Flame spread in laminar mixing layers: The triple flame

Kioni, Paul Ndirangu; Rogg, B.; Bray, K.N.C.; Liñán, A.

doi:10.1016/0010-2180(93)90132-m

Cited by 243 publications

(104 citation statements)

References 9 publications

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“…Ref. [3] is mostly significant for its modeling contribution and essentially repeated the same type of experiments of Ref. [4], albeit in a vertical configuration.…”

Section: Introductionmentioning

confidence: 93%

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Propagation of edge flames in counterflow mixing layers: Experiments and theory

Santoro

Liñán

Gomez

2000

Proceedings of the Combustion Institute

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Edge flames were investigated in a methane/O 2 /N 2 counterflow diffusion flame burner. In a typical experiment, a stable counterflow diffusion flame in an axysymmetric configuration was perturbed by lowering the relevant Damkö hler number slightly below the extinction value, Da ext . As a result, the flame extinguished in the vicinity of the burner axis where conditions were uniform. An edge flame extinction front quickly propagated in the radial direction, turned into an ignition edge flame, and eventually stabilized as a standing triple flame at a radial position larger than the burner radius. This sequence of events resulted from an increase of Da as a function of the radial direction, consequent to a decrease in the strain rate in the radial direction. The edge flame propagation velocity in the ignition mode was measured for propagating edge flames at moderate Da and for standing triple flames at large Da, using a combination of laser Doppler velocimetry of seeded particles, formaldehyde planar laser-induced fluorescence, and natural chemiluminescence imaging. The propagation velocity, nondimensionalized with the premixed laminar flame speed of the unburned stoichiometric mixture, was correlated with Da. The latter was calculated using a thermal diffusive model and velocity measurements. The nondimensional velocity reached a value of 2.6 at large Da, in good agreement with the estimated square root of the ratio of the unburned gas density to the burned gas density, as suggested by scaling considerations.

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“…Ref. [3] is mostly significant for its modeling contribution and essentially repeated the same type of experiments of Ref. [4], albeit in a vertical configuration.…”

Section: Introductionmentioning

confidence: 93%

“…Such flames are referred to as triple flames and are characterized by positive laminar flame speeds, that is, they propagate toward the unburned mixture. In the extinction mode, the edge flames present a simple edge without any tribrachial nature, that recedes away from the unburned mixture with negative flame speed [3].…”

Section: Introductionmentioning

confidence: 99%

Propagation of edge flames in counterflow mixing layers: Experiments and theory

Santoro

Liñán

Gomez

2000

Proceedings of the Combustion Institute

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“…Liñ án [8] and Kioni et al [9] have shown theoretically that in laminar flows, lifted flames are stabilized by a triple-flame configuration. Veynante et al [10] and Favier and Vervisch [11] have demonstrated that triple flames are able to survive strong interactions with vortices by adjusting their structure to a new transient environment, thus being more robust than pure diffusion flames.…”

Section: Introductionmentioning

confidence: 99%

Flamelet modeling of lifted turbulent methane/air and propane/air jet diffusion flames

Chen

Herrmann

Peters

2000

Proceedings of the Combustion Institute

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The stabilization mechanism of lifted turbulent jet diffusion flames is a test problem for models of partially premixed turbulent combustion. In these flames, combustion processes occur in both the nonpremixed and the premixed mode. For the flame stabilization process, however, flame propagation of the premixed branches seems to play a crucial role. In this paper, a flamelet model for partially premixed turbulent combustion is presented that combines flamelet models for non-premixed and premixed combustion. A new model for the turbulent burning velocity in partially premixed flows is proposed. It is based on a formulation for a conditional turbulent burning velocity which depends on mixture fraction. The effect of partially premixing is taken into account by using the presumed probability density function (pdf) approach in terms of the mixture fraction. Mean scalar quantities on both sides of the premixed flame front are calculated in the same way. From a computational point of view, the model has the advantage that the calculation of the chemical processes can be decoupled from the flow calculation, allowing for simulations of realistic configurations, yet retaining detailed chemistry. The model is used to simulate the stabilization process of turbulent methane/air and propane/air jet diffusion flames. The calculated lift-off heights compare favorably with experimental data from various authors.

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“…(3) has not been addressed yet. It has been noted in the past studies that the mixture stratification in the transverse direction yields triple flames (Kioni et al, 1993;Ruetsch et al, 1995;Plessing et al, 1998). Also, the behaviour and contributions of these additional terms in the presence of significant flame curvature, complex chemical kinetics, differential diffusion effects and a wide range of local flow and mixture conditions are not investigated yet.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Flame Stretch in Turbulent Lifted Jet Flame

Ruan

Swaminathan

Mizobuchi

2014

Combustion Science and Technology

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DNS data of a laboratory-scale turbulent lifted hydrogen jet flame has been analysed to show that this flame has mixed mode combustion not only at the flame base but also in downstream locations. The mixed mode combustion is observed in instantaneous structures as in earlier studies and in averaged structure, in which the predominant mode is found to be premixed combustion with varying equivalence ratio. The nonpremixed combustion in the averaged structure is observed only in a narrow region at the edge of the jet shear layer. The analyses of flame stretch show large probability for negative flame stretch leading to negative surface averaged flame stretch. The displacement speed-curvature correlation is observed to be negative contributing to the negative flame stretch and partial premixing resulting from jet entrainment acts to reduce the negative correlation. The contribution of turbulent straining to the flame stretch is observed to be negative when the scalar gradient aligns with the most extensive principal strain rate. The physics behind the negative flame stretch resulting from turbulent straining is discussed and elucidated through a simple analysis of the flame surface density transport equation.

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Flame spread in laminar mixing layers: The triple flame

Cited by 243 publications

References 9 publications

Propagation of edge flames in counterflow mixing layers: Experiments and theory

Propagation of edge flames in counterflow mixing layers: Experiments and theory

Flamelet modeling of lifted turbulent methane/air and propane/air jet diffusion flames

Investigation of Flame Stretch in Turbulent Lifted Jet Flame

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