Proceedings of 24th European Workshop on Thermal … properties enhanced through material...
Transcript of Proceedings of 24th European Workshop on Thermal … properties enhanced through material...
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85
Appendix F
Development of numerical tools for design and verification ofablative thermal protection systems
Marco Giardino Elena Campagnoli(Politecnico of Turin, Italy)
Gianni Pippia(Sofiter System Engineering, Italy)
Massimo Antonacci(Thales Alenia Space, Italy)
24th European Workshop on Thermal and ECLS Software 1617 November 2010
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86Development of numerical tools for design and verification of ablative thermal protection
systems
Abstract
In recent years there has been a great collaborative work between Thales Alenia Space Italia and theEnergetic Department of Politecnico of Turin devoted to the study of ablative heat shields. Two differentnumerical tools for the analysis of the behaviour of charring ablative materials have been developedwithin the frame of a co-founded internal research program.The first of these tools, called Ablatherm, is a Matlab R-based code that can be used during the initialdesign phase: it implements a simple model (that uses a very reduced set of material properties), it hasa short case settings time and execution time and it is very flexible (it can be used both through a scriptfile or a Graphical User Interface). This tool was tested using analytical benchmarks and real test casesand is now used by TAS-I for heat shield design.The second tool, still under development, uses the state of the art both for the model and for the toolimplementation, in order to perform rapid, full 3D simulations. This tool, developed on OpenFoamplatform, implementing a more complex model and requiring higher test case setup time and a hugeamount of material data that must be provided for a full run, is mainly intended for final verification ofthe full system configuration. For an intermediate design phase, it is also possible to use this second toolwith a reduced set of parameters.
24th European Workshop on Thermal and ECLS Software 1617 November 2010
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24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
DEVELOPMENTOFNUMERICALTOOLSFORDESIGN ANDVERIFICATION
OFABLATIVETHERMALPROTECTIONSYSTEMS
MarcoGiardino
(Politecnico
ofTurin,Italy)ElenaCampagnoli
(Politecnico
ofTurin,Italy)
GianniPippia
(Sofiter
SystemEngineering,Italy)MassimoAntonacci
(ThalesAlenia
Space,Italy)
24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
Index
Ablativeheatshields
Characteristicoftheusedmodels
1Dmodel
AblaTherm
Specifications
Necessarydata
Implementation
Validationvs.CMA
Validation
vs.SAMCEFAmaryllis
3Dmodel
Specifications
Necessarydata
Implementation
Testcasedefinition
Testcaseresults
Validation
vs.AblaTherm
Futureworks
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24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
Ablativeheatshields
Notreusable.
Lightweight.
Adaptabletomissionconstraints.
Heatinsulationpropertiesenhanced throughmaterialdegradation.
SuitableforentryvehicleandSRCs.
24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
Characteristicoftheusedmodels
1DMODELABLATHERM
Local1Dassumption.
Simplemodel.
Reducedsetofparameters.
Multilayercapability.
Extremelylowsetuptimeand executiontime.
Idealduringinitialdesignphase.
3DMODEL
Full3DCartesiansolver.
Stateoftheartmodel.
Highnumberofparameters (possibleuseofareducedset).
Multiplematerialwithin
thedomain
Isnottoomuchuserfriendly.
Relativelylongsetupandruntime.
Tobeusedforfinal,fullbody simulation.
88Development of numerical tools for design and verification of ablative thermal protection
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24th European Workshop on Thermal and ECLS Software 1617 November 2010
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24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
1DModel
Analyticalmodel
Oneequationmodel(energyconservation)+BC:
Charringmaterial(Arrheniusequation).
Internalheatfluxqc
(t):adiabatic,convectiveand/orradiative
heatflux.
Surfaceheatfluxboundarycondition:
)(),(
)(,0
0
0),(),(
0
tqttsxxT
tqtxxT
xTtTt
THxTT
xtTTc
w
c
p
heatRecession
fluxheat radiative
Surface
flux External
Blowingfluxheat
Net wall00
sQqqqq carbreceradradconvw
24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
1DModel
Necessarydata
Materialproperties:
Virginandcharreddensities.
