Structure of laminar flames

Dixon‐Lewis, G.

doi:10.1016/s0082-0784(06)80274-2

Cited by 125 publications

(51 citation statements)

References 45 publications

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“…The stream velocity in typical opposed-flow diffusion flames is on the order of 10 -1~1 m/s [26,40], whereas that in the ITM reactor is limited by low oxygen permeation rates, which is on the order of 10 -1~1 μmol/cm 2 /s [20] or 10 -4~1 0 -3 m/s. Accordingly, the fuel stream must be fed to the sweep side at a low flow rate to satisfy the requisite stoichiometry and stabilize the reaction zone between the membrane and the sweep gas inlet.…”

Section: Reaction Environment Supported By An Itmmentioning

confidence: 99%

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Laminar oxy-fuel diffusion flame supported by an oxygen-permeable-ion-transport membrane

Hong

Kirchen

Ghoniem

2013

Combustion and Flame

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A numerical model with detailed gas-phase chemistry and transport was used to predict homogeneous fuel conversion processes and to capture the important features (e.g., the location, temperature, thickness and structure of a flame) of laminar oxy-fuel diffusion flames stabilized on the sweep side of an oxygen permeable ion transport membrane (ITM). We assume that the membrane surface is not catalytic to hydrocarbon or syngas oxidation. It has been demonstrated that an ITM can be used for hydrocarbon conversion with enhanced reaction selectivity such as oxy-fuel combustion for carbon capture technologies and syngas production. Within an ITM unit, the oxidizer flow rate, i.e., the oxygen permeation flux, is not a pre-determined quantity, since it depends on the oxygen partial pressures on the feed and sweep sides and the membrane temperature. Instead, it is influenced by the oxidation reactions that are also dependent on the oxygen permeation rate, the initial conditions of the sweep gas, i.e., the fuel concentration, flow rate and temperature, and the diluent. In oxy-fuel combustion applications, the sweep side is fuel-diluted with CO2, and the entire unit is preheated to achieve a high oxygen permeation flux. This study focuses on the flame structure under these conditions and specifically on the chemical effect of CO2 dilution. Results show that, when the fuel diluent is CO2, a diffusion flame with a lower temperature and a larger thickness is established in the vicinity of the membrane, in comparison with the case in which N2 is used as a diluent. Enhanced OH-driven reactions and suppressed H radical chemistry result in the formation of products with larger CO and H2O and smaller H2 concentrations. Moreover, radical concentrations are reduced due to the high CO2 fraction in the sweep gas. CO2 dilution reduces CH3 formation and slows down the formation of soot precursors, C2H2 and * Corresponding author. Tel.: +1 617 253 2295; Fax: +1 617 253 5981 Email address: ghoniem@mit.edu (Ahmed F. Ghoniem) 2 C2H4. The flame location impacts the species diffusion and heat transfer from the reaction zone towards the membrane, which affects the oxygen permeation rate and the flame temperature.

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Section: Reaction Environment Supported By An Itmmentioning

confidence: 99%

“…3. In addition, low strain rate flames result from the low oxygen permeation flux, as compared to the strain rate of conventional opposed-flow diffusion flames which is on the order of 10 2~1 0 3 s -1 [26,40].…”

Section: Flame Location and Oxygen Permeationmentioning

confidence: 99%

Laminar oxy-fuel diffusion flame supported by an oxygen-permeable-ion-transport membrane

Hong

Kirchen

Ghoniem

2013

Combustion and Flame

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“…The flamelet model, used in the non-premixed combustion model to account for chemical non-equilibrium, regards the turbulent flame as an ensemble of thin, laminar, locally one-dimensional flamelet structures embedded within the turbulent flow field [21,22,[24][25][26]. Here 67 flamelets, with χ 0 = 1 and Δχ = 2, have been used to describe combustion, where…”

Section: Turbulence and Combustion Modelsmentioning

confidence: 99%

“…In the "Flamelet simulation", combustion is modeled by means of 67 "flamelets" pre-calculated and stored in look-up tables [21][22][23][24][25][26][27][28] using detailed chemistry [29] (GRIMech3.0, 53 species and 325 reactions, using Arrhenius relations).…”

Section: Introductionmentioning

confidence: 99%

LES of a Meso Combustion Chamber with a Detailed Chemistry Model: Comparison between the Flamelet and EDC Models

Minotti

Sciubba

2010

Energies

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Abstract:The goal of this paper is to contribute to the design of high-performance mesocombustors, a field currently under rapid development, in particular for propulsion, e.g., for UAVs, and micro/meso-electrical power generators. This study is focused on a cylindrical combustor of 29 cm 3 , fuelled by methane and air, which provides 2 kW of thermal power. The device was entirely designed and built at the Sapienza University of Rome and coupled with an ultra-micro turbine. Two 3D LES simulations with detailed chemistry are presented. They differ only for the combustion models, so that a model comparison can be carried out. The calculated maximum temperature inside the chamber, the gas exhaust temperature and the combustion efficiency are compared and discussed. The results, reported at two different physical times, show the effects of the different combustion models, which predict different temperature and species concentration maps, but similar values for the combustion efficiency. Thermal, chemical and kinematic maps show that the Eddy Dissipation Concept allows for a more accurate estimatation of the performance parameters for application to first-order design procedures.

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“…The distance between this isotherm and the front of the preheat zone where temperature began to rise was predicted from the one-dimensional laminar theory of a stoichiometric premixed flame, and then the temperature distribution was estimated from the same theory. (15) The concentration profile in front of the flame edge was corrected with this temperature distribution, referring to the relationship between the LIF signal intensity and the temperature proposed by Thurber. (12) The distance from the isotherm of the silicon-oil vanishing plane to the maximum heat-release plane was predicted to be 0.32mm by the one-dimensional premixed flame theory.…”

Section: Fuel Concentration Measurement With Acetone Lifmentioning

confidence: 99%

Measurement of Fuel Concentration Profile at Leading Edge of Lifted Flame with Acetone Laser-Induced Fluorescence

Hirota

Sekine

Hashimoto

et al. 2009

JTST

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This is a study of the leading-edge characteristics of a methane-air triple flame. Few experiment results are available for physical examination of such characteristics, so further experimental investigations are strongly needed to understand the stability mechanism in a mixture with a steep concentration gradient. To this end, we measured concentration profiles at the leading edge of a flame using acetone laser-induced fluorescence (acetone LIF). The results demonstrated that the lifted height of the flame changed when acetone was added to the mixture and correlated well with increased C 2 radical behind the flame edge. However, the OH radical luminous intensity, measured with a spectroscope, did not change with addition of acetone. Moreover, the burning velocity obtained by the Bunsen-burner method remained constant when acetone was added to the mixture. Therefore, acetone had little influence on burning intensity. Acetone LIF can thus be employed to measure the local concentration gradient at the leading edge of a flame. The acetone LIF signals could be corrected to consider the thermal effect by using silicone oil vanishing-plane data. From the corrected acetone LIF data, the width between the lean and rich flammability limits (flammability limit width) in the flow upstream of the flame with a steep concentration gradient was clearly observed and could be quantitatively compared with the recent numerical results.

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Structure of laminar flames

Cited by 125 publications

References 45 publications

Laminar oxy-fuel diffusion flame supported by an oxygen-permeable-ion-transport membrane

Laminar oxy-fuel diffusion flame supported by an oxygen-permeable-ion-transport membrane

LES of a Meso Combustion Chamber with a Detailed Chemistry Model: Comparison between the Flamelet and EDC Models

Measurement of Fuel Concentration Profile at Leading Edge of Lifted Flame with Acetone Laser-Induced Fluorescence

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