material response characterization of new-class ablators

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Material response characterization of new-class ablators in view of numerical model calibration

!B. Helber

1,2, A. Turchi

1, T. E. Magin

1

!1Aeronautics and Aerospace Department, von Karman Institute for Fluid Dynamics, Belgium

2Research Group Electrochemical and Surface Engineering, Vrije Universiteit Brussel

1

6th Ablation Workshop April 10, 2014

Urbana Champaign, Illinois

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TPM for Atmospheric Reentry

NASA Stardust probe, reentry: Jan. 15, 2006 (12.9 km/s) (AIAA 2008-1202)

2

Missions Sample return, ISS serving (Dragon, ARV, …), MPCV

• Atm. reentry speeds > 10km/s • Ablative materials

Mass loss and surface recession Prediction of material response required High margins decrease payload

New materials (1990’s) • Phenolic impregnated carbon fiber

preform • Very porous low density ablators

!

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Complex Multiphysics - Multiscale problem

Gas-Surface Interaction

Coupled phenomena

3

C248

NH (A−X)

OH (A−X)

CN violet (B−X)

CH (A−X)

C2 Swan

Na

Hβ

Hα

NO777 N lines

Air plasmaNitrogen plasma

Material

Radiation

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We aim at improvement of

Experimental Methods (VKI)

4

TPS Design / Material (VUB, Astrium, ESA)

Material Response Modeling & Validation (VKI, collaborations)

Calibration (AIAA G-077-1998) The process of adjusting numerical or physical modeling parameters in the computational model for the purpose of improving agreement with experimental data.

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In the following

!

(2) Gas-phase ➪ BL emission & temp (3) Surface ➪ Char blowing rates (4) Material ➪ Pyrolysis outgassing

5

GAS - PHASE

MATERIAL

chem. active surface

(1) Materials and Methods for Ablation Characterization

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Approach for ablation modeling (Kendall et al.[1])

Boundary condition from experiments & plasma free-stream Experimental data for validation

GOAL: Coupling 1-D SL-code & material code (P. Schrooyen)

VKI: 1D Stagnation line description w/ surface ablation (A. Munafo[2] / A. Turchi, VKI)

6

species diffusionmass blowing HOT GAS

MATERIAL

CONTROL VOLUME


convectedenthalpy

convective flux

HOT GAS

MATERIAL

enthalpy by diffusion radiation re-radiation

material conductionenthalpy char mass loss

Surface Mass Balance (SMB)Surface Energy Balance (SEB)

[1] Kendall et al., NASA CR 1060 (1968)![2] A. Munafò, PhD Thesis, Ecole Central Paris, 2014

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Materials of InvestigationCarbon fiber preform, non-pyrolyzing (Mersen Scotland Holytown Ltd.)

7

AQ61, carbon-phenolic (AIRBUS DS)

650μm

13μm

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1.2-MW Inductively Coupled Plasmatron

Gas: Power:

Heat Flux: Pressure:

8

water&cooled+calorimeter+

test+sample+

pitot+probe+

spectrometer+op1cs+

sample+condi1on+

control+system

+

High+speed+camera+

op1cal+access+pyrometer+

op1cal+access+radiometer+

Air, N2, CO2, Ar 1.2-MW > 12 MW/m2

10 mbar - 1 atm

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Our interest !

Surface temperature Emissivity Internal Temperature In-situ recession analysis Volumetric recession Chemical composition Temperature estimation

(AIAA 2013-2770)

9

!test!sample!

plasma!torch!

light!collec/on!system!(lens!&!mirrors)!!

exhaust!&!!!!!heat!exchanger!!

reac/ve!boundary!!!!!layer!

op/cal!fibre!ends!

High!speed!camera!

test!chamber!

HR=4000!spectrometer!

Func/on!generator!

2=color!pyrometer!

