Laser Diagnostics for Hypersonic Ground...

Laser Diagnostics for Hypersonic Ground TestRonald K. Hanson and Jay B. JeffriesHigh Temperature Gasdynamics LaboratoryStanford University

1. TDL sensors: vision/fundamentals

2. Sensing for dual-mode @ UVa

3. Sensing for HyPulse @ ATK

4. Advanced concepts for future needs

CO2, T for hydrocarbon fuel

Normalized WMS to suppress noise

Scanned WMS for simultaneous multi-parameter sensing

AFOSR/NASA National Center for Hypersonic Combined Cycle Propulsion, Review, June 2011

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National Center for Hypersonic Combined Cycle Propulsion

Vision for Laser Sensing in Hypersonic Propulsion

– Diode laser sensors offer prospects for time-resolved, multi-parameter, multi-location sensing for performance testing, model validation, feedback control

Exhaust(T, species, UHC, velocity, thrust)

Inlet and Isolator(velocity, mass flux, species,

shocktrain location)

Combustor(T, species, stability)

1 2 3 4 5

Diode Lasers

Fiber Optics

Acquisition and Feedback to Actuators

6

– Project focuses on new tools and data for hypersonic ground test• Develop, test, and validate at Stanford; targets are T, H2O, CO2, O2, V, & HCs• Apply to ground test facilities @ UVa• Transition to application in HyPulse @ ATK

– Future opportunities in other test facilities, flight?2

National Center for Hypersonic Combined Cycle Propulsion 333

Absorption Fundamentals: The Basics

TDL absorption: non-intrusive, time-resolved line-of-sight measurements Beer-Lambert relation

Spectral absorption coefficient

Mass and momentum flux from and V Many-line data for non-uniform T(x), Xi(x)… Approaches: Direct absorption or WMS

LnLkII

io

t exp)exp(

PPTTSk ii ),,()(

Wavelength-multiplexing for multi-parameters Ratios of lines yield T T and yield i (mole fraction) or ni or

absorbance

Unshifted line

1 2 3

Doppler shifted lines

I0

It

L

Multiplexed-cw-lasersVisible, NIR, extended

NIR, mid-IRV

Shifts & shape of contain information (T,P,i) V from Doppler shift of spectra


Comparison of Direct Absorption and WMS (2f/1f)

WMS2f&1f

Direct Absorption

Gas sample

Io It

Direct absorption: Simpler, if absorption is strong enough WMS: More sensitive especially for small signals (near zero baseline)

Ratio of two WMS-2f signals provides T (same as direct absorption) WMS with TDLs improves noise rejection (especially for non-absorption losses) Since both 2f and 1f signals are proportional to I; 2f/1f independent of optical losses

Injection current tuning

+ Injection current modulation @f

4

i’

i 0.4 0.5 0.6 0.7

0.00

0.25

0.50

0.75

Abs

orba

nce

W avelength (re lative cm -1)

D irect absorption lineshape

0.4 0.5 0.6 0.7 0.8 0.9 1.00.0

0.1

0.2

0.3 Direct Absorption Scan

Lase

r Int

ensi

ty S

igna

l

T ime(ms)

Baselinefit

for Io

Lockin@1f, 2f

-0.02

0.00

0.02

0.04

WMS-2f lineshapeNor

mal

ized

2f s

igna

l

Wavelength (relative cm-1)0.4 0.5 0.6 0.7

0

2

4

6

8

WMS Scan

WM

S S

igna

l

Time (ms)0.4 0.5 0.6 0.7 0.8 0.9 1.0


Diagnostics to Support Dual-Mode Combustion ModelingBenchmark Measurements in Combustion Tunnel @UVa

UVa facility provides steady operation Stanford TDL diagnostics will target combustor and combustor inflow

Time resolution (cw sensors allow frequency analysis) Spatial resolution

Translate LOS (vertical) for spatial resolution Monitor at multiple locations: Inflow & three downstream Targets: H2O & T for H2 fuel; CO2 & T for HC fuel

Future plans will add velocity

Mach 2 Nozzle

Isolator

CombustorTomography

Extender& CARS

TDL measurement planes

5


Stanford TDLAS Timeline for UVa Tests

Measurement Campaign 1 (March 2010) UVa exit plane measurements

Measurement Campaign 2 (November 2010) 2D-resolution measurements via windows in the combustor Inflow plane characterization (with steam injection) revealed window leaks Flame-holding instabilities led to window failure preventing combustion exps

Plans for measurement campaign 3 (fall 2011) Complete 2D T and χH2O measurements in combustor

Final window design awaits combustion stability tests


Review of Year 1: Exit Plane Results Stanford–UVa exit plane diagnostics

LOS path-averaged T and χH2O

Comparison of direct absorption and WMS WMS increased sensitivity with reduced uncertainty

Test Cases Validation of facility steam injection

Simulated vitiation with 9% and 12% H2O H2-Air Combustion w/ ϕ=.33

Results show complete combustion at tunnel exit

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Mode Expected Value DA WMS 9% Steam 700-900K 860±30K 831±9KExit value 9.1±0.4% 9.1±0.2% 9.1±0.1%

