Turbulent opposed-jet flames: A critical benchmark experiment for combustion LES☆

Geyer, D.; Kempf, Andreas; Dreizler, Andreas; Janicka, J.

doi:10.1016/j.combustflame.2005.08.032

Cited by 79 publications

(95 citation statements)

References 32 publications

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“…1), originally developed by Geyer et al [11], was extensively used by Geipel et al [10] and Goh et al [8,31,32,33] and is identical to the the configuration used by Hampp et al [22,23]. A cross fractal grid (CFG; [34]) was installed 50 mm upstream the UN exit, featuring a BR of 65 % with maximum and minimum bar widths of 2.0 mm and 0.50 mm.…”

Section: Methods Assumptions and Proceduresmentioning

confidence: 99%

“…The opposed jet geometry has been extensively utilised to investigate turbulent (and laminar) non-premixed, partially premixed and premixed combustion as well as, more recently, regime transitions [6,7,8,9]. The geometry entails decisive advantages rendering it indispensable for experimental combustion studies as well as computational model development and validation [10,11]. These are: (i) Excellent optical access for laser-based diagnostic measurements; (ii) Accurate experimental control of boundary conditions; (iii) Aerodynamic flame stabilisation, rather than through pilot flames, leading to flame dynamics and extinction being directly related to the intrinsic aerothermochemistry of the combustion process; (iv) Individual control of variables affecting the chemical and turbulent time-scale and (v) a compact physical domain ideal for LES and other computational studies.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Distributed Low Temperature Combustion: Fundamental Understanding of Combustion Regime Transitions

Lindstedt¹,

Hampp²,

Kraus³

et al. 2016

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Section: Methods Assumptions and Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Distributed Low Temperature Combustion: Fundamental Understanding of Combustion Regime Transitions

Lindstedt¹,

Hampp²,

Kraus³

et al. 2016

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“…The opposed jet geometry has been extensively utilised to investigate -laminar as well as turbulent -non-premixed, partial premixed, and premixed combustion and, more recently, combustion regime transitions for aviation fuels (Goh et al 2013b). The configuration has notable advantages for combustion studies (Mastorakos et al 1995, Geyer et al 2005, Geipel et al 2010): (i) excellent optical access for laser-based diagnostic measurements, (ii) accurate experimental control of boundary conditions, (iii) aerodynamic flame stabilisation, rather than via pilot flames, leading to flame dynamics and extinction being related to the inherent aerothermochemistry of the combustion process; and (iv) individual control of variables affecting the chemical and turbulent time-scale. The last two points identify the facility as ideal for investigations of combustion regime transitions.…”

Section: Introductionmentioning

confidence: 99%

Fractal Grid Generated Turbulence—A Bridge to Practical Combustion Applications

Hampp

Lindstedt

2016

Fractal Flow Design: How to Design Bespoke Turbulence and Why

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Abstract.Practical applications typically feature high turbulent Reynolds numbers and, increasingly, low Damköhler numbers leading to distributed combustion. Such conditions are difficult to achieve on a laboratory scale that permits detailed experimental investigations. The aerodynamically stabilised turbulent opposed jet flame configuration is a case point -an exceptionally flexible canonical geometry traditionally featuring low turbulence levels. Fractal grids can be used to increase the turbulent Reynolds number, without any negative impact on other parameters, and to remove the classical problem of a relatively low ratio of turbulent to bulk strain. The use of fractal grids to ameliorate such problems is exemplified for fuel lean combustion with combustion regime transitions achieved through the stabilisation of turbulent premixed flames against hot combustion products. An analysis is presented in the context of a multi-fluid formalism that extends the customary bimodal pdf approach to include multiple fluid states. The approach is quantified via simultaneous OH-PLIF and PIV, permitting the identification of five separate states (reactant, combustion product, mixing, mildly reacting and flamelet fluids). The sensitivity of the distribution between the fluid states to threshold values is also evaluated. The work suggests that a consistent treatment of the delineating thresholds is necessary when comparing different types of simulations (e.g. DNS) and experiments for reacting fluids with multiple states. The use of fractal grids in a flame driven shock tube provides a further example and is shown to generate turbulent Re numbers of the order 10 5 for flows with Mach numbers approaching unity. The conditions are of relevance to flame stabilisation in hypersonics and are analysed through OH-PLIF and high speed PIV with optimal fractal grids selected on the basis of maximum flame acceleration.

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“…The opposed jet geometry used as a starting point in the current work consists of two nozzles in a vertical arrangement originally designed by Geyer et al [5,31] and is identical to that described by Geipel et al [6]. Both nozzles were water-cooled to prevent differences in the reactant densities due to preheating.…”

Section: Experimental Configuration Techniques and Uncertaintiesmentioning

confidence: 99%

“…The comparatively simple flame stabilisation method and essentially adiabatic conditions lead to flame dynamics and extinction being related to the aerothermochemistry of the combustion process rather than heat losses. Combined with the comparatively simple boundary conditions, the opposed jet geometry provides an attractive standard test case for the assessment of fuel effects and closure approximations as proposed by Bray et al [1], Lindstedt and Váos [2,3] and subsequently by Geyer et al [4,5] in the context of large eddy simulations (LES). Preparatory isothermal flow studies have also been presented by a number of investigators (e.g.…”

Section: Introductionmentioning

confidence: 99%

Lean premixed opposed jet flames in fractal grid generated multiscale turbulence

Goh

Geipel

Lindstedt

2014

Combustion and Flame

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The opposed jet configuration presents an attractive canonical geometry for the evaluation of burning properties of turbulent flames with past studies typically limited to low Reynolds numbers. Fractal grid generated turbulence was used to remove the low turbulence level limitations associated with conventional perforated plate generators with the turbulent Reynolds number range moved from 50-120 to 130-318. Optimal grid configurations were determined with particular emphasis on reducing the impact of the flow upstream of the turbulence generators in order to facilitate simpler boundary conditions for computational studies. The resulting flow structures were analysed using proper orthogonal decomposition and conditional proper orthogonal decomposition. Velocity and reaction progress variable statistics, including conditional velocities and scalar fluxes, are reported for fuel lean methane, ethylene and propane flames approaching extinction. The instrumentation comprised particle image velocimetry with the flows to both nozzles seeded with 1 µm silicon oil droplets or 3 µm Al2O3 particles. Probability density functions were determined for the instantaneous location of the stagnation point to eliminate the possibility of low frequency bulk motion distorting velocity statistics. Probability density functions of flame curvature were determined using a multi-step flame front detection algorithm with estimates of the turbulent burning velocity provided along with a discussion of alternative determination methods. The data sets show that fractal grids generate multi-scale broadband turbulence and present an opportunity for a systematic evaluation of calculation methods for premixed turbulent flames that undergo a transition from non-gradient to gradient turbulent transport while approaching extinction.

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Turbulent opposed-jet flames: A critical benchmark experiment for combustion LES☆

Cited by 79 publications

References 32 publications

Distributed Low Temperature Combustion: Fundamental Understanding of Combustion Regime Transitions

Distributed Low Temperature Combustion: Fundamental Understanding of Combustion Regime Transitions

Fractal Grid Generated Turbulence—A Bridge to Practical Combustion Applications

Lean premixed opposed jet flames in fractal grid generated multiscale turbulence

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