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Plasmadynamics and Lasers Award Lecture
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Thermal Mode Nonequilibriumin Gas Dynamic and Plasma Flowsin Gas Dynamic and Plasma Flows
byIgor Adamovich, Walter Lempert,
Vish Subramaniam and William Rich
The Michael A. ChaszeykaNonequilibrium Thermodynamics Laboratories
Dept of Mechanical EngineeringDept. of Mechanical EngineeringThe Ohio State University
AIAA 39th Plasmadynamics and Lasers ConferenceSeattle, Washington, June 25, 2008
Outline
Nonequilibrium Thermodynamics Laboratories The Ohio State University
• What is thermal mode nonequilibrium?Emphasis on high density, collision-dominated flows,cold molecular plasmas
• Environmentsi) Cool Electric Discharge Plasmas
Self-Sustained vs. Preionized ii) Optically Pumped Plasmas
Excitation of Vibrational StatesKinetics and Energy Transfer Studies
iii) Gas Dynamic Flowsiii) Gas Dynamic FlowsSupersonic Expansions of High Enthalpy GasesStrong Shock Waves
A li ti• Applications i) Plasma Wind Tunnelsii) Gas Lasersiii) Chemistry: Isotope Separation
• Summary: Where do we go with this?
What is thermal mode equilibrium?
Nonequilibrium Thermodynamics Laboratories The Ohio State University
ni/gi ~ exp ( - Ei/kT ), ln (n /g )i/gi e p ( i/ ),
N = ∑ ni , and E = ∑ niEi
ln (ni/gi)Increasing T
If we know the energy levels, Ei, and the gas temperature, T, we cancalculate the whole ideal gascalculate the whole ideal gas thermodynamic table: Ei
What is thermal mode nonequilibrium?
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Thermal nonequilibrium exists whenever:
• The populations, ni/N, of one or more modes are distributed according to the Boltzmann law but thedistributed according to the Boltzmann law, but thetemperature, T, of at least one mode differs from thatof the others.OR• The populations, ni/N, of one or more modes are notdistributed according to the Boltzmann law.
Environments: Energy Input Among NonequilibriumPlasma Modes in a Self-Sustained Electrical Glow Discharge
Nonequilibrium Thermodynamics Laboratories The Ohio State University
g
Fraction of Power intoeach Mode, as a function
f E/N E/N i i t lof E/N. E/N is approximatelyproportional to the meanenergy of the free electrons.
1. Rotational mode2. Vibrational mode3. Electronic mode
Ratio of Electric Field, E, to total
3. Electronic mode 4. Ionization
Plasma Tube Ratio of Electric Field, E, to total number density of molecules, N
L
Plasma Tube
Electric Field = Voltage/Electrode Separation_ +
L Electric Field = Voltage/Electrode SeparationE = V/L
Environments: Preionized Electrical Glow DischargeShort Pulse HV Ionizer, D.C. Sustainer - Geometry
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Pulser electrodes in top and bottom walls
DC electrodes in side walls
Flow direction left to right
Dimensions: 1 cm x 5 cm, 10 cm long
Mach number: M~0.2
Discharge pressure: up to 160 torr
(O2-He, O2-Ar)
M fl t t 12 /Mass flow rate: up to 12 g/sec
Environments: Preionized Electrical Glow DischargeShort Pulse HV Ionizer, D.C. Sustainer -Performance
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Ionizing pulse (~10 nsec duration)~10 μsecVoltage
1E+13
1E+14Species concentrations
DC (MHD) voltage
~1O kV
1E+11
1E+12
electrons
O atoms
Time1E+10
1E+11
1E-9 1E-8 1E-7 1E-6 1E-5 1E-4
1E+9
Time, sec
O th l ft i t ti ft th i i i lOn the left, species concentrations after the ionizing pulse,on the right, schematic of the pulsed and d.c. dischargeoperation. P=0.1 atm, T=300 K, E/Nmax=350 Td, Emax=8.5a akV/cm, τpulse=10 nsec
Environments: Preionized Electrical Glow DischargeShort Pulse HV Ionizer, D.C. Sustainer -Photos
Nonequilibrium Thermodynamics Laboratories The Ohio State University
P=300 torr, 10 kHz P=500 torr, 10 kHz
Environments: Optical Pumping – Excitation of Vibrational Mode by CO Laser Radiation. Vibration-Vibration (V-V) Exchange
Nonequilibrium Thermodynamics Laboratories The Ohio State University
EEk ⎞⎛ ΔΔ1
TEE
expkk w,1w1v,v
r
k >⎟⎟⎠
⎞⎜⎜⎝
⎛ Δ−Δ= +−
krkfw+1
w
v
.
