University of Florence - Italy
M. Cerutti, L. Mangani
HTC GroupDepartment of Energy
Engineering“Sergio Stecco”
Via Santa Marta, 3 - 50139 Florence - Italy
e-mail: [email protected]
OpenFOAM Workshop July 10-11 2008 - Milan, Italy
RADIATIVE AND COMBUSTION MODELING FOR
TURBOMACHINERY APPLICATIONS
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy2
Outline
Introduction to reactive CFD analyses requirements in industrial Gas Turbine applications
Objective of the workOpen-FOAM upgrade
o Development of a CFD suite for gas turbine combustion simulations
Turbulent combustion and radiative heat transfer models consideredImplementation
Validation test casesTurbulent premixed and non premixed gaseous flames
Radiation benchmark solutions
Jet flame with soot and radiative heat transfer
Conclusions and acknowledgements
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy3
Introduction: CFD in Gas Turbine applications
Reactive CFD has become integral part of gas turbine engines designNeed to model several physical phenomena on complex geometries
o Turbulent mixing
o Chemical reactions
o Spray
o Radiative and convective heat transfer
Steady RANS simulations still represent the fundamental tests during the main part of design flow
Reactive LES is still limited to very late design steps or advanced analyses
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy4
Objective of the work: OpenFOAM upgrading
OpenFOAMreleased version
solvers
turbulence models
thermophysical models
combustion models
radiation models
• SIMPLE – All mach
• Conjugate
• Pseudo-transient
• Low-RE compressible
• Advanced Wall function
• External look-up table−Flamelet models
• Progress variable - TFC
• Level-set – G-equation
• Non premixed β-PDF
• P1
• Finite Volume Method
• Gray gasOpenFOAMupgraded version
boundary conditions• Generic grid interface
GT2008-51117GT2008-51118
• Zonal Method
• Weighted Sum of Gray Gases
• EDC
• Liquid fuel
development
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy5
Turbulent combustion models (1/2)
Selection of suitable models for GT combustionPremixed flames
o Turbulent Flame Closure , TFC – Prof. Zimont– Progress variable transport– Fast chemistry
o Level set model, G-equation - Prof. Peters– Wider range of turbulent combustion regimes– Laminar flamelet modeling
» Effects of turbulent stretch
Non premixed flameso Presumed shaped “β-function” PDF approach
– Transport of mean, variance and dissipation rate of mixture fraction– Diffusive flamelet integration
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy6
Turbulent combustion models (2/2)
Details of code developmentStandard implementation and assumptions for TFC and β-PDF models
Level Set Flamelet modelTransport of scalar
o Flame front tracking– Geometrical approach– First order approximation
Transport of o Width of flame brush
– Gaussian PDF assumed
Transport of
G~
2~G ′′
Tσ~
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy7
SIMPLE loop
h, hu transport
, , transport
re-initialization
h transport
ξ, ξ”2, χ transport
ThermophysicalModels
combustionMixture base class
Combustion developed library
flameletMixture
premixedFlameletMixture
diffusionFlameletMixture
derived classes
interpolateXYZ supply class
integrated flamelet look-up tables
G~ 2~G ′′ Tσ~
,~G ,~ 2G ′′ Tσ~
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy8
Radiation models (1/2)
Radiative heat transfer for GT combustionDirectional model
o P1-approximation– advantages
» only one pde to be solved– drawbacks
» Fails within optically thin media» Inaccurate with large temperature gradients
o Finite volume method– advantages
» well adapting to irregular geometries» accuracy and robustness with STEP discretization scheme
– drawbacks» computational cost increases with angular discretization
Gas properties modelo Gray gas
– Temperature, pH20 and pCO2 dependent mean absorption coefficiento Weighted Sum of Gray Gas model (WSGG)
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy9
Radiation models (2/2)
Details of code developmentStandard implementation and assumptions for P1 and gas properties models
Finite Volume Method modelAngular discretization
o RTE is solved for each direction si as common scalar– Implicit source term– InletOutlet like boundary condition following si
» Diffusive emitting walls assumption to estimate the reference value» Explicit iterative treatment
Weighted Sum of Gray GasesSpectral discretization
o RTE solution algorithm is called for each gas (usually 4), then solution fields are weighted
