Turbulence Production in Premixed Turbulent Flames

Bray, K. N. C.; Libby, Paul A.; Masuya, Goro; Moss, J.B.

doi:10.1080/00102208108547512

Cited by 225 publications

(83 citation statements)

References 8 publications

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“…Both theoretical and experimental research (Bray et al, 1981(Bray et al, , 1982Shepherd et al, 1982) have shown the occurrence of counter-gradient transport in some turbulent flames: flames where the turbulent flux " " pu i c and the _'gradient, _'C/OXi, have the same sign in opposition with the prediction of Eq. (2).…”

Section: Ve_l_tante F_ T Poinsotmentioning

confidence: 69%

“…For example, we expect that imposing a pressure gradient on a turbulent flame exhibiting counter-gradient diffusion may lead to a gradient-diffusion situation. This change could affect the flame brush thickness, the turbulent flame speed, and finally the complete structure of the turbulent flame brush, as described in a number of papers by Masuya & Libby, 1981;Bray et al, 1982. Our objective in this study is to explore the effects of pressure gradients on premixed turbulent flames using direct numerical simulations. We will first recall the physics of this phenomenon and how pressure gradients may be included in a simulation for reacting flows in Section 2.…”

Section: Ve_l_tante F_ T Poinsotmentioning

confidence: 99%

“…A simple algebraic closure based on the eddy viscosity concept cannot be used here. In the Bray-Moss-Libby model, closure is achieved by a transport equation for pu i''c'' (Bray 1980, Bray et aL1989, Bray 1990 Bray et at. (1981) studied each term in Eq.…”

Section: Pressure Gradients In Premixed Flamesmentioning

confidence: 99%

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Effects of pressure gradients on turbulent premixed flames

Veynante

Poinsot

1997

J. Fluid Mech.

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In most practical situations, turbulent premixed flames are ducted and, accordingly, subjected to externally imposed pressure gradients. These pressure gradients may induce strong modifications of the turbulent flame structure because of buoyancy effects between heavy cold fresh and light hot burnt gases. In the present work, the influence of a constant acceleration, inducing large pressure gradients, on a premixed turbulent flame is studied using direct numerical simulations.A favourable pressure gradient, i.e. a pressure decrease from unburnt to burnt gases, is found to decrease the flame wrinkling, the flame brush thickness, and the turbulent flame speed. It also promotes counter-gradient turbulent transport. On the other hand, adverse pressure gradients tend to increase the flame brush thickness and turbulent flame speed, and promote classical gradient turbulent transport. As proposed by Libby (1989), the turbulent flame speed is modified by a buoyancy term linearly dependent on both the imposed pressure gradient and the integral length scale lt.A simple model for the turbulent flux u″c″ is also proposed, validated from simulation data and compared to existing models. It is shown that turbulent premixed flames can exhibit both gradient and counter-gradient transport and a criterion integrating the effects of pressure gradients is derived to differentiate between these regimes. In fact, counter-gradient diffusion may occur in most practical ducted flames.

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Section: Ve_l_tante F_ T Poinsotmentioning

confidence: 69%

Section: Ve_l_tante F_ T Poinsotmentioning

confidence: 99%

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Effects of pressure gradients on turbulent premixed flames

Veynante

Poinsot

1997

J. Fluid Mech.

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“…Mantel and Borghi [58] developed a transport equation based closure for the scalar dissipation rate ( c ) via an order-of-magnitude analysis and suggested a scaling for the square of the second derivative term in Eq. (20). By neglecting higher moments and covariances (see Appendix A) the following approximation can be derived,…”

Section: Dilatation and Scrambling Termsmentioning

confidence: 99%

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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“…The website: http://www.amcm.pcz.pl/ Conducted literature studies make it possible to state that the existing tests usually pertain to diffusion flames [5,6]. In a smaller, insufficient degree they focus upon the turbulence generated in strongly kinetic and kinetic-diffusion flames [7,8], and particularly in the high-temperature sphere in the area of combustion front. From the perspective regarding the effectiveness analysis of combustion process and its modeling, it is a particularly significant range, in which strong gradients of factor, specific volume and displacement effects lead to the intensification of secondary air extraction from the surroundings.…”

Section: Introductionmentioning

confidence: 99%

Methodology pertaining to component evaluation of turbulence energy balance in a premixed jet flame with dissipation

Grodzki

2012

Sci. Res. Inst. Math. Comp. Sci.

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Abstract. This paper consists of an analysis of existing methods and their limitations pertaining to defining the dissipation rate as one of the components of the turbulent kinetic energy balance equation. Careful attention has been paid with reference to the method used during tests conducted in a burning round jet by means of laser Doppler anemometry. This paper covers the developed algorithms for digital signal processing of LDA, examples of output data sets for calculations and chosen profiles of energy balance components of dissipation and production.

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Turbulence Production in Premixed Turbulent Flames

Cited by 225 publications

References 8 publications

Effects of pressure gradients on turbulent premixed flames

Effects of pressure gradients on turbulent premixed flames

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

Methodology pertaining to component evaluation of turbulence energy balance in a premixed jet flame with dissipation

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