Advanced

Numerical Modeling of Turbulent Combustion and Flame Spread

Yan, Zhenghua LU (1999)
Abstract
Theoretical models have been developed to address several important aspects of numerical modeling of turbulent combustion and flame spread. The developed models include a pyrolysis model for charring and non-charring solid materials, a fast narrow band radiation property evaluation model (FASTNB) and a turbulence model for buoyant flow and flame.



In the pyrolysis model, a completely new algorithm has been proposed, where a moving dual mesh concept was developed and implemented. With this new concept, it provides proper spatial resolution for both temperature and density and automatically considers the regression of the surface of the non-charring solid material during its pyrolysis. It is simple, very efficient and... (More)
Theoretical models have been developed to address several important aspects of numerical modeling of turbulent combustion and flame spread. The developed models include a pyrolysis model for charring and non-charring solid materials, a fast narrow band radiation property evaluation model (FASTNB) and a turbulence model for buoyant flow and flame.



In the pyrolysis model, a completely new algorithm has been proposed, where a moving dual mesh concept was developed and implemented. With this new concept, it provides proper spatial resolution for both temperature and density and automatically considers the regression of the surface of the non-charring solid material during its pyrolysis. It is simple, very efficient and applicable to both charring and non-charring materials.



FASTNB speeds up significantly the evaluation of narrow band spectral radiation properties and thus provides a potential of applying narrow band model in numerical simulations of practical turbulent combustion.



The turbulence model was developed to improve the consideration of buoyancy effect on turbulence and turbulent transport. It was found to be simple, promising and numerically stable. It has been tested against both plane and axisymmetric thermal plumes and an axisymmetric buoyant diffusion flame. When compared with the widely used standard buoyancy-modified model, it gives significant improvement on numerical results.



These developed models have been fully incorporated into CFD (Computational Fluid Dynamics) code and coupled with other CFD sub-models, including the DT (Discrete Transfer) radiation model, EDC (Eddy Dissipation Concept) combustion model, flamelet combustion model, various soot models and transpired wall function. Comprehensive numerical simulations have been carried out to study soot formation and oxidation in turbulent buoyant diffusion flames, flame heat transfer and flame spread in fires. The gas temperature and velocity, soot volume fraction, wall surface temperature, char depth, radiation and convection heat fluxes, and heat release rate were calculated and compared with experimental measurements.



In addition, to provide comprehensive data for comparison, experiments on room corner fire growth were undertaken, where the gas temperature, solid fuel surface temperature, radiative heat flux, char depth and heat release rate were all measured. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Prof. Magnussen, Björn, SINTEF, The Norwegian Fire Research Lab (NBL), N-7034 TRONDHEIM, Norway
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Technological sciences, Flame Spread, Pyrolysis, Heat Transfer, Radiation, CFD, Turbulent Combustion Modeling, Teknik
pages
186 pages
publisher
Center of Combustion Science and Technology, and Department of Fire Safety Engineering, Lund University, Box 118, S-22100, Lund, Sweden,
defense location
John Ericssons väg 1, Hörsal A
defense date
1999-03-05 10:15
ISSN
1102-8246
language
English
LU publication?
yes
id
bdeb8efd-7502-498c-a31a-f15a04ba7176 (old id 39372)
date added to LUP
2007-08-01 14:24:17
date last changed
2016-09-19 08:44:54
@phdthesis{bdeb8efd-7502-498c-a31a-f15a04ba7176,
  abstract     = {Theoretical models have been developed to address several important aspects of numerical modeling of turbulent combustion and flame spread. The developed models include a pyrolysis model for charring and non-charring solid materials, a fast narrow band radiation property evaluation model (FASTNB) and a turbulence model for buoyant flow and flame.<br/><br>
<br/><br>
In the pyrolysis model, a completely new algorithm has been proposed, where a moving dual mesh concept was developed and implemented. With this new concept, it provides proper spatial resolution for both temperature and density and automatically considers the regression of the surface of the non-charring solid material during its pyrolysis. It is simple, very efficient and applicable to both charring and non-charring materials.<br/><br>
<br/><br>
FASTNB speeds up significantly the evaluation of narrow band spectral radiation properties and thus provides a potential of applying narrow band model in numerical simulations of practical turbulent combustion.<br/><br>
<br/><br>
The turbulence model was developed to improve the consideration of buoyancy effect on turbulence and turbulent transport. It was found to be simple, promising and numerically stable. It has been tested against both plane and axisymmetric thermal plumes and an axisymmetric buoyant diffusion flame. When compared with the widely used standard buoyancy-modified model, it gives significant improvement on numerical results.<br/><br>
<br/><br>
These developed models have been fully incorporated into CFD (Computational Fluid Dynamics) code and coupled with other CFD sub-models, including the DT (Discrete Transfer) radiation model, EDC (Eddy Dissipation Concept) combustion model, flamelet combustion model, various soot models and transpired wall function. Comprehensive numerical simulations have been carried out to study soot formation and oxidation in turbulent buoyant diffusion flames, flame heat transfer and flame spread in fires. The gas temperature and velocity, soot volume fraction, wall surface temperature, char depth, radiation and convection heat fluxes, and heat release rate were calculated and compared with experimental measurements.<br/><br>
<br/><br>
In addition, to provide comprehensive data for comparison, experiments on room corner fire growth were undertaken, where the gas temperature, solid fuel surface temperature, radiative heat flux, char depth and heat release rate were all measured.},
  author       = {Yan, Zhenghua},
  issn         = {1102-8246},
  keyword      = {Technological sciences,Flame Spread,Pyrolysis,Heat Transfer,Radiation,CFD,Turbulent Combustion Modeling,Teknik},
  language     = {eng},
  pages        = {186},
  publisher    = {Center of Combustion Science and Technology, and Department of Fire Safety Engineering, Lund University, Box 118, S-22100, Lund, Sweden,},
  school       = {Lund University},
  title        = {Numerical Modeling of Turbulent Combustion and Flame Spread},
  year         = {1999},
}