mixture-averaged molecular diffusivities are adopted and Lewis number $Le$ is significantly less than unity and (ii) an equidiffusive flame where all molecular diffusivities are set equal to molecular heat diffusivity of the mixture and $Le=1$ , with other things being equal. Reported results show that significantly higher turbulent burning rates simulated in the former flames result mainly from an increase in the local fuel consumption rate, whereas an increase in flame surface area plays a secondary role, especially in more intense turbulence. The rate increase stems from (i) an increase in the peak local fuel consumption rate and (ii) an increase in a width of a zone where the rate is significant. The latter phenomenon is of more importance in richer flames and both phenomena are most pronounced in the vicinity of the flame leading edges, thus indicating a crucial role played by the leading edge of a premixed turbulent flame in its propagation. Moreover, mean displacement speed differs significantly from the laminar flame speed even in the equidiffusive flames, varies substantially across flame brush and may be negative at the leading edges of highly turbulent flames.

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Synergistic interactions of thermodiffusive instabilities and turbulence in lean hydrogen flames

Cited by 77 publications

References 61 publications

Turbulent burning velocity and thermo-diffusive instability of premixed flames

Turbulent burning velocity and thermo-diffusive instability of premixed flames

Flame fingers and interactions of hydrodynamic and thermodiffusive instabilities in laminar lean hydrogen flames

Displacement speed, flame surface density and burning rate in highly turbulent premixed flames characterized by low Lewis numbers

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