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Ultra-high temperature emittance measurements for space and missile applications

Dr. Jan Rogers, NASA-Marshall Space Flight Center (MSFC), Huntsville, ALMr. David Crandall, AZ Technology, Inc., Huntsville, AL

Advanced modeling and design efforts for many aerospace components requirehigh temperature emittance data. Applications requiring emittance data includepropulsion systems, radiators, aeroshells, heatshields/thermal protection systems,and leading edge surfaces. The objective of this work is to provide emittance dataat ultra-high temperatures. MSFC has a new instrument for the measurement ofemittance at ultra-high temperatures, the Ultra-High Temperature EmissometerSystem (Ultra-HITEMS). AZ Technology Inc. developed the instrument,designed to provide emittance measurements over the temperature range 700-3500K. The Ultra-HITEMS instrument measures the emittance of samples,heated by lasers, in vacuum, using a blackbody source and a Fourier TransformSpectrometer. Detectors in a Nicolet 6700 FT-IR spectrometer measure emittanceover the spectral range of 0.4-25 µm. Emitted energy from the specimen andoutput from a Mikron M390S blackbody source at the same temperature withmatched collection geometry are measured. Integrating emittance over thespectral range yields the total emittance. The ratio provides a direct measure oftotal hemispherical emittance. Samples are heated using lasers. Opticalpyrometry provides temperature data. Optical filters prevent interference from theheating lasers. Data for Inconel 718 show excellent agreement with results fromliterature and ASTM 835. Measurements taken from levitated sphericalspecimens provide total hemispherical emittance data; measurements taken fromflat specimens mounted in the chamber provide near-normal emittance data.Data from selected characterization studies will be presented. The Ultra-HITEMStechnique could advance space and missile technologies by advancing theknowledge base and the technology readiness level for ultra-high temperaturematerials.

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Ultra-high temperature emittancemeasurements for space and missile

applications

Dr. Jan RogersNASA Marshall Space Flight Center

Huntsville, ALand

David CrandallAZ TechnologyHuntsville, AL

National Space & Missile Materials Symposium, June 22-26, 2009

Emittance• Directional v. Hemispherical

— Directional illumination and hemispherical collection or viceversa

• Near-normal is a special case of directional where the angleof incidence is near the normal vector of the sample surface

— Hemispherical illumination and hemispherical collection• Just about impossible to build a reflectance mode instrument

that does this• Classically determined by calorimetry

• Flat surface (ESL) --> near-normal emittance• Sphere (ESL) -> hemispherical emittance

Other options for high temperaturemeasurements

Other High Temperature Emissometers

Temp range Mode Spectral Angular Extentrange

NPL 150 to 1800 °C direct 0.6 to 9.6-um 0 to 700

Advanced Fuel 100 to 1000 (2000) °C both 0.8 to 20-um naResearch

Southern Research 1500 to 5000 OF direct not naInstitute applicable

BNM-LNE ambient - TBD reflected 0.8 to 14-um 12, 24, 36, 48,60°

Alternative strategiesCalorimetryPyrometryAdvantages and disadvantages

Ultra-High Temperature Emissivity MeasurementSystem (Ultra HITEMS) Background

• Emissivity data at operatingtemperature needed for thermaldesign.

• System originally developed formeasurement of small (-2mm),smooth levitated specimens.

• New customers (J-2X and CEV)have requirements for larger, flatsamples with special surfacetreatments.

• The instrument is being adaptedto meet the new requirements.

• New apparatus, optics andprotocols are beingdeveloped/implemented to meetnew customer needs.

Ultra-High Temperature Emissivity System

Configuration A: Blackbody Calibration

Specimen

Heating Laser

Turbopump

Y_'v, Pyrometer `

Video

Configuration B: Emissivity Measurements

Specimen

Heating Laser

Turbopump

I

Pyrometer

Blackbody

SpectrometerNicolet FT-IR

^,.. •f---------Blackbody

------ -

SpectrometerNicolet FT-IR-. r

-- -I-- - -- - -- - e- +

Video

Figure 1. Schematic of the Emmissivity Measurements

• Fully opprodeattle • Bettor Than a2 nm pc

ti i • 5 to 1.000 Hz phase n

• 0.9 to 3.5 'il h. phast

I*..

