Turbulent flows with premixed reactants

Bray, K.N.C.

doi:10.1007/3540101926_10

Cited by 230 publications

(150 citation statements)

References 47 publications

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“…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%

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: Pressure Gradients In Premixed Flamesmentioning

confidence: 99%

Effects of pressure gradients on turbulent premixed flames

Veynante

Poinsot

1997

J. Fluid Mech.

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“…For premixed flames, the famous BML (Bray Moss Libby) approach, for example, which is the workhorse of many theories for turbulent premixed flames [12,13] assumes that a single variable (the progress variable c ) is sufficient to describe the flow: this is true only when the flow is adiabatic. In the same way, many usual methods for chemistry tabulation such as FPV [14] , FPI [15] or FGM [16] assume that chemistry can be described using only two variables, the mixture fraction z and the progress variable c , which implies that the flames must be adiabatic.…”

Section: Introductionmentioning

confidence: 99%

Joint experimental and numerical study of the influence of flame holder temperature on the stabilization of a laminar methane flame on a cylinder

Miguel-Brebion

Mejía

Xavier

et al. 2016

Combustion and Flame

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. a b s t r a c tThe mechanisms controlling laminar flame anchoring on a cylindrical bluff-body are investigated using DNS and experiments. Two configurations are examined: water-cooled and uncooled steel cylinders. Comparisons between experimental measurements and DNS show good agreement for the flame root locations in the two configurations. In the cooled case, the flame holder is maintained at about 300 K and the flame is stabilized in the wake of the cylinder, in the recirculation zone formed by the products of combustion. In the uncooled case, the bluff-body reaches a steady temperature of about 700 K in both experiment and DNS and the flame is stabilized closer to it. The fully coupled DNS of the flame and the temperature field in the bluff-body also shows that capturing the correct radiative heat transfer from the bluff-body is a key ingredient to reproduce experimental results.

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“…Simple algebraic closure models have been proposed for flame surface density, R (Bray, 1980;Bray et al, 1985). The Bray-Moss-Libby model (Bray et al, 1985) for R is based on the spatial distribution of flame crossings along a contour of mean progress variable, hci, which is 0 in the reactants and 1 in the products.…”

Section: Introductionmentioning

confidence: 99%

Flame Surface Densities in Premixed Combustion at Medium to High Turbulence Intensities

Gülder

Smallwood

2007

Combustion Science and Technology

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The surface densities of flame fronts in turbulent premixed propane= air flames were determined experimentally. The instantaneous flame fronts were visualized using laser induced fluorescence (LIF) of OH on two Bunsen type burners of 11.2 and 22.4 mm diameters. Nondimensional turbulence intensity, u 0 =S L , was varied from 0.84 to 15, and the Reynolds number, based on the integral length scale, varied from 34 to 467. These flames are in the flamelet combustion regime as defined by the most recent turbulent premixed combustion diagrams. From 100 to 800 images were recorded for each experimental condition. Flame surface densities were obtained from the instantaneous maps of the progress variable, which is zero in the reactants and unity in the products. These flame surface densities were corrected for the mean direction cosines of the flame fronts, which had a typical value of 0.69 for the Bunsen flames. In the non-dimensional turbulence intensity range of up to 15, it was found that the maximum flame surface density and the integrated flame surface density across the flame brush do not show any significant dependence on turbulence intensity. This was discussed in the framework of a flame surface density-based turbulent premixed flame propagation closure model.

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Turbulent flows with premixed reactants

Cited by 230 publications

References 47 publications

Effects of pressure gradients on turbulent premixed flames

Effects of pressure gradients on turbulent premixed flames

Joint experimental and numerical study of the influence of flame holder temperature on the stabilization of a laminar methane flame on a cylinder

Flame Surface Densities in Premixed Combustion at Medium to High Turbulence Intensities

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