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

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

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  1. 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.

  2. 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

  3. 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

  4. t Flow Response: Impulsively Started Plasma Actuator Phase-averaged PIV Long-time Average

  5. Example Application: Cylinder Wake, ReD=30,000 Video OFF ON

  6. (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

  7. Current/Light Emission ~ (t)

  8. xmax dx/dt Current/Light Emission ~ (x,t) t/T Voltage

  9. Electron Transport Key to Efficiency a c d More Optimum Waveform b

  10. Steps to model actuator in flow • Space-time electric potential, • Space-time body force • Flow solver with body force added

  11. 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

  12. 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

  13. xmax dx/dt Model Space-time Characteristics Experiment Illumination Model Ip(t)

  14. Plasma Propagation Characteristics Effect of Vapp dxp/dt vs Vapp (xp)maxvs Vapp Model Model

  15. Plasma Propagation Characteristics Effect of fa.c. dxp/dt vs fa.c. (xp)maxvs fa.c. Model Model

  16. Numerical solution for (x,y,t) Model provides time-dependent B.C. for

  17. Body Force, fb(x,t)  t/Ta.c.=0.2 Normalized fb(x,t) t/Ta.c.=0.7

  18. Example: LE Separation Control Computed cycle-averaged body force vectors NACA 0021 Leading Edge

  19. Example: Impulsively Started Actuator Velocity vectors t=0.01743 sec 2 = -0.001 countours

  20. Base Flow Example: AoA=23 deg. U∞=30 m/s, Rec=615K Steady Actuator

  21. 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).

  22. 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

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

  24. 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

  25. Plasma Actuator: x/c=0.67, Re=50k Ret. Actuator Location Sep. Steady Actuator

  26. 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%

  27. 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

  28. Experimental Setup Pak-B blades: 4.14” axial chord Flow

  29. 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

  30. 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

  31. 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

  32. Cpt and Loss Efficiency

  33. 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”

  34. Turbulent Flow Separation Control Wall-mounted hump model used in NASA 2004 CFD validation. Ref: AIAA-2007-0935

  35. R S S Baseline: Benchmark Cp and Cf k- SST best up to x/c=0.9 k- best for (x/c)ret

  36. SDBD Plasma Actuator Simulation and Experiment ΔRx/c

  37. 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

  38. 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.

  39. 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

  40. 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

  41. Real Time Demodulation FPGA-based digital acquisition board allows host based demodulation in real time. GnuRadio Modulated signal recovered

  42. Real-time Measurement of Blade Passing Flow Video Jet f=1-2kHz

  43. 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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