.
.
w
v-1
krkf
CO(v)+CO(w) → CO(v-1)+CO(w+1)
Environments: Optical Pumping – Excitation of Vibrational Modeby CO Laser Radiation. Measurement of Vibrational State
Populations Vibrational Distribution FunctionNonequilibrium Thermodynamics Laboratories The Ohio State University
Populations – Vibrational Distribution Function
1E+0Relative population
1E-2
1E-1 T=1200 K
1E-3Measured nonequilibriumdistribution
1E-5
1E-4Boltzmann distrubitionat T=4100 K
0 10 20 30Vibrational quantum number
Environments: Optical Pumping of Nitrogen Vibration byRaman Absorption – Excitation of High Vibrational
States by V-V Energy Exchange
Nonequilibrium Thermodynamics Laboratories The Ohio State University
States by V V Energy Exchange
(b)(a)Each peak is from a (b)
6.E+04
8.E+04
1.E+05
tens
ity
(a)
6.E+04
8.E+04
1.E+05
tens
ity v=0
psuccessive vibrational state, v, ground state signal on the right. The time
0.E+00
2.E+04
4.E+04
Int
0.E+00
2.E+04
4.E+04
Int
delay between the pump and probe pulse is (a) 150 ns, (b) 1 ms, (c) 5 ms, (d) 10
(d)1.E+05
600 602 604 606 608 610nm
(c)1.E+05
600 602 604 606 608 610nm
10 ms.
4.E+04
6.E+04
8.E+04
Inte
nsity
4 E+04
6.E+04
8.E+04
Inte
nsity
0.E+00
2.E+04
4.E 04
600 602 604 606 608 610nm
0.E+00
2.E+04
4.E+04
600 602 604 606 608 610nm
Optically Pumped Plasmas: Kinetics StudiesExperimental Setup for CO Plasma
Nonequilibrium Thermodynamics Laboratories The Ohio State University
CO laserCO laser
Optically Pumped Plasmas: Kinetics StudiesEnergy Transfer and Kinetics Processes in a CO Plasma
Nonequilibrium Thermodynamics Laboratories The Ohio State University
gy
Relative population
1 0E 1
1.0E+0
CO laserIonization:
CO(v)+CO(w) →(CO)2+ + e-
V-E:
1.0E-2
1.0E-1
V V
V-E: CO(X1Σ,v~40)+M→CO(A1Π)+M
Chem. Reactions:
1.0E-3
V-V CO(v)+CO(w) →CO2+C
1.0E-4 V-T
0 10 20 30 401.0E-5
Vibrational quantum numberT = 600 K
2 torr CO, 100 torr Ar, T=600 K, Tv=3300 K
CO Laser power 10 W c.w.
2 Torr CO, 100 Torr Ar, CO laser power 10 W c.w.
T 600 KTv = 3300 K
Optically Pumped Plasmas: Kinetics StudiesOptically Pumped CO Plasma Photo
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Optically Pumped Plasmas: Kinetics StudiesSteady –State Vibrational Excitation of a Flowing Dry Air Mixture
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Steady State Vibrational Excitation of a Flowing Dry Air Mixture
Vibrational energy level populations for an optically pumped air plasma. If energy were equilibrated, temperature of
Intensity 1.0E+0Relative population
vibrational modes would be ~ 2000K. Measured as kinetic temperature is only 500 K. Extreme nonequilibrium is created in a steady state, atmospheric pressure, molecular gas plasma. Gas mixture is CO/N2/O2=5/75/20, P=1 atm. Pump laser power is 10 W.
