Direct and indirect thermal expansion effects in turbulent premixed flames

Robin, Vincent; Mura, Arnaud; Champion, Michel

doi:10.1017/jfm.h2011.409

Cited by 9 publications

(12 citation statements)

References 50 publications

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“…The (near) planar nature of the flames suggests a possible approximation using a one-dimensional Favre-averaged Navier-Stokes formulation. The resulting flames propagate normal to themselves in a uniform stream of reactants featuring a constant initial turbulence field extracted from DNS data at the leading edge of the flames [17,33]. The thermodynamic parameters are consistent with the DNS databases as listed in Table 3.…”

Section: One-dimensional Planar Flamessupporting

confidence: 60%

“…It is noted that "dilatation" effects within flamelets accelerate the velocity field u n normal to the flame front (e.g. [33]) with u i , the projection of u n , on axis x i . To evaluate Eq.…”

Section: Discussionmentioning

confidence: 99%

“…The preferential acceleration effects [31] are introduced in Section 3.3 as the impact of volume expansion is significant in the flamelet regime of combustion (e.g. [33,36,41]). …”

Section: Extended Treatment Of Variable Density Effectsmentioning

confidence: 99%

“…This implies that "dilatation" effects (Case 2) are significant in the flamelet regime of combustion (e.g. [33,36,41]). The closure with the molecular diffusion term (Case 3) further improves agreement in accordance with suggestions regarding the potential importance of such terms [38,39].…”

Section: Pressure Dilatation/flamelet Scrambling Effectsmentioning

confidence: 99%

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The impact of dilatation, scrambling, and pressure transport in turbulent premixed flames

Tian

Lindstedt

2017

Combustion Theory and Modelling

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Premixed turbulent flames feature strong interactions between chemical reactions and turbulence that affect scalar and turbulence statistics. The focus of the present work is on clarifying the impact of pressure dilatation/flamelet scrambling effects with a comprehensive second-moment closure used for evaluation purposes. Model extensions that take into account flamelet orientation and molecular diffusion are derived. Isothermal pressure transport is included with an additional variable density contribution derived for the flamelet regime of combustion. The full closure is assessed by comparisons with direct numerical simulations (DNS) of statistically "steady" fully developed premixed turbulent planar flames at different expansion ratios. Subsequently, the prediction of lean premixed turbulent methane-air flames featuring fractal grid generated turbulence in an opposed jet geometry is considered. The overall agreement shows that "dilatation" effects contribute to counter-gradient transport and can also increase the turbulent kinetic energy significantly. Levels of anisotropy are broadly consistent with the DNS data and key aspects of opposed jet flames are well predicted. However, it is also shown that complications arise due to interactions between the imposed pressure gradient and combustion and that redistribution is affected along with the scalar flux at the leading edge. The latter is strongly affected by the reaction rate closure and, potentially, by pressure transport. Overall, the derived models offer significant improvements and can readily be applied to the modelling of premixed turbulent flames at practical rates of heat release.

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Section: One-dimensional Planar Flamessupporting

confidence: 60%

Section: Discussionmentioning

confidence: 99%

“…The preferential acceleration effects [31] are introduced in Section 3.3 as the impact of volume expansion is significant in the flamelet regime of combustion (e.g. [33,36,41]). …”

Section: Extended Treatment Of Variable Density Effectsmentioning

confidence: 99%

Section: Pressure Dilatation/flamelet Scrambling Effectsmentioning

confidence: 99%

See 2 more Smart Citations

The impact of dilatation, scrambling, and pressure transport in turbulent premixed flames

Tian

Lindstedt

2017

Combustion Theory and Modelling

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“…Since the data were comprehensively discussed by various research groups, [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] we will restrict ourselves to a brief summary of those compressible simulations. They dealt with statistically 1D, planar, adiabatic flames modeled by unsteady 3D continuity, Navier-Stokes, and energy equations, as well as the ideal gas state equation.…”

mentioning

confidence: 99%

Letter: Does flame-generated vorticity increase turbulent burning velocity?

et al. 2018

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Direct numerical simulation data obtained from a statistically stationary, 1D, planar, weakly turbulent, premixed flame, which is associated with the flamelet combustion regime, are analyzed in order to show that generation of vorticity due to baroclinic torque within flamelets can impede wrinkling the reaction surface, reduce its area, and decrease the burning rate. These data call for revisiting the widely accepted concept of combustion acceleration due to flame-generated turbulence.

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Influence of Thermal Expansion on Potential and Rotational Components of Turbulent Velocity Field Within and Upstream of Premixed Flame Brush

Lipatnikov

Sabelnikov

Nikitin

et al. 2020

Flow Turbulence Combust

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Direct Numerical Simulation (DNS) data obtained earlier from two statistically stationary, 1D, planar, weakly turbulent premixed flames are analyzed in order to examine the influence of combustion-induced thermal expansion on the flow structure within the mean flame brushes and upstream of them. The two flames are associated with the flamelet combustion regime and are characterized by significantly different density ratios, i.e. = 7.53 and 2.5. The Helmholtz-Hodge decomposition is applied to the DNS data in order to extract rotational and potential velocity fields. Comparison of the two fields shows that combustion-induced thermal expansion can significantly change the local structure of the incoming constantdensity turbulent flow of unburned reactants by significantly increasing the relative magnitude of the potential velocity fluctuations when compared to the rotational velocity fluctuations in the flow. Such effects are documented not only within the mean flame brush, but also well upstream of it. The effect magnitude is increased by the density ratio , with the effects being well (weakly) pronounced at = 7.53 (2.50, respectively). Moreover, the potential and rotational velocity fields can cause opposite variations of the local area of an iso-scalar surface , =const within flamelets by generating the local strain rates of opposite signs.

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Direct and indirect thermal expansion effects in turbulent premixed flames

Cited by 9 publications

References 50 publications

The impact of dilatation, scrambling, and pressure transport in turbulent premixed flames

The impact of dilatation, scrambling, and pressure transport in turbulent premixed flames

Letter: Does flame-generated vorticity increase turbulent burning velocity?

Influence of Thermal Expansion on Potential and Rotational Components of Turbulent Velocity Field Within and Upstream of Premixed Flame Brush

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