Nonequilibrium Gas Dynamics: Understandinggg of High-Speed … · 2019-12-12 · The Ohio State University Nonequilibrium Thermodynamics Laboratories Nonequilibrium Gas Dynamics:

Nonequilibrium Thermodynamics Laboratories The Ohio State University

Nonequilibrium Gas Dynamics: Understanding of High-Speed Flows g g p

at Strong Energy Mode Disequilibrium

Igor V. Adamovich

Seminar at the Department of Aeronautical Engineering

January 28 2008January 28, 2008

NETL Group


Faculty:

Igor Adamovich Walter Lempert Bill Rich Vish SubramaniamIgor Adamovich, Walter Lempert, Bill Rich, Vish Subramaniam

Post-docs:

Naibo Jiang, Evgeny Mintusov, Munetake Nishihara, Anna Serdyuchenko

Students:

Sherrie Bowman, John Bruzzese, Inchul Choi, Ashim Dutta, Saurabh Keshav, Mruthunjaya Uddi, Matt Webster, Yvette Zuzeek

Scope of Research


• Generation and sustaining of stable high-pressure weakly ionized plasmas

• High-speed flow control by nonequilibrium plasmas / MHDg p y q p

• Ignition, combustion, and flameholding by nonequilibrium plasmas

• Molecular gas lasers

• Kinetics of gases, plasmas, and liquids at extreme thermodynamicdisequilibrium

• Molecular energy transfer processes: excitation and relaxation of vibrationaland electronic levels, chemical reactions among excited species, plasmaradiation

• Electron and ion kinetics: ionization, recombination, electron attachmentand detachment, charge transfer, inelastic electron-molecule collisions

• Flow visualization and optical diagnostics• Flow visualization and optical diagnostics

NETL: Major Research Projects ($11M since 1997)


“Air Plasma Ramparts Using Metastable Molecules” (AFOSR MURI ′97-′02)

“Anomalous Shock Wave Propagation and Dispersion in Weakly Ionized Plasmas”(AFOSR ′99-′01, NASA ′99-′00)

“Effect of Vibrational Nonequilibrium on Electron Kinetics in High Pressure Molecular Plasmas” (NSF/DOE, ′00-′06)

(AFRL/DAGSI, ′01-′03) “Non-Thermal Ignition Phenomena for Aerospace Applications”(AFRL/DAGSI, 01 03) Non Thermal Ignition Phenomena for Aerospace Applications

“Generation and Characterization of Stable, Weakly Ionized Air Plasmas in Hypersonic Flows” (AFRL/DAGSI, ′01-′03)

“E T f R t d M h i f H l it V hi l R di ti ” (AFOSR“Energy Transfer Rates and Mechanisms for Hypervelocity Vehicle Radiation” (AFOSR, ′01-′07)

“Effect of MHD Forces on Stability and Separation of Nonequilibrium Ionized Supersonic Fl ” (AFOSR ′02 ′04)Flow” (AFOSR, ′02-′04)

“Plasma Flow Control Technology for Hypersonic Boundary Layer Transition Control” (AFRL, ′02-′05)

“Electric Discharge Oxygen-Iodine Laser” (AFRL, ′04-′06)

NETL: Major Research Projects (continued)


“Pl A i t d I iti M d l f A P l i S t ” (AFOSR ′04 ′06)“Plasma Assisted Ignition Module for Aerospace Propulsion Systems” (AFOSR, ′04-′06)

“Nonequilibrium Supersonic Magnetogasdynamic Wind Tunnel” (AFOSR, ′05-′07)

“Instrumentation for Generation and Optical Diagnostics of Repetitively Pulsed Fast f p g f p yIonization Wave Plasmas in Supersonic Flows” (AFOSR DURIP, ′05-′06)

“Active Control of Jet Noise Using Plasma Actuators” (NASA ′02, ′05-′06, with GDTL)

“Electric Discharge Oxygen Iodine Laser Operating at High Pressure” (JTO ′06 ′08)Electric Discharge Oxygen-Iodine Laser Operating at High Pressure (JTO, 06- 08)

“Kinetic Studies of Plasma Assisted Combustion By Non-Equilibrium Discharges” (AFOSR, ′07-′09)

“Nonequilibrium Ignition and Flameholding in High-Speed Reacting Flows” (NASA, ′07-′09)

“Supersonic Jet Noise Suppression Using Plasma Actuators” (NASA ′07-′09, with GDTL)

“Nonequilibrium Gas Dynamics” (AFOSR ′08-′10)


NETL Research in Broader Context:NETL Research in Broader Context:National Hypersonic Basic Research Plan (AFOSR, NASA, SNL)