v=0
N2
1.0E-1
1.0E+0
N2 , experiment
CO, experiment
O2 , experiment
N calculation
601 602 603 604 605 606 607 608 609
Wavelength, nm
v=41.0E-2
N2 , calculation
CO, calculation
O2 , calculation
Intensity
v=0O2
1.0E-4
1.0E-3
570 572 574 576 578 580
Wavelength, nm
v=8
0 10 20 30Vibrational quantum number
Experimental Vibrational State Populations
Raman SpectraInferred from Raman Spectra. Calculated State Populations from Master Equation Kinetic Model
Optically Pumped Plasmas: Kinetics StudiesAssociative Ionization in Optically Pumped Plasmas I
CO(v) + CO(w) → (CO) + + e- E + E > E
Nonequilibrium Thermodynamics Laboratories The Ohio State University
CO(v) + CO(w) → (CO)2 + e , Ev + Ew > Eion
Thomson discharge Microwave absorption
DC Electrodes
Laser
MicrowaveWaveguideg
Electron density: Electron production rate: k 10 13 3/ ne≅ 1011 cm-3kion~10-13 cm3/s
Optically Pumped Plasmas: Kinetics StudiesAssociative Ionization in Optically Pumped Plasmas II
CO(v) + CO(w) → (CO)2+ + e- , E + E > Ei
Nonequilibrium Thermodynamics Laboratories The Ohio State University
CO(v) + CO(w) → (CO)2 + e , Ev + Ew > Eion
Current-voltage characteristicsof the DC Thomson discharge atdifferent helium partial
Vibrational distribution functionsof carbon monoxide at differenthelium partial pressuresdifferent helium partial
pressureshelium partial pressures
Optically Pumped Plasmas: Kinetics StudiesCoupling of Vibrational Populations with Free Electrons
Nonequilibrium Thermodynamics Laboratories The Ohio State University
p g p
Optically Pumped Plasmas: Kinetics StudiesMeasurements of Electron Density Decay (by microwave attn)
for E beam Created Plasma Experimental Schematic
Nonequilibrium Thermodynamics Laboratories The Ohio State University
for E-beam Created Plasma – Experimental Schematic
Optically Pumped Plasmas: Kinetics StudiesMeasurements of Electron Density Decay (by microwave attn) for E-beam
C t d Pl I hibiti f El t L P i C ld Ai
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Created Plasma – Inhibition of Electron Loss Processes in Cold Air
Plasma Power Consumption at 1013 Electrons/cm3 in 1 Atm, 560 K Air:
Electron-Ion Recombinationβ=2.5x10-7 cm3sec-1
Nonequilibrium: 56 W cm-3
Electron Attachment to O2keff=2.3x10-33cm6sec-1
Nonequilibrium: 1 2 W cm-3
as a owe Co su pt o at 0 ect o s/c t , 560 :
Nonequilibrium: 56 W cmEquilibrium: 450 W cm-3
Nonequilibrium: 1.2 W cmEquilibrium: 1.4 kW cm-3
Optically Pumped Plasmas: Kinetics StudiesInhibition of Electron Loss Processes in Cold Air
Influence of Temperature on O Attachment and Detachment Rates
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Influence of Temperature on O2 Attachment and Detachment Rates
Attachment is weakly dependent upon heavy species temperatureAttachment is weakly dependent upon heavy species temperature whereas detachment is highly dependent
MOMeO +⇔++ −−22
O2 Electron Affinity ~0.43 eV ( T Vib ti l Q t )(~Two Vibrational Quanta)
Optically Pumped Plasmas: Kinetics StudiesInhibition of Electron Loss Processes in Cold Air
Radially-Resolved Filtered Rotational Raman Temperature Measurement
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Radially Resolved Filtered Rotational Raman Temperature Measurement
200/18/35 N /CO/O O ti ll P d200/18/35 N2/CO/O2 – Optically Pumped(Diameter of Vibrationally Excited Region ~ 1 mm)
345350
k)
330335340
pera
ture
(k
315320325
Tem
p
310-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8
Radial Position (mm)
Gas Dynamic Flows: Vibrational mode nonequilibrium in a supersonic nozzle expansion
Nonequilibrium Thermodynamics Laboratories The Ohio State University
in a supersonic nozzle expansion
Average energy permolecule in electronV ltVolts. (0.1 eV = 1,161 ºK)
Expansion of a gasExpansion of a gasmixture of 20% CO,20% N2, 60% Ar, Stagnation Pressure =Stagnation Pressure 100 atm.Stagnation Temperature =2,000 ºK.
