RadiativeAndCombustionModelingForTurbomachineryApplications~1

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



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



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



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



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~



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~



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)



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



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



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



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



VanderBilt Lean Premixed CombustorTemperature profiles at x/D = 0.1, 0.8, 1.0 and 6.0



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



TNF Bluff Body Flame

0.8

2.4

y/D

Mixture Fraction, CO and CO2 profiles at y/D = 0.8, and 2.4



Radiative heat transfer benchmark evaluations

P1-approx – comparison with analytical solution

Finite volume method – RADIARE workshopUniform/non uniform temperature

Uniform gray gas



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



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



Jet-A flame with soot and radiationCenterline profiles of mixture fraction, temperature soot volume fraction and radiative heat sink term



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



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

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RadiativeAndCombustionModelingForTurbomachineryApplications~1