PLASMAENHANCED AERODYNAMICS A NOVEL APPROACH AND FUTURE DIRECTIONS

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 Honeywell Seminar July 19, 2007

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 Honeywell Seminar July 19, 2007

Flow Response: Impulsively Started Plasma Actuator Phase-averaged PIV Long-time Average t Honeywell Seminar July 19, 2007

Example Application: Cylinder Wake, Re. D=30, 000 Video OFF Honeywell Seminar July 19, 2007 ON

Physics of Operation Electrostatic Body Force D - Electric Induction (Maxwell’s equation) (given by Boltzmann relation) (x, t) solution of equation - Body Force electric potential Y Honeywell Seminar July 19, 2007 Y Y

Current/Light Emission ~ (t) Honeywell Seminar July 19, 2007

t/T Current/Light Emission ~ (x, t) xmax dx/dt Voltage Honeywell Seminar July 19, 2007

Electron Transport Key to Efficiency a More Optimum Waveform c d b Honeywell Seminar July 19, 2007

Steps to model actuator in flow • Space-time electric potential, • Space-time body force • Flow solver with body force added Honeywell Seminar July 19, 2007

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 Honeywell Seminar July 19, 2007

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 Honeywell Seminar July 19, 2007

Model Space-time Characteristics Experiment Illumination Model Ip(t) xmax dx/dt Honeywell Seminar July 19, 2007

Plasma Propagation Characteristics Effect of Vapp dxp/dt vs Vapp (xp)max vs Vapp Model Honeywell Seminar July 19, 2007

Plasma Propagation Characteristics Effect of fa. c. dxp/dt vs fa. c. (xp)max vs fa. c. Model Honeywell Seminar July 19, 2007

Numerical solution for (x, y, t) Model provides time-dependent B. C. for Honeywell Seminar July 19, 2007

Normalized fb(x, t) Body Force, fb(x, t) t/Ta. c. =0. 2 t/Ta. c. =0. 7 Honeywell Seminar July 19, 2007

Example: LE Separation Control NACA 0021 Leading Edge Honeywell Seminar July 19, 2007 Computed cycle-averaged body force vectors

Example: Impulsively Started Actuator Velocity vectors t=0. 01743 sec Honeywell Seminar July 19, 2007 2 = -0. 001 countours

Example: Ao. A=23 deg. U∞ =30 m/s, Rec=615 K Base Flow Steady Actuator Honeywell Seminar July 19, 2007

Comparison to Other FC Actuators? • “Zero-mass Unsteady Blowing” generally uses voice-coil system. • Current driven devices, V~I. • Losses result in I 2 R heating. • Flow simulations require actuator velocity field (flow dependent). • SDBD plasma actuator is voltage driven, fb ~V 7/2. • 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). Honeywell Seminar July 19, 2007

Maximizing SDBD Plasma Actuator Body Force At Fixed Power Material Quartz Kapton Teflon Imax 3. 8 3. 4 2. 0 Imax All previous SDBD flow control Honeywell Seminar July 19, 2007 Imax

Sample Applications • LPT Separation Control • Turbine Tip-Clearance-Flow Control • Turbulent Flow Separation Control • A. C. Plasma Anemometer Honeywell Seminar July 19, 2007

LPT Separation Control Span = 60 cm • C=20. 5 cm Pak-B Cascade • Flow Plasma Side Ref: AIAA J. 44, 7, 51 -58, 2006 AIAA J. 44, 7, 1477 -1487, 2006 Honeywell Seminar July 19, 2007

Plasma Actuator: x/c=0. 67, Re=50 k Ret. Actuator Location Sep. Steady Actuator Honeywell Seminar July 19, 2007

Plasma Actuator: x/c=0. 67, Re=50 k Deficit Pressure Base Flow Unsteady Plasma Act. f Ls /Ufs=1 Loss Coeff. vs Re 200% 20% Honeywell Seminar July 19, 2007

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 Honeywell Seminar July 19, 2007

Experimental Setup Pak-B blades: 4. 14” axial chord Flow Honeywell Seminar July 19, 2007

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 Honeywell Seminar July 19, 2007

Unsteady Excitation Response Re=500 k No Plasma 0 y/pitch 0. 1 0. 2 0. 3 0. 4 0. 5 0. 8 0. 9 1 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 Honeywell Seminar July 19, 2007

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. 8 y/pitch 0. 7 0. 1 0. 2 0. 6 0. 5 0. 4 0. 3 0. 2 0. 4 0. 1 0. 5 0. 8 0. 9 z/span 1 Honeywell Seminar July 19, 2007 0 0. 8 0. 9 1 -0. 1

Cpt and Loss Efficiency 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% Honeywell Seminar July 19, 2007

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” Honeywell Seminar July 19, 2007

Turbulent Flow Separation Control Wall-mounted hump model used in NASA 2004 CFD validation. Ref: AIAA-2007 -0935 Honeywell Seminar July 19, 2007

Baseline: Benchmark Cp and Cf R S S k- SST best up to x/c=0. 9 k- best for (x/c)ret Honeywell Seminar July 19, 2007

SDBD Plasma Actuator Simulation and Experiment ΔRx/c Honeywell Seminar July 19, 2007

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 Honeywell Seminar July 19, 2007

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 20 x 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. Honeywell Seminar July 19, 2007

Honeywell Seminar July 19, 2007

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. Honeywell Seminar July 19, 2007 Flow Principle of Operation:

Plasma Sensor Amplitude Modulated Output ac carrier at fc = ~2 MHz Plasma Sensor RF Amplifier electrode Velocity Fluctuations at frequency, fm Amplitude Modulated Output electrode Frequency Domain Output fc - f m Honeywell Seminar July 19, 2007 fc fc + f m

Real Time Demodulation FPGA-based digital acquisition board allows host based demodulation in real time. Gnu. Radio Modulated signal recovered Honeywell Seminar July 19, 2007

Real-time Measurement of Blade Passing Flow Video Jet f=1 -2 k. Hz Honeywell Seminar July 19, 2007

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” Honeywell Seminar July 19, 2007