Purdue University - School of Aeronautics and Astronautics Molecular Sensors Temperature Sensitive Paint John Sullivan Professor – School of Aeronautics

Purdue University - School of Aeronautics and Astronautics

Molecular SensorsTemperature Sensitive

PaintJohn Sullivan

Professor – School of Aeronautics and AstronauticsDirector - Center for Advanced Manufacturing

Purdue University

Special Government Employee – NASA

West Lafayette, IN 47907-2022Telephone (765)494-1279

Fax (765)[email protected]

mailto:[email protected]


Objective

• Measure temperature distribution and heat transfer distribution on a hydraulic experiment at Beihang University in the next three weeks.


Lamp LED

CCD camera

Temperature Sensitive Paint

Luminescent

MoleculeExcitation

Emission

QuantitativeHeat Flux

Mach 10 –Tunnel 9

Feature Detection-Transition-Vortices-Separation

High-mass planetary probes are affected by transitionLaminar flow results in 2-8 times less aeroheating


TSP -Temperature Sensitive Paint PSP - Pressure Sensitive Paint

E m is s io n

O p tic a lF ilte r

E x cita tio nU V L a m pL a s e rF la s h L a m p

D etec to rC C DP M TP D

B in d e r P o ly m e r P o ro u s S o lid

L u m in e s c e n t M o le c u le

Calib rate O u tp u tfor Tem p eratu reor P res s u re

Photo-physical process:

-absorb a photon

-transition to excited state

-Oxygen quenching (PSP)

or thermal quenching (TSP)

=> Pressure and/or temperature

dependent luminescent intensity

and luminescent lifetime


Temperature Sensitive Paint High temperature causes non-radiative decay “thermal quenching”• Obeys Arrhenius relation: For limited temp. range

lT T Tref ref

nI(T)

I

E

Rref g( )

1 1

• Similar molecules to PSP, but in oxygen impermeable binder

I

T

to

C~

1 5%0


Luminescent Paint (TSP/PSP)

coated model

Excitation

short-pass filter

excitation source

Acquisition

photodetector

long-pass filter

Iref/IP/Pref

Data Processing

Iref/I

P/Pref

calibration

surface maplow costeasy to apply


Current State of the Art of PSP/TSP

•Temperature Sensitive Paint–T= -196 C to 200 C M=.01 to 10–Accuracy 1 Degree Centigrade Resolution <. 01 C–Time Response 1 sec Typical (<1 ms demonstrated)

•Pressure Sensitive Paint–P=.001 to 2 atm M=.05 to 5–Accuracy 1.0 mbar Resolution .5 mbar–Time response .5 sec Typical

( 1 microsec demonstrated)


Basic Photophysics


Jablonski Diagram

f ph kic kisc

kisc

S0

T1S1

(triplet state)

(ground state)

(singlet state)

vibration intersystem crossing (ISC)

internal conversion (IC)

fluorescence phosphorescenceexcitation

kic

kic

S2

Sn


Data Reduction Methods


Data Reduction Methods

• Intensity Reference• Multi-luminophore Paint• Time Based Methods


Intensity Reference

• Wind Off / Wind On• Corrects for non-uniform model

motion, nonuniform concentration

ref

refref

p

pTBTA

I

I)()(


Multi-luminophore Paint

• Luminescent molecules with different pressure and temperature sensitivities, overlapping excitations and different emission wavelengths


Time Based Methods

• Direct Decay• Phase Based


Direct Decay• Modulated Light Source

– Pulse, Sine wave, square wave• Point Systems• Camera Systems with image intensifier

Time

Intensity


Phase Based• Lock-in Amplifier• FLIM (Fluorescent Lifetime Imaging Method)

t(arb)

0 5 10 15

am

plit

ude(a

rb)

0

1

2

3

ExcitationEmission

ref

P

PD(t)C(t)ref

tan()=


Temperature Sensitive PaintTSP

Same or similar Luminophore as in PSP

Oxygen impermeable binder


Temperature Sensitive PaintThermographic Phosphors Infrared CameraTemperature Sensitive Liquid CrystalsArray of Thermocouples

Global Surface Temperature Measurements

Toolbox


Temperature Sensitive Paint

• Surface Temperature– Correction for Pressure Sensitive Paint

• Transition Detection• Quantitative Heat Transfer• Shear Stress - Heat transfer Analogy


Temperature Sensitive Paint Calibrations


TSP Time Response

c

h

Laser Pulse Heating

density of polymer c specific heat paint thickness h convection heat transfer coefficient


Ruthenium based TSP tris(2,2’-bipyridyl)ruthenium - Ru(bpy)

Wavelength (nm)

200 300 400 500 600 700 800 900

Inte

nsity

(ar

b un

its)

0

100

200

300

400

Excitation Emission

UVUVlamplamp

BlueBlueLEDs LEDs

Greenlaser

Excitation and Emission Spectrum of a Ruthenium Based Paint


EuTTA based TSP Europium III Thenoyltrifluoroacetonate EuTTA

Excitation Spectrum Emission Spectrum


EuTTA in Model Airplane Dope


Applications Temperature Sensitive Paint

(TSP)

• Transition Detection– Low Speed– Cryogenic Wind Tunnel

• Quantitative Heat Transfer– Camera Based – M=10– Scanning System Laser Spot Heating


Transition DetectionLow Speed

TSP –EuTTA in dope

Wing heated with photographic spot lampsto ~20 C above ambient

8 bit Camera


Raw Image(false color)

ResultsLow Speed Transition


Quantitative Heat Transfer


Heat Transfer Data Reduction• Model make out of Thermally Insulating material• Measure

• Match the temperature to analytic solution for a semi-infinite body (Cook-Felderman)

• Make Model out of a Conductor with a thin insulator on the surface

)(tTsurface

)(/ modelsurface TTkq

Method 1

Method 2

1 model k

1 model k


Tunnel #9M=10Run time ~1.0 sec1.5 meter Diameter


TSP - EuTTA in dopeMetal modelInsulating Layer – mylar film (model airplane monokote) 50 microns thick

Raw Image




Mach-6 Quiet Tunnel

National Aeronautics and Space Administration

www.nasa.gov 35

-1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1x 10

4

Qpa

ints

[W

/m2 ]

run8.tif

-1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1x 10

4

QH

FS-4

[W

/m2 ]

HIFiRE-5 Model

Quiet Flow, α=0

Re = 2.6*106 /ft


Temperature profile of machining acquired with TSP sensor (Rubpy)

350 400 450 500 550 600

250

300

350

400

450

20

30

40

50

60

70

80

Area of

Interestworkpiece

Cutting toolChip

degree C

350 400 450 500 550 600

250

300

350

400

450

20

30

40

50

60

70

80

Area of

Interestworkpiece

Cutting toolChip

350 400 450 500 550 600

250

300

350

400

450

20

30

40

50

60

70

80

Area of

Interest

350 400 450 500 550 600

250

300

350

400

450

20

30

40

50

60

70

80

Area of

Interestworkpiece

Cutting toolChip

degree C

Temperature profiles from TSP measurement of grinding stainless steel at spark-out condition

TSP Measurements ofMaterial Temperature

Documents

Purdue University - School of Aeronautics and Astronautics Molecular Sensors Temperature Sensitive Paint John Sullivan Professor – School of Aeronautics