honeywell seminar july 19, 2007 plasma-enhanced aerodynamics – a novel approach and future...

Honeywell SeminarJuly 19, 2007

PLASMA-ENHANCED AERODYNAMICS – A NOVEL APPROACH AND FUTURE DIRECTIONS

FOR ACTIVE FLOW CONTROL

Thomas C. Corke

Clark Chair ProfessorUniversity of Notre Dame

Center for Flow Physics and ControlAerospace and Mechanical Engineering Dept.

Notre Dame, IN 46556

Ref: J. Adv. Aero. Sci., 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


Single-dielectric barrier discharge (SDBD)

Plasma Actuator

• 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.

Ref: AIAA J., 42, 3, 2004

exposed electrode

dielectric

AC voltage source

covered electrode

substrate

The SDBD is stable at atmospheric pressure because it is self-limiting due to charge accumulation on the dielectric surface.


Flow Response: Impulsively Started Plasma ActuatorPhase-averaged PIV

Long-time Average

t


Example Application: Cylinder Wake, ReD=30,000

OFF ON

Video


Physics of OperationElectrostatic Body Force

D - Electric Induction

(Maxwell’s equation)

(given by Boltzmann relation)

solution of equation -electric potential

E

Body

Force Y Y Y

(x,t)


Current/Light Emission ~ (t)


Current/Light Emission ~ (x,t)

Voltage

t/T

dx/dt

xmax


More OptimumWaveform

Electron Transport Key to Efficiency

a

b

c d


Steps to model actuator in flow

• Space-time electric potential,

• Space-time body force

• Flow solver with body force added


Space-Time Lumped Element Circuit

Model: Boundary Conditions on (x,t)

Electric circuit with N-sub-

circuits

(N=100)

exposed electrode

dielectric

AC voltage source

covered electrode

substrate

Ref: AIAA-2006-1206


Space-time Dependent Lumped Element Circuit Model (governing

equations)

Voltage on the dielectric surface in the n-th sub-circuit

Plasma current

air capacitor dielectric capacitor


dx/dt

xmax

Model Ip(t)Experiment Illumination

Model Space-time Characteristics


Plasma Propagation Characteristics

Effect of Vapp

dxp/dt vs Vapp (xp)max vs Vapp

Model

Model


Plasma Propagation Characteristics

Effect of fa.c.dxp/dt vs fa.c. (xp)max vs fa.c.

Model

Model


Numerical solution for (x,y,t)

Model provides time-dependent B.C. for


Body Force, fb(x,t)N

orm

aliz

ed f

b(x

,t)

-5.08 0.0 5.080.0

1.14

x, mm

y,

mm

-5.08 0.0 5.08

0.0

0.5

1.0

x, mm

| f b |

-5.08 0.0 5.080.0

1.14

x, mm

y,

mm

-5.08 0.0 5.08

0.0

0.5

1.0

x, mm

| f b |

t/Ta.c.=0.2

t/Ta.c.=0.7


Example: LE Separation Control

Computed cycle-averaged body force vectors NACA 0021 Leading Edge


Example: Impulsively Started Actuator

t=0.01743 secVelocity vectors 2 = -0.001 countours


Example: AoA=23 deg.

Base Flow

Steady Actuator

U∞ =30 m/s, Rec=615K


Comparison to Other FC Actuators?

• 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).

• “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).


Material Quartz 3.8 Kapton 3.4Teflon 2.0

Imax

Imax

Imax

Imax

Maximizing SDBD Plasma Actuator Body ForceAt Fixed Power

All previous SDBD flow control


Sample Applications

• LPT Separation Control

• Turbine Tip-Clearance-Flow Control

• Turbulent Flow Separation Control

• A.C. Plasma Anemometer


LPT Separation Control• Span = Span = 60cm60cm• C=20.5cmC=20.5cm

PlasmaSide

Flow

Pak-B Cascade

Ref: AIAA J. 44, 7, 51-58, 2006 AIAA J. 44, 7, 1477-1487, 2006


Plasma Actuator: x/c=0.67, Re=50k

ActuatorLocation

Steady Actuator

Sep.

Ret.


f Ls /Ufs=1

Plasma Actuator: x/c=0.67, Re=50kDeficit Pressure

Loss Coeff. vs Re

200%

20%

Base Flow Unsteady Plasma Act.