Arrheniuscoefficients.
Pyrolysis
reactionandsurfacerecessionenthalpy.
Temperaturedependenceofspecificheat,thermalconductivity, surfaceemissivity,bothforvirginandcharredmaterial.
Heatfluxdata(asfunctionofsurfacetemperature,coldwallevaluation, netvalues).
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24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
1DModel
Implementation
FiniteElementMethod(FEM)discretisation.
NonlinearNewtonRaphson
methodforfastandaccuratenonlinearity resolution(surfaceradiation).
Automaticgridgeneration,withlinearpluslogarithmicspacing;
formulti layercases,thenumberofelementsperlayercalculatedthrough
mean
conductivity.
Blowing
evaluation
atrun
time.
Initialsteadystatetemperaturedistributionevaluation.
ImplementedusingMatlab
environment.
Usable
as
command
line
function
orthrough
aGraphical
User
Interface (GUI).
24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
Performedbymeansofcomparisonwithcommercial1Dsoftware(CMA):
Testcases sizingofasiliconbasedablatorondifferentareasofthe externalsurfaceofareentryvehicle.
Availablethermalablativepropertieshavebeenimplementedin bothcodes.
Thermalsimulationextendedinthe1Dsimplifiedcodetothe reproductionoftheconvectiveandradiative
heatexchangeinside
thevehicle.
Thepyrolysis
heatbehaviourasfunctionofmaterialtemperaturehas
beenintroducedinAblaTherm.
W.r.t.CMA,AblaTherm
doesnotaccountfor:
Surfacetransportofchemicalenergy.
Convectivetransferbypyrolysis
gases:
Differenceinsizingresultslowerthan
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24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
CMA simulation
AblaTherm
simulation
Caseonvehiclereentry.
Differentmodellingofsurfacethermo chemistry.
Sizingresults(i.e.shieldthickness)differfor lessthan10%.
1DModel
Validationvs.CMA
24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
-200
0
200
400
600
800
1000
1200
1400
1600
0 50 100 150 200 250
1)2)3)4)5)
-120
-100
-80
-60
-40
-20
0
20
40
60
80
0 50 100 150 200 250
2)3)4)5)
ComparisonwithsimulationresultsofaMarsentryvehiclefrontshield:
SHIELDSURFACE
1) Amaryllis simulation results2) Empty3) AblaTherm
results, with prescribed heat fluxes correction4) AblaTherm, with ABLAT heat fluxes correction5) AblaTherm, with foam conductivity as function of atmospheric pressure
T [
C]
time
[s]
T
[C
]
time
[s]
1DModel
Validationvs.SAMCEFAmaryllis
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-50
0
50
100
150
200
0 50 100 150 200 250
1)2)3)4)5)
T [
C]
time
[s]
-120
-100
-80
-60
-40
-20
0
20
40
60
80
0 50 100 150 200 250
2)3)4)5)
T
[C
]
time
[s]
1) Amaryllis simulation results2) Empty3) AblaTherm
results, with prescribed heat fluxes correction4) AblaTherm, with ABLAT heat fluxes correction5) AblaTherm, with foam conductivity as function of atmospheric pressure
ComparisonwithsimulationresultsofaMarsentryvehiclefrontshield:
ABLATIVE/COLDSTRUCTUREINTERFACE
1DModel
Validationvs.SAMCEFAmaryllis
24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
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0
50
100
150
200
0 50 100 150 200 250
1)2)3)4)5)
T [
C]
time
[s]
-4
-2
0
2
4
6
8
10
12
0 50 100 150 200 250
2)3)4)5)
T [
C]
time
[s]
1) Amaryllis simulation results2) Empty3) AblaTherm
results, with prescribed heat fluxes correction4) AblaTherm, with ABLAT heat fluxes correction5) AblaTherm, with foam conductivity as function of atmospheric pressure
ComparisonwithsimulationresultsofaMarsentryvehiclefrontshield:
COLDSTRUCTURE/INTERNALFOAMINTERFACE
1DModel
Validationvs.SAMCEFAmaryllis
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3DModel Analitical model
3equationmodel(energy,solidmassandgasmassconservationequations)+ closureequations(Idealgaslaw,Darcylaw)+BC(Amar,A.J.Modelingof
OneDimensionalAblationwithPorousFlowUsingFiniteControlVolume Procedure,NorthCarolinaStateUniversity,2006
).