Thrust Areas

• Boundary Layer Physics

• Nonequilibrium Flows*

Sh k D i t d Fl• Shock-Dominated Flows

• Environment-Material Interactions

• High-Temperature Materials

• Supersonic Combustion*p* studied in NETL


C iti l S t I tCritical System Impact of Nonequilibrium Hypersonic Flows

• TPS Design: Current uncertainties for reacting air (andother gases) at re-entry and cruise create estimated factor oft i di ti h t l d d d i i l ditwo errors in predicting heat load and designing leadingedges, TPS

• Aerodynamic Control: High-altitude aerodynamicsincluding pitching moments and reaction controlsystems/surfaces not predictable Wake heating and largesystems/surfaces not predictable. Wake heating and largeangle-of-attack flows not predictable

Nonequilibrium Hypersonic Flows:Key Technical Issues


Key Technical Issues

Planetary Entry

Boundary LayerTransition

Very High AoA Aerodynamics

Plasma/Comm Issues

AerothermodynamicGl b l St ik /

StagnationHeating

yplasma generation

Wake Flow & Separation

Leading Edges and RCS

Global Strike / Responsive Space

AblationSmall-Scale

Geometric Effects

Wake Flow & SeparationDynamics

Nonequilibrium Hypersonic Flows:Key Technical Issues (continued)


Key Technical Issues (continued)

Pl bl k tPlasma blackout:plasma generated by hypersonic flow blocks telemetry – big issue for both

d l t d tidevelopment and operation

Space Situational Awareness: track/ID unknown missiles / satellites

using their EM signatures

How Good is the Current State of the Art (SOA)?


Temperature behind a 12 km/sec shock Static temperature and NO fractionTemperature behind a 12 km/sec shockpredicted by SOA model is not even closeto experiment (in pure nitrogen!)

Matsuda et al, JTHT, 2004

Static temperature and NO fractionpredicted by SOA model in a M=15expansion “air” flow are off.

Experiment: LENS, M=15, run timeMatsuda et al, JTHT, 2004 Experiment: LENS, M 15, run time~1 msec

Candler et al, AIAA Paper, 2007

Experiment ModelFlow velocity, m/s 4517 4354Temperature, K 250-300 620Temperature, K 250 300 620NO fraction, % 1.5 5.4

We have a problem (might be both

Basic research vision for the next 30 years must include development and

We have a problem (might be both with experiment and modeling)

validation of design tools that simulate hypersonic vehicleaerothermodynamics and propulsion

Key Challenges


• Due to shock waves, boundary layers, or rarefaction, concept of singleDue to shock waves, boundary layers, or rarefaction, concept of singletemperature breaks down, fluid dynamic equations break down,chemistry is not well understood

• Understanding / predicting these flows requires insight into molecular /• Understanding / predicting these flows requires insight into molecular /surface / radiation / plasma interactions

• Four interacting research areas:

B i h i l

Ground test, flight data:Facilities, advanced diagnostics

Basic chemical physics

Aerothermo simulations:speed, validity

Simplified “good enough” models:gases, gas-surface, plasma

N d t di t lib i h i fl b d d h iNeed to predict nonequlibrium hypersonic flows based on sound physics, not extrapolations of measurements or empirical correlations


St t i (L T ) G l

F t d l t f b th t h i l d h f th

Strategic (Long Term) Goals

Foster development of both technical and human resources for theexploration, characterization and control of flows at high Machnumbers with significant thermochemical nonequilibrium.

• Development of validated physics-based tools for prediction ofheating, aerodynamics, etc of hypersonic system

• Transfer of proven, physics-based models and simulation methodsand complementary technical expertise to industry and appliedresearch

• Development and maintenance of essential human resources topcapitalize on and continue progress in this area.


Objectives Defined by Nonequilibrium Thrust Panel

Near term (<5 years):

Objectives Defined by Nonequilibrium Thrust Panel at NASA / Air Force Workshop, June 2007

( y )• Measure key air reaction rates and mechanisms at higher temperatures• Develop improved catalytic wall-boundary condition for hypersonic flow with

typical surface• Plan design fund facilities for well-characterized reacting hypersonic flow data• Plan, design, fund facilities for well-characterized reacting hypersonic flow data• Obtain ground and/or flight data with spectral, species, or spatially-resolved

reacting hypersonic flow. Utilize/coordinate with NATO RTO results

Mid t (5 10 )Mid-term (5-10 years):• Measure / accurately calculate all important atmospheric (earth/other) gas

reactions at ultra-high temperatures• Validate advanced ultra-high temperature models for excited states, relaxation,

f lli i l i bl isurface collisions, catalysis, ablation• Complete integrated radiation transport models; accurate ultra-high

temperature gas transport properties• Well-characterized reacting hypersonic flow data using advanced diagnostics• Fast CFD and kinetic simulation tools with integrated physics models

