Measurements of conditional velocities in turbulent premixed flames by simultaneous OH PLIF and PIV

Frank, Jonathan H.; Kalt, P.; Bilger, R.W.

doi:10.1016/s0010-2180(98)00041-8

Cited by 110 publications

(59 citation statements)

References 25 publications

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“…Earlier experiments in premixed flames have resorted to various means of stabilization with different levels of success. Flows with backward facing steps [15,16], pilot flames [17][18][19], swirl [20,21], as well as V-shaped flames with rod-stabilization [22,23], have achieved modest to high levels of turbulence. There are several significant experimental configurations [24][25][26] that utilize strong swirl, recirculation and wall bounded flow to stabilize low Damköhler (Da) number premixed combustion, simulating the strongly swirling flow field features typically found in gas turbine combustors.…”

Section: Introductionmentioning

confidence: 99%

Finite Rate Chemistry Effects in Highly Sheared Turbulent Premixed Flames

Dunn

Masri

Bilger

et al. 2010

Flow Turbulence Combust

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Detailed scalar structure measurements of highly sheared turbulent premixed flames stabilized on the piloted premixed jet burner (PPJB) are reported together with corresponding numerical calculations using a particle based probability density function (PDF) method. The PPJB is capable of stabilizing highly turbulent premixed jet flames through the use of a small stoichiometric pilot that ensures initial ignition of the jet and a large shielding coflow of hot combustion products. Four lean premixed methane-air flames with a constant jet equivalence ratio are studied over a wide range of jet velocities. The scalar structure of the flames are examined through high resolution imaging of temperature and OH mole fraction, whilst the reaction rate structure is examined using simultaneous imaging of temperature and mole fractions of OH and CH 2 O. Measurements of temperature and mole fractions of CO and OH using the Raman-Rayleigh-LIF-crossed plane OH technique are used to examine the flame thickening and flame reaction rates. It is found that as the shear rates increase, finite-rate chemistry effects manifest through a gradual decrease in reactedness, rather than the abrupt localized extinction observed in nonpremixed flames when approaching blow-off. This gradual decrease in reactedness is accompanied by a broadening in the reaction zone which is consistent with the view that turbulence structures become embedded within the instantaneous flame front. Numerical predictions using a particle-based PDF model are shown to be able to Submitted to the Special Issue of Flow, Turbulence and Combustion dedicated to S.B. Pope. 622Flow Turbulence Combust (2010) 85:621-648 predict the measured flames with significant finite-rate chemistry effects, albeit with the use of a modified mixing frequency.

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Section: Introductionmentioning

confidence: 99%

Finite Rate Chemistry Effects in Highly Sheared Turbulent Premixed Flames

Dunn

Masri

Bilger

et al. 2010

Flow Turbulence Combust

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“…Experiments presented, for example, in [16] and [17] demonstrate that the scalar transport of reacting variables can be of both the countergradient or gradient type. We explain this by the existence of two physical mechanisms controlling the scalar flux in the premixed flame: (a) Random velocity fluctuation due to turbu- lence and (b) an effect of the pressure gradient across the flame generated by combustion.…”

Section: Paradoxes Of the Turbulent Premixed Flamesmentioning

confidence: 99%

“…In our joint RANS/LES numerical simulations we noticed that assuming U t ≈ U t when using a rather large grid size ∼ L gives good results as at Da 1 the main increase of the flamelet sheet area takes place at the subgrid level and LES wrinkling gives a relatively small effect on the speed U t . This gives the opportunity to omit the empirical constant A • in Equation (17). So in our joint RANS/LES simulations presented below we applied Equation (12) instead of Equation (17) using RANS fields of k and ε for estimation of the speed U t , and Equation (16) for the subgrid viscosity and diffusion coefficients.…”

Section: Joint Rans/les Formulation Of the Problemmentioning

confidence: 99%

Joint RANS/LES Approach to Premixed Flame Modelling in the Context of the TFC Combustion Model

Zimont

Battaglia

2006

Flow Turbulence Combust

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We present an original timesaving joint RANS/LES approach to simulate turbulent premixed combustion. It is intended mainly for industrial applications where LES may not be practical. It is based on successive RANS/LES numerical modelling, where turbulent characteristics determined from RANS simulations are used in LES equations for estimation of the subgrid chemical source and viscosity. This approach has been developed using our TFC premixed combustion model, which is based on a generalization of the Kolmogorov's ideas. We assume existence of small-scale statistically equilibrium structures not only of turbulence but also of the reaction zones. At the same time, non-equilibrium large-scale structures of reaction sheets and turbulent eddies are described statistically by model combustion and turbulence equations in RANS simulations or follow directly without modelling in LES. Assumption of small-scale equilibrium gives an opportunity to express the mean combustion rate (controlled by small-scale coupling of turbulence and chemistry) in the RANS and LES sub-problems in terms of integral or subgrid parameters of turbulence and the chemical time, i.e. the definition of the reaction rate is similar to that of the mean dissipation rate in turbulence models where it is expressed in terms of integral or subgrid turbulent parameters. Our approach therefore renders compatible the combustion and turbulent parts of the RANS and LES sub-problems and yields reasonable agreement between the RANS and averaged LES results. Combining RANS simulations of averaged fields with LES method (and especially coupled and acoustic codes) for simulation of corresponding nonstationary process (and unsteady combustion regimes) is a promising strategy for industrial applications. In this work we present results of simulations carried out employing the joint 306 Flow Turbulence Combust (2006) 77: 305-331 RANS/LES approach for three examples: High velocity premixed combustion in a channel, combustion in the shear flow behind an obstacle and the impinging flame (a premixed flame attached to an obstacle).

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“…The role of the laminar flame thickness was recognized as an important parameter for study and comprehension of the flame/turbulence interactions [9]. Various studies have tried to analyze the influence of chemical reaction due to combustion on turbulence field flame [3,4,[10][11][12][13][14]. Chekired et al [15] using Peters and Williams mechanism, showed good agreement between the numerical results and the experimental ones of the Aachen flame F3.…”

Section: Introductionmentioning

confidence: 98%

Experimental study of the dynamic field of turbulent premixed methane/air flame using PIV technique

Boulahlib¹,

Chekired²,

Benzitouni³

et al. 2016

Int. J. CMEM

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This work is an experimental study of the dynamic fields of a turbulent premixed methane-air flame in a Bunsen burner. The Particle Image Velocimetry (PIV) is used to determine the dynamic fields, and Laser Sheet Tomography (LST) for the flame fronts. The turbulent main jet has a Reynolds number Re = 10 000. Turbulence is generated using perforated grids having three whose provide different inlet turbulence intensities. Velocity fields are measured for various equivalence ratio (F = 0.6-1.3) and different axial flame positions. For the reactive jet, interesting results are obtained concerning the dynamic field and the flame front. It is shown that radial profiles of U and V correspond to the axial positions located before the end of the potential core in the reactive jet. The velocity increases at the jet center to 20 m/s, and is less influenced by turbulent mixing in the flame. The greatest velocity and turbulent kinetic energy are obtained using the grid with the smallest ratio (d/M). Most important values of the radial velocity correspond to the lean flames.

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Measurements of conditional velocities in turbulent premixed flames by simultaneous OH PLIF and PIV

Cited by 110 publications

References 25 publications

Finite Rate Chemistry Effects in Highly Sheared Turbulent Premixed Flames

Finite Rate Chemistry Effects in Highly Sheared Turbulent Premixed Flames

Joint RANS/LES Approach to Premixed Flame Modelling in the Context of the TFC Combustion Model

Experimental study of the dynamic field of turbulent premixed methane/air flame using PIV technique

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