12% Steam 700-900K 875±50K 850±6KExit value 12.0±0.5% 12.1±0.5% 11.5±0.1%

H2/Air Combustion 1800-2200K 1802±94K 1765±41K=0.33 Exit value 13% 12.8±0.5% 11.5±0.1%


Review of Year 2 Measurements

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2D measurement system Optics on computer-controlled translation stages Measurements at multiple axial locations (Y)

Sub-mm spatial resolution on each plane (X) Measurement plan

Combustor inflow measurements with steam injection (completed Nov 2010)

Combustion measurements at 3 axial locations downstream of fuel injection Unstable flameholding and subsequent

window failure delayed these measurements (planned for fall of 2011)

X

Y


Inflow-Plane Measurements Revealed T GradientDistribution of LOS T transverse

to inflow w/11% added steam

Error Bars Represent ±1 from 500 samples average (0.5 seconds)

≈ 0.04” From Wall Opposite Fuel Injector

Gradient in T likely due to cold-air leak around window on ramp wall side Observation of unstable flameholding consistent with leak

Next measurement campaign awaits successful/stable flameholding at UVaSCF (tentatively fall 2011)

Ramp wall

Inflow measurement

plane

Translating LOS for TDL

Fuel injection


Diagnostics to Support HyPulse Testing @ATKBenchmark Measurements in HyPulse @ATK

M5 Facility Nozzle Test Article

Driver gas Air (test) gas

Reflected Shock Tunnel @ ATK GASLMach 5-25

Diaphragm

10


Diagnostics to Support HyPulse Testing @ATKBenchmark Measurements in HyPulse @ATK

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P = 60 kPaT = 1700 K10-15 ms test time

Planned test conditions:

Inlet

Flow exit

Ramp fuel injectionH2 fuel

Need: data for CFD validation of combustion efficiency (completeness of combustion), fuel penetration, flow characterization, etc.

Plan: Simultaneous T and χH2O at multiple lines-of-sight at several axial locations in HyPulse hydrogen fueled combustor

Challenge: High-speed (10-15ms test time), compact, multi-LOS sensor design Requires fast, sensitive sensor concepts Requires miniaturized optical components


Miniaturization of Optical SystemNew Fiber Optics Enable Five LOS over 1” Flowpath

Five measurement LOS in each downstream plane Spatially-resolved measurements needed to validate model results Axial measurement plane locations monitored sequentially

Challenge: Optical system engineering New fiber collimators designed, fabricated, and laboratory tested

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Supersonic Air Exhaust

Optical Fibers

5 Beam PathsH2 Fuel Injector Ramp

L~1”


Two-Color TDL Sensor for H2O and T

Line selection Selected H2O features at 1338.3 nm and 1391.7 nm

Database and sensor performance measured in Stanford heated cell

Absorption measurement strategies Scanned-Wavelength Direct Absorption – 20kHz bandwidth 1f-normalized WMS-2f – 250kHz bandwidth w/ improved SNR

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T sensor validation in heated cell

Heated cell


Stanford TDLAS Timeline for ATK Tests

Completed (Spring 2011): Sensor design

(line selection, measurement techniques and locations) Validation of spectroscopic database Fiber-coupled 3 mm collimation optics designed, fabricated and tested

Remaining tasks (Summer 2011) Test article modifications @ ATK Test sensor package in Stanford shock tube or expansion tube

First HyPulse measurement campaign Planned for Fall 2011

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Continued Development of New Sensor Concepts

Advanced sensor concepts to meet future needs in ground test at UVa & ATK1. New sensor for CO2,T – needed for hydrocarbon fuels

Demonstration measurements in shock tubes - Complete2. 2/1f normalization strategy for WMS – to suppress noise from non-absorption

losses in transmitted intensity Demonstration measurements of gas T in presence of liquid aerosol- complete

3. New scanned-WMS concepts for simultaneous, multi-parameter sensing based on refined model that accounts for simultaneous laser intensity and wavelength modulation – needed for precision velocity Demonstration measurements in Stanford expansion tube – just initiated

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Access to CO2 enabled by new DFB lasers for >2.5 m

The band strength near 2.7 m is orders of magnitude stronger than NIR

CO2, T Sensor Using Extended-NIR Extended NIR Enables Large Increase in Sensitivity

Many candidate transitions for optimum line pair (depending on T)


Extended-NIR Sensor for CO2, T

1. An optimum line pair (R(20) and P(70) was selected Isolated from H2O, wide separation in E”

2. Validate in shock tube Demonstrate achievable precision

NIR Fiber-coupled Diodes

Extended-NIR

E”=316.77 cm-1

E”=1936.09 cm-1

m

1%CO2, L=10cm

Strategy: Sense T by ratio of absorption by two CO2 transitions


Shock-Tube Validation of Extended NIR CO2, T SensorPrecision Time-Resolved T from WMS-2f/1f of CO2

