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Henning Bockhorn - One of the best experts on this subject based on the ideXlab platform.
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Catalytic stabilization of lean Premixed Combustion: Method for improving NOx emissions
Combustion and Flame, 1996Co-Authors: Andreas Schlegel, W Weisenstein, T Griffin, Peter Benz, Henning BockhornAbstract:An experimental and numerical investigation is reported of NO{sub x} emissions from both catalytically stabilized and noncatalytic, lean Premixed, atmospheric Combustion of methane. Experiments were in a tubular, adiabatic flow reactor with catalytically active or inactive honeycomb structures and with adiabatic flame temperatures from 1,300 to 1,500 C. In order to study the effect of catalytic conversion on NO{sub x} formation, the fraction of fuel converted within the catalyst was varied within the range of 0% (corresponding to noncatalytic Combustion) to 100%. In all cases, complete burnout is accomplished in a subsequent, homogeneous Combustion zone. NO{sub x} emissions were computed with combinations of ideal reactor models such as one-dimensional flames, perfectly stirred and plug flow reactors, and catalytic oxidation reactors (Cat). In the Cat model, it is assumed that no intermediates and no NO{sub x} are formed, whereas for the homogeneous Combustion models a detailed chemical reaction mechanism including NO{sub x} formation is employed. The NO{sub x} emissions of catalytically stabilized, Premixed Combustion are remarkably lower than those of noncatalytic, Premixed Combustion and depend on the fraction of catalytically converted fuel. The higher this fraction, the lower are the NO{sub x} emissions. The calculated results compare well with the experimentalmore » data, hence validating the modeling assumptions.« less
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Catalytic stabilization of lean Premixed Combustion: Method for improving NO(x) emissions
Combustion and Flame, 1996Co-Authors: Andreas Schlegel, W Weisenstein, Paul Benz, T Griffin, Henning BockhornAbstract:An experimental and numerical investigation is reported of NO(x) emissions from both catalytically stabilized and noncatalytic, lean Premixed, atmospheric Combustion of methane. Experiments were in a tubular, adiabatic flow reactor with catalytically active or inactive honeycomb structures and with adiabatic flame temperatures from 1300° to 1500°C. In order to study the effect of catalytic conversion on NO(x) formation, the fraction of fuel converted within the catalyst was varied within the range of 0% (corresponding to noncatalytic Combustion) to 100%. In all cases, complete burnout is accomplished in a subsequent, homogeneous Combustion zone, NO(x) emissions were computed with combinations of ideal reactor models such as one dimensional flames, perfectly stirred and plug flow reactors, and catalytic oxidation reactors (Cat). In the Cat model, it is assumed that no intermediates and no NO(x) are formed, whereas for the homogeneous Combustion models a detailed chemical reaction mechanism including NO(x) formation is employed. The NO(x) emissions of catalytically stabilized, Premixed Combustion are remarkably lower than those of noncatalytic, Premixed Combustion and depend on the fraction of catalytically converted fuel. The higher this fraction, the lower are the NO(x) emissions. The calculated results compare well with the experimental data, hence validating the modeling assumptions.
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Catalytic stabilization of lean Premixed Combustion: method for improving NO sub x emissions
Combustion and Flame, 1996Co-Authors: Andreas Schlegel, W Weisenstein, Paul Benz, T Griffin, Henning BockhornAbstract:An experimental and numerical investigation is reported of NO sub x emissions from both catalytically stabilized and noncatalytic, lean Premixed, atmospheric Combustion of methane. Experiments were in a tubular, adiabatic flow reactor with catalytically active or inactive honeycomb structures and with adiabatic flame temperatures from 1300 degree to 1500 degree C. In order to study the effect of catalytic conversion on NO sub x formation, the fraction of fuel converted within the catalyst was varied within the range of 0% (corresponding to noncatalytic Combustion) to 100%. In all cases, complete burnout is accomplished in a subsequent, homogeneous Combustion zone. NO sub x emissions were computed with combinations of ideal reactor models such as one-dimensional flames, perfectly stirred and plug flow reactors, and catalytic oxidation reactors (Cat). In the Cat model, it is assumed that no intermediates and no NO sub x are formed, whereas for the homogeneous Combustion models a detailed chemical reaction mechanism including NO sub x formation is employed. The NO sub x emissions of catalytically stabilized, Premixed Combustion are remarkably lower than those of noncatalytic, Premixed Combustion and depend on the fraction of catalytically converted fuel. The higher this fraction, the lower are the NO sub x emissions. The calculated results compare well with the experimental data, hence validating the modeling assumptions. (Author abstract) 24 Refs.
Thomas Sattelmayer - One of the best experts on this subject based on the ideXlab platform.