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy10
radiationModel
finiteVolumeMethod
P1approximation
zonalMethod
mediaPropertiesModel
uniform grayGas
T, pH20 and pCO2dependent grayGas
WSGG
Temperature field
base classes
derived classes
runTime selection via “AutoPtr” objects instantiation
Radiative developed library
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy11
Validation test cases
Preliminary assessment of code accuracy and reliability of proposed solution schemes
Premixed flameNon premixed flameRadiative heat transfer benchmark evaluationsSooty kerosene jet flame
Soot modelTransport of soot volume fractionSource terms from flamelet library of Lund University
o Particle inceptiono Surface growtho Particle fragmentationo Particle oxidation
Additional soot contribution to mean absorption coefficient for radiative computations
Additional model
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy12
VanderBilt Lean Premixed CombustorVanderbilt University burner [Nandula, 2003]
Fully premixed natural gas bluff-body flameo Typical DLN combustor regime - thin reaction zone
o High flame stretching in the shear layer
TFC modelo Unstretched laminar flame speed
o Fast chemistry
Level Set modelo Opposed Jets Laminar Flamelets
– GRI2.11 mechanism
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy13
VanderBilt Lean Premixed CombustorTemperature profiles at x/D = 0.1, 0.8, 1.0 and 6.0
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy14
TNF Bluff Body Flame
Bluff Body stabilized non premixed flame TNF Workshop http://www.ca.sandia.gov/TNF
o HM1E case
Atmospheric CH4/H2 flame with co-flow
Laminar Flamelet Modelo Opposed Jets Diffusion Flamelets
– GRI 2.11 mechanism
– Chem 1D code - Prof. De Goey
0.6
1.3
2.4
y/D
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy15
TNF Bluff Body Flame
0.8
2.4
y/D
Mixture Fraction, CO and CO2 profiles at y/D = 0.8, and 2.4
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy16
Radiative heat transfer benchmark evaluations
P1-approx – comparison with analytical solution
Finite volume method – RADIARE workshopUniform/non uniform temperature
Uniform gray gas
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy17
Weighted Sum of Gray GasesUniform temperature pure water vapor (T=1000K)
Given temperature distribution, mixture (H2O 20%, CO2 10%)o Coefficients from Viskanta
Radiative heat transfer benchmark evaluations
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy18
Jet-A flame with soot and radiationCranfield Jet-K test case
Kerosene diffusion jet flameo Fully pre-vaporized fuel jet-A
Diffusion flame PDF modelo Kundu, 1999 C12H23 mechanism
– 16 species, 23 reactions
φ 155 mmQuartz walls
Nozzle
L 6
00
mm
Air coflowφ 1.5 mm
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy19
Jet-A flame with soot and radiationCenterline profiles of mixture fraction, temperature soot volume fraction and radiative heat sink term
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy20
Conclusions
A suitable library of sub-models has been implemented into an object-oriented CFD code, based on Open-FOAM, to make it capable of reactive CFD analysis in Gas Turbine combustion
Models for both premixed and non premixed flames have been considered, including radiative heat transfer evaluation and soot modeling
Models have been validated by means of well known literature test cases
Incoming tasks:Extension to partially premixed flames of flamelet models
Development of EDC based model
Implementation of lagrangian particle tracking model into SIMPLE algorithm for steady state calculations
Encapsulation of all models to build a combustion models base class
University of University of FlorenceFlorence -- ItalyItalyRadiative and Combustion Modeling for Turbomachinery Applications
OpenFOAM Workshop July 10-11 2008 - Milan, Italy21
Acknowledgements
Part of this work was performed during the project
funded by European Commission which is gratefully acknowledge
Many thanks go to prof. R. Bialecki for providing useful radiative benchmarks
This work was conceivable thanks to
that still demonstrates faith and interest in the development of an open source code
University of Florence - Italy
M. Cerutti, L. Mangani
HTC GroupDepartment of Energy
Engineering“Sergio Stecco”
Via Santa Marta, 3 - 50139 Florence - Italy
e-mail: [email protected]
OpenFOAM Workshop July 10-11 2008 - Milan, Italy
RADIATIVE AND COMBUSTION MODELING FOR
TURBOMACHINERY APPLICATIONS