Pressure Sensitive Paint (PSP)/ Temperature Sensitive ...

Copyright Copyright ©© by Dr. by Dr. HuiHui HuHu @ Iowa State University. All Rights Reserved!@ Iowa State University. All Rights Reserved!

HHui Huui HuDepartment of Aerospace Engineering, Iowa State University Department of Aerospace Engineering, Iowa State University

Ames, Iowa 50011, U.S.AAmes, Iowa 50011, U.S.A

Pressure Sensitive Paint (PSP)/ Temperature Pressure Sensitive Paint (PSP)/ Temperature Sensitive Paint (TSP)Sensitive Paint (TSP)

Part 2Part 2

AerEAerE 545 class notes #15545 class notes #15

Copyright Copyright ©© by Dr. Hui Hu @ Iowa State University. All Rights Reserved!by Dr. Hui Hu @ Iowa State University. All Rights Reserved!

Lab 2: Power spectrum of turbulent velocityLab 2: Power spectrum of turbulent velocity

LogLog--scalescale

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Basic Principles of Pressure Sensitive Paint (PSP)Pressure Sensitive Paint (PSP)

•• Intensity based Methods (most common)Intensity based Methods (most common)–– FullFull--field using camerafield using camera–– Point systems using scanning laserPoint systems using scanning laser

•• lifetime based Methods (lifetime decay)lifetime based Methods (lifetime decay)–– FullFull--field using camerafield using camera–– Point systems using scanning laserPoint systems using scanning laser

••


Intensity based PSPIntensity based PSP

•• The SternThe Stern--VolmerVolmer equation is rewritten in the equation is rewritten in the popular intensity ratio form:popular intensity ratio form:

•• A and B are highly dependent on the A and B are highly dependent on the luminophoreluminophore and binder material as well as and binder material as well as the temperature sensitivity of the materials the temperature sensitivity of the materials used to make the paint. A 2nd order curve used to make the paint. A 2nd order curve generated from calibration data is most often generated from calibration data is most often used.used.


Intensity based PSPIntensity based PSP

•• Requires two readings, a reference at Requires two readings, a reference at constant pressure (wind off) and an constant pressure (wind off) and an unknown data point (windunknown data point (wind--on)on)

•• Ratio of intensities IRatio of intensities IREFREF/I is inversely /I is inversely proportional to the air pressureproportional to the air pressure

•• The excitation and detection systems must be The excitation and detection systems must be spectrally separated, (>10spectrally separated, (>10--6 attenuation in 6 attenuation in stop band).stop band).

•• Simplest technique, most sensitive Simplest technique, most sensitive •• Very sensitive to motion between windVery sensitive to motion between wind--off off

and windand wind--onon•• A long period of time can elapse between A long period of time can elapse between

reference and data.reference and data.•• images resulting in significant changes in images resulting in significant changes in

contamination of paint, light stability, etc contamination of paint, light stability, etc that cannot be normalized by the reference that cannot be normalized by the reference condition.condition.


Intensity based PSPIntensity based PSP--temperature compensationtemperature compensation

•• Advantages:Advantages:•• Measure temperature to compensate Measure temperature to compensate

for temperature sensitivity of PSP.for temperature sensitivity of PSP.•• This technique requires all four This technique requires all four

images to be aligned.images to be aligned.


LifetimeLifetime--based PSPbased PSP

•• Easiest to do with a point measurement, but Easiest to do with a point measurement, but can use time resolved cameras to measure can use time resolved cameras to measure lifetime decays of the probe molecules.lifetime decays of the probe molecules.

•• Point measurements require a pulsed light Point measurements require a pulsed light source and detector (PMT, PD)source and detector (PMT, PD)

•• Time resolved imaging requires a double Time resolved imaging requires a double pulse type experiment to measure the decay pulse type experiment to measure the decay times (gated camera, interline transfer times (gated camera, interline transfer camera capable of multiple flash integration).camera capable of multiple flash integration).