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A spectral model for the sound pressure from turbulent Premixed Combustion
Proceedings of the Combustion Institute, 2007Co-Authors: C. Hirsch, J. Wäsle, A. Winkler, Thomas SattelmayerAbstract:We present a model for the spectral distribution of heat release in turbulent Premixed Combustion and show how it can be applied to the calculation of sound pressure. Experimental data are presented from Premixed swirling jet flames at three thermal powers, three equivalence ratios and for a variation of the fuel composition. A simultaneous PIV-LIF technique was used to determine the spatial spectra of the progress variable variance and turbulence kinetic energy. It was found that the spectra of progress variable correspond well with model spectra derived for homogeneous turbulence. Mapping these Eulerian spatial spectra to Lagrangian time spectra, we show how the integral frequency spectrum of heat release fluctuation can be computed using local values of time averaged heat release rate density, turbulence kinetic energy and turbulence lengthscale. With these the spectral distribution of sound pressure from turbulent Premixed Combustion is calculated and compared with measured sound pressure spectra. Very good quantitative agreement is obtained in all cases. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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A spectral model for the sound pressure from turbulent Premixed Combustion
Proceedings of the Combustion Institute, 2006Co-Authors: C. Hirsch, J. Wäsle, A. Winkler, Thomas SattelmayerAbstract:Abstract We present a model for the spectral distribution of heat release in turbulent Premixed Combustion and show how it can be applied to the calculation of sound pressure. Experimental data are presented from Premixed swirling jet flames at three thermal powers, three equivalence ratios and for a variation of the fuel composition. A simultaneous PIV-LIF technique was used to determine the spatial spectra of the progress variable variance and turbulence kinetic energy. It was found that the spectra of progress variable correspond well with model spectra derived for homogeneous turbulence. Mapping these Eulerian spatial spectra to Lagrangian time spectra, we show how the integral frequency spectrum of heat release fluctuation can be computed using local values of time averaged heat release rate density, turbulence kinetic energy and turbulence lengthscale. With these the spectral distribution of sound pressure from turbulent Premixed Combustion is calculated and compared with measured sound pressure spectra. Very good quantitative agreement is obtained in all cases.
D. Veynante - One of the best experts on this subject based on the ideXlab platform.
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Experimental Study of the Filtered Progress Variable Approach for LES of Premixed Combustion
Fluid Mechanics and Its Applications, 2020Co-Authors: R. Knikker, D. VeynanteAbstract:A filtered progress variable approach for large eddy simulation of Premixed Combustion is investigated using experimental data obtained in a V-shaped turbulent flame. The filtered flame surface density, related to the consumption rate, is extracted from visualizations of the instantaneous flame front. Modeling of the subgrid-scale contribution to the flame surface density is discussed and a new model, based on the curvature of the resolved flame, is proposed.
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a filtered tabulated chemistry model for les of Premixed Combustion
Combustion and Flame, 2010Co-Authors: Benoit Fiorina, Ronan Vicquelin, Pierre Auzillon, Nasser Darabiha, Olivier Gicquel, D. VeynanteAbstract:A new modeling strategy called F-TACLES (Filtered Tabulated Chemistry for Large Eddy Simulation) is developed to introduce tabulated chemistry methods in Large Eddy Simulation (LES) of turbulent Premixed Combustion. The objective is to recover the correct laminar flame propagation speed of the filtered flame front when subgrid scale turbulence vanishes as LES should tend toward Direct Numerical Simulation (DNS). The filtered flame structure is mapped using 1-D filtered laminar Premixed flames. Closure of the filtered progress variable and the energy balance equations are carefully addressed in a fully compressible formulation. The methodology is first applied to 1-D filtered laminar flames, showing the ability of the model to recover the laminar flame speed and the correct chemical structure when the flame wrinkling is completely resolved. The model is then extended to turbulent Combustion regimes by including subgrid scale wrinkling effects in the flame front propagation. Finally, preliminary tests of LES in a 3-D turbulent Premixed flame are performed.
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a thickened flame model for large eddy simulations of turbulent Premixed Combustion
Physics of Fluids, 2000Co-Authors: Olivier Colin, D. Veynante, F Ducros, Thierry PoinsotAbstract:A subgrid scale model for large eddy simulations of turbulent Premixed Combustion is developed and validated. The approach is based on the concept of artificially thickened flames, keeping constant the laminar flame speed sl0. This thickening is simply achieved by decreasing the pre-exponential factor of the chemical Arrhenius law whereas the molecular diffusion is enhanced. When the flame is thickened, the Combustion–turbulence interaction is affected and must be modeled. This point is investigated here using direct numerical simulations of flame–vortex interactions and an efficiency function E is introduced to incorporate thickening effects in the subgrid scale model. The input parameters in E are related to the subgrid scale turbulence (velocity and length scales). An efficient approach, based on similarity assumptions, is developed to extract these quantities from the resolved velocity field. A specific operator is developed to exclude the dilatational part of the velocity field from the estimation of...