Pyrolysis
gasinlocalthermalequilibrium.
Pyrolysis
energyabsorptionthroughmixtureinternalenergyevaluation.
Charring
material(Arrheniusequation).
Surface
BCunderdevelopment.
gg
g
V Vgmeshg
Vgg
Vg
Vi
Vmesh
Vi
Vmesh
VVggg
V
MTp
pKv
dVmdSnvdSnvdVdtd
nidVmdSnvdVdtd
dSnvhdSnTkdSnvhedVdtd
,..,1for
0
24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
3DModel
Necessarydata
Materialandgasproperties:
VirginandcharredsubdensitiesandArrheniuscoefficientsforeach decompositionreaction,materialcompositioncoefficients.
Solid:temperaturedependenceofspecificheat,thermalconductivity, surfaceemissivity,bothforvirginandcharredmaterial.Extent
of
reactionsdependenceofporosityandgaspermeability.
Gas:temperaturedependenceofspecificheat,gasmolecularmass andviscosity.
Formationenthalpyandreferencetemperatureforvirgin,charand gas.
BC:differentstandardconditions,somespecificunderdevelopment.
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3DModel
Implementation
FiniteVolumeMethod(FVM)discretization.
ImplementedusingtheopensourceOpenFOAM
suite.Advantages:
parallelruninbothsharedanddistributedmemorymachines(MPI protocol,onworkstationorclusters).
Basedonopensourceplatform(Linux)andopensourcesuite.
Useunstructuredgrid(complexgeometricshapes,differentcellshapes).
Gridimportationcapabilities.
Simplifiedmodelwich
canrunneglectingthegaseffects(nongasdata needed)
24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
3DModel
testcase
Geometry
andgrid:10x10cm,100x400cells.
Boundary
conditions:
Northside:time
variable,uniform
external
heat
flux
:
with
surface
reradiation;time
variable
uniform
pressure:
SouthandEastside:adiabatic
andimpermeable.
Westside:impermeable,time
variable
uniform
temperature:
Materialdata:PICA15
NASATM110440(1997).
22 1000100100sin611100 mWttettq
Patetp 200
52
KttT 3001000
sin25002
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3DModel
Results
1
Performances:solution
time
ona8coreworkstation
1400s.
Following
moviedescription:
Backgroundcolor:materialdensity(red
max,blue
min).
Colored
lines:isotemperaturelines,colored
with
temperaturescale; lines
at[(300:20:400)(600:200:3800)]K.
Vectors:oriented
using
pyrolysis
gasvelocity
andcolored
using pyrolysis
gasvelocity
magnitude.
24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
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systems
Slow Normal Fast Play/Pause Stop
24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
3DModelValidationvs.AblaTherm
Thesolutionsobtainedusingthetwocodesarecompared.Toperformthe comparison,thefollowingstepswereperformed:
Ablatherm
runwasperformedneglectingsurfacerecessionand applyingthesameprofilefortheheatflux(withouttheblowing correction).
3Dcoderun:temperaturesolutionextractedontheEastsideofthe domain(negligible2Deffects).
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video2d.swfMedia File (application/x-shockwave-flash)
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3DModel
Validation
vs.AblaTherm
Slow Normal Fast Play/Pause Stop
24th European Workshop on Thermal and ECLS Software 1617 November 2010
videocomparison.swfMedia File (application/x-shockwave-flash)
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3DModel
Validation
vs.AblaTherm
24th European Workshop on Thermal and ECLS Software ESTEC, 16-17 November 2010
Futureworks
Finalization
of
the3Dcode:
surface
recession
models
implementation.
Different
surface
heat
flux
Boundary
Conditions
implementation.
Studies
for
integration
with
ESATAN.
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ANYQUESTIONS?
THANKSFORYOURATTENTION.
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24th European Workshop on Thermal and ECLS Software 1617 November 2010