Transcript Plasma Actuators for Landing Gear Noise Control

Parametric Optimization of Single
Dielectric Barrier Discharge (SDBD)
Plasma Actuators*
Alexey V. Kozlov, Flint O. Thomas †
20th Aerospace and Mechanical Engineering Graduate Student Conference
Notre Dame, Indiana 19 October 2006
•Supported by NASA Langley NAG1-03076
by NASA Langley Research Center
†Advisor
Motivation and Objectives
•
There has been growing interest in flow control using
dielectric barrier discharge plasma actuators in recent years.
However, studies regarding optimization of plasma actuators
are relatively scarce.
•
The Center for Flow Physics and Control at Notre Dame is
involved in the development of single dielectric barrier
discharge plasma actuators (SDBD) for several aerodynamic
applications of active separation control.
•
Flow control experiments show that the performance of
present-day plasma actuators at high freestream velocities
(high Reynolds numbers) is not enough.
•
A primary objective is to optimize single dielectric barrier
discharge plasma actuator toward growing demands of the
flow control science.
.
Overview of SDBD Plasma Actuators
+
+ qv +
+ +
induced air flow
E , Fb
plasma
h
exposed
electrode
substrat
dielectric
AC voltage
insulated
electrode
• DBD discharge consists of numerous short-time small-scale
microdischarges (streamers) distributed randomly in time and in surrounding
air volume
• Plasma volume charge in the presence of an electric field, E*, results in a
body force, Fb.
• Plasma formation is accompanied by a coupling of directed momentum to
the surrounding air.
Dielectric barrier dischage
Uniform glow
Filamentary form
Plasma body force, power dissipation and
maximum induced velocity estimation
Maximum electric field strenght for dry air E  25...30 kV cm
Assume that the electric field strength in plasma
does not vary significan tly along the dielectric surface.
 airV 2
2

 0 E2
2
 V  E
0
8.85 10 12 F m
5
 30 10 V m 
 8m s
3
 air
1.2 kg m
2
Fb  qv E   0 E2 h  8.85 10 12
F 
V
N
  30 105  10 3 m  0.08
m 
m
m
20U 03 f
W
, E0  5...10 kV cm
3E0 d
Length of plasma layer
L
U0
E0
The Plasma Generation Circuit
• High voltage for the excitation of the plasma actuators is obtained
from the secondary coil of the transformer.
• Anti noise filter suppresses radio frequency electromagnetic noise radiation
from high voltage wires. Accurate hot-wire measurements in the vicinity
of the plasma discharge are now possible.
Schematic of the experimental setup for thrust
measurement
Power dissipation versus applied voltage
dielectric material: quartz glass (dielectric constant 3.7)
dielectric thickness 1/4”, encapsulated electrode width 2”
Thrust versus applied voltage
Thrust versus power dissipation
X/D = 10, y/D =2
10
Maximum Thrust, N m
Optimal Frequency, kHz
Relation between voltage, optimal frequency and thrust
8
6
4
2
20 40 60 80 100
Voltage pk pk, kV
0.14
0.12
0.1
0.08
0.06
0.04
0.02
2
4
6
8
Frequency, kHz
10
Voltage waveform comparison
Thrust vs. voltage for ramp (sawtooth) and sinusoidal waveforms
Pitot probe velocity measurements
Plasma induced velocity profile
Multiple actuators
f =48 Hz
Thrust vs. applied voltage
Plasma induced velocity profile
Summary & Focus of Current Work
•
Optimize plasma actuator design by consideration of:
(1) Increase of dielectric thickness and applied voltage and
using optimal frequency greatly improve plasma actuator
performance.
(2) Experiments clearly show the benefit of using ramp
(sawtooth) waveform.
(3) Multiple actuators (plasma array) significantly increase the
body force and plasma induced velocity.
•
Additional measurements to investigate the influence of
the dielectric thickness on the optimal frequency and body
force are planned.