Transcript PlumePresent.ppt

The Ohio State University
Nonequilibrium Thermodynamics Laboratories
Chemi-Ionization and Visible/UV
Emission from Supersonic Flows of Combustion Products
Saurabh Keshav, Yurii G. Utkin, J .William Rich
and Igor V. Adamovich
Dept. of Mechanical Engineering
The Ohio State University
Support
AFOSR, Space Power and Propulsion Program
The Ohio State University
Nonequilibrium Thermodynamics Laboratories
Motivation

Control of UV / visible emission from high altitude rocket plumes

Study combustion diagnostic by chemi-ionization
Objective

Study energy transfer, chemi-ionization, and emission in
supersonic flows of combustion products
Schematic of a Rocket Plume Flow
Nonequilibrium Thermodynamics Laboratories
The Ohio State University
Flow
Rocket Engine
Mixing Layer
Oxidizer
+ Fuel
Combustion
Chamber
Nozzle
Expansion
(Supersonic)
Mixing Layer
Dominant Emitting Species
Ultra-Violet: -CO 4th Positive, NO  Bands, OH
Visible: -
CH, C2 Swan
Infrared: -
CO, CO2, H2O
Background: “Lights Out” experiment
in CO-N2 optically pumped plasma
Nonequilibrium Thermodynamics Laboratories
The Ohio State University
CO + hυ => CO (v)
v ~ 10
CO (v-1) + CO (w+1)
CO (v) + CO (w)
v, w ~ 40
CO2 + C
(CO)2+ + e
Ionization
CO (v) + e => CO (A 1Π) + e
(CO/N2=1/100, T = 300K, P=500 torr, CO laser power 15 W)
CN and C2 Swan bands emission disappears when electrons removed
No DC voltage applied
2 kV DC voltage applied
Schematic of the Experiment Setup
Nonequilibrium Thermodynamics Laboratories
The Ohio State University
Flow
3 Sparkplugs
Static Pressure
Ports
Flameholder
MgF2 Optical
Access Windows
Air or
O2/Ar
To Vacuum
system
M=3
Nozzle
Angle step
Diffuser
Ballast
Fuel
Injection
Port
Stagnation
Stagnation
Pressure
Pressure
Port
Port
Plenum: P0 = 1 atm
Fuel: C2H4
Oxidizer: air, O2/Ar
Spark ignition
Power
Supply
Flushed
Electrodes
Test section: M=3.2 – 3.4 , P=15-20 torr
Background theory on Chemi- Ionization
and Electron Removal
The Ohio State University
Nonequilibrium Thermodynamics Laboratories
Combustion Chamber

CH + O => CHO+ + e

Electronically excited, radiating species (CH*, C2*, OH*, O*, H*)
are created

Do electrons help excited species generation?
Removal of Electrons from M = 3 flow

Applying voltage to electrodes to draw off electrons
(Thomson discharge)
Emission Spectra from Combustion Chamber and M = 3 Flow
(C2H4 / air)
Nonequilibrium Thermodynamics Laboratories
The Ohio State University
Combustion Chamber
OH 3064 oA
system
H and O atomic lines also detected
Similar results for C2H4/O2/Ar
290
295
300
305
310
Wavelength (nm)
315
M = 3 flow
M = 3 flow
CH 4300 oA
system
C2 Swan System
500
505
510
515
520
Wavelength (nm)
525
530
410
420
430
Wavelength (nm)
440
450
Current-Voltage characteristic
C2H4 / O2/Ar combustion products, M = 3
Nonequilibrium Thermodynamics Laboratories
The Ohio State University
Current, µA
250
200
150
ne = (1 - 2) x 109 cm-3
100
50
0
0
100
200
300
400
Voltage, V
Similar results in C2H4/air
500
C2H4 / O2/Ar: Current and Visible Emission in M =3 Flow
Nonequilibrium Thermodynamics Laboratories
The Ohio State University
Current (A)
Current (A)
Emission
Current
500
Emission
Current
800
400
600
300
400
200
200
100
0
1
3
5
7
Time (s)
9
C2 Swan (516 nm)
11
13
0
1
3
5
7
Time (s)
CH (430 nm)
Voltage = 200 V (current saturated)
9
11
13
C2H4 / O2/Ar: Current and Visible Emission in M =3 Flow
(continued)
Nonequilibrium Thermodynamics Laboratories
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Voltage Off
Voltage On
0
2
4
6
Time (s)
Voltage off
Voltage on
8
C2 Swan (516 nm)

10
12
0
2
4
6
8
10
Time (s)
CH (430 nm)
No detectable change in CH and C2 emission intensity when
electrons are removed
12
C2H4/air flame: CH (431 nm) emission in plenum
and chemi-ionization current in M=3 flow
Nonequilibrium Thermodynamics Laboratories
The Ohio State University
Current (mA)
Emission Intensity (Arbitrary Units)
Emission
Current
1
0.8
0.6
0.4
0.2
0
50
100
150
200
250
Time (msec)
Flame “bursts” due to combustion instability
Very good correlation between emission and current
Same result for C2 Swan band emission (516 nm)
Summary
The Ohio State University
Nonequilibrium Thermodynamics Laboratories

Self sustained combustion and flameholding achieved

Electron density measured in supersonic flows of combustion
products, correlated with flame emission

No effect on C2 Swan band and CH emission when electrons are
removed
Future work
The Ohio State University
Nonequilibrium Thermodynamics Laboratories

Further measurements in M = 4 flows and different
equivalence ratios in both steady and unsteady flames

Injection of air, N2, CO, and NO into supersonic flow to study
energy transfer from combustion products to these species