1 2 3

Techniques for In-Situ Ablation Characterization

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Boundary Layer Radiation Profiles

CN Production: gas phase: CO + N ⇌ CN + O wall: Cw + Nw ⟶ CN

Experimental: Spatial CN violet emission

10

01

23

360 380400 420

20

40

60

80

dist. surf., mmλ, nm

I, W

/(m2 .s

r.nm

)

0 1 2 3 4 5 6 70

200

400

600

800

1000

1200

Distance from surface, mm

I λ1λ2 [W

/(m2 .s

r)]

T = 2180K, ps = 15mbar

Spectrometer 1

Spectrometer 2Spectrometer 3

0 1 2 3 4 5 6 70

200

400

600

800

1000

1200

T = 2180K, ps = 15mbar


I λ1λ2 [W

/(m2 .s

r)]

Exp. dataPolynomial fit95% Conf. bnd

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Boundary Layer Radiation Profiles

Simulate line-of-sight measurement

Numerical: Simplified approach using Specair slab

11

boundary layer

slab width Δyi at xi

stagn. line solution χi, Ti, pi,

SPECAIR

locations xi

ablating surface

x

y

Ii(λ)

boundary layer

slab width Δyi at xi

stagn. line solution χi, Ti, pi,

SPECAIR

locations xi

ablating surface

x

y

Ii(λ) Perspective: Radiation Coupling (J.B. Scoggins)

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Comparison of Boundary Layer Radiation Profiles

Locations of maxima BL thickness Order of magnitude

Very preliminary approach but promising comparison

12

0 1 2 3 4 5 6 70

200

400

600

800

1000

1200

T = 2020K, ps = 200mbar


I λ1λ2 [W

/(m2 .s

r)]

Exp. dataPolynomial fit95% Conf. bndNum. data

0 1 2 3 4 5 6 70

2000

4000

6000

8000

10000

12000

T = 2848K, ps = 15mbar


I λ1λ2 [W

/(m2 .s

r)]


0 1 2 3 4 5 6 70

2000

4000

6000

8000

10000

12000

T = 2783K, ps = 200mbar


I λ1λ2 [W

/(m2 .s

r)]


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CN Radiation Simulation for Temperature EstimationNon-equilibrium?

13

Non-thermal vibrational level distribution at low pressure (AIAA 2013-2770) ➟ Thermal non-equilibrium? ➟ Deviation from Boltzmann distribution?

370 380 390 400 410 420 4300

0.2

0.4

0.6

0.8

1

wavelength [nm]

norm

aliz

ed in

tens

ity [−

]

ASTERM, ps = 15mbar, TS = 2130K

Trot = 9281K ± 640K

Tvib = 14912K ± 1100K

Experimental spectrumSPECAIR simulation

370 380 390 400 410 420 4300

0.2

0.4

0.6

0.8

1

wavelength [nm]no

rmal

ized

inte

nsity

[−]

ASTERM, ps = 100mbar, TS = 2097K

Trot = 6311K ± 350K

Tvib = 7878K ± 320K

Experimental spectrumSPECAIR simulation

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Boundary Layer Temperature ProfileNon-equilibrium at the wall?

14

0 1 2 3 4 5 2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

distance from surface [mm]

tem

pera

ture

[K]

ps = 15mbar, TS = 2130K

TrotTvib

0 1 2 3 4 5 2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

distance from surface [mm]te

mpe

ratu

re [K

]

ps = 100mbar, TS = 2097K

TrotTvib

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In-situ Recession Analysis (HSC)

15

0 20 40 60 800

1

2

3

4

5

Time, s

Rec

essi

on, m

m

Preform

1724K, 15mbar2180K, 15mbar2020K, 200mbar2848K, 15mbar2783K, 200mbar

0 5 10 15 20 25

0

1

2

Time, s

Rec

essi

on, m

m

2167K, 15mbar1890K, 200mbar

0 20 40 60 800

1

2

3

4

5

Time, s

Rec

essi

on, m

m

AQ61

2167K, 15mbar1890K, 200mbar2884K, 15mbar2906K, 200mbar

0 5 10 15 20 25

0

1

2

Time, s

Rec

essi

on, m

m

1724K, 15mbar2020K, 200mbar

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Ablation Regimes of Preform and AQ61

➟ diffusion limited ablation and sublimation regime ➟ recession not much influenced by pressure!