NETL Contribution: OutlineNonequilibrium Thermodynamics Laboratories The Ohio State University

I. Ability to generate and sustain steady-state supersonic flows withstrong energy mode disequilibrium and targeted energy loading

II. In-depth flow characterization using advanced optical diagnostics

III. Physics-based, validated molecular energy transfer andnonequilibrium chemical reaction models

IV. New research program: characterization of nonequilibriumsupersonic flows, developing instrumentation for use at a nationalp , p ghypersonic facility (LENS)

V. Future research thrusts

A Bit of History: Shock Weakening by Weakly Ionized Plasmas


Shock Weakening by Weakly Ionized Plasmas

Ballistic range / glow discharge experiments

(Russia, 1980’s; U.S., 1990’s)

• shock stand-off distance increases

• wave drag reduction up to 50%

Suggested Interpretations

• vibrational relaxation

• ion-acoustic wave

• nonuniform heatingBow shock around a sphere. Air, P=9.5 torr, u=1600 m/s g, ,(AEDC, 1999)

Case 1: Steady State Plasma Shock Experiment

Nonequilibrium Thermodynamics Laboratories The Ohio State UniversityTransverse RF discharge electrodes

Aerodynamically Stabilized DC Gl Di hDC Glow Discharge

M=2 plasma flows with and without RF ionization


P0=250 torr,N2/He=50/50 mixture,

Ptest=48 torrtest

RF discharge offn 109 cm-3ne~109 cm 3

RF discharge onne=(1-3)⋅1011 cm-3

e ( )

Stable, uniform, and diffuse plasmas in both cases

Shock weakening by the plasma


Shock angle

112

116Shock angle

RF off

108

100

104

RF on

1 2 3 4 5 6 7 8 9 10 11 12 13

96

Time, sec

Shock weakening by the RF plasma: Δα=150, ΔM=-0.2

Frame numberSlow shock weakening and recovery:

thermal effect

Flow temperature measurements(CO FT infrared emission spectroscopy – with 4% CO added)


l [I /(J'+J"+1)]Intensity

(CO FT infrared emission spectroscopy with 4% CO added)

l [I /(J'+J"+1)]-4.0

ln[Iem/(J'+J"+1)]

230 W DC

T=190 K (J'=1-12)

DC discharge on (230 W)-4.0

ln[Iem/(J'+J"+1)]

230 W DC, 200 W RF

T=200 K (J'=1-12)

-6.0

T=221 K (J'=12-19)

-6.0

T=271 K (J'=12-19)

-8.0-8.0 with RF

0 100 200 300 400

-10.0

2140 2160 2180 2200 2220

RF discharge on (200 W)

0 100 200 300 400

-10.0

no RF

J'(J'+1)

Al t fl h ti b th di h

Wavenumbers J'(J'+1)

Almost no core flow heating by the dischargeNoticeable boundary layer heating

Temperature measurements summary


Rotational temperature, K

280

300

Low J' fit (J'=1-12)

High J' fit (J'=12-19)

ΔT=15 K (low J′ fit)

260

Fit to all data (J'=1-19)

ΔT=50 K (high J′ fit)

220

240

ΔT=35 K

(all available data fit)200

(all available data fit)

0 40 80 120 160 200

180

RF power, W

Temperature rise consistent with shock angle change (ΔM=-0.2 for both)Thermal effect

Case 2: Supersonic Flow Control by Low-Temperature MHD


by Low Temperature MHD

Optical access window

up

• Pulsed electric field perpendicular to the flow, parallel to magnetic field

Flow

Static pressure portdown

p

Sustainer current

p g

• DC sustainer field perpendicular both to flow

DC electrode

Pulsed electrode block MTV pump laser

b

and pulsed electric field

• Optical access along vertical and horizontal line-of-sightblock

Optical access window

beam

B

Magnet pole

Flow

west

and horizontal line of sight

• Four combinations of

Static pressure east

current and magnetic field directions: Accelerating or decelerating Lorentz force,p

porteast

Decelerating force Accelerating force

decelerating Lorentz force, j x B

Low-temperature MHD test sections (M=3, M=4)


Static pressure port

• Contoured nozzle

p p

• 12 cm long, 4 cm x 2 cm test section• Equipped with pressure ports and Pitot ports• Ceramic/copper pulsed and DC electrode blocks

St ti P 0 2 1 0 t• Stagnation pressure P0=0.2-1.0 atm• Ionization: repetitively pulsed discharge

Plenum M=4 nozzle insert M=4 test section Diffuser insert

Flow

Laser Differential Interferometry (LDI) diagnostics: BL density fluctuation spectra measurements


