Study of Alternative Descriptions of Methane Oxidation for CFD Modeling of Turbulent Combustors

Brink, Anders; Kilpinen, Pia; Hupa, Mikko; Kjäldman, Lars

doi:10.1080/00102209908924182

Cited by 13 publications

(18 citation statements)

References 18 publications

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“…The calculations presented here however can only be used as very qualitative guidelines since real flames are not at thermodynamic equilibrium and do exhibit very strong kinetic and mixing effects. 39…”

Section: Equilibrium Gas Composition During Reducing Flame Synthesismentioning

confidence: 99%

Gas phase synthesis of fcc-cobalt nanoparticles

2006

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Air stable cobalt nanoparticles have been prepared continuously at a production rate of 30 g h 21 by a modified flame synthesis method under highly reducing conditions. Nanoparticles of 20-60 nm in diameter consisted of metallic face-centered-cubic cobalt. The metal particles were protected against oxidation by a surface layer of less than 1 nm of cobalt oxide. The material was highly magnetic exhibiting a high saturation magnetisation (>124 emu g 21 ) together with a low (,100 Oe) coercivity. Experiments under varying fuel to oxygen ratio were combined with thermodynamic calculations to illustrate the necessity for highly reducing conditions and enhanced gas mixing to enable the formation of metallic cobalt nanoparticles in flames.

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Section: Equilibrium Gas Composition During Reducing Flame Synthesismentioning

confidence: 99%

Gas phase synthesis of fcc-cobalt nanoparticles

2006

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“…This method can be combined with techniques like the formation of global reactions , and others mentioned above, for further optimization of the reduced mechanism. The challenge in forming global reactions is to find a set of suitable global reactions that is capable of reproducing the detailed mechanism to a high degree.…”

Section: Introductionmentioning

confidence: 99%

Optimal Reduction of the C1–C3 Combustion Mechanism for the Simulation of Flaring

Lou

Chen

Martin

et al. 2012

Ind. Eng. Chem. Res.

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Flaring is a combustion process designed to relieve pressures and safely dispose of vent gases from chemical and petrochemical plants. An industrial flaring activity typically involves various combustible waste gases and a large number of reactions and species. Because most of the detailed kinetic mechanisms for the speciation study of flaring events are too complicated to use in the computational fluid dynamics simulation of industrial-scale flares, several techniques for reduction of the detailed combustion mechanisms have been developed. In this paper, a new rigorous skeleton mechanism (RSM) based reduction technique, namely, the LU 2.0 algorithm, is proposed. It falls under the category of identification of redundancy. Other techniques in this category try to remove redundant species and reactions based on criteria such as sensitivity and quasi-steadystate analyses. These are highly dependent on the preanalysis of the mechanism and require species concentration sets for the conditions of interest. This algorithm tries to find out the skeleton mechanism with the lowest possible error. It works by rigorously testing all of the possible combinations of species sets. This RSM-based optimized mechanism was validated successfully against experimental data for various key performance indicators (laminar flame speeds, burner-stabilized flame, adiabatic flame temperature, and ignition delay) for methane, ethylene, and propylene flames. The efficacy of this algorithm was demonstrated by its improved predictability.

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“…Since many of the today used simplified mechanisms have been developed for totally different conditions than can be found at the combustion zones in biomass furnaces, could the performance and applicability of them be questionable. To get an answer to the question of how well they work for these different conditions, one-dimensional modeling studies of six simplified schemes, − and modifications of Duo by Jensen and Johnsson, Brouwer et al, and Brink et al have been performed. Brink et al differs from the others by giving the conversion factors of NH 3 to NO and N 2 explicitly instead of giving reaction rates.…”

Section: Introductionmentioning

confidence: 99%

“…The fuel was assumed to consist of a mixture of CO, H 2 , and methane. In a study by Brink et al, where the regression-based model was compared to the reduced mechanism for the nitrogen chemistry of Glarborg et al, they pointed out that when using the regression-based NO x model, it is important that the conditions respond to those the model was set up for. This restricts the use of the regression-based NO x model to systems where the main part of the NO x is formed from fuel-N, and the contribution from thermal-NO is only minor.…”

Section: Introductionmentioning

confidence: 99%

Comparisons of the Validity of Different Simplified NH₃−Oxidation Mechanisms for Combustion of Biomass

et al. 2000

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In this work comparisons and validations of several simplified ammonia oxidation mechanisms at conditions relevant for combustion of biomass have been performed. The aim of the investigation was to clarify the weakness and the strength of the available simplified mechanisms for computational fluid dynamics (CFD) based prediction of NO x emissions. The mechanisms have been tested at typical conditions for biomass combustion, considering temperature and gas composition. All the simplified mechanisms have been compared against a validated comprehensive elementary reaction mechanism containing 340 reversible reactions between 56 chemical species. In comparing the simplified mechanisms, the mixing pattern between the species was described by a continuous stirred tank reactor, with typical residence times in eddy dissipation concept fine structure. The results show that, for substoichiometric conditions at low temperatures (<1000 °C), all tested simplified mechanisms have poor agreement with the comprehensive mechanism. This is especially evident at short residence times. Typically, the simplified mechanisms fail to predict any nitric oxide formed at those conditions, whereas the comprehensive mechanism indicates up to 30% oxidation of ammonia to nitric oxide. The study shows that more accurate simplified models are necessary for a better description of ammonia oxidation when modeling furnaces in which these conditions are present. Black liquor recovery boilers and other combustors with staged combustion belong to that group of furnaces. At higher temperatures (>1000 °C) and at oxidizing conditions the mechanisms worked better. The deviation from the results obtained with the comprehensive mechanism are in the range of 20% in nitric oxide levels and ammonia consumption at longer residence times, whereas the deviations increases up to 90% at shorter residence times.

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Study of Alternative Descriptions of Methane Oxidation for CFD Modeling of Turbulent Combustors

Cited by 13 publications

References 18 publications

Gas phase synthesis of fcc-cobalt nanoparticles

Gas phase synthesis of fcc-cobalt nanoparticles

Optimal Reduction of the C1–C3 Combustion Mechanism for the Simulation of Flaring

Comparisons of the Validity of Different Simplified NH₃−Oxidation Mechanisms for Combustion of Biomass

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Study of Alternative Descriptions of Methane Oxidation for CFD Modeling of Turbulent Combustors

Cited by 13 publications

References 18 publications

Gas phase synthesis of fcc-cobalt nanoparticles

Gas phase synthesis of fcc-cobalt nanoparticles

Optimal Reduction of the C1–C3 Combustion Mechanism for the Simulation of Flaring

Comparisons of the Validity of Different Simplified NH3−Oxidation Mechanisms for Combustion of Biomass

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Comparisons of the Validity of Different Simplified NH₃−Oxidation Mechanisms for Combustion of Biomass