Validate fast, sensitive strategy for CO2, T using a shock tube

Shock wave Test mixture

InSb Detector

DFB laser

Ratio of WMS-2f signals sensitive to temperature, insensitive to pressure (1-2 atm) Sensor provides accurate and precise time-resolved temperature

Ratio of WMS-2f/1f signals for R(28) and P(20) CO2 transitions

900 1000 1100 1200 1300 1400 1500 1600

1.5

2.0

2.5

3.0

3.5

4.0 P = 1.0 atm P = 2.0 atm

2f s

igna

l rat

io

Temperature [K]

1~2743nm2~2752nm


Shock-Tube Validation of Extended NIR CO2, T SensorTemperature vs Time in Shock-Heated Ar/CO2 Mixtures

Temperature data agree well with T5 determined from ideal shock relations Temperature precision of 3 K demonstrated! Unique capability for real-time monitoring of T in reactive flows High potential for supersonic combustion applications

0 3 6 9 12-30

-20

-10

0

10

20

30

5 K

Diff

eren

ce o

f Mea

sure

d T

& T

5 [K]

Time [ms]

0 K

Reflected shock arrival

0 3 6 9 120

300

600

900

1200

0.0

0.6

1.2

1.8

2.4

Time [ms]P

ress

ure

[atm

]

Tem

pera

ture

[K]

Reflected shock arrival

Incident shock arrival

1.2 atm, 2%CO2 in Ar

Tideal

National Center for Hypersonic Combined Cycle Propulsion20

Demonstrate normalized WMS-2f/1f No loss of signal when beam attenuated (e.g., scattering losses) No loss of signal when optical alignment is spoiled by vibration

Normalized WMS-2f/1f signals free from window fouling and particulate loading

1f-normalized WMS-2f Improves SNRAccounts for Non-Absorption Transmission Loss

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.350.00

0.03

0.06

0.09

0.12

2f/1

f Mag

nitu

de

Time (s)

0.0

0.2

0.4

0.6

1f M

agni

tude

0.00

0.02

0.04

0.06

2f/1f

1f Magnitude

2f M

agni

tude

2f Magnitude

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.70.00

0.03

0.06

0.09

0.12

2f/1

f Mag

nitu

de

Time (s)

0.0

0.2

0.4

0.6

1f M

agni

tude

0.00

0.02

0.04

0.06

2f/1f

1f Magnitude

2f M

agni

tude

2f Magnitude

1392 nm, Partially Blocking Beam 1392 nm, Vibrating Pitch Lens

Modulated TDL near 1392nm

Pitch LensDetector

Fixed WMS-2f/1fAmbient H2O (T=296 K, 60% RH) L=29.5 cm, ~6% absorbance)

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1f-Normalized WMS-2f for CO2 with Scattering from ParticlesValidate in Aerosol-Laden Gases

Aerosol shock tube experiment: 2% CO2 /Ar in n-dodecane aerosol, L=10 cm P2=0.5 atm; P5=1.5 atm

2f/1f TDL sensor successfully measures T in presence of aerosol!

May prove useful in silane-H2 fueled combustion

W. Ren, J.B. Jeffries, R.K. Hanson. Measurement Science and Technology 21 (2010)


New Extension of WMS Theory for TDLs

Existing Strategy: Fixed- WMS Well-established: improves sensitivity and noise rejection

High data rate & and facile real-time analysis Calibration-free with inclusion of laser tuning and spectroscopic models

The Opportunity: Rapid scanning of WMS would allow simultaneous monitoring of i, T, & V 2f/1f spectra include lineshape information (T, P)

The Problem: Rapid wavelength scanning with TDLs Simultaneous variation in and I from current-tuned TDLs distort laser WMS

The Solution: New model includes phase shifts and non-linear signal coupling Experiments underway to validate new model

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Stanford Expansion Tube Supersonic flow facility capable of producing a wide range of

flight conditions with realistic chemistry but with limited test time

Planned Measurements to Demonstrate Scanned WMS

Pressure trace identifies well-characterized test time

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Test Section

Dump TankExpansion SectionDriven SectionDriver

Section

Test

Sec

tion

Pres

sure

[kP

a]

Time [s]

Expansion Gas Arrival

Test Gas Arrival

Test Time End


Supersonic Demonstration of Scanned WMS

Scanned WMS demonstration in Stanford expansion tube Flow model with configurable beam paths T, V, and XH2O data rate: 25 kHz

Demonstration experiments underway

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Summary and Acknowledgements Summary

Sensor and hardware for spatially-resolved gas T ready for dual mode @UVa Status: Measurement campaign planned fall 2011

Miniaturized, multi-path sensor for ATK nearly ready for shock tube/expansion tube validation Status: Validation test underway, planned campaign fall 2011

New sensor strategies New extended-NIR CO2, T sensor – combustion efficiency for HC fuels 1f-normalization of WMS suppresses flow-field noise – enabling technology New model for -scanned-WMS – high speed velocity, T, XH2O sensor

Acknowledgements Collaborators: Goyne & McDaniel at UVa, Cresci & Tsai at ATK Current students: Chris Goldenstein, Ian Schulz, Wei Ren, Christopher Strand

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