'3.N

Smart S

More of

• Electra

sum-cofive-Ye;

• Turbo

Designed to minimize uncertainty

• Commonality between reference/background paths and samplepaths— Same collection geometries

• Matched radianceSame solid angle collection,Same area collection

— Same number of transport altering surfaces• Goal to maximize common path

— Equivalent path lengths• Purge benefit

— Effect of violating these on uncertainty• Sensitivity• Calibration factors

0

•

0.250

0.200

.N 0.150

E 0.100

m

0.050

0 000

Inconel 718 718 polished, ASTM 0835(vacuum, calorimetric)

x 718 polished, literature value,Tanda and Misale, J, HeatTransfer, vol 128, 2006, pp. 302-306 (vacuum, calorimetric)

x 718 'same polished sample",room temp reflectance data,extrapolated to high temp (FTIR)

XX

Xx

HITEMS Calibration

•

•

No clear calibration standards for hightemperature emissivity. Very difficult toachieve quantitative comparisons betweendifferent labs, using different test conditionsand different samples. An example of datafor different samples of, measured indifferent labs RCC is shown in the adjacentgraph.Polished Inconel 718 used for initialcalibration. Results shown in graph below— Ni-based alloy with published emissivity data

for polished surface available— Polished surface chosen for reproducibility

High emissivity calibration material is beingsought. Materials examined include SiC andgraphite. An AZ tech coating was alsoevaluated, but it was not stable in testconditions.Hexoloy SA SiC from St. Gobain has beenused as a high emissivity calibrationmaterial.— Additional emissivity tests are planned using

this calibration factor

IP n q g. qCl q o q n

O• O• • O

^. • • •

0-4- Design pO JSC normal •• JSC-new normal •

ARC normalq SRI normal •n SRI-flown normal •o GRC-Virgin hemispherical •• GRC-flown hemisphericalO TPRL-1 hemispherical• TPRL-2 hemispherical Q

O

050 500 1000 1500 2000 2500 3000 3500

0 500 1000 1500 • 718 Ultra-HITEMS `sametemp C polished sample' (vacuum,

FT)R

1.0

0.9

0.8

0.7

0.6

Haynes 230 Emissivity Measurements

1000 1200 1400 1600 1800 2000

Temperature (F)

• J2X 002 64 machine finishJ2X-003 RT reflectance "

x J2X-004 64 machine finishx J2X-014 Chem milled finish• RX-018 Heat Treatn J2X-00364 machine finish+ Haynes 230 DOE 82 C reflectance

Haynes 230 DOE 82 C reflectance after oxide formedLinear (J2k003 RT reflectance "' )

—Linear (J2X.014 Chem milled finish)—Linear (J2)004 64 machine finish)—Linear (J2k002 64 machine finish)

i

,F t

1

0.s

0.8

0.7

0.6N

E 0.5III

0.4

0.3

0.2

0.1

Emissivity Measurements Haynes 230 HITEMS,and reflectance data from AZ Tech and DOE report

• HITEMS from heating at 2050 F and — 10-6Torr data for Haynes 230 is in goodagreement with data from room temperaturereflectance data from AZ Tech on samesamples

• HITEMS data for Haynes 230 appears to bein good agreement with reflectance-baseddata Taken at 82 C from DOE study with500 hour vacuum anneal at 2012 F and10-5 Torr.

• The 0.23 value from the DOE study basedon measurements prior to the anneal

• The 0.67 value from the DOE study is fromthe same sample, after the anneal. Theauthors of the study report the formation ofan oxide layer on the surface of the sampleduring the anneal which changed theemissivity.

• This value is similar to the value from theHITEMS for a sample which had been heattreated in hydrogen at 2000 F and in air at1950 F. The sample had a visible oxidelayer.

Near-normal spectral emittance forHaynes 230, Chem-milled

Chem-milled Haynes 230 2050 F

1.4

E_ 1.2

1

0.8

0.6a^

0.4

0.2

0

1*_S e ri e S 11

0 5 10 15 20 25 30

wavelength, microns

Error due to TemperatureMismatch

1.2

a^

1.15 Surface 5% lower in-j temperature than background

1.1

1. 05 - 1L

5000 10000 15000 20000

v 0.95

cn 0.9Peak in blackbody curve

Near-normal spectral emittance forHaynes 230, 64 machine finish

1.4

E 1.20 1

0.8

0.6a^

0.4

0.2

0 0

Haynes 230, 64 machine finish 2050 F

[Series 1

0 5 10 15 20 25 30

wavelength microns

Future Plans

Continue efforts to improve, understand and validate theH ITEMS system— This test method can provide the required spectral data in

relevant environment

— Use of extrapolated reflectance data has been suggested, butissues can arise when materials and materials properties changeat high temperature. For reactive systems, this is very likely.

— Post-test reflectance data could identify changes in the materialbut would not be able to predict emissivity at temperature.

• Lack of accepted calibration standard(s) for material— Significant discrepancies exist in among data sets from different

labs— Some options proposed by N IST and are being explored