Andreas Schlegel - One of the best experts on this subject based on the ideXlab platform.
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Catalytic stabilization of lean Premixed Combustion: Method for improving NOx emissions
Combustion and Flame, 1996Co-Authors: Andreas Schlegel, W Weisenstein, T Griffin, Peter Benz, Henning BockhornAbstract:An experimental and numerical investigation is reported of NO{sub x} emissions from both catalytically stabilized and noncatalytic, lean Premixed, atmospheric Combustion of methane. Experiments were in a tubular, adiabatic flow reactor with catalytically active or inactive honeycomb structures and with adiabatic flame temperatures from 1,300 to 1,500 C. In order to study the effect of catalytic conversion on NO{sub x} formation, the fraction of fuel converted within the catalyst was varied within the range of 0% (corresponding to noncatalytic Combustion) to 100%. In all cases, complete burnout is accomplished in a subsequent, homogeneous Combustion zone. NO{sub x} emissions were computed with combinations of ideal reactor models such as one-dimensional flames, perfectly stirred and plug flow reactors, and catalytic oxidation reactors (Cat). In the Cat model, it is assumed that no intermediates and no NO{sub x} are formed, whereas for the homogeneous Combustion models a detailed chemical reaction mechanism including NO{sub x} formation is employed. The NO{sub x} emissions of catalytically stabilized, Premixed Combustion are remarkably lower than those of noncatalytic, Premixed Combustion and depend on the fraction of catalytically converted fuel. The higher this fraction, the lower are the NO{sub x} emissions. The calculated results compare well with the experimentalmore » data, hence validating the modeling assumptions.« less
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Catalytic stabilization of lean Premixed Combustion: Method for improving NO(x) emissions
Combustion and Flame, 1996Co-Authors: Andreas Schlegel, W Weisenstein, Paul Benz, T Griffin, Henning BockhornAbstract:An experimental and numerical investigation is reported of NO(x) emissions from both catalytically stabilized and noncatalytic, lean Premixed, atmospheric Combustion of methane. Experiments were in a tubular, adiabatic flow reactor with catalytically active or inactive honeycomb structures and with adiabatic flame temperatures from 1300° to 1500°C. In order to study the effect of catalytic conversion on NO(x) formation, the fraction of fuel converted within the catalyst was varied within the range of 0% (corresponding to noncatalytic Combustion) to 100%. In all cases, complete burnout is accomplished in a subsequent, homogeneous Combustion zone, NO(x) emissions were computed with combinations of ideal reactor models such as one dimensional flames, perfectly stirred and plug flow reactors, and catalytic oxidation reactors (Cat). In the Cat model, it is assumed that no intermediates and no NO(x) are formed, whereas for the homogeneous Combustion models a detailed chemical reaction mechanism including NO(x) formation is employed. The NO(x) emissions of catalytically stabilized, Premixed Combustion are remarkably lower than those of noncatalytic, Premixed Combustion and depend on the fraction of catalytically converted fuel. The higher this fraction, the lower are the NO(x) emissions. The calculated results compare well with the experimental data, hence validating the modeling assumptions.
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Catalytic stabilization of lean Premixed Combustion: method for improving NO sub x emissions
Combustion and Flame, 1996Co-Authors: Andreas Schlegel, W Weisenstein, Paul Benz, T Griffin, Henning BockhornAbstract:An experimental and numerical investigation is reported of NO sub x emissions from both catalytically stabilized and noncatalytic, lean Premixed, atmospheric Combustion of methane. Experiments were in a tubular, adiabatic flow reactor with catalytically active or inactive honeycomb structures and with adiabatic flame temperatures from 1300 degree to 1500 degree C. In order to study the effect of catalytic conversion on NO sub x formation, the fraction of fuel converted within the catalyst was varied within the range of 0% (corresponding to noncatalytic Combustion) to 100%. In all cases, complete burnout is accomplished in a subsequent, homogeneous Combustion zone. NO sub x emissions were computed with combinations of ideal reactor models such as one-dimensional flames, perfectly stirred and plug flow reactors, and catalytic oxidation reactors (Cat). In the Cat model, it is assumed that no intermediates and no NO sub x are formed, whereas for the homogeneous Combustion models a detailed chemical reaction mechanism including NO sub x formation is employed. The NO sub x emissions of catalytically stabilized, Premixed Combustion are remarkably lower than those of noncatalytic, Premixed Combustion and depend on the fraction of catalytically converted fuel. The higher this fraction, the lower are the NO sub x emissions. The calculated results compare well with the experimental data, hence validating the modeling assumptions. (Author abstract) 24 Refs.
