1. Honeywell Seminar July 19, 2007 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. 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

3. Honeywell Seminar July 19, 2007 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.

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

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

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

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

8. Honeywell Seminar July 19, 2007 Current/Light Emission ~  ( x,t ) Voltage t/T dx/dt x max

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

10. 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

11. Honeywell Seminar July 19, 2007 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

12. Honeywell Seminar July 19, 2007 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

13. Honeywell Seminar July 19, 2007 dx/dt x max Model  I p (t)  Experiment Illumination Model Space-time Characteristics

14. Honeywell Seminar July 19, 2007 Plasma Propagation Characteristics Effect of V app dx p /dt vs V app (x p ) max vs V app Model

15. Honeywell Seminar July 19, 2007 Plasma Propagation Characteristics Effect of f a.c. dx p /dt vs f a.c. (x p ) max vs f a.c. Model

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

17. Honeywell Seminar July 19, 2007 Body Force, f b ( x,t )  Normalized f b (x,t) t/T a.c.=0.2 t/T a.c.=0.7

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

19. Honeywell Seminar July 19, 2007 Example: Impulsively Started Actuator t=0.01743 sec Velocity vectors 2 = -0.001 countours

20. Honeywell Seminar July 19, 2007 Example: AoA=23 deg. Base Flow Steady Actuator U ∞ =30 m/s, Re c =615K

21. Honeywell Seminar July 19, 2007 Comparison to Other FC Actuators? SDBD plasma actuator is voltage driven,  f b  ~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). “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).

22. Honeywell Seminar July 19, 2007 Material  Quartz 3.8 Kapton 3.4 Teflon 2.0 I max Maximizing SDBD Plasma Actuator Body Force At Fixed Power All previous SDBD flow control

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

24. Honeywell Seminar July 19, 2007 LPT Separation Control Span = 60cm Span = 60cm C=20.5cm C=20.5cm Plasma Side Flow Pak-B Cascade Ref: AIAA J. 44, 7, 51-58, 2006 AIAA J. 44, 7, 1477-1487, 2006

25. Honeywell Seminar July 19, 2007 Plasma Actuator: x/c=0.67, Re=50k Actuator Location Steady Actuator Sep. Ret.

26. Honeywell Seminar July 19, 2007 f L s /U fs =1 Plasma Actuator: x/c=0.67, Re=50k Deficit Pressure Loss Coeff. vs Re 200% 20% Base FlowUnsteady Plasma Act.

27. Honeywell Seminar July 19, 2007 Document tip gap flow behavior.Document tip gap flow behavior. Investigate strategies to reduce pressure- Investigate strategies to reduce 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 effects?Active Techniques: Emulate passive effects? Turbine Tip-Clearance-Flow Control Approach: Reduce losses associated with tip-gap flow Objective: Ref: AIAA-2007-0646

28. Honeywell Seminar July 19, 2007 Experimental Setup Flow Pak-B blades: 4.14” axial chord

29. Honeywell Seminar July 19, 2007 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

30. Honeywell Seminar July 19, 2007 Re=500k 0.80.91 0 0.1 0.2 0.3 0.4 0.5 y/pitch No Plasma z/span Unsteady Excitation Response 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. Honeywell Seminar July 19, 2007 0.80.91 0 0.1 0.2 0.3 0.4 0.5 y/pitch No Plasma 0.80.91 0 0.1 0.2 0.3 0.4 0.5 z/span F+F+ = 0.03, (f = 500 Hz) 0.80.91 0 0.1 0.2 0.3 0.4 0.5 F+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 Cp t Unsteady Excitation Response: Selected F + C pt /C ptbase =0.95C pt /C ptbase =0.92

32. Honeywell Seminar July 19, 2007 g/ct/gF+F+ C pt Δη No Squealer5%2.83N/A0.301-- Squealer5%2.83N/A0.1940.7% Winglet5%4.30N/A0.2470.3% No Actuator4%3.52N/A0.251-- Actuator4%3.520.070.2320.1% C pt and Loss Efficiency

33. Honeywell Seminar July 19, 2007 Turbine Tip-Clearance-Flow Control Future Directions “Plasma Roughness” Rao et al. ASM GT 2006-91011 “Plasma Winglet” “Plasma Squealer” Active Casing Flow Turning Suction-side Blade “Squealer Tip”

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

35. Honeywell Seminar July 19, 2007 Baseline: Benchmark C p and C f k- SST best up to x/c=0.9 k- best for (x/c) ret S S R

36. Honeywell Seminar July 19, 2007 SDBD Plasma Actuator Simulation and Experiment ΔR x/c

37. Honeywell Seminar July 19, 2007 Turbulent Separation Control: Future Applications Flight control without moving surfaces Miley 06-13-128 Simulation Plasma Actuator Low-Speed Separated Flow Region Reattached Flow Region BWB Inlet with 30% BLI Aggressive Transition Ducts AIAA-2006-3495, AIAA-2007-0884

38. 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 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. Honeywell Seminar July 19, 2007

40. Honeywell Seminar July 19, 2007 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:

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

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

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

44. 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”