Fluid Mechanics Aspects of Fire and Smoke Dynamics in Enclosures
Auteurs : Merci Bart, Beji Tarek
Introduction
The candle flame
The importance of chemistry, heat transfer and fluid mechanics in fires
Chemistry
Heat transfer
Fluid mechanics and turbulence
Combustion and fire
Fire modelling
Turbulent flows with chemical reaction
Fluid properties – state properties – mixtures
Fluid properties
Mass density
Viscosity
Specific heat
Conduction coefficient
Diffusion coefficient
State properties
Pressure
Temperature
Internal energy
Enthalpy
Entropy
Equation of state
Mixtures
Combustion
Chemical reaction
Thermodynamics
Enthalpy
Temperature
Chemical kinetics
Transport equations
Conservation of mass
Momentum equations
Conservation of energy
Convection
Conduction
Radiation
Transport of species
Mixture fraction
Bernoulli
Hydrostatics
Buoyancy
Non-dimensional numbers
Fluid properties
Flow properties
Scaling laws
Turbulence
Reynolds number
Reynolds averaging
Turbulence modeling
Energy cascade
Turbulent scales
Turbulence modelling
Boundary layer flow
Internal flows – pressure losses
Entrainment
Impinging flow
Evaporation
Pyrolysis
Turbulent flames and fire plumes
Flammability
Flammability limits – threshold temperature
Addition of gases
Flammability of liquid fuels
Premixed flames
Laminar premixed flame structure
Laminar burning velocity
The effect of turbulence
Diffusion flames
Laminar diffusion flame structure
The effect of turbulence
Jet flames
Extinction of flames
Premixed flames
Diffusion flames
Fire plumes
Free fire plumes
Average flame height
Temperature evolution
Kelvin-Helmholtz instability
The effect of wind 1
Transition from buoyancy-driven to momentum-driven jets
Correlations
Interaction with non-combustible walls
Interaction with non-combustible ceiling
The effect of ventilation
Reduced oxygen at ambient temperature
Oxygen-enriched fire plumes
Vitiated conditions
Fire whirls
Flame spread
Flame spread velocity – a heat balance
Opposed flow flame spread over a thermally thick fuel
Opposed flow flame spread over a thermally thin fuel
Concurrent flow flame spread over a thermally thick fuel
Concurrent flow flame spread over a thermally thin fuel
Gas phase phenomena
Horizontal surface
Natural convection
Concurrent airflow
Counter-current airflow
Vertical surface
Inclined surface
Parallel vertical plates configuration
Corner configuration
Smoke plumes
Introduction
Axisymmetric plume
Theory and mathematical modelling
Model development under the Boussinesq approximation
Experiments
Line plume
Description of the configuration
Conservation equations
Experimental studies
Transition from line to axisymmetric plume
Wall and corner interaction with plumes
Detailed example: line plume bounded by an adiabatic wall
General correlations for wall and corner configurations
Interaction of a plume with a ceiling
Description of a ceiling-jet
Alpert’s Integral model
Simplified correlations
Additional considerations
Smoke layer build-up in a room
Balcony and window spill plumes
Balcony spill plumes
Window plumes
Scaling laws and buoyant releases
Exercises
Analytical solution for the Line plume problem
Design of a reduced-scale helium/air mixture experiment of a car fire in a tunnel
Fire and smoke dynamics in enclosures
Some fundamentals on flows through openings
Growing fire
Fire source
Fuel-controlled growing fire
Ventilation-controlled growing fire
Smoke dynamics
Flows through openings
Horizontal openings
Vertical openings
Natural and mechanical ventilation
Zone modeling
Fully developed fire
Fire source
Smoke dynamics
Flows through openings
Horizontal openings
Vertical openings
Natural and mechanical ventilation
Zone modeling
Pulsating fire
Backdraft
Fires in well-confined enclosures
Driving forces in smoke and heat control
Buoyancy – the stack effect
Natural stack effect
Fire-induced buoyancy
Pressurization
Natural ventilation
Mechanical ventilation
Vertical ventilation
Horizontal ventilation
Tunnels
Other underground structures
Smoke extraction
The effect of wind
Positive pressure ventilation
Air curtains
Exercises
Impact of water on fire and smoke dynamics
Individual evaporating water droplet
Heat and mass transfer
Flow equations
Sprays of water droplets
Characterization of sprays
Region near the nozzle
Water flow rate
Droplet size and velocity distribution
Spray cone angle
Spray-induced momentum
Water curtains
Heat absorption by water
Interaction of water with smoke
Sprinkler and water mist sprays
Water curtain
Fire fighting
Interaction of water with flames
Water as fire suppressant
Introduction to fire modelling in computational fluid dynamics
Introduction
Laminar diffusion flames
