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Order of Magnitude Improvement of SDBD Actuator Effect

Order of Magnitude Improvement of SDBD Actuator Effect

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Order of Magnitude Improvement of SDBD Actuator Effect

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  1. Order of Magnitude Improvement of SDBD Actuator Effect T. Corke, F. Thomas, D. Orlov, M. Iqbal, A. Kozlov, H. Othman, D. Shatzman Center for Flow Physics and Control Aerospace and Mechanical Engineering University of Notre Dame AF Academy Workshop on Plasma Actuators

  2. Questions: • How do we improve the performance of SDBD plasma actuators? • What are the governing properties? • What is the ultimate performance limit? AF Academy Workshop on Plasma Actuators

  3. Approach: • Develop space-time model for ionization in SDBD operation. • Include amplitude and frequency effects. • Not including maximum limits. • Compare to experiments. • Perform experiments that investigate limiting conditions on SDBD design and operation parameters. • Develop a theory to be included in space-time model. AF Academy Workshop on Plasma Actuators

  4. SDBD Actuators: What we know • Three time scales: • Micro discharges (nsec) • a.c. period (.1ms) • Fluid response (10ms) • Ionization space-time dependent. • Static models give wrong results (e.g. fb~V2). • Temporal/space-uniform models give correct V-dependence (fb~V7/2), need spatial weighting • Space-time models give correct V, frequency and space dependence (Orlov, 2006). AF Academy Workshop on Plasma Actuators

  5. Steps to model actuator in flow • Space-time electric potential,  • Space-time body force • Flow solver with body force added AF Academy Workshop on Plasma Actuators

  6. Space-time model Physical space over the encapsulated electrode is divided into N parallel networks. Each parallel network consists of air capacitor, dielectric capacitor, plasma resistive elements and zenor diodes. AF Academy Workshop on Plasma Actuators

  7. Model circuit elements air capacitor dielectric capacitor Voltage on the dielectric surface in the n-th sub-circuit Plasma current AF Academy Workshop on Plasma Actuators

  8. Model Time Series Vn (t) Ipn (t) 5 1 5 1 t/Ta.c. t/Ta.c. AF Academy Workshop on Plasma Actuators

  9. (xp)max dxp/dt Model Space-time Characteristics Experiment Illumination Model Ip(t) AF Academy Workshop on Plasma Actuators

  10. Plasma Propagation Characteristics Effect of Vapp dxp/dt vs Vapp (xp)maxvs Vapp AF Academy Workshop on Plasma Actuators

  11. Plasma Propagation Characteristics Effect of fa.c. dxp/dt vs fa.c. (xp)maxvs fa.c. AF Academy Workshop on Plasma Actuators

  12. Numerical solution for (x,y,t) Model provides time-dependent B.C. for  AF Academy Workshop on Plasma Actuators

  13. Body Force, fb(x,t) Y t/Ta.c.=0.2 Normalized fb(x,t) t/Ta.c.=0.7 AF Academy Workshop on Plasma Actuators

  14. Frequency Dependence of fb & Wp Impact: Optimum frequency for body force. Depends on actuator capacitance. AF Academy Workshop on Plasma Actuators

  15. What limits maximum body force? • SDBD Plasma actuator is voltage driven, fb~V7/2. • Not current driven like voice-coil type actuators. • For fixed power (I·V), one needs to limit current to maximize voltage. • What governs maximum achievable voltage for fixed power? AF Academy Workshop on Plasma Actuators

  16. Maximum Voltage Optimization Investigated different parameters on thrust produced by actuator AF Academy Workshop on Plasma Actuators

  17. Material  Quartz 3.8 Kapton 3.4 Teflon 2.0 Imax Imax Imax Imax Order of Magnitude Improvement AF Academy Workshop on Plasma Actuators

  18. Premise • The maximum voltage at fixed power is limited by local electric field exceeding breakdown of air. • Thicker dielectrics and/or lower dielectric constants reduce capacitance of actuator and reduce concentration of electric field lines. • Other parameters? AF Academy Workshop on Plasma Actuators

  19. 8kHz 4kHz 2kHz 1kHz Effect of frequency on Vmax 0.25in. quartz glass Vmax(f) AF Academy Workshop on Plasma Actuators

  20. Effect of dielectric thickness on Vmax quartz glass; 1,2,4,8kHz Tmax ~ Vmax fa.c. ~ (t/)d AF Academy Workshop on Plasma Actuators

  21. Tmax Efficiency 0.25in. quartz glass AF Academy Workshop on Plasma Actuators

  22. Answers to Questions: • To improve the performance of SDBD plasma actuators? • Maximize V for fixed power. • Minimize I by preventing formation of strong plasma filaments. • Governing properties? • Dielectric design (t & ) and a.c. frequency. • Ultimate performance limit? • Maximum local E-field for air breakdown? AF Academy Workshop on Plasma Actuators

  23. Further Improvements: Additive Effect AF Academy Workshop on Plasma Actuators