LifetimeLifetime--based PSPbased PSP

•• Benefits:Benefits:–– Eliminates the need for aligning two or three Eliminates the need for aligning two or three

images since the pair of (or three ) images are images since the pair of (or three ) images are taken at the same condition relatively close in taken at the same condition relatively close in time (microtime (micro--seconds).seconds).

–– Pressure and temperature distributions can be Pressure and temperature distributions can be determined simultaneously. determined simultaneously.

•• Disadvantages:Disadvantages:–– Requires three gates to generate two equations Requires three gates to generate two equations

of gate ratios to solve for pressure and of gate ratios to solve for pressure and temperature at each point (pixel).temperature at each point (pixel).

–– Camera noise is much higher, especially gated Camera noise is much higher, especially gated intensified cameras.intensified cameras.

–– Paints have tended to be more spatially noisy Paints have tended to be more spatially noisy from lifetime differences between molecules from lifetime differences between molecules (homogeneity problem).(homogeneity problem).


PSP/TSP coatingsPSP/TSP coatings

•• PSP coatings used at NASA GRCPSP coatings used at NASA GRC–– Boeing PF2B Boeing PF2B –– ruthenium ruthenium bathophenanthrolinebathophenanthroline in silicone rubber binder in silicone rubber binder

(soft(soft–– paint, chlorinated solvent)paint, chlorinated solvent)–– UW (ISSI) FIB UW (ISSI) FIB –– PtTFPPPtTFPP in FIB copolymer binder (hard, good steady state in FIB copolymer binder (hard, good steady state

paint)paint)–– NASA Langley NASA Langley –– PtTFPPPtTFPP in FEM (very hard, very smooth finish)in FEM (very hard, very smooth finish)–– ISSI solISSI sol--gel gel –– Ru(ph2Ru(ph2--phen) and phen) and PtTFPPPtTFPP on solon sol--gels (higher frequency gels (higher frequency

response)response)–– Anodized aluminum Anodized aluminum –– dip coated Ru(ph2dip coated Ru(ph2--phen) on anodized surface (very phen) on anodized surface (very

high freq. response)high freq. response)–– UW UW PtOEPPtOEP in MAX acrylic copolymer (ice paint)in MAX acrylic copolymer (ice paint)

•• TSP coatings TSP coatings –– Boeing TSP (range: 0 to 100Boeing TSP (range: 0 to 100°°C, sensitivity ~ C, sensitivity ~ --3%/3%/°°C)C)–– EuTTAEuTTA in commercial clear or shellac (in commercial clear or shellac (--20 to 8020 to 80°°C, ~ C, ~ --4%/4%/°°C)C)–– ThermographicThermographic phosphors in high temp binders (phosphors in high temp binders (--20 to >100020 to >1000°°C)C)


Intensity based PSPIntensity based PSP•• Excitation:Excitation:

–– Continuous Sources: Continuous Sources: LEDsLEDs, Filtered lamps , Filtered lamps (Halogen, Xenon), Lasers(Halogen, Xenon), Lasers

–– Pulsed Sources for instantaneous or periodic Pulsed Sources for instantaneous or periodic measurements: measurements: LEDsLEDs, Xenon, strobes/flash, Xenon, strobes/flash

•• DetectorsDetectors–– Cooled Scientific grade CCD cameras (slow Cooled Scientific grade CCD cameras (slow

scan, low noise), PMT, PDscan, low noise), PMT, PD

Typical PSP absorption and emission spectra Typical PSP absorption and emission spectra [from [from McLachlanMcLachlan and Bell, 1995]and Bell, 1995]


Calibration for PSPCalibration for PSP•• AA--priori Calibrationspriori Calibrations•• Paints are typically calibrated in a cell that varies pressure aPaints are typically calibrated in a cell that varies pressure and temperature and has a nd temperature and has a

reference measurement reference measurement –– this calibration is used when no onthis calibration is used when no on--model instrumentation model instrumentation exists. exists.

