Transcript Document 7732829

PLASMA-ENHANCED AERODYNAMICS –
A NOVEL APPROACH AND FUTURE DIRECTIONS
FOR ACTIVE FLOW CONTROL
Thomas C. Corke
Clark Chair Professor
University of Notre Dame
Center for Flow Physics and Control
Aerospace and Mechanical Engineering Dept.
Notre Dame, IN 46556
Ref: J. Adv. Aero. Sci., 2007.
Honeywell Seminar
July 19, 2007
Presentation Outline:
• Background SDBD Plasma Actuators
– Physics and Modeling
– Flow Control Simulation
– Comparison to Other FC Actuators
• Example Applications
– LPT Separation Control
– Turbine Tip-gap Flow Control
– Turbulent Separation Control
• Summary
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Single-dielectric barrier discharge (SDBD)
Plasma Actuator
exposed
electrode
dielectric
covered
electrode
substrate
AC voltage
source
• High voltage AC causes air to ionize
(plasma).
• Ionized air in presence of electric
field results in body force that acts
on neutral air.
• Body force is mechanism of flow
control.
The SDBD is stable at atmospheric
pressure because it is self-limiting
due to charge accumulation on the
dielectric surface.
Ref: AIAA J., 42, 3, 2004
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Flow Response: Impulsively Started Plasma Actuator
Phase-averaged PIV
Long-time Average
t
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Example Application: Cylinder Wake, ReD=30,000
Video
OFF
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ON
Physics of Operation
Electrostatic Body Force
D - Electric Induction
(Maxwell’s equation)
E  
(given by Boltzmann relation)
(x,t)
solution of equation - Body Force
electric potential 
Y
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Y
Y
Current/Light Emission ~ (t)
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t/T
Current/Light Emission ~ (x,t)
xmax
dx/dt
Voltage
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Electron Transport Key to Efficiency
a
More Optimum
Waveform
c d
b
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Steps to model actuator in flow
• Space-time electric potential, 
• Space-time body force
• Flow solver with body force added
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Space-Time Lumped Element Circuit Model:
Boundary Conditions on
exposed
electrode
dielectric
(x,t)
covered
electrode
substrate
AC voltage
source
Electric circuit with
N-sub-circuits
(N=100)
Ref: AIAA-2006-1206
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Space-time Dependent Lumped Element
Circuit Model (governing equations)
air capacitor
dielectric capacitor
Voltage on the dielectric
surface in the n-th sub-circuit
Plasma current
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Model Space-time Characteristics
Experiment
Illumination
Model Ip(t)
xmax
dx/dt
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Plasma Propagation Characteristics
Effect of Vapp
dxp/dt vs Vapp
(xp)max vs Vapp
Model
Model
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Plasma Propagation Characteristics
Effect of fa.c.
dxp/dt vs fa.c.
(xp)max vs fa.c.
Model
Model
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Numerical solution for (x,y,t)
Model provides time-dependent B.C. for
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

y, mm
Body Force, fb(x,t)
1.14
Normalized fb(x,t)
0.0
-5.08
0.0
x, mm
5.08
1.0
| fb |
0.5
0.0
y, mm
t/Ta.c.=0.2
-5.08
0.0
x, mm
5.08
-5.08
0.0
x, mm
5.08
1.14
0.0
1.0
| fb |
0.5
0.0
t/Ta.c.=0.7
-5.08
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0.0
x, mm
5.08
Example: LE Separation Control
NACA 0021 Leading Edge
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Computed cycle-averaged body
force vectors
Example: Impulsively Started Actuator
Velocity vectors
t=0.01743 sec
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2 = -0.001 countours
Example: AoA=23 deg.
U∞ =30 m/s, Rec=615K
Base Flow
Steady Actuator
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Comparison to Other FC Actuators?
• “Zero-mass Unsteady Blowing”
generally uses voice-coil system.
• Current driven devices, V~I.
• Losses result in I2R heating.
• Flow simulations require actuator
velocity field (flow dependent).
• SDBD plasma actuator is voltage driven, fb~V7/2.
• For fixed power (I·V), limit current to maximize voltage.
• Low ohmic losses.
• Flow simulations require body force field (not affected by external
flow, solve once for given geometry).
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Maximizing SDBD Plasma Actuator Body Force
At Fixed Power
Material
Quartz
Kapton
Teflon
Imax