Magnet pole

BL density fluctuation spectra measurements

He-Ne laser

Magnet pole

Flow

To vacuum

Mirror Magnet coil

FlowReference beam Probe

beamMirrorPhotodiode

Boundary layer visualization by laser sheet scattering:comparison with a 3 D compressible Navier Stokes flow code


comparison with a 3-D compressible Navier-Stokes flow code

2

5

5

ICCD camera

Laser sheetOptical window

Distance to wall

Test section

P0=250 torr, 2 mm from the wall

0

Flow

Scattering signal

λ/4 plateCylindrical lens

Mirror

LaserCylindrical lens

P0=150 torr, 2 mm from the wall

Repetitively pulsed discharge (40 kHz rep rate)+ DC sustainer in M=4 air flow


+ DC sustainer in M=4 air flow

Air, M=4, B=1.5 T Shock train , ,P0=1 atm, Ptest=13 torr, Umax=13 kV

Pl l i if d t bl f ti f l d

Shock train in a M=3 low-pressure diffuser

Plasma always remains uniform and stable for run times of several seconds

How did we achieve that?

Pulser-sustainer discharge: stable plasmas at high powersM=3 nitrogen flow P0=1/3 atm Pt t=8 torr


M 3 nitrogen flow, P0 1/3 atm, Ptest 8 torr

Current [A]Voltage [kV]

1.0

2.0[ ]

5

10g

25 μs

0.05

0

-1.0-10

-530 ns

0 25 50 75 100Time [μs]

-2.00 25 50 75

Time [μs]

-15

<I> = 0.9 A

DC discharge power 1.4 kWPulse energy 1-2 mJ

Time averaged pulsed discharge

<σ>=0.073 mho/m , B=1.5 T

g p gpower 40-80 W

MHD effect on boundary layer density fluctuations:Accelerating vs retarding Lorentz force


Accelerating vs. retarding Lorentz force

Intensity, dBDecelerating force

40

-35y,Decelerating force

Bj

B

-45

-40

Air

B B

j

-50

R=0.5 kOhm, <I>=0.78 A6 mm away from the wall

retarding forceFlow

10000 100000-55

accelerating force

no MHD forceAccelerating force

Flow

10000 100000Frequency, Hz

Air, M=3, P0=250 torr

jBB

, , 0Boundary layer fluctuations

increase by retarding Lorentz forcej

Flow acceleration / deceleration by MHD:Static pressure measurements in M=3 air flows


Static pressure measurements in M 3 air flows

Air, P0=250 torr, Ptest=8.7 torr

UPS=2 kV, R=0.5 kΩ, <I>=1.2 A1.3

Normalized pressure

di f

Dry air: B=1.5 T, R=1.0 kΩ

Pulsed discharge duration 0.5 s1.2

Retarding force

B east, j down

B west, j up

11.0=Δ−Δ

ppp AR1.1

Accelerating force

B east, j up

B west, j down

Joule heating factor:

p1.0

Joule heating factor:

α=0.10(90% of discharge energy

1.0 2.0 3.0i

0.9Pulser alone

(90% of discharge energy stored in N2 vibrations)

Time [s]

Comparison with quasi-1-D theory


Normalized pressure N li d diff1.3

Normalized pressure

Joule heating factor

α = 0.1

0.15Normalized pressure difference

1.1

1.2 α = 0.05

α = 0.0 0.10

1.0

Ai

0.05 Nitrogen

Dry air

-2.0 -1.0 0.0 1.0 2.00.9

Air

Nitrogen

0.0 0.5 1.0 1.50.00

Eq. (9)

Eqs. (2-5)

Decelerating force Accelerating force

Current [A] Current [A]

( ) LBjMpp ⋅+−

⋅≅Δ−Δ112

2γDecelerating force Accelerating force

ΔM±=-0.13 at I = ±1.0 A in air

LBjM

pp zyAR ⋅−

⋅≅Δ−Δ1

2 2

Very good agreement with experiment

Comparison with 3-D Navier-Stokes code:velocity and pressure profiles


velocity and pressure profiles

10Wall pressure, torr

6

8

10MHD forcing region

2

4

baseline

accelerating

d l ti

accelerating force

0 2 4 6 8 10 12 14 16 180

Distance from throat, cm

decelerating

Centerline velocity m/s

decelerating

680

700

Centerline velocity, m/s

MHD forcing region

decelerating force

620

640

660

baseline

accelerating

Predicted velocity change Δu=14 m/sec (2%)0 2 4 6 8 10 12 14 16 18

600

Distance from throat, cm

decelerating

Further insight: Molecular Tagging Velocimetry (MTV) in NO-seeded MHD flows


in NO seeded MHD flows

1% O iSi l i t ti

355nm PumpNd:YAG Laser

1% NO in N2

Images of “painted” line at t=0 ns and

Flow

Signal integration

350‐500 pixels

452 nmOPO Cavity

line at t 0 ns and t=600 ns

FluorescenceNO(A2Σ) → NO(X2Π)