•• InIn--situ Calibrationsitu Calibration–– Uses standard onUses standard on--model instrumentation to calibrate the paint/images in placemodel instrumentation to calibrate the paint/images in place–– Compensates for temperature differences from reference data, spaCompensates for temperature differences from reference data, spatial temperature tial temperature

differences are averaged among all the points used to generate adifferences are averaged among all the points used to generate a calibrationcalibration•• In practice both calibrations are typically usedIn practice both calibrations are typically used


Calibration setupCalibration setup

Heat sinkHeat sink--external flowexternal flow

Silica quartz windowSilica quartz window

Pressure Pressure GuageGuage

DSA ModuleDSA Module

UV LampUV Lamp

Test sample insideTest sample inside

CCDCCDCameraCamera FilterFilter

Pressure controlPressure control

• Pressure air pipe to control the pressure in the chamber• Water recirculation to control the temperature on the

sample plate


PSP calibration image processPSP calibration image process

X (mm)

Y(m

m)

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1.41.351.31.251.21.151.11.0510.950.90.850.80.750.70.650.60.550.5

IntensityRatio

X (mm)

Y(m

m)

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120011001000900800700600500400300200100

Intensity

X (mm)

Y(m

m)

-10 -5 0 5 10-10

-5

0

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120011001000900800700600500400300200100

Intensity

X (mm)Y

(mm

)

-10 -5 0 5 10-10

-5

0

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1.41.351.31.251.21.151.11.0510.950.90.850.80.750.70.650.60.550.5

IntensityRatio

X (mm)

Y(m

m)

-10 -5 0 5 10-10

-5

0

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120011001000900800700600500400300200100

Intensity

X (mm)

Y(m

m)

-10 -5 0 5 10-10

-5

0

5

120011001000900800700600500400300200100

Intensity

Reference Intensity: Iref

Reference Intensity: Iref

P/Pref=7.2: Intensity Intensity ratio: Iref/I

P/Pref=0.23 Intensity Intensity ratio: Iref/I


Calibration curve Calibration curve –– Positive pressurePositive pressure

• Fit function: y=0.00149x^3-0.0510x^2+0.672x+0.436• Error level is below 1%

Calibration curve for the paint positive pressure and error analysis

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Intensity ratio under different pressureEr

ror %

((I r-I av

e)/Iav

e100%

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y = +0.00149x3 -0.0510x2 +0.672x1 +0.436, max dev:0.0241, r2=1.00

P/Pref

Inte

nsity

Rat

io, I

ref/I


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y = +0.217x3 -0.617x2 +0.946x1 +0.456, max dev:0.00550, r2=1.00

Pressure Ratio P/Prref

Inte

nsity

Rat

io I re

f /I

Calibration curve Calibration curve –– Vacuum pressureVacuum pressure

Calibration curve for the PSP paint under vacuum pressure and error analysis

Fit function: y=0.217x^3-0.617x^2+0.946x+0.456Error level is below 1%

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Pressure ratioEr

orr%

(( Ir- I

r ef)/

I r ef1

00%

)


Uncertainty for PSPUncertainty for PSP•• Characterization of the paint and calibration errors (aCharacterization of the paint and calibration errors (a--priori, inpriori, in--situ calibration, situ calibration,

photo degradation, paint contamination, paint intrusiveness, timphoto degradation, paint contamination, paint intrusiveness, time response)e response)•• Measurement system errors (detector noise, illumination spectralMeasurement system errors (detector noise, illumination spectral and temporal and temporal

stability, spectral leakage)stability, spectral leakage)•• Signal analysis errors (registration from model motion and deforSignal analysis errors (registration from model motion and deformation, mation,

incomplete temperature compensation, self illumination, incomplete temperature compensation, self illumination, resectioningresectioning on a nonon a non--deformed grid)deformed grid)

•• The major contributor is temperature uncertainty which can accouThe major contributor is temperature uncertainty which can account for up to nt for up to 90% of the total uncertainty90% of the total uncertainty

Pressure Sensitive Paint (PSP)/ Temperature Sensitive ...

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