3.8
3.4
2.0
Imax
Imax
All previous SDBD flow control
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Imax
Sample Applications
• LPT Separation Control
• Turbine Tip-Clearance-Flow Control
• Turbulent Flow Separation Control
• A.C. Plasma Anemometer
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LPT Separation Control
Pak-B Cascade
•
•
Span = 60cm
C=20.5cm
Flow
Plasma
Side
Ref: AIAA J. 44, 7, 51-58, 2006
AIAA J. 44, 7, 1477-1487, 2006
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Plasma Actuator: x/c=0.67, Re=50k
Ret.
Actuator
Location
Sep.
Steady Actuator
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Plasma Actuator: x/c=0.67, Re=50k
Deficit Pressure
Base Flow
Unsteady Plasma Act.
f Ls /Ufs=1
Loss Coeff. vs Re
200%
20%
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Turbine Tip-Clearance-Flow Control
Objective:
• Reduce losses associated with
tip-gap flow
Approach:
•Document tip gap flow behavior.
• Investigate strategies to reduce pressurelosses due to tip-gap-flow.
•Passive Techniques: How do they work?
•Active Techniques: Emulate passive effects?
Ref: AIAA-2007-0646
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Experimental Setup
Pak-B blades:
4.14” axial chord
Flow
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Pti  Pte
cp 
Pedyn
Under-tip Flow Morphology
g/c=0.05
t/g =2.83
Separation line:
Receptive to active flow control.
t/g =4.30
Tip-flow Plasma Actuator
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Unsteady Excitation Response
Re=500k
No Plasma
0
y/pitch
0.1
0.2
0.3
0.4
0.5
0.8
0.9
1
z/span
F 
f l
U
Shear Instability: 0.01<F+<0.04, U = maximum shear layer velocity, l = momentum thickness
Viscous Jet Core: 0.25<F+<0.5, U = characteristic velocity of jet core, l = gap size, g
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Unsteady Excitation Response: Selected F+
Cpt/Cptbase=0.95
Cpt/Cptbase=0.92
F+ = 0.07, (f = 1250 Hz) Cp t
F+ = 0.03, (f = 500 Hz)
No Plasma
0
0
0.8
0
y/pitch
0.7
0.1
0.1
0.1
0.2
0.2
0.2
0.6
0.5
0.4
0.3
0.3
0.3
0.4
0.4
0.4
0.3
0.2
0.1
0.5
0.5
0.8
0.9
1
0.5
0.8
0.9
1
z/span
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0
0.8
0.9
1
-0.1
Cpt and Loss Efficiency
s   R ln
Pte

Pti
Pte
Pti
g/c
1
 Pse 

1  c pt 1 
 Pte 


 s  P 
1   exp   t 2 
 R  Pt1 


 Pt 2 
1   
 Pt1 
F+
Cpt
Δη
No Squealer
5%
2.83
N/A
0.301
--
Squealer
5%
2.83
N/A
0.194
0.7%
Winglet
5%
4.30
N/A
0.247
0.3%
4%
3.52
N/A
0.251
--
4%
3.52
0.07
0.232
0.1%
 1
Pte  1
2
No Actuator
 1    1M e 
Pse  2

 1

t/g
Actuator
 1

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Turbine Tip-Clearance-Flow Control
Future Directions
Suction-side Blade “Squealer Tip”
“Plasma Squealer”
Active Casing Flow Turning
“Plasma Roughness”
Rao et al.
ASM GT 2006-91011
“Plasma Winglet”
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Turbulent Flow Separation Control
Wall-mounted hump model used in
NASA 2004 CFD validation.
Ref: AIAA-2007-0935
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Baseline: Benchmark Cp and Cf
R
S
S
k- SST best up to x/c=0.9
k- best for (x/c)ret
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SDBD Plasma Actuator Simulation and Experiment
ΔRx/c
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Turbulent Separation Control:
Future Applications
•
Flight control without moving surfaces
Aggressive Transition Ducts
Plasma Actuator
Miley 06-13-128 Simulation
BWB Inlet with 30% BLI
Low-Speed
Separated
Flow Region
AIAA-2006-3495,
AIAA-2007-0884
Reattached
Flow Region
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Plasma Flow Control
Summary
• The basis of SDBD plasma actuator flow control is the
generation of a body force vector.
• Our understanding of the process leading to improved plasma
actuator designs resulted in 20x improvement in performance.
• With the use of models for ionization, the body force effect can
be efficiently implemented into flow solvers.
• Such codes can then be used as tools for aerodynamic designs
that include flow control from the beginning, which holds the
ultimate potential.
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A.C. Plasma Anemometer
Originally developed for mass-flux measurements in
high Mach number, high enthalpy flows.
•
Flow transports charge-carrying ions
downstream from electrodes.
•
Loss of ions reduces current flow across gapincreases internal resistance – increases
voltage output.
•
Mechanism not sensitive on temperature.
•
Robust, no moving parts.
•
Native frequency response > 1 MHz.
•
Amplitude modulated ac carrier gives excellent
noise rejection.
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Flow
Principle of Operation:
Plasma Sensor Amplitude Modulated
Output
ac carrier at
fc = ~2 MHz
RF Amplifier
Plasma
Sensor
electrode
Velocity
Fluctuations
at frequency, fm
Amplitude Modulated
Output
electrode
Frequency Domain
Output
fc - fm
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fc
fc + fm
Real Time Demodulation
FPGA-based digital acquisition board allows host based
demodulation in real time.
GnuRadio
Modulated signal recovered
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Real-time Measurement of Blade Passing Flow
Video
Jet
f=1-2kHz
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Plasma Anemometer
Future Applications
•Engine internal flow sensor:
- Surge/stall sensor
- Casing flow separation sensor
- Combustion instability sensor
T.C. wire forms electrode
pair with gap = ~0.005”
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