[PPT] - O 2 ( 1 ) PRODUCTION AND OXYGEN-IODINE KINETICS IN FLOWING PowerPoint Presentation

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O2(1∆) PRODUCTION AND OXYGEN-IODINE KINETICS IN FLOWING AFTERGLOWS FOR ELECTRICALLY EXCITED CHEMICAL-OXYGEN-IODINE LASERS*

Ramesh Arakoni, Natalia Y. Babaeva, and Mark J. Kushner Iowa State University Ames, IA 50011, USA arakoni@iastate.edu natalie5@iastate.edu mjk@iastate.edu http://uigelz.ece.iastate.edu October 2006 * Work supported by Air Force Office of Scientific Research and National

Science Foundation.

GEC2006_Natalie_01

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Iowa State University Optical and Discharge Physics

AGENDA

Introduction to eCOIL
Description of the model
Oxygen-iodine kinetics mechanism
NO/NO2 addition, I2 dissociation
Concluding Remarks

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Iowa State University Optical and Discharge Physics

ELECTRICALLY EXCITED OXYGEN-IODINE LASERS

In chemical oxygen-iodine lasers (COILs), oscillation at 1.315 µm

I(2P1/2)→ I(2P3/2) occurs by excitation transfer of O2(1∆) to I2 and I.

Plasma production of O2(1∆) in electrical COILs (eCOILs) eliminates

liquid phase generators.

I2 injection and supersonic expansion (required to lower Tgas for

inversion) occurs downstream of the plasma zone.

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Ref: CU Aerospace

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Iowa State University Optical and Discharge Physics

NO AND NO2 INJECTION

Excitation of O2(1∆) optimizes at Te = 1 eV whereas self sustaining

discharges require Te = 2-3 eV.

NO additive (lower ionization potential) to inlet flow may lower Te to

a more optimum value.

Significant electron impact dissociation of O2 produces large

fluxes of O atoms which:

Quench the upper laser level → Increases O2(1∆) for oscillation.
Dissociate I2 → Decreases O2(1∆) required to produce I atoms.
NO2 injection may be used to control O atom inventory

NO2 + O → O2 + NO

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Iowa State University Optical and Discharge Physics

GEOMETRY FOR CAPACITIVE EXCITATION

Cylindrical flow tube 6

cm diameter

Capacitive excitation

(10s MHz) using ring electrodes.

Ring injection nozzles
Typical Conditions:

He/O2=70/30, 3 Torr 10s to 100 W

Outflow:

O2(1∆)/O2 = 0.15 - 0.25

He/NO2 Injection He/I2 Injection Primary inflow He/O2/NO

NO2

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Outflow

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Electron impact [0.9 eV] and excitation of O2(1Σ) with quenching to

O2(1∆) are the main channels of O2(1∆) production.

O atom and O3 production result in quenching and I2-oxygen

chemistry downstream.

Iowa State University Optical and Discharge Physics

O2(1∆) KINETICS IN He/O2 DISCHARGES

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I2 is rapidly dissociated by atomic
xygen and O2(1∆, 1Σ).
Population inversion by excitation

transfer of O2(1∆) to I(2P3/2).

Iowa State University Optical and Discharge Physics

OXYGEN-IODINE AND NOx KINETICS

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NO/NO2 recycling chain

scavenges O atoms.

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Iowa State University Optical and Discharge Physics

THE ROLE OF ADDITIVES

The roles of additives (NO, NO2), their synergy with I2 injection and

production of I(2P1/2) in eCOILS were computationally investigated.

Global modeling: Basic kinetics and scaling
2-d modeling: Hydrodynamics and injection strategies.
What are tradeoffs in using additives to optimize I(2P1/2)?

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Iowa State University Optical and Discharge Physics

Poisson’s equation, continuity equations and surface charge are

simultaneously solved using a Newton iteration technique.

Electron energy equation:

∑

+ = Φ ∇ ⋅ ∇ −

j s j jq

N ρ ε

j j j

S t N + ⋅ −∇ = ∂ ∂ φ r

∑

Φ −∇ ⋅ ∇ − + ⋅ ∇ − = ∂ ∂

j j j j s

S q t )) ( ( ) ( σ φ ρ r

( )

e i e i i e e

q j T N n E j t n φ λ εϕ κ ∂ ε ∂ r r r r = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∇ − ⋅ ∇ − − ⋅ =

∑

, 2 5

DESCRIPTION OF 2d-MODEL: CHARGED PARTICLES, SOURCES

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Iowa State University Optical and Discharge Physics

Fluid averaged values of mass density, mass momentum and

thermal energy density obtained using unsteady algorithms.

Individual fluid species diffuse in the bulk fluid.