Pascale Domingo - One of the best experts on this subject based on the ideXlab platform.
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LES of Partially Premixed Combustion
IUTAM Symposium on Turbulent Mixing and Combustion, 2020Co-Authors: Luc Vervisch, Pascale DomingoAbstract:Numerical studies devoted to partially Premixed Combustion are first reviewed. Then a Large Eddy Simulation procedure is proposed for these flames when they develop in turbulent flows. The corresponding subgrid Combustion modeling is tested for the case of a turbulent lifted-flame.
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Hybrid transported-tabulated chemistry for partially Premixed Combustion
Computers & Fluids, 2019Co-Authors: Bastien Duboc, Guillaume Ribert, Pascale DomingoAbstract:Abstract The integration of Combustion chemistry into a fully compressible numerical solver is presently achieved using the hybrid transported-tabulated chemistry (HTTC). With HTTC, the main species are transported while most minor species are tabulated, which means that differences with a fully transported chemistry (FTC) solver are limited and concern mainly table reading for minor species. The implementation steps of HTTC are given in detail and an optimization of the code is proposed by tabulating the properties of the pure species as well as the reaction rates of the elementary reactions as a function of the temperature to speed up simulations. The original version of HTTC, validated for Premixed Combustion, has been also extended to partially Premixed Combustion by adding a prolongation of the lookup table for minor species outside the flammability limits. Two strategies are proposed and evaluated on a methane / air edge flame featuring a very high mixing fraction gradient. The results agree favorably by comparison with a reference flame simulated with a detailed chemistry. As the minor species are no longer transported with the flow using HTTC, the calculation cost is found divided by about 5 compared to the FTC solver.
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multidimensional flamelet generated manifolds for partially Premixed Combustion
Combustion and Flame, 2010Co-Authors: Phucdanh Nguyen, Luc Vervisch, Vallinayagam Subramanian, Pascale DomingoAbstract:Flamelet-generated manifolds have been restricted so far to Premixed or diffusion flame archetypes, even though the resulting tables have been applied to nonPremixed and partially Premixed flame simulations. By using a projection of the full set of mass conservation species balance equations into a restricted subset of the composition space, unsteady multidimensional flamelet governing equations are derived from first principles, under given hypotheses. During the projection, as in usual one-dimensional flamelets, the tangential strain rate of scalar isosurfaces is expressed in the form of the scalar dissipation rates of the control parameters of the multidimensional flamelet-generated manifold (MFM), which is tested in its five-dimensional form for partially Premixed Combustion, with two composition space directions and three scalar dissipation rates. It is shown that strain-rate-induced effects can hardly be fully neglected in chemistry tabulation of partially Premixed Combustion, because of fluxes across iso-equivalence-ratio and iso-progress-of-reaction surfaces. This is illustrated by comparing the 5D flamelet-generated manifold with one-dimensional Premixed flame and unsteady strained diffusion flame composition space trajectories. The formal links between the asymptotic behavior of MFM and stratified flame, weakly varying partially Premixed front, triple-flame, Premixed and nonPremixed edge flames are also evidenced.
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dns analysis of partially Premixed Combustion in spray and gaseous turbulent flame bases stabilized in hot air
Combustion and Flame, 2005Co-Authors: Pascale Domingo, Luc Vervisch, Julien ReveillonAbstract:Direct numerical simulations of weakly turbulent-lifted flame bases are examined in the case of both gaseous and spray fuel jet injection. Simplified transport properties and an adjustable single-step chemistry that matches the flame response to equivalence ratio are used. The flames are stabilized within a coflowing stream of heated air. The properties of the zone where burning starts are found to strongly depend on the type of fuel injection. The gaseous flame base is essentially composed of an edge flame, with a large contribution of partially Premixed Combustion. This partially Premixed flame takes two different forms, a nearly stoichiometric propagating kernel and a rich trailing flame whose burning rate is diffusion controlled. The rich Premixed flame is parallel to the stoichiometric line, along which a diffusion flame burns the fuel left by this rich trailing flame, up to the very leading edge of the flame base. In the spray case, a nonnegligible amount of oxidizer is entrained within the dilute spray, also leading to an important contribution of partially Premixed burning. However, diffusion and Premixed burning are found more distributed in space in the spray case than with gaseous injection. A progress variable that is generalized to partially Premixed Combustion is discussed and the relative contributions of the terms of its balance equation are analyzed from the DNS. A flame partitioning into Premixed and diffusion types is then examined and the stabilization zone is decomposed into basic flame prototypes. A subgrid scale flame decomposition is further discussed from a direct filtering of DNS and some a priori tests of subgrid scale modeling are reported.