16

1500 2000 2500 3000 35000

0.05

0.1

0.15

0.2

0.25

Temperature, K

Rec

essi

on ra

te, m

m/s

PreformAQ61

: 15 and 200mbar: 15 and 200mbar

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Diffusion Limited Ablation and Code Comparison

15mbar: good agreement, possibly misleading measurement? (AIAA 2012-2876) 17

Surface temperature driven by catalytic reactions: N + N ⟶ N2

➟ Modeling of tests in nitrogen

2000 2200 2400 2600 2800 30000.005

0.01

0.015

0.02

0.025

200mbar num.

200mbar exp.

15mbar num.15mbar exp.

Mean surface temperature, K

Mas

s lo

ss, k

g/(m

2 .s)

Exp. & num. Preform ablation rates

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Pyrolysis-Gas Blowing Rate Determination

mpg + mc = (ρV)w

!

mpg = mpg -

18

0 10 20 30 40 500

5

10

15

20

25

30

length [mm]

radi

us [m

m]

P6, 3MW/m2, 200mbar, 30s

original shapeablated shape

(Vabl ˙ ρc) texp

Carbon Preform (non-pyrol.): ➟ mc = mtot = Vabl ˙ ρc

Pyrolyzing Ablators: ➟ char density required

Non-pyrolyzing carbon-preform

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19

Non-pyrolyzing carbon-preform

1 2 3 4 5 6 7 8 9 10 110

2

4

6

8

10

Uncertainty HSC

Test case, #

Tota

l mas

s lo

ss, g

weighedestim. HSC

discrepancy: - water - initial density - damage by

deinstallation

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charred AQ61: ρc = 80-85% ρv

Thermogravimetric Analysis (TGA)

20

0 500 1000 150050

60

70

80

90

100

110

Temperature, C

Wei

ght,

%

DurezAQ61Preform

0 500 1000 15000

0.005

0.01

0.015

Temperature, C

Mas

s lo

ss ra

te, 1

/s

DurezAQ61Preform

Preform

AQ61

Durez resin AQ61

Durez resin

Argon (20-200 ml/min), 10 K/min, 1 atm

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mpg + mc = (ρV)w

!

mpg = mpg -

21

0 10 20 30 40 500

5

10

15

20

25

30

length [mm]

radi

us [m

m]

AQ61, 3MW/m2, 15mbar, 30s

original shapeablated shape

(Vabl ˙ ρc) texp

AQ61 (carbon-phenolic): mmeas = 4.03 g mc,HSC = 2.26 ± 0.4 g ➟ mpg = 1.77 g ± 0.4 g

Carbon - phenolic: AQ61

Main challenges: Side-wall outgassing, non-1D effects, too-long test times

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Ongoing Work

Nitridation negligible for recession

➟ Match of Ts for γN

Rebuilding of ablation tests in nitrogen plasmas → γN

22

0 20 40 60 80 1001800

2000

2200

2400

2600

2800 AIR, 3MW/m2

N2, 3MW/m2

AIR, 1MW/m2

N2, 1MW/m2

Surface Temperatures: Preform

Injection time, s

Tem

pera

ture

, K

1 2 3 40

10

20

30

40

50

60

Test caseR

eces

sion

rate

, µm

/s

Recession rates Preform: AIR / N2

2180K (air)2838K (air)

2030K (N2)

2644K (N2)

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Conclusions

Which chemical and physical phenomena matter?23

(1) Materials and Methods • hemispherical samples • HSC imaging • coupled w/ 3 Spectrometers

(2) BL emission • steady ablation process • preliminary comparison num/exp radiation

profiles (3) Char blowing rates

• diffusion limited ablation and sublimation • deviation from num. model

(4) Pyrolysis outgassing • Vol. ablation + TGA ➞ ṁpg

GAS - PHASE

MATERIAL


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ACKNOWLEDGEMENTS

Funding and materials supply:

24

In particular: !Jean-Marc Bouilly & Gregory Pinaud (Airbus Defence & Space) !N.N. Mansour (NASA ARC), J. Lachaud (UC Santa Cruz), F. Panerai (University of Kentucky) for informative support !VKI Plasmatron & Ablation Team !VUB SURF research team

material response characterization of new-class ablators

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