Effect of stoichiometry and strain rate on transient flame response

Knio, Omar M.; Najm, Habib N.

doi:10.1016/s0082-0784(00)80588-3

Cited by 11 publications

(2 citation statements)

References 22 publications

(41 reference statements)

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“…Using a more detailed C 1 C 2 chemical mechanism (GRImech1.2 with 32 species and 177 reactions [58,59], and later a quite complete mechanism with 40 species and 216 reactions [60]), a thorough comparison with experimental measurements has been afterwards carried out for the same configuration. In spite of a good agreement between computation and experiment for HCO, noticeable quantitative discrepancies are observed for the transient response of very important species like CH and OH.…”

Section: Premixed Flat Flame Interacting With a Vortexmentioning

confidence: 99%

Impact of detailed chemistry and transport models on turbulent combustion simulations

Hilbert

Tap

El-Rabii

et al. 2004

Progress in Energy and Combustion Science

142

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Section: Premixed Flat Flame Interacting With a Vortexmentioning

confidence: 99%

Impact of detailed chemistry and transport models on turbulent combustion simulations

Hilbert

Tap

El-Rabii

et al. 2004

Progress in Energy and Combustion Science

142

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“…These studies include experimental work [18], vortex-flame interactions which show combined strain and curvature effects [19,20], asymptotic analysis [21], and one-dimensional counterflow simulations with time-varying strain [22,23]. The rate at which premixed flames respond to changing strain rates increases with the flame temperature [23] and equivalence ratio [20]. The Lewis number of the deficient reactant [21,23] also has a strong effect, however the effect depends on the frequency with which the strain rate changes.…”

Section: Introductionmentioning

confidence: 99%

Effects of equivalence ratio variation on lean, stratified methane–air laminar counterflow flames

Richardson

Granet

Eyssartier

et al. 2010

Combustion Theory and Modelling

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The effects of equivalence ratio variations on flame structure and propagation have been studied computationally. Equivalence ratio stratification is a key technology for advanced low emission combustors. Laminar counterflow simulations of lean methaneair combustion have been presented which show the effect of strain variations on flames stabilized in an equivalence ratio gradient, and the response of flames propagating into a mixture with a time-varying equivalence ratio. 'Back supported' lean flames, whose products are closer to stoichiometry than their reactants, display increased propagation velocities and reduced thickness compared with flames where the reactants are richer than the products. The radical concentrations in the vicinity of the flame are modified by the effect of an equivalence ratio gradient on the temperature profile and thermal dissociation. Analysis of steady flames stabilized in an equivalence ratio gradient demonstrates that the radical flux through the flame, and the modified radical concentrations in the reaction zone, contribute to the modified propagation speed and thickness of stratified flames. The modified concentrations of radical species in stratified flames mean that, in general, the reaction rate is not accurately parametrized by progress variable and equivalence ratio alone. A definition of stratified flame propagation based upon the displacement speed of a mixture fraction dependent progress variable was seen to be suitable for stratified combustion. The response times of the reaction, diffusion, and cross-dissipation components which contribute to this displacement speed have been used to explain flame response to stratification and unsteady fluid dynamic strain. Nomenclature Englishproperties at location of peak heat release rate m value midway between boundary values Subscripts fu fuel st stoichiometric max maximum R component due to chemical reaction D component due to molecular diffusion CR component due to cross-dissipation IntroductionProgress in combustion technology depends heavily on the ability of engineers to combine demands for higher efficiency with those for lower emissions from stable combustion devices. Stratified combustion is becoming an increasingly widespread strategy for internal combustion engines and gas turbine engines to meet these combined requirements. Stratified combustion occurs when an inhomogeneous fuel-air mixture is either entirely lean or entirely rich, precluding the occurrence of edge flames. Nevertheless this mode of combustion has in the past received relatively little research attention, in comparison with the dominant premixed and diffusion flame accounts of combustion. Current capabilities for the measurement [1-5] and simulation [6-8] of turbulent stratified flames have begun to allow some interrogation of turbulent stratified flame structure and propagation. In

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Numerical simulation of unsteady reacting flow with detailed kinetics

Knio¹,

Najm²

2001

Computational Fluid and Solid Mechanics

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Effect of stoichiometry and strain rate on transient flame response

Cited by 11 publications

References 22 publications

Impact of detailed chemistry and transport models on turbulent combustion simulations

Impact of detailed chemistry and transport models on turbulent combustion simulations

Effects of equivalence ratio variation on lean, stratified methane–air laminar counterflow flames

Numerical simulation of unsteady reacting flow with detailed kinetics

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