Modeling of NOx Formation in Circular Laminar Jet Flames PDF Download
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Author: Vivek Siwatch
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Emissions of oxides of nitrogen (NOx) from combustion devices is a topic of tremendous current importance. The bulk of the review of NOx emissions has been in the field of turbulent jet flames. However laminar jet flames have provided much insight into the relative importance of NOx reaction pathways in non premixed combustion for various flame conditions. The existing models include detailed chemistry kinetics for various species involved in the flame. These detailed models involve very complex integration of hundreds of chemical reactions of various species and their intermediates. Hence such models are highly time consuming and also normally involve heavy computational costs. This work proposes a numerical model to compute the total production of NOx in a non-premixed isolated circular laminar jet flame. The jet consists of the fuel rich inner region and the O2 rich outer region. The model estimates both thermal NOx and prompt NOx assuming single step kinetics for NOx formation and a thin flame model. Further the amount of air entrainment by jet depends upon the Sc number of fuel. The higher the Sc number, the higher is the air entrained which lowers the flame temperature and hence NOx formation. With increasing Sc number, flame volume increases which leads to an increase in the NOx formation. The effect of the Sc number variation on the net production of NOx and flame structure is also investigated. The effect of equilibrium chemistry for CO2 - CO + 1/2 O2 and H2O - H2 +1/2 O2 on total NOx emission is studied. Also the effect of both CO2 and H2O equilibrium is considered simultaneously and the net NOx formation for propane is 45 ppm. The splitbetween pre-flame and post-flame regions is also investigated. For Propane, 96% of NOx emissions occur in the pre-flame region and about 4% in the post-flame region. The model predictions are compared with experimental values of NOx missions reported elsewhere.
Author: Vivek Siwatch
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Emissions of oxides of nitrogen (NOx) from combustion devices is a topic of tremendous current importance. The bulk of the review of NOx emissions has been in the field of turbulent jet flames. However laminar jet flames have provided much insight into the relative importance of NOx reaction pathways in non premixed combustion for various flame conditions. The existing models include detailed chemistry kinetics for various species involved in the flame. These detailed models involve very complex integration of hundreds of chemical reactions of various species and their intermediates. Hence such models are highly time consuming and also normally involve heavy computational costs. This work proposes a numerical model to compute the total production of NOx in a non-premixed isolated circular laminar jet flame. The jet consists of the fuel rich inner region and the O2 rich outer region. The model estimates both thermal NOx and prompt NOx assuming single step kinetics for NOx formation and a thin flame model. Further the amount of air entrainment by jet depends upon the Sc number of fuel. The higher the Sc number, the higher is the air entrained which lowers the flame temperature and hence NOx formation. With increasing Sc number, flame volume increases which leads to an increase in the NOx formation. The effect of the Sc number variation on the net production of NOx and flame structure is also investigated. The effect of equilibrium chemistry for CO2 - CO + 1/2 O2 and H2O - H2 +1/2 O2 on total NOx emission is studied. Also the effect of both CO2 and H2O equilibrium is considered simultaneously and the net NOx formation for propane is 45 ppm. The splitbetween pre-flame and post-flame regions is also investigated. For Propane, 96% of NOx emissions occur in the pre-flame region and about 4% in the post-flame region. The model predictions are compared with experimental values of NOx missions reported elsewhere.
Author: Weizhen Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 576
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Author: Chaoqun Liu
Publisher:
ISBN:
Category : Multigrid methods (Numerical analysis)
Languages : en
Pages : 43
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An implicit multigrid time-stepping technique is applied to the laminar diffusion methane-air combustion with detailed description of NOx formation in a 3-D channel. The chemical reaction model is assumed to have 48 species and 229 finite-rate, reversible reaction steps. The computation requires about 90 time steps to reduce the residual by 3 orders of magnitude on a 34 x 18 x 18 grid.
Author:
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ISBN:
Category :
Languages : en
Pages : 5
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This paper reports on a combined experimental and modeling investigation of NOx formation in nitrogen-diluted laminar methane diffusion flames seeded with ammonia. The methane-ammonia mixture is a surrogate for biomass fuels which contain significant fuel-bound nitrogen. The experiments use flue-gas sampling to measure the concentration of stable species in the exhaust gas, including NO, O2, CO, and CO2. The computations evolve a two-dimensional low Mach number model using a solution-adaptive projection algorithm to capture fine-scale features of the flame. The model includes detailed thermodynamics and chemical kinetics, differential diffusion, buoyancy, and radiative losses. The model shows good agreement with the measurements over the full range of experimental NH3 seeding amounts. As more NH3 is added, a greater percentage is converted to N2 rather than to NO. The simulation results are further analyzed to trace the changes in NO formation mechanisms with increasing amounts of ammonia in the fuel.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721129454
Category :
Languages : en
Pages : 110
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Book Description
This is the final report of a research program considering interactions between flow and soot properties within laminar diffusion flames. Laminar diffusion flames were considered because they provide model flame systems that are far more tractable for theoretical and experimental studies than more practical turbulent diffusion flames. In particular, understanding the transport and chemical reaction processes of laminar flames is a necessary precursor to understanding these processes in practical turbulent flames and many aspects of laminar diffusion flames have direct relevance to turbulent diffusion flames through application of the widely recognized laminar flamelet concept of turbulent diffusion flames. The investigation was divided into three phases, considering the shapes of nonbuoyant round laminar jet diffusion flames in still air, the shapes of nonbuoyant round laminar jet diffusion flames in coflowing air, and the hydrodynamic suppression of soot formation in laminar diffusion flames. Dai, Z. and Lin, K.-C. and Sunderland, P. B. and Xu, F. and Faeth, G. M. Glenn Research Center NAG3-661
Author: Feng Tao
Publisher:
ISBN: 9789172912489
Category :
Languages : en
Pages : 144
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Author: N. K. Rizk
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 702
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Author: Meghdad Saffaripour
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Turbulent hydrogen diffusion flames diluted with nitrogen are currently being studied to assess their ability to achieve the DOE Turbine Program's aggressive emissions goal of 2 ppm NOx in a hydrogen-fueled IGCC gas turbine combustor. Since the unstrained adiabatic flame temperatures of these diluted flames are not low enough to eliminate thermal NOx formation the focus of the current work is to study how the effects of flame residence time and global flame strain can be used to help achieve the stated NOx emissions goal. Dry NOx measurements are presented as a function of jet diameter nitrogen dilution and jet velocity for a turbulent hydrogen/nitrogen jet issuing from a thin-lipped tube in an atmospheric pressure combustor. The NOx emission indices from these experiments are normalized by the flame residence time to ascertain the effects of global flame strain and fuel Lewis Number on the NOx emissions. In addition dilute hydrogen diffusion flame experiments were performed in a high-pressure combustor at 2 4 and 8 atm. The NOx emission data from these experiments are discussed as well as the results from a Computational Fluid Dynamics modeling effort currently underway to help explain the experimental data.