Side wall

BBOCrystal

226 nmTo the nozzle

NO(A Σ) → NO(X Π)

Cold flow velocity: 647 ±4 m/s1 0 Cold flow 647 ±4 m/s3-D Navier-Stokes code prediction:660 m/s

0.6

0.8

1.0

ensi

ty

Cold flow 0 ns delay 600 ns delay

Pulser + DC 600 ns delay

Optical system for generation of 226 nm beam 0.2

0.4Inte Flow velocity with

plasma/MHD on: 471 ±9 m/sMuch slower than

4000 4200 4400 4600 4800 50000.0

Distance (Microns)

predicted by code (evidence of stronger Joule heating?)

Case 3: Electric Discharge Excited Oxygen-Iodine Laser (λ=1 3 μm c w power 1 5 W)


Oxygen Iodine Laser (λ 1.3 μm, c.w. power 1.5 W)

Nozzle throatNozzle exit Cavity exitCrossed discharge section DC electrode

Resonator arm

Main O2 / He flow To vacuum

Iodine injectorPulsed electrode blockGain window or laser mirror

Optical window

Optical access

DC electrodeOptical window

Pulsed electrode

Flow

Discharge volume 50 cm3, pressures up to 460 torr, flow rate up to 0.1 mole/sec (O2), 1 mole/sec (He)

Crossed pulser-sustainer discharge characterization:10% O in He P =120 torr


20

Voltage, kV

10% O2 in He, P0 =120 torr

5

10

15

5 nsec FWHM

Current (A) and Voltage (kV)

215

20

Voltage, kV

00 10 20 30 40

Time, ns

1

1.5 CurrentVoltage5

10

15

29 μsec

0 50 100 150 200 2500

0.5

Time (s)

-10

-5

0

0 10 20 30 40 50 60 70

FID pulser: Sustainer discharge voltage and current

Time (s)Time (μsec)Time, microseconds

40 kV peak voltage, 5 ns pulse duration, 100 kHz pulse rep rate, duty cycle <1/2,000

Crossed pulser-sustainer discharge: targeted energy loading (controlled by T , or E/N)


targeted energy loading (controlled by Te, or E/N)

Input power percentage501.4

E/N, 10-16 V cm2

30

40

0.8

1.0

1.2

10

20 10% O2-He

20% O2-He

O20 2

0.4

0.6P0=60 torr

P0=120 torr

00 0.5 1 1.5

E/N (10-16 V cm2)0.5 1.0 1.5 2.0

0.0

0.2

Discharge power, kW

10% O2 in He:t 30% f i t t O ( 1Δ) t tup to 30% of input power goes to O2(a1Δ) state

Discharge Excited Oxygen-Iodine Laser (DOIL) Kinetics


13

(DOIL) Kinetics

eaOeXO +Δ→+Σ 12

32 )()(

IIXOnIaOn ++Σ⋅→+Δ⋅ 322

12 )()(

IXOIaO +Σ↔+Δ *32

12 )()(

νhII +→*

Need as much O2(a1Δ) as can be produced

Need low temperature to shift equilibriumin reaction (3) to the right (i.e. more I*)

Singlet delta oxygen yield measurements by emission spectroscopy (radiative lifetime 75 min)


emission spectroscopy (radiative lifetime 75 min)

Yield, %Intensity (arbitrary units)

5

6

7Intensity (arbitrary units)

2

3

4Atomic emission lines

0 0 0 5 1 0 1 5 2 0 2 50

1

2 P0=60 torr

P0=120 torr

1240 1250 1260 1270 1280 1290 1300

P0, torr Discharge P, torr M T, K SDO yield, % Threshold Power stored

0.0 0.5 1.0 1.5 2.0 2.5

Discharge power, kWWavelength, nm

0,power, kW

, ,yield, % in SDO, W

60 1.6 1.9 3.0 120±15100±10

5.7±0.85 2.31.2

110

120 2.1 3.8 3.0 120±15100±15

5.0±0.75 2.31.2

200

Case 4: Low-temperature plasma assisted combustionIgnition in C H /air: P=70 torr u=15 m/s Φ=0 9 ν=40 kHz


Ignition in C2H4/air: P=70 torr, u=15 m/s, Φ=0.9, ν=40 kHz

Pulsed plasma image

N2 emission: plasma temperature

p g(5 kHz, 50 pulse average, 300 nsec gate)

