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PLASMA-ENHANCED AERODYNAMICS – A NOVEL APPROACH AND FUTURE DIRECTIONS FOR ACTIVE FLOW CONTROL

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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

Ref: J. Adv. Aero. Sci., 2007.

- 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

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

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

Steps to model actuator in flow

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

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

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

Numerical solution for (x,y,t)

Model provides time-dependent B.C. for

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).

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

- LPT Separation Control
- Turbine Tip-Clearance-Flow Control
- Turbulent Flow Separation Control
- A.C. Plasma Anemometer

- 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

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

Base Flow

Unsteady Plasma Act.

Deficit Pressure

Loss Coeff. vs Re

200%

20%

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

g/c=0.05

Separation line:

Receptive to active flow control.

t/g =2.83

t/g =4.30

Tip-flow Plasma Actuator

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

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

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”

Turbulent Flow Separation Control

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

Ref: AIAA-2007-0935

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

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.

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

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

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

GnuRadio

Modulated signal recovered

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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