Download N. Zouzou

Smoke Particle Velocity Measurements
in Point to Plane
Corona Discharges
Noureddine ZOUZOU*
Eric MOREAU
Gérard TOUCHARD
Laboratoire d’Etudes Aérodynamiques (LEA)
Poitiers University, FRANCE
I. Introduction
II. Experimental setup
III. Electrical Properties
IV. Flow Visualization and Velocity Profiles
V. System Efficiency
VI. Conclusions
N. Zouzou
2
I. Introduction
DC-Corona Discharges and Electrostatic Precipitation
+ Positive Corona
- Negative Corona
Needle
Needle
eN
e-
Ionization
region
+
e-
+
e-
Drift
region
N
-
e-
+
+
Electron
Gas molecule
Negative ion
Positive ion
N
N
+
+
Particles
(dusts)
e-
-
-
-
N
Corona
wind
Grounded Electrode
N. Zouzou
Positive ions are directly created in
the ionisation region (ions act like
an extension of the active electrode)
Negative ions are created in
ionisation and drift regions
3
I. Introduction
Influence of Corona Polarity ….
Current pulses
Discharge progress
Ozone generation
+ Positive Corona
- Negative Corona
Streamer
Trichel
Continuous
Non-continuous
Low
High
What about:
Ionic wind velocity (magnitude and profile) ?
System Efficiency (Power output / Power input)?
N. Zouzou
4
II. Experimental Setup
2M
Laser
sheet
HV
supply
 40 kV
r axis
10-50 mm
A
N. Zouzou
Camera
acquisition
z axis
Glass box: V=252525 cm3
Needle curvature:  100 µm
PIV system: LAVISION 
5
III. Results
Electrical Properties
+ Positive Corona
- Negative Corona
400
Air
h=10mm
20mm
30mm
40mm
50mm
80
60
Air with particles
h=10mm
20mm
30mm
40mm
50mm
40
20
0
300
Air with particles
h=10mm
20mm
30mm
40mm
50mm
Negative Corona
200
100
0
0
5
10
15
20
25
30
Applied voltage (kV)
N. Zouzou
Air
h=10mm
20mm
30mm
40mm
50mm
Positive corona
Corona Current (µA)
Corona Current (µA)
100
35
40
0
5
10
15
20
25
30
35
40
Applied voltage (kV)
 Corona current  Air > Air + particles
 Corona current  Negative > Positive
 Flashover voltage  Negative > Positive
6
IV. Results
Flow Visualization and Velocity Profiles
+ Positive Corona (40mm,10kV)
Needle
Plane
N. Zouzou
7
IV. Results
Flow Visualization and Velocity Profiles
+ Positive Corona (40mm,10kV)
N. Zouzou
8
IV. Results
Flow Visualization and Velocity Profiles
0
0
5
5
10
10
15
15
20
r=0mm, h=40mm
+10kV
+15kV
+20kV
+25kV
+30kV
+32kV
25
30
35
40
0
1
2
3
-1
Velocity (m.s )
N. Zouzou
- Negative Corona
4
z (mm)
z (mm)
+ Positive Corona
20
r=0mm, h=40mm
-10kV
-15kV
-20kV
-25kV
-30kV
-35kV
-40kV
25
30
35
40
0
1
2
3
4
5
6
7
8
-1
Velocity (m.s )
 Velocity profile is asymmetric
 Velocity  0 m/s near the electrodes
 Particle acceleration distance is slight ( 3mm)
9
IV. Results
Flow Visualization and Velocity Profiles
- Negative Corona
0,0
0,2
0,2
0,4
0,4
-1
vz (m.s )
0,0
-1
vz (m.s )
+ Positive Corona
0,6
0,8
1,0
1,2
-30
z=5mm/point
10mm
15mm
20mm
25mm
30mm
35mm
-20
-10
V=+10kV
h=40mm
0
r (mm)
N. Zouzou
10
20
30
0,6
0,8
1,0
1,2
-30
z=5mm/point
10mm
15mm
20mm
25mm
30mm
35mm
-20
-10
V=-10kV
h=40mm
0
10
20
30
r (mm)
 Impacting jet is non-conic
 Velocity peak magnitude  Positive > Negative (mobility)
 Velocity peak width  Negative > Positive (space charge)
10
IV. Results
Flow Visualization and Velocity Profiles
+ Positive Corona
- Negative Corona
4
7
-1
2
Positive Corona
h=10mm
20mm
30mm
40mm
50mm
60mm
1
0
0
20
40
60
Corona current (µA)
N. Zouzou
Velocitymax (m.s )
3
-1
Velocitymax (m.s )
6
80
100
5
4
Negative Corona
3
2
h=10mm
20mm
30mm
40mm
50mm
1
0
0
100
200
300
400
Corona current (µA)
 Velocity can reach 6 m/s
 Velocity maximum  Negative > Positive (current limitation)
 Velocity  square root of the current
11
IV. Results
Flow Visualization and Velocity Profiles
4x10
5
3x10
5
2x10
5
1x10
5
2
v max  B  I
-2
-1
B(m .s .A )
Positive Corona
Negative Corona
0
0
10
20
30
40
50
60
h (mm)
 B is proportional to the gap distance
 B value  Positive > Negative (mobility)
N. Zouzou
12
V. Results
10
1
10
0
-1
Velocitymax (m.s )
System Efficiency
10
Positive corona
h=10mm
20mm
30mm
40mm
50mm
60mm
Negative corona
h=10mm
20mm
30mm
40mm
50mm
-1
10
-3
10
-2
-1
10
0
10
1
10
Electric Power (W)
 Power Input maximum  Negative > Positive
 Velocity  cube root of input power
N. Zouzou
13
V. Results
System Efficiency
Mechanic power associated with a domain (D)
PKine.( D) 

 t
D( t )

1
2

v 2 dV 


2
1
div

v
v dV
2

D ( t )
Stationary regime
PKine.( D )   12 v 2 v  ndS
S1
S
r axis
S3
If (D) is cylindrical in shape
PKine.( D ) 

1
2
v 2 v z dS   12 v 2 v z dS   12 v 2 v r dS
S2
S1
S2
z axis
S3
Electro-kinetic conversion efficiency
η(%)  100 
N. Zouzou
PKine.( ON)  PKine.( OFF)
PElec.
14
V. Results
System Efficiency
0,3
h=20mm
30mm
40mm
 (%)
0,2
0,1
0,0
-40
N. Zouzou
-30
-20
-10
0
10
20
Applied Voltage (kV)
 At low voltages  Efficiency 
 At high voltages Negative Efficiency
 Positive Efficiency 
30
40
15
IV. Conclusion
 Corona current  with voltage, however it  with the
presence of incense particles
 The axial and radial profiles of the velocity show some
differences associated with the discharge polarity
(Velocity  6 m/sec)
 Velocity  (current)1/2 , and Velocity  (Input Power)1/3
 Electro-kinetic conversion efficiency  0.2 %, it  with
Negative applied voltage
N. Zouzou
16