Presentation on theme: "NON-THERMAL ATMOSPHERIC PRESSURE PLASMAS FOR AERONAUTIC APPLICATIONS Richard B. Miles, Dmitry Opaits, Mikhail N. Shneider, Sohail H. Zaidi - Princeton."— Presentation transcript:
NON-THERMAL ATMOSPHERIC PRESSURE PLASMAS FOR AERONAUTIC APPLICATIONS Richard B. Miles, Dmitry Opaits, Mikhail N. Shneider, Sohail H. Zaidi - Princeton Sergey macheret – Lockheed Alexander Likhanskii – Penn State U. HAKONE XI Oleron Island September 7-12, 2008
Outline Dielectric Barrier Discharge (DBD) Configuration Performance with Sinusoidal Driver Modeling of Pulse Sustained DC Driven Experimental Set up Visualization technique Surface Charge Effects Surface Charge measurement Bias Switching Experiments Schlieren Movies and results Thrust Stand Tests New Electrode Configuration Conclusions
Offset DBD Configuration for Flow Control
Limitations of Sinusoidal Driven DBD Control Breakdown occurs randomly during each cycle There is a significant backward component of the thrust during the cycle Thrust is not generated equally in the positive and negative portion of the cycle The duty cycle is low – part of the time no thrust is being generated
Pulse Sustained, DC Driven DBD Concept Dielectric material: kapton tape thickness 100 μm Electrodes: copper foil width 25 mm spanwise dim. 50 mm The circuit is designed so as to superimpose short pulses on a low frequency bias voltage without interference between the pulser and the low-frequency power supply. The pulses and the bias voltage are controlled independently
Main differences between pulses with arbitrary bias and sine voltage Sine VoltagePulses with Bias Two functions simultaneously: Plasma generation and body force on the gas Bias produces the body force on the gas Pulses efficiently generate plasma The parameters of pulse-bias configuration – peak pulse voltage, pulse repetition rate, pulse burst rate, duty cycle, and both the frequency and amplitude of the time-depended bias voltage – can be varied independently, greatly increasing flexibility of control and optimization of the DBD actuator
Terminology Terminology used in the paper for the pulse and bias voltage polarities. The encapsulated electrode is always considered to be at zero potential. The sign of potential of the exposed electrode relative to the encapsulated one determines the pulse and bias polarity.
Predicted Streamer Like Ionization with 3kV, 4 nsec positive pulses and 1 kV positive DC bias
Predicted Average Force with 3kV, 500kHz, 4 nsec positive pulses and 1 kV positive DC bias
Predicted Momentum Transfer with 4 nsec pulses Blue and green lines correspond to the negative pulses with amplitudes -4.5 and kV with positive bias of 0.5 kV, and the pink line corresponds to the positive pulses with 3 kV amplitude and positive bias of 1 kV. FWHM for all pulses is 4 ns.
Predicted Surface Jet Generated Vortex with pulse burst
Schlieren technique for the DBD plasma actuator induced flow Schlieren technique, burst mode of plasma actuator operation, and 2-D fluid numerical model coupled together allow to restore the entire two- dimensional unsteady plasma induced flow pattern as well as the characteristics of the plasma induced force. 0.5 m/sec at 17 mm 7 m/sec in the plasma region! x
Results DC Bias experiments Pulses: 50 kHz - 20 μs between pulses 500 pulses per burst - 10 ms per burst 1000 pulses per period - 50 bursts per second 5kV pulse voltage -2 kV.. +2 kV DC bias voltage
Results Surface charge experiments Positive pulses 10 s 20 s 60 s wiped 0 kV → +2 kV 10 s 20 s 60 s wiped First run 0 kV Bias Voltage +2 kV Bias Voltage
Results Bias switch experiments Switching the polarity of the bias voltage has a dramatic effect on the DBD operation: much faster jets and vortices are generated compared with the constant-bias cases Reason - accumulation of surface charge on the dielectric
Charge Build-up Along Surface with Sinusoidal Applied Voltage 3kHz, 10kV peak-to-peak. Non-contacting Trek Model Electrostatic Voltmeter with Trek Model 6000B-13C Electrostatic Voltmeter Probe. Fast response time (less then 3 ms for a 1kV step) Operating range from 0 to +/- 3 kV DC or peak AC. Spatial resolution of ~1 mm.
Surface Charge Build up with 2kV DC bias and 4kV pulses at 20 kHz
Charge Build-up Rate
Charge Bleed Off Rate
Single Sided Versus Double Positive pulses Although some of the pulse bursts do not create a strong wall jet, they still play an important role in the DBD operation. Their task is to discharge/recharge the dielectric surface and thus to increase the efficiency of the other bursts.
Single Sided Versus Double Negative pulses In the absence of the pulse burst during the other half-cycle, the induced wall jet speed becomes 2-3 times lower. The wall jets induced by negative pulses evolve into two-vortex formations whereas the ones from the positive pulses do not.
Results Sinusoidal bias experiments Bias: 60 Hz sinusoidal 2.6 kV peak-to-peak voltage Pulses: 50 kHz - 20 μs between pulses 208 pulses per burst ms per burst 416 pulses per period bursts per second 5kV peak voltage Totally different from conventional sinusoidal profile!!
Conclusions Offset dielectric barrier discharges can generate strong surface jets for aerodynamic control Using AC to drive the offset DBD is not optimal Reverse thrust component Low duty cycle Uncontrolled plasma formation A new voltage waveform, consisting of high-voltage nanosecond repetitive pulses superimposed on a DC voltage was proposed The experiments showed that the charge build-up on the dielectric surface shields both the applied DC and AC electric field Charge build up was overcome with high voltage pulse sustained plasma and A high-voltage low-frequency sinusoidal or square wave bias voltage A partially covered electrode configuration operating with a DC bias Bias voltage is the most important parameter for thrust generation