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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.

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slide1

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.

slide2

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
slide3

dielectric

exposed electrode

covered electrode

substrate

AC voltage source

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.

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

slide4

t

Flow Response: Impulsively Started Plasma Actuator

Phase-averaged PIV

Long-time Average

slide6

(x,t)

Y

Y

Y

Physics of OperationElectrostatic Body Force

D- Electric Induction

(Maxwell’s equation)

(given by Boltzmann relation)

solution of equation -

electric potential

Body Force

slide8

xmax

dx/dt

Current/Light Emission ~ (x,t)

t/T

Voltage

slide9

Electron Transport Key to Efficiency

a

c d

More Optimum

Waveform

b

slide10

Steps to model actuator in flow

  • Space-time electric potential,
  • Space-time body force
  • Flow solver with body force added
slide11

dielectric

exposed electrode

covered electrode

substrate

AC voltage source

Space-Time Lumped Element Circuit Model: Boundary Conditions on(x,t)

Electric circuit with N-sub-circuits

(N=100)

Ref:AIAA-2006-1206

slide12

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

slide13

xmax

dx/dt

Model Space-time Characteristics

Experiment

Illumination

Model Ip(t)

slide14

Plasma Propagation Characteristics

Effect of Vapp

dxp/dt vs Vapp

(xp)maxvs Vapp

Model

Model

slide15

Plasma Propagation Characteristics

Effect of fa.c.

dxp/dt vs fa.c.

(xp)maxvs fa.c.

Model

Model

slide16

Numerical solution for (x,y,t)

Model provides time-dependent B.C. for

slide17

Body Force, fb(x,t)

t/Ta.c.=0.2

Normalized fb(x,t)

t/Ta.c.=0.7

slide18

Example: LE Separation Control

Computed cycle-averaged body force vectors

NACA 0021 Leading Edge

slide19

Example: Impulsively Started Actuator

Velocity vectors

t=0.01743 sec

2 = -0.001 countours

slide20

Base Flow

Example: AoA=23 deg.

U∞=30 m/s, Rec=615K

Steady Actuator

slide21

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).
slide22

Material

Quartz 3.8

Kapton 3.4

Teflon 2.0

Imax

Imax

Imax

Imax

All previous SDBD flow control

Maximizing SDBD Plasma Actuator Body Force

At Fixed Power

sample applications
Sample Applications
  • LPT Separation Control
  • Turbine Tip-Clearance-Flow Control
  • Turbulent Flow Separation Control
  • A.C. Plasma Anemometer
slide24

LPT Separation Control

  • Span = 60cm
  • C=20.5cm

Pak-B Cascade

Flow

Plasma

Side

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

AIAA J. 44, 7, 1477-1487, 2006

slide25

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

Ret.

Actuator

Location

Sep.

Steady Actuator

slide26

f Ls /Ufs=1

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

Base Flow

Unsteady Plasma Act.

Deficit Pressure

Loss Coeff. vs Re

200%

20%

slide27

Turbine Tip-Clearance-Flow Control

Objective:

  • Reduce losses associated with
  • tip-gap flow

Approach:

  • Document tip gap flow behavior.
  • Investigate strategies to reduce pressure-
  • losses due to tip-gap-flow.
    • Passive Techniques: How do they work?
    • Active Techniques: Emulate passive effects?

Ref: AIAA-2007-0646

slide28

Experimental Setup

Pak-B blades:

4.14” axial chord

Flow

slide29

Under-tip Flow Morphology

g/c=0.05

Separation line:

Receptive to active flow control.

t/g =2.83

t/g =4.30

Tip-flow Plasma Actuator

slide30

No Plasma

0

0.1

0.2

y/pitch

0.3

0.4

0.5

0.8

0.9

1

Unsteady Excitation Response

Re=500k

z/span

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

slide31

Cp

No Plasma

F+

= 0.03, (f = 500 Hz)

F+

= 0.07, (f = 1250 Hz)

t

0.8

0

0

0

0.7

0.1

0.1

0.1

0.6

0.5

0.2

0.2

0.2

y/pitch

0.4

0.3

0.3

0.3

0.3

0.2

0.4

0.4

0.4

0.1

0.5

0.5

0.5

0

-0.1

0.8

0.9

1

0.8

0.9

1

0.8

0.9

1

z/span

Unsteady Excitation Response: Selected F+

Cpt/Cptbase=0.95

Cpt/Cptbase=0.92

slide33

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”

slide34

Turbulent Flow Separation Control

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

Ref: AIAA-2007-0935

slide35

R

S

S

Baseline: Benchmark Cp and Cf

k- SST best up to x/c=0.9

k- best for (x/c)ret

slide37

Aggressive Transition Ducts

BWB Inlet with 30% BLI

Low-Speed

Separated

Flow Region

Plasma Actuator

Reattached

Flow Region

Turbulent Separation Control:

Future Applications

  • Flight control without moving surfaces

Miley 06-13-128 Simulation

AIAA-2006-3495,

AIAA-2007-0884

slide38

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.
slide40

A.C. Plasma Anemometer

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

Principle of Operation:

  • Flow transports charge-carrying ions downstream from electrodes.
  • Loss of ionsreduces 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.

Flow

slide41

ac carrier at

fc = ~2 MHz

RF Amplifier

Plasma

Sensor

fc

fc - fm

fc + fm

electrode

Velocity Fluctuations

at frequency, fm

electrode

Plasma Sensor Amplitude Modulated Output

Amplitude Modulated

Output

Frequency Domain

Output

slide42

Real Time Demodulation

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

GnuRadio

Modulated signal recovered

slide44

T.C. wire forms electrode

pair with gap = ~0.005”

Plasma Anemometer

Future Applications

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