) pumps , inlets ( ) v ( t + ⋅ −∇ = r ρ ∂ ρ ∂

( ) ( ) ( )

∑

+ ⋅ ∇ − ⋅ ∇ − ∇ =

i i i i

E N q v v NkT t v v r r r µ ρ ∂ ρ ∂

( ) ( )

∑ ∑

⋅ + − ⋅ ∇ + + ∇ − −∇ =

i i i i i f i p p

E j H R v P T c v T t T c r r r ∆ ρ κ ∂ ρ ∂

( ) ( ) ( )

S V T i T i f i i

S S N t t N N D v t N t t N + + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + ∇ − ⋅ ∇ − = + ∆ ∆ r

DESCRIPTION OF 2d-MODEL: NEUTRAL PARTICLE TRANSPORT

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Iowa State University Optical and Discharge Physics

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[NO] INLET ADDITIVE

The effect of NO
n electron

density is small.

O atoms are

rapidly depleted by NO.

Global model

captures trends.

He/O2/NO=

70/30/0-3 3 Torr, 40W, 25 MHz, 6000 sccm

Global Model
2d Model

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Iowa State University Optical and Discharge Physics

BASE CASE PARAMETERS

Peak Te above that for
ptimum O2(1∆)

production.

Electron density

localized due to rapid attachment.

O2(1∆) yield is 15%.
O atoms consumed

primarily by O3 production.

He/O2=70/30, 3 Torr,

40W, 25MHz, 6000 sccm

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MIN MAX

He/O2=70/30, 6000 sccm 3 Torr, 40W, 25 MHz

He/O2

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Iowa State University Optical and Discharge Physics

0.2 sccm NO2 AND I2 INJECTION

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Injection:

He/NO2=0.995/0.005, 36 sccm

Injection:

He/I2=0.995/0.005, 36 sccm

Atomic O nominally

depleted by NO2

Excess atomic
xygen totally

dissociates small amount of injected iodine.

He/O2 He/NO2 He/I2 MIN MAX

He/O2=70/30, 6000 sccm 3 Torr, 40W, 25 MHz

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He/NO2 He/I2 He/O2 Iowa State University Optical and Discharge Physics

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Injection:

He/NO2=0.9/0.1, 36 sccm

Injection:

He/I2=0.9/0.1, 36 sccm

MIN MAX

Atomic oxygen is almost

completely scavenged by NO2

O2(1∆) is rapidly depleted

by I2 in pumping reaction.

Only fraction of injected I2

is dissociated.

I* peaks near inlet.
He/O2=70/30, 6000 sccm 3 Torr, 40W, 25 MHz

3.6 sccm NO2 AND I2 INJECTION

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Iowa State University Optical and Discharge Physics

EFFECT OF ADDITIVES ON GAS TEMPERATURE

MIN MAX

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He/NO2=0.995/0.005
He/I2=0.995/0.005

He/NO2 He/I2 or He/I (36 sccm)

Gas temperature increases due to exothermicity of scavenging

and dissociation reactions NO2 + O → O2 + NO O + I2 → IO + I

Injection of I atoms reduces downstream Tgas.
He/NO2=0.9/0.1
He/I2=0.9/0.1
He/NO2=0.9/0.1
He/I=0.9/0.1

Predissociated iodine

He/O2=70/30, 6000 sccm 3 Torr, 40W, 25 MHz

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Iowa State University Optical and Discharge Physics

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Injection:
He/NO2=0.9/xxx, 36 sccm
He/I2=0.995/0.005, 36 sccm
Injection:
He/NO2=0.9/xxx, 36 sccm
He/I2=0.9/0.1, 36 sccm
NO2 injection has little effect on O2(1∆).
I2 and I quenching (laser pumping reactions) rapidly deplete O2(1∆).

O2(1∆) vs ADDITIVES

He/O2=70/30, 6000 sccm 3 Torr, 40W, 25 MHz

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Iowa State University Optical and Discharge Physics

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ATOMIC OXYGEN vs ADDITIVES

Injection:
He/NO2=0.9/xxx, 36 sccm
He/I2=0.995/0.005, 36 sccm
Injection:
He/NO2=0.9/xxx, 36 sccm
He/I2=0.9/0.1, 36 sccm
Optimum NO2 flow rate scavenges excess O atoms

leaving enough atoms to dissociate injected I2.

He/O2=70/30, 6000 sccm 3 Torr, 40W, 25 MHz

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Iowa State University Optical and Discharge Physics

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Injection:
He/NO2=0.995/0.005, 36 sccm
He/I2=0.995/0.005, 36 sccm
Injection:
He/NO2=0.9/0.1, 36 sccm
He/I2=0.9/0.1, 36 sccm
Optimum NO2 injection will optimize density of I* for a given O2(1∆)

production.

