The Soret effect in naturally propagating, premixed, lean, hydrogen–air flames

Grcar, Joseph F.; Bell, John B.; Day, Marc

doi:10.1016/j.proci.2008.06.075

Cited by 69 publications

(34 citation statements)

References 38 publications

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“…A recent study [13] underscores the role of these terms on the quantitative flame propagation characteristics in a freely-propagating (no turbulence) two-dimensional setting. However, it was also shown that the simpler mixture-averaged transport formulation retained much of the qualitative behaviour of these flames, and there is no reason to suggest that the same is not true in the present setting.…”

Section: Discussionmentioning

confidence: 99%

Turbulence-chemistry interaction in lean premixed hydrogen combustion

Aspden

Day

Bell

2015

Proceedings of the Combustion Institute

104

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This paper presents three-dimensional direct numerical simulations of lean premixed hydrogen flames at an equivalence ratio of ϕ = 0.4 over a range of turbulence levels from Ka = 1 to 36. The simulations form part of a larger effort to construct a DNS database that can be used by the community for model construction and validation. We have focussed on producing well-resolved simulations at conditions representative of atmospheric laboratory-scale flames. After an overview of phenomenological trends with increasing Karlovitz number, we examine the factors that lead to an observed decorrelation between fuel consumption and heat release in the flame at Ka = 36. We show that in this flame the fuel consumption is greatly enhanced in regions of positive curvature. We also show that the radical pool is enriched throughout the entire flame as Ka is increased. In particular, we identify three reactions that, driven by high molar concentrations of radicals at low temperatures, are responsible for high levels of heat release away from regions of fuel consumption, thereby accounting for the observed decorrelation between fuel consumption and heat release.

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Section: Discussionmentioning

confidence: 99%

Turbulence-chemistry interaction in lean premixed hydrogen combustion

Aspden

Day

Bell

2015

Proceedings of the Combustion Institute

104

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“…The results are shown in Figure 6 and Figure 7 for H 2 O and NH 3 , respectively. When we use the TRANLIB program and its supporting data for H 2 0, we obtain very good agreement with experiment.…”

Section: Polar Moleculesmentioning

confidence: 96%

“…The DRFM parameter set does not contain potential parameters for NH 3 , so we obtain them by fitting ε i and ζ i to yield the best fit to data. The values for the dipole moment and polarizability are taken from the Handbook of Chemistry [66].…”

Section: Polar Moleculesmentioning

confidence: 99%

Transport properties for combustion modeling

Brown

Bastien

Price

2011

Progress in Energy and Combustion Science

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This review examines current approximations and approaches that underlie the evaluation of transport properties for combustion modeling applications. Discussed in the review are: the intermolecular potential and its descriptive molecular parameters; various approaches to evaluating collision integrals; supporting data required for the evaluation of transport properties; commonly used computer programs for predicting transport properties; the quality of experimental measurements and their importance for validating or rejecting approximations to property estimation; the interpretation of corresponding states; combination rules that yield pair molecular potential parameters for unlike species from like species parameters; and mixture approximations. The insensitivity of transport properties to intermolecular forces is noted, especially the non-uniqueness of the supporting potential parameters. Viscosity experiments of pure substances and binary mixtures measured post 1970 are used to evaluate a number of approximations; the intermediate temperature range 1 < T* < 10, where T* is kT/ε, is emphasized since this is where rich data sets are available. When suitable potential parameters are used, errors in transport property predictions for pure substances and binary mixtures are less than 5 %, when they are calculated using the approaches of Kee et al.; Mason, Kestin, and Uribe; Paul and Warnatz; or Ern and Giovangigli. Recommendations stemming from the review include (1) revisiting the supporting data required by the various computational approaches, and updating the data sets with accurate potential parameters, dipole moments, and polarizabilities; (2) characterizing the range of parameter space over which the fit to experimental data is good, rather than the current practice of reporting only the parameter set that best fits the data; (3) looking for improved combining rules, since existing rules were found to under-predict the viscosity in most cases; (4) performing more transport property measurements for mixtures that include radical species, an important but neglected area; (5) using the TRANLIB approach for treating polar molecules and (6) performing more accurate measurements of the molecular parameters used to evaluate the molecular heat capacity, since it affects thermal conductivity, which is important in predicting flame development. (1) revisiting the supporting data required by the various computational approaches, and updating the data sets with accurate potential parameters, dipole moments, and polarizabilities; (2) characterizing the range of parameter space over which the fit to experimental data is good, rather than the current practice of reporting only the parameter set that best fits the data; (3) looking for improved combining rules, since existing rules were found to under-predict the viscosity in most cases; (4) performing more transport property measurements for mixtures that include radical species, an important but neglected area; (5) using the TRANLIB approach for treating polar...

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“…Note that this will require a careful treatment of boundary conditions as explained later at the end of this section. The same studies [31,32] have shown that the Dufour effect, by which an energy flux is created by species gradients, is negligible.…”

Section: Problem Set-up and Numerical Simulationmentioning

confidence: 96%

“…Species diffusion by temperature gradients (the Soret effect) is included, following [31], [32], where its influence in the onset of cellular instabilities in planar flames, and the shape and heat release rate of curved hydrogen flames was shown. Our previous study [19] showed also that for hydrogen flames propagating in adiabatic channels the inclusion of the Soret effect results in appreciably faster flames, by favoring transport of hydrogen to hot regions.…”

Section: Problem Set-up and Numerical Simulationmentioning

confidence: 99%

Propagation of symmetric and non-symmetric lean hydrogen–air flames in narrow channels: Influence of heat losses

Jiménez

Kurdyumov

2017

Proceedings of the Combustion Institute

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In this paper we present results of direct numerical simulations of lean hydrogen-air flames freely propagating in a planar narrow channel with varying flow rate, using detailed chemistry and transport and including heat losses through the channel walls. Our simulations show that double solutions, symmetric and non-symmetric, can coexist for a given set of parameters. The symmetric solutions are calculated imposing symmetric boundary conditions in the channel mid-plane and when this restriction is relaxed non-symmetric solutions can develop. This indicates that the symmetric solutions are unstable to non-symmetric perturbations, as predicted before within the context of a thermo-diffusive model and simplified chemistry. It is also found that for lean hydrogen-air mixtures an increase in heat losses leads to a discontinuity of the steady state response curve, with flames extinguishing inside a finite interval of the flow rate. Non-symmetric flames burn more intensely and in consequence are much more robust to flame quenching by heat losses to the walls. The inclusion of the non-symmetric solutions extends therefore the parametric range for which flames can propagate in the channel. This analysis seems to have received no attention in the literature, even if it can have important safety implications in micro-scale combustion devices burning hydrogen in a lean premixed way.

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The Soret effect in naturally propagating, premixed, lean, hydrogen–air flames

Abstract: Comparatively little attention has been given to multicomponent diffusion effects in lean hydrogen-air flames, in spite of the importance of these flames in safety and their potential importance to future energy technologies.

Cited by 69 publications

References 38 publications

Turbulence-chemistry interaction in lean premixed hydrogen combustion

Turbulence-chemistry interaction in lean premixed hydrogen combustion

Transport properties for combustion modeling

Propagation of symmetric and non-symmetric lean hydrogen–air flames in narrow channels: Influence of heat losses

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