Distance from nozzle throat, in centimeters
15 º Half Angle Nozzle, Expands to M = 10 at100 cm downstream of throat ,
Gas Dynamic Flows: Thermal mode nonequilibrium behind a hypersonic shock wave
Nonequilibrium Thermodynamics Laboratories The Ohio State University
yp
Tt = translational mode temperatureTr = rotational mode temperatureTv = vibrational mode temperature
ModeTemperature
v pDegrees K
Distance behind shock front, in meters
Plasma Wind Tunnels: A supersonic tunnel with energy loadingof selected internal states in the plenum
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Nozzle throatNozzle exit Test section exitCrossed discharge section
M i
DC electrode
Main Gas flow To vacuum
Gas Injection Pulsed electrode block
Optical access
Schematic of the wind tunneldischarge section / nozzle / test section assembly
Plasma Wind Tunnels: A supersonic tunnel with energy loadingof selected internal states – photo of plenum in operation
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Photograph of a discharge in the nozzle plenum. Dimensions 4x4x10 cm. A uniform cold gas fills the plenum;A uniform, cold gas fills the plenum;
O2/He mixture shown, similar uniformity for air; P0 to 1 atm.
Plasma Wind Tunnels: A supersonic tunnel with energy loadingof selected internal states – objects in a 2-D, M = 3 test section
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Plasma Wind Tunnels: Calculated M =4 Flow over a 0.5 cm Diasemicylinder. Vibrationally Excited N2 Expanding from 1 atm.
Nonequilibrium Thermodynamics Laboratories The Ohio State University
From E. Josuyla, AFRL
Plasma Wind Tunnels: Calculated M =4 Flow over a 0.5 cm Diasemicylinder. Vibrationally Excited N2 Expanding from 1 atm.
Nonequilibrium Thermodynamics Laboratories The Ohio State University
From E. Josuyla, AFRL
Plasma Wind Tunnels: An M = 4 MHD Tunnel,with transverse pre-ionized discharge and a 2 Tesla Field in test section
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Plasma Wind Tunnels: An M = 4 MHD Tunnel. Lorentz force effect on turbulent boundary layer density fluctuation spectra
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Signal dB
turbulent boundary layer density fluctuation spectra
-30Signal, dB
j
jxB
40
-35j
B
-45
-40
Both B field directions Laser beam midway
B jxB
-50
500 W RF, B=1.5 T, U=1500 V (accelerating MHD force)
500 W RF, B=1.5 T, U=1500 V (decelerating MHD force) j
10000 100000Frequency, Hz
Nitrogen, M=3, P0=1/3 atmNitrogen, M 3, P0 1/3 atmBoth accelerating and decelerating Lorentz force are created
for two possible combinations of B and E fields, as shown
CO potentialNonequilibrium Thermodynamics Laboratories The Ohio State University
V(R)
R
R is the separation ofthe C and O nuclei.Re is the equilibrium e q(nonvibrating) separation.
V(R) = 1/2 K(R – Re)2 is the potential energy stored in the oscillator
RRe
Gas Lasers: Carbon Monoxide Electric Discharge Laser - Schematic
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Gas Lasers: Carbon Monoxide Electric Discharge Laser –Photo during operation
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Gas Lasers: Carbon Monoxide Electric Discharge Laser –Kinetic Modeling of CO Fundamental Band Laser,
Comparison with OSU Laser Performance
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Comparison with OSU Laser Performance
P W
2 0
2.5Power, W
experiment
1.5
2.0 experiment
calculations
1.0
0.0
0.5
0 2 4 6 8 10 12 14 16 18 20
0.0
Vibrational quantum number
.