Flow directionCH emission: flame temperature

Plasma temperature: N2 visible emission spectraSpecies concentrations: FTIR absoprtion spectra


Species concentrations: FTIR absoprtion spectra

3000 0.25

2000

a.u.

experiment modelling

0.15

0.20

CO2ance

1000Inte

nsity

,

0.10

0.15

H2OC2H4

CO2

COAbs

orba

370 372 374 376 378 3800

2000 2500 3000 3500 40000.00

0.05C2H2CH2O

λ, nm wavenumber, cm-1

Ethylene/air: different flow velocities


Temperature [ oC] Unreacted fuel [%]

500

600Temperature [ oC]

P=70 torr, Φ=1

Air-Ethylene

Air 80

100

Air-ethyleneP=70 torr, Φ=1

[%]

300

400

Air

60

100

200

20

40

10 20 30 40 500

Flow Velocity [m/s]10 20 30 40 50

0

Flow velocity [m/s]

P=70 torr, Φ=1.0, ν=50 kHzSignificant fuel oxidation, resultant flow temperature rise

y [ ] Flow velocity [m/s]

Kinetic analysis suggests that pulsed discharge generates significant amounts of O atoms (chemically active radicals)

Nonequilibrium air flow characterization: What species do we need to measure?

Nonequilibrium Thermodynamics Laboratories The Ohio State UniversityHow are we going to generate them?

N2(electronically excited) + O2 → N2 + O + O

O2(electronically excited) → O + O

N2(v), O2(v), O2(a1Δ), O, and NO

Pulser-sustainer discharge operated at different E/N

How are we going to measure these species?


Air species vibrational level population measurement:

Relative population

Air species vibrational level population measurement: Spontaneous Raman spectroscopy

CO laser • Uses CO laser (up to 50% efficiency),scalable to high powers

O2V-V CO-O2

• Based on resonance absorption of laser radiation by CO molecules

• V T losses are small ⇒• V-T losses are small ⇒Energy remains lockedin molecular vibrational modes

V-V CO-N2

N2CO

• Works at high pressures (P>1 atm), low temperatures (T~500 K),modest power densities (~100 W/cm2),

Vibrational Energy

Optical pumping of air with a CO laser


Absorption cell

Dual CO laser system

Optically pumped plasma

Schematic of Raman spectroscopy measurements

Nonequilibrium Thermodynamics Laboratories The Ohio State UniversityProbe electrodes

Nd:YAGbNd:YAG laser probe beambeam

CO laserCO laser

probe beam

CO laserbeam

ExcitedRegion

CO laser pump beam

Region

To FTIREmission Spectroscopy:

Li f Si h I i

To OMARaman Spectroscopy:

P i t M tLine-of-Sight Integration Point Measurement

Species: CO, NO, CO2Species: CO, N2, O2

Spatially resolved Raman spectra of N CO and O at 1 atm

Nonequilibrium Thermodynamics Laboratories The Ohio State UniversityIntensity (arbitrary units)

of N2, CO, and O2 at 1 atm

N2

CO/N2/O2=5/75/20, P=1 atm(laser power 10 W)

COO2 Spatial resolution 250 µm

( se powe 0 W)

570 580 590 600 610

O2 spectra

CO spectraN2 spectra

Vibrational temperatures and level populations of N CO and O at 1 atm


Relative population

of N2, CO, and O2 at 1 atm

1.0E-1

1.0E+0

N2 , experiment

CO, experiment

i

1.0E-2

O2 , experiment

N2 , calculation

CO, calculation

O2 , calculation

1.0E-3

0 10 20 30

1.0E-4

Vibrational quantum numberq

Vibrational temperatures: 2000-3000 K, rotational temperature: 300 K

Good agreement with master equation modeling

Raman spectra and vibrational level populations of N CO and O at 0 5 atm


Relative population

of N2, CO, and O2 at 0.5 atm

Intensity (arb. units)

NO CO

1.0E+000

N2 , experimentCO, experimentO2 , experimentN2O2 CO

v 13v=16

v=5

1.0E-001 N2 , calculationCO, calculationO2 , calculation

v=13 v=51.0E-002

570 580 590 600 610

Wavelength, nmVibrational quantum number

0 4 8 12 16 201.0E-003

CO/N2/O2=8/88/4, P=0.5 atm (laser power 10 W)

5 vibrational levels of N 16 vibrational levels of O5 vibrational levels of N2, 16 vibrational levels of O2

Good agreement with master equation modeling

Schematic of pulsed Raman pumping of N2(w/o CO laser)


(w/o CO laser)

