Effects of stretch on the local structure of preely propagating premixed low-turbulent flames with various lewis numbers

Renou, Bruno; Boukhalfa, Abdelkrim; Puechberty, D.; Trinité, M.

doi:10.1016/s0082-0784(98)80480-3

Cited by 76 publications

(50 citation statements)

References 14 publications

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“…Capture of the flow field velocity ahead of the flame, and knowledge of the direction in which the flame front burns normal to its surface allows the calculation of the local tangential strain rate, Stt. Renou et al (1998) based on a where ut is the tangential velocity of the fresh mixture ahead of the flame, and s is the distance along the flame surface. Having calculated the tangential strain rate, Renou et al (1998) also proposed the calculation of the local flame stretch rate, K, such that…”

Section: Resultsmentioning

confidence: 99%

A Study of premixed propagating flame vortex interaction

Hargrave

Jarvis

2006

J Vis

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Experimental data is presented for the interaction between a propagating flame and a simple vortex flow field structure generated in the wake of solid obstacles. The interaction between gas movement and obstacles creates vortex shedding forming a simple flow field recirculation. The presence of the simple turbulent structure within the gas mixture curls the flame front increasing curvature and enhancing burning rate. A novel twin camera Particle Image Velocimetry, PIV, was employed to characterise the flow field recirculation and the interaction with the flame front. The technique allowed the quantification of the flame/vortex interaction. The twin camera technique provides data to define the spatial variation of both the velocity of the flow field and flame front. Experimentally obtained values of local flame displacement speed and flame stretch rate are presented for simple flame/vortex interactions.

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Section: Resultsmentioning

confidence: 99%

A Study of premixed propagating flame vortex interaction

Hargrave

Jarvis

2006

J Vis

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“…18 It is worth noting here that alternative methods of assigning a characteristic Lewis number have been proposed based on heat release measurements 30,31 and mole fractions of the mixture constituents. 32 In the past, the significant effects of characteristic Lewis number Le on various aspects of premixed combustion (e.g., thermo-diffusive instability of laminar flames, burning rate, scalar gradient statistics, and combustion modelling) have been addressed analytically, [33][34][35][36] experimentally, [37][38][39][40][41][42][43] and numerically. 18,[44][45][46][47][48][49][50][51][52][53] Various concepts, which have been developed in order to explain such effects in turbulent flames, are reviewed elsewhere.…”

Section: Introductionmentioning

confidence: 99%

Effects of Lewis number on vorticity and enstrophy transport in turbulent premixed flames

2016

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The effects of Lewis number Le on both vorticity and enstrophy transport within the flame brush have been analysed using direct numerical simulation data of freely propagating statistically planar turbulent premixed flames, representing the thin reaction zone regime of premixed turbulent combustion. In the simulations, Le was ranged from 0.34 to 1.2 by keeping the laminar flame speed, thermal thickness, Damköhler, Karlovitz, and Reynolds numbers unchanged. The enstrophy has been shown to decay significantly from the unburned to the burned gas side of the flame brush in the Le ≈ 1.0 flames. However, a considerable amount of enstrophy generation within the flame brush has been observed for the Le = 0.34 case and a similar qualitative behaviour has been observed in a much smaller extent for the Le = 0.6 case. The vorticity components have been shown to exhibit anisotropic behaviour within the flame brush, and the extent of anisotropy increases with decreasing Le. The baroclinic torque term has been shown to be principally responsible for this anisotropic behaviour. The vortex stretching and viscous dissipation terms have been found to be the leading order contributors to the enstrophy transport for all cases, but the baroclinic torque and the sink term due to dilatation play increasingly important role for flames with decreasing Le. Furthermore, the correlation between the fluctuations of enstrophy and dilatation rate has been shown to play an important role in determining the material derivative of enstrophy based on the mean flow in the case of a low Le.

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“…In general, the instantaneous flame stretch is both positive and negative as has been noted in many earlier studies (Rutland and Trouvé, 1993;Bray and Cant, 1991;Chen and Im, 1998;Nye et al, 1996;Renou et al, 1998;Kostiuk and Bray, 1993). However, these studies suggested that there is 50% or less probability for the flame stretch to be negative and this probability can be calculated by integrating the pdf shown in Fig. 14 from −∞ to 0.…”

Section: Flame Surface Density and Flame Stretchmentioning

confidence: 77%

“…The instantaneous flame stretch can be positive or negative; a positive value implies that the flame surface area increases due to the combined effects of turbulence and flame propagation and negative stretch suggests that the flame surface is compressed resulting in the loss of flame area per unit volume. Earlier numerical (Rutland and Trouvé, 1993;Bray and Cant, 1991;Chen and Im, 1998), experimental (Nye et al, 1996;Renou et al, 1998) and modelling (Kostiuk and Bray, 1993) studies have demonstrated that there is 20-50% probability for the flame stretch to be negative. In the view of RANS methodology the average value of the flame stretch, Φ s , is expected to be predominantly positive and many modelling methods have been proposed in the past with this view.…”

Section: Introductionmentioning

confidence: 98%

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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Effects of stretch on the local structure of preely propagating premixed low-turbulent flames with various lewis numbers

Cited by 76 publications

References 14 publications

A Study of premixed propagating flame vortex interaction

A Study of premixed propagating flame vortex interaction

Effects of Lewis number on vorticity and enstrophy transport in turbulent premixed flames

Investigation of Flame Stretch in Turbulent Lifted Jet Flame

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