IODINE SPECIES vs ADDITIVES

He/O2=70/30, 6000 sccm 3 Torr, 40W, 25 MHz

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Iowa State University Optical and Discharge Physics

OPTIMIZING I* PRODUCTION

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Injection:
He/NO2=0.9/xxx, 36 sccm
He/I2=0.995/0.005, 36 sccm
Injection:
He/NO2=0.9/xxx, 36 sccm
He/I2=0.9/0.1, 36 sccm
Predissociation of I2 lessens the need to have a small O

atom flow for dissociation of I2.

Optimum NO2 completely scavenges O atoms.

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Iowa State University Optical and Discharge Physics

CONCLUDING REMARKS

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Oxygen-iodine kinetics in flowing afterglows for electrically

excited chemical-oxygen-iodine lasers has been computationally investigated.

NO2 injection scavenges O atoms.
Reduces amount of quenching of I*.
Also reduces the amount of dissociation of I2.
End result is delicate balance is required.
Injection of pre-dissociated I2 eliminates competition between

O2(1∆) PRODUCTION AND OXYGEN-IODINE KINETICS IN FLOWING AFTERGLOWS FOR ELECTRICALLY EXCITED CHEMICAL-OXYGEN-IODINE LASERS*

Ramesh Arakoni, Natalia Y. Babaeva, and Mark J. Kushner Iowa State University Ames, IA 50011, USA arakoni@iastate.edu natalie5@iastate.edu mjk@iastate.edu http://uigelz.ece.iastate.edu October 2006 * Work supported by Air Force Office of Scientific Research and National

AGENDA

ELECTRICALLY EXCITED OXYGEN-IODINE LASERS

I(2P1/2)→ I(2P3/2) occurs by excitation transfer of O2(1∆) to I2 and I.

liquid phase generators.

inversion) occurs downstream of the plasma zone.

NO AND NO2 INJECTION

discharges require Te = 2-3 eV.

a more optimum value.

fluxes of O atoms which:

NO2 + O → O2 + NO

GEOMETRY FOR CAPACITIVE EXCITATION

cm diameter

(10s MHz) using ring electrodes.

He/O2=70/30, 3 Torr 10s to 100 W

O2(1∆)/O2 = 0.15 - 0.25

O2(1∆) are the main channels of O2(1∆) production.

chemistry downstream.

O2(1∆) KINETICS IN He/O2 DISCHARGES

transfer of O2(1∆) to I(2P3/2).

OXYGEN-IODINE AND NOx KINETICS

scavenges O atoms.

THE ROLE OF ADDITIVES

production of I(2P1/2) in eCOILS were computationally investigated.

simultaneously solved using a Newton iteration technique.

∑

+ = Φ ∇ ⋅ ∇ −

N ρ ε

S t N + ⋅ −∇ = ∂ ∂ φ r

∑

Φ −∇ ⋅ ∇ − + ⋅ ∇ − = ∂ ∂

S q t )) ( ( ) ( σ φ ρ r

( )

q j T N n E j t n φ λ εϕ κ ∂ ε ∂ r r r r = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∇ − ⋅ ∇ − − ⋅ =

∑

, 2 5

thermal energy density obtained using unsteady algorithms.

) pumps , inlets ( ) v ( t + ⋅ −∇ = r ρ ∂ ρ ∂

( ) ( ) ( )

∑

+ ⋅ ∇ − ⋅ ∇ − ∇ =

E N q v v NkT t v v r r r µ ρ ∂ ρ ∂

( ) ( )

∑ ∑

⋅ + − ⋅ ∇ + + ∇ − −∇ =

E j H R v P T c v T t T c r r r ∆ ρ κ ∂ ρ ∂

( ) ( ) ( )

S S N t t N N D v t N t t N + + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + ∇ − ⋅ ∇ − = + ∆ ∆ r

[NO] INLET ADDITIVE

density is small.

rapidly depleted by NO.

captures trends.

70/30/0-3 3 Torr, 40W, 25 MHz, 6000 sccm

BASE CASE PARAMETERS

production.

localized due to rapid attachment.

primarily by O3 production.

40W, 25MHz, 6000 sccm

0.2 sccm NO2 AND I2 INJECTION

depleted by NO2

dissociates small amount of injected iodine.

completely scavenged by NO2

by I2 in pumping reaction.

is dissociated.

3.6 sccm NO2 AND I2 INJECTION

EFFECT OF ADDITIVES ON GAS TEMPERATURE

and dissociation reactions NO2 + O → O2 + NO O + I2 → IO + I

O2(1∆) vs ADDITIVES

ATOMIC OXYGEN vs ADDITIVES

leaving enough atoms to dissociate injected I2.

production.

IODINE SPECIES vs ADDITIVES

OPTIMIZING I* PRODUCTION

atom flow for dissociation of I2.

CONCLUDING REMARKS

excited chemical-oxygen-iodine lasers has been computationally investigated.

these two processes and more easily optimizes I*.