Instantaneous transport equations
Combustion modelling
Infinitely fast chemistry
Finite-rate chemistry
Turbulence modelling
DNS
RANS
LES
Turbulent non-premixed combustion
Infinitely fast chemistry with a presumed PDF
Flame sheet model
Chemical equilibrium model
Steady Laminar Flamelet Modelling (SLFM)
Finite rate chemistry
Eddy Break-Up (EBU) model and Eddy Dissipation Model (EDM)
Eddy Dissipation Concept (EDC)
Conditional Moment Closure (CMC)
Transported PDF models
Radiation modelling
Models for radiative transfer
The P-1 Radiation Model
The Finite Volume Method (FVM)
Models for the absorption coefficient
Turbulence Radiation Interaction (TRI)
The soot problem
Soot nature, morphology and general description of its chemistry
Importance of soot modelling
Sootiness and radiation
Interaction of soot with carbon monoxide
The sootiness of fuels
The laminar smoke point height
The Threshold Sooting Index (TSI)
Soot modelling
Laminar flames
Turbulent flames
Basics of numerical discretization
Discretization schemes
Description of a 1-D example
Explicit scheme
Implicit scheme
Initial and boundary conditions
Properties of numerical methods
Consistency
Stability
Convergence
Conservativeness
Boundedness
Pressure-velocity coupling
The importance of the computational mesh
Boundary conditions
Fire source
Gaseous fuel
Liquid fuel
Solid fuel
Turbulence inflow boundary conditions
Walls
Velocity
Temperature
Open boundary conditions (natural ventilation)
Velocity and scalars
Pressure
Mechanical ventilation and pressure effects
Fixed velocity
Fan curves and pressure effects
Examples of cfd simulations
Non-reacting buoyant plume
Test case description
Simulation set-up
Results
Hot air plume impinging on a horizontal plate
Test case description
Simulation set-up
Results
Free-burning turbulent buoyant flame
Test case description
Simulation set-up
Results
Over-ventilated enclosure fire
Test case description
Simulation set-up and Results
Interaction of a hot air plume with a water spray
Test case description
Simulation set-up
Results
Underventilated enclosure fire with mechanical ventilation
Test case description
Simulation set-up
Results
Fire spread modelling
References
Subject Index
Prof. Bart Merci obtained his PhD, entitled ‘Numerical Simulation and Modelling of Turbulent Combustion’, at the Faculty of Engineering at Ghent University in the year 2000. As postdoctoral fellow of the Fund for Scientific Research – Flanders (FWOVlaanderen), he specialized in numerical simulations of turbulent non-premixed combustion, with focus on turbulence – chemistry interaction and turbulence – radiation interaction. He reoriented his research towards fire safety science, taking the fluid mechanics aspects as central research topic. He became lecturer at Ghent University in 2004 and Full Professor in 2012. He is the head of the research unit ‘Combustion, Fire and Fire Safety’ in the Department of Flow, Heat and Combustion Mechanics. Since 2009, Bart Merci coordinates the ‘International Master of Science in Fire Safety Engineering’, with Lund University and The University of Edinburgh as partners. He has been the President of The Belgian Section of The Combustion Institute since 2009 and Associate Editor of Fire Safety Journal since 2010. He is member of the Executive Committee of the International Association for Fire Safety Science. He is author of more than 100 journal papers.
Dr. Tarek Beji obtained his PhD, entitled "Theoretical and Experimental Investigation on Soot and Radiation in Fires", at the University of Ulster in 2009. He joined Ghent University in 2011 as a post-doctoral researcher in the department of Flow, Heat and Combustion Mechanics and worked on the novel topic of fire forecasting. Since 2012 he has been very active in a large international collaborative research program called PRISME, focusing on mechanical ventilation and fire dynamics in nuclear facilities. Since he joined Ghent University he participated actively in the 'International Master of Science in Fire Safety Engineering' as lecturer and member of the program steering committee.
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Ajouter au panierThèmes de Fluid Mechanics Aspects of Fire and Smoke Dynamics in... :
Mots-clés :
Smoke Layer; Scalar Dissipation Rate; Mixture Fraction; Standard Formation Enthalpy; Pre-heat Zone; Laminar Burning Velocity; 2αt X2; Fire Heat Release Rate; Spray Envelope; Adiabatic Flame Temperature; Mass Flow Rate; HRR; Smoke Plume; Enclosure Fire; Fire Source; TRI; Water Mist Systems; Preheat Zone; Air Curtain; Smoke Extraction; Soot Mass Fraction; Line Plume; Premixed Combustion; Premixed Flames; Fuel Mass Loss Rate