Pump Nd:YAG laser operates at 10 HzStokes signal generated in a high-pressure Raman cell

Pulsed Raman pumping: time-resolved vibrational level populations of N


time-resolved vibrational level populations of N2

“Instantaneous” v=1 pumping(single pump laser pulse ~ 10 nsec)

Time resolution ~0.1 µsec, spatialresolution ~100 µm

Rates of vibration-vibration energyRates of vibration vibration energyexchange for N2-N2 inferred fromlevel populations

Pulsed Raman pumping: time-resolved vibrational level populations of O


0.06

time-resolved vibrational level populations of O2

3v=2

0 03

0.04

0.05

al p

opul

atio

n 1E-12Relaxation Rate Constant, cm3/s

Price et al.

Park & Slanger

Klatt et al.

Kalogerakis et al.

0.01

0.02

0.03

frac

tiona

1E-13

FHO-FR (analytic)

DIDIAV (semiclassical)

Quantum calculations

0.000 2 4 6μs

7.E-03

1E-14

v=4

4.E-03

5.E-03

6.E-03

popu

latio

n

0 5 10 15 20 25 301E-15

1.E-03

2.E-03

3.E-03

frac

tiona

l p

0 5 10 15 20 25 30Vibrational Quantum Number

Rates of vibration-vibration0.E+00

0 2 4 6μs

energy exchange for O2-O2inferred from level populations

O atom concentration measurements:Two-Photon Absorption Laser Induced Fluorescence (TALIF)

ith X C lib tiNonequilibrium Thermodynamics Laboratories The Ohio State University

with Xenon Calibration

4

Measuring ratio of spectrally integratedO atom TALIF signal to that of xenonwith identical laser beams, signal

ll ti ti t l filt i d

109837

88631

λ = 844 6 nm

3P 2, 1, 0

O+(4S° )3/2

collection optics, spectral filtering andPMT gain

Relative signal converted to absolute O

76795

Laser

3S° 1

λ 844.6 nm

Relative signal converted to absolute Oatom number density

2271591

03P

λ = 225.7 nmLaser

02 OxygenG-4582

Estimated combined uncertainty of absolute O atom density about 40%

O atom number density after a single high-voltage nanosecond discharge pulse: TALIF measurements


O atom mole fraction O atom mole fraction

nanosecond discharge pulse: TALIF measurements

4 0E-5

5.0E-5Air

Air-methane, Φ=1.04.0E-5

5.0E-5Air

Air-ethylene, Φ=0.5

2 0E 5

3.0E-5

4.0E 5

2 0E 5

3.0E-5

4.0E 5

1.0E-5

2.0E-5

0 0 0

1.0E-5

2.0E-5

0.0E+0 1.0E-3 2.0E-3 3.0E-3 4.0E-30.0E+0

Time, seconds1.0E-7 1.0E-6 1.0E-5 1.0E-4 1.0E-3 1.0E-2

0.0E+0

Time, seconds

Ai d h i i Ai d h l i iAir and methane-air mixture

P=60 torr, Φ=1.0

Air and ethylene-air mixture

P=60 torr, Φ=0.5

Peak O atom density in air: 0 9 1014 cm-3 / pulse decay time: 2 msecPeak O atom density in air: 0.9·1014 cm 3 / pulse, decay time: 2 msec

Kinetic model correctly predicts O atom densities and decay rates in all three cases

TALIF O atom number density measurements after a burst of high-voltage pulses


after a burst of high-voltage pulses

O t t ti -3

1E+16

O atom concentration, cm-3

1E+15 P=60 torr

air

air/CH4, Φ=0.5

1E+14

4,

air/C2H4, Φ=0.5

0.0 0.2 0.4 0.6 0.8 1.01E+13

Time, msec

Air, methane-air, and ethylene-air mixtures, P=60 torr, Φ=1.0, pulse burst (up to 100 pulses/msec)

Si ifi t O t l ti ft 100 l i i 0 2%

,

Significant O atom accumulation after 100 pulses in air: 0.2%

Half of input pulse energy goes to oxygen dissociation

How are we going to predict effect of these species on the flow?


p

Vibrational energy transfer and molecular dissociation rate models

1E-12Relaxation Rate Constant, cm3/s

Price et al.

Park & Slanger

gy

ϕ1

ϑ1

v1E-13

g

Klatt et al.