Gas Lasers: Carbon Monoxide Electric Discharge Laser –Kinetic Modeling of CO Overtone Band Laser,
Comparison with OSU Laser Performance
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Comparison with OSU Laser Performance
Theoretically Predicted Output Line IntensitiesExperimentally Measured
Output Line Intensities
Gas Lasers: An Electric Discharge-Excited Oxygen-Iodine Laser (DOIL) –Boltzmann equation solver results: electron energy balance
Nonequilibrium Thermodynamics Laboratories The Ohio State University45
25
30
35
40
a Pr
oduc
tion
5
10
15
20
% S
ingl
et D
elta
10% Oxygen-Helium 20% Oxygen-Helium
Pure Oxygen
O2-He
0
5
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
E/N (10^-16 V cm^2)
50
30
35
40
45
Prod
uctio
n
O2-Ar
10
15
20
25
% S
ingl
et D
elta
P
10% Oxygen-Argon 20% Oxygen-Argon
Pure Oxygen
O2 ArHighest estimated
O2(1Δ) yield achieved
0
5
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
E/N (10^-16 V cm^2)
so far ~10 %
Gas Lasers: An Electric Discharge-Excited Oxygen-Iodine Laser (DOIL) Schematic of Electric Discharge SDO Generator
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Schematic of Electric Discharge SDO Generator
Advantages of transverse vs. axial discharge: Large volume, stable at high pressures / powers, rapid convective cooling vs. slow wall cooling. Used in most high power electrically excited lasers.
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
DC electrodeOptical window
Optical access
Flow
Discharge volume 50 cm3, pressures up to 460 torr, flow rate up to 0.1 mole/sec (O2), 1 mole/sec (He)
Pulsed electrode
Gas Lasers: An Electric Discharge-Excited Oxygen-Iodine Laser (DOIL) Gain at Optimized Conditions: 0.12 %/cm at T=100 K (Currently!)
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Gain at Optimized Conditions: 0.12 %/cm at T 100 K (Currently!)
0.05
0.06
Absorption/gain, %/cm
0 035
0.045
Gain, %/cm
Experiment Doppler Fit
0.02
0.03
0.04
0.015
0.025
0.035
-0.01
0.00
0.01
0 2 4 6 8 10 12 14 16
-0.005
0.005
2900 3100 3300 3500 3700
Adding NO: major discharge stabilization factor
0 2 4 6 8 10 12 14 16
Time, secFrequency, MHz
Adding NO: major discharge stabilization factor
Discharge power increased from 1.9 kW to 2.4 kW
P0=107 torr, 15% O2 - He flow, NO 0.2 mmole/sec (550 ppm), ν=34 kHz, UPS=3.1 kV I 1 54 A di h 2 4 kW I 70 l / (190 )kV, I=1.54 A, discharge power 2.4 kW, I2 70 μmole/sec (190 ppm).
Gain may be limited by I2 flow rate
Chemistry: Separation of Heavy Carbon Isotopes I
Nonequilibrium Thermodynamics Laboratories The Ohio State University
1
12CO: experiment
0.01
0.1
popu
latio
n
12CO: model 13CO: model
1E-4
1E-3
rela
tive
0 5 10 15 20 25 30 35 40
1E-4
vibrational level
Vibrationally excited CO prepared in cell reacts according to:
CO(v)+CO(w) → CO2 +C
Chemistry: Separation of Heavy Carbon Isotopes II
Nonequilibrium Thermodynamics Laboratories The Ohio State University
25
30 13CO/12CO 13CO2/
12CO2
15
20
s ra
tio
10
15
isot
opes
2 4 6 8 10 12 14 16 18 20 220
5
CO content in mixture, %
Summary
Nonequilibrium Thermodynamics Laboratories The Ohio State University
What have we learned?• Improved methods to sustain extreme mode disequilibrium in gases:
High densities, low gas kinetic temperatures, large volumes• New data on mechanisms and rates of some critical energy transfer
processes in molecular gases of aerospace interest• Methods for selective excitation of internal energy states • New applications: improved high power c.w. gas lasers, novel chemical
syntheses, new aerodynamic control techniques y , y qFuture directions?• Special purpose supersonic aerodynamic testing• Modeling code validation• Modeling code validation• High power c.w lasers and applications: novel refrigeration?• More chemistry: new products
Thanks!
Nonequilibrium Thermodynamics Laboratories The Ohio State University
Support:USAF:AFOSR Space Power & Propulsion Programp p gAFOSR Unsteady Aerodynamics and Hypersonics ProgramAFRL Air Vehicles DirectorateAFRL Directed Energy DirectorateNASA Glenn Research CenterNSFThe Michael A. Chaszeyka Gift
Collaborators:Univ. of Bonn Physics Dept; Heat and Mass Transfer Institute, Belarussian
Academy of Physics; Gas Laser Lab Lebedeev Physical InstituteAcademy of Physics; Gas Laser Lab, Lebedeev Physical Institute, Moscow Physical Technical Institute
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