•Document tip gap flow behavior. Document tip gap flow behavior. • Investigate strategies to reduce Investigate strategies to reduce pressure-pressure-

losses due to tip-gap-flow.losses due to tip-gap-flow.•Passive Techniques: How do they work?Passive Techniques: How do they work?•Active Techniques: Emulate passive Active Techniques: Emulate passive effects?effects?

Turbine Tip-Clearance-Flow Control

Approach:

• Reduce losses associated with tip-gap flow

Objective:

Ref: AIAA-2007-0646


Experimental Setup

FlowPak-B blades:4.14” axial chord

edyn

tetip P

PPc


Under-tip Flow Morphology

t/g =2.83

t/g =4.30

g/c=0.05

Separation line: Receptive to active flow control.

Tip-flow Plasma Actuator


Re=500k

0.8 0.9 1

0

0.1

0.2

0.3

0.4

0.5

y/p

itch

No Plasma

z/span

Unsteady Excitation Response

U

lfF

Shear InstabilityShear Instability: 0.01<F+<0.04, U = maximum shear layer velocity, l = momentum thickness: 0.01<F+<0.04, U = maximum shear layer velocity, l = momentum thicknessViscous Jet Core:Viscous Jet Core: 0.25<F+<0.5, U = characteristic velocity of jet core, l = gap size, g 0.25<F+<0.5, U = characteristic velocity of jet core, l = gap size, g


0.8 0.9 1

0

0.1

0.2

0.3

0.4

0.5

y/pi

tch

No Plasma

0.8 0.9 1

0

0.1

0.2

0.3

0.4

0.5

z/span

F+ = 0.03, (f = 500 Hz)

0.8 0.9 1

0

0.1

0.2

0.3

0.4

0.5

F+ = 0.07, (f = 1250 Hz)

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Cpt

Unsteady Excitation Response: Selected F+

Cpt/Cptbase=0.95 Cpt/Cptbase=0.92


121

2

11

11

1

ln

ese

te

te

sept

ti

te

ti

te

MP

P

P

Pc

P

P

P

PRs g/c t/g 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%

No Actuator 4% 3.52 N/A 0.251 --

Actuator 4% 3.52 0.07 0.232 0.1%

1

1

2

1

1

2

1

exp1

t

t

t

t

PP

PP

Rs

Cpt and Loss Efficiency


Turbine Tip-Clearance-Flow ControlFuture Directions

“Plasma Roughness” Rao et al. ASM GT 2006-91011

“Plasma Winglet”

“Plasma Squealer”

Active Casing Flow Turning

Suction-side Blade “Squealer Tip”


Turbulent Flow Separation Control

Wall-mounted hump model used in NASA 2004 CFD validation.

Ref: AIAA-2007-0935


Baseline: Benchmark Cp and Cf

k- SST best up to x/c=0.9k- best for (x/c)ret

S

S

R


SDBD Plasma Actuator Simulation and Experiment

ΔRx/c


Turbulent Separation Control:Future Applications

• Flight control without moving surfaces

Miley 06-13-128 Simulation

Plasma Actuator

Low-SpeedSeparated

Flow Region

Reattached Flow Region

BWB Inlet with 30% BLI

Aggressive Transition Ducts

AIAA-2006-3495,AIAA-2007-0884


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.


A.C. Plasma Anemometer

• Flow transports charge-carrying ions downstream from electrodes.

• Loss of ions reduces current flow across gap- increases 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.

Originally developed for mass-flux measurements in high Mach number, high enthalpy flows.

Flow

Principle of Operation:


Plasma Sensor Amplitude Modulated Output

Velocity Fluctuations

at frequency, fm

ac carrier at fc = ~2 MHz

Plasma Sensor

RF Amplifier

electrode

electrode

Amplitude Modulated

Output

fc fc + fmfc - fm

Frequency DomainOutput


Real Time Demodulation

FPGA-based digital acquisition board allows host based demodulation in real time.

GnuRadioModulated signal recovered


Real-time Measurement of Blade Passing Flow Video

f=1-2kHz

Jet


Plasma AnemometerFuture Applications

•Engine internal flow sensor:- Surge/stall sensor- Casing flow separation sensor- Combustion instability sensor

T.C. wire forms electrodepair with gap = ~0.005”

honeywell seminar july 19, 2007 plasma-enhanced aerodynamics – a novel approach and future...

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