FHO-FR (analytic)

DIDIAV (semiclassical)

Quantum calculations

ϕ2

Rb

ϑ2Ω1

1E-14

Ω2

0 5 10 15 20 25 301E-15

Vibrational Quantum Number

• Applicable for non-collinear collisions of rotating molecules

• Applicable in a wide range of gas temperatures (T~300-10,000 K)

• Excellent agreement with 3-D computer calculations

• Fully analytic

Rate models applicable up to very high temperatures


1E-9V-T Rate constant, cm3/s

(40 0 39 0)

1E-12

1E-11

1E-10

(1,0→0,0)

(40,0→39,0)

1E-14

1E-13

(1,0→0,0)

(10,0→9,0)

1E-17

1E-16

1E-15

0 2000 4000 6000 8000 10000

Temperature, K

Model validation: NO IR and UV emission behind strong shocks


NO IR and UV emission behind strong shocks

NO(A2Σ), 1010 cm3/secNO IR i i W/ 3

0.6( )

Experiment1.2

1.5NO IR emission, mW/cm3.sr

Experiment

0 2

0.4 Revised model

0.6

0.9Model

0 0

0.2

0 0

0.3

0 20 40 60 800.0

Laboratory time, μsec0 20 40 60 80

0.0

Laboratory time, μsec

IR emission, us=3.85 km/sec

UV emission, us=3.78 km/sec

NO emission profiles behind the normal shock in air. Po=2.25 torr

Effect of vibrational relaxation on shock standoff distance: quite noticeable


on shock standoff distance: quite noticeable

Nitrogen, M=4, T=300 K, Tv=3000 K, P=10 torr, nose radius 5 mmv

With and without 1% of water vaporStand-off distances increases from 0.9 to 1.3 mm

New Research Program: Effect of Excited Species (N (v) O (v) O atoms and O (a1Δ)) on M=5 Flow Field


(N2(v), O2(v), O atoms, and O2(a Δ)) on M=5 Flow Field

Flow

Stagnation enthalpy: 0.3-0.6 MJ/kg

Steady-state flow (~ 10 sec)

LENS: 10-15 MJ/kg

Run time ~ 1 msec

Objectives


• Stable high pressure nanosecond pulser DC sustainer discharge• Stable, high-pressure, nanosecond pulser – DC sustainer discharge in nozzle plenum (P 0 ~ 1 atm)

• Flows: air, N2/He, O2/He, N2/Ar, and O2/Ar2 2 2 2

• Varying DC voltage (E/N): targeted energy loading into O2(a1Δ)(E/N=5-10 Td), N2(v), O2(v) (10-50 Td), and O atoms (100-200 Td, no DC)DC)

• M=5 flow in supersonic test section (P ~ 1 torr)

• Blunt body in test section (D 5 mm) shock stand off distance 1• Blunt body in test section (D~5 mm), shock stand-off distance ~ 1 mm

• Schlieren and plasma shock visualization; shock stand-off distance p ;measurements with and without excited species present

• First spatially resolved measurements of rotational temperature, O ( 1Δ) N ( ) O ( ) d O t b hi d th M 5 b h k IRO2(a1Δ), N2(v), O2(v), and O atoms behind the M=5 bow shock: IR emission, spontaneous Raman, CARS, TALIF (~100 µm resolution)

Objectives (continued)


• Strong vibrational excitation of N2, O2, and H2 using a pulse-burst laser for Raman pumping (20-30 pulses at 1 pulse/µsec rep rate). Measuring vibrationally induced dissociation at high energy loading g y g gy g(several vibrational quanta per molecule) using TALIF

• Comparison with coupled compressible Navier-Stokes / master eq ation modeling and rate model alidation: state specificequation modeling and rate model validation: state-specific vibrational energy transfer and dissociation rates, rates of NO production, O2(a1Δ) quenching rates

• Developing instrumentation for using at LENS hypersonic flow facility

D l i h i b d d i t l ilib i fl d l• Developing physics-based design tool nonequilibrium flow models with predictive capabilities

Other Future Research Thrusts in High-Speed Propulsion and Power


in High-Speed Propulsion and Power

• Confident ignition / flameholding / relight in high-speed flows(using large-volume nonequilibrium plasmas)

• Demonstrating scaling potential of DOIL laser power to makeThe Application feasible: tens to hundreds of W in a laboratoryThe Application feasible: tens to hundreds of W in a laboratoryscale setup

• MHD: electrical power generation in reentry flows, opening up“transmission windows” through reentry plasma using B field,power generation in scramjets (stagnation temperature too highfor a turbine)

Plasma assisted ignition / flameholding in high-speed flows


in high-speed flows

High voltagepulse electrode

Straight channelS g c eor nozzle inserts

Fuel injectioncavity filledwith plasma

Optical accesswindows

Flowwith plasma

DOIL Laser Scaling


Documents

Nonequilibrium Gas Dynamics: Understandinggg of High-Speed … · 2019-12-12 · The Ohio State University Nonequilibrium Thermodynamics Laboratories Nonequilibrium Gas Dynamics: