-1.5
Positive pulses Negative bias Surface potential, mm
2.0
Surface potential, V
1.5
1 pulse 10 pulses 100 pulses 1000 pulses
-1.0
1 pulse 10 pulses 100 pulses 1000 pulses
Main differences between pulses with arbitrary bias and sine voltage
Sine Voltage Pulses with Bias
Two functions simultaneously: Plasma generation and body force on the gas
Schlieren technique, burst mode of plasma actuator operation, and 2-D fluid numerical model coupled together allow to restore the entire twodimensional unsteady plasma induced flow pattern as well as the characteristics of the plasma induced force.
Predicted Momentum Transfer with 4 nsec pulses
Blue and green lines correspond to the negative pulses with amplitudes -4.5 and 1.5 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.
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
Offset DBD Configuration for Flow Control
Surface Plasma
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
Positive pulses
2.5 2.0 Positive bias Zero bias Negative bias
Negative pulses
2.0 1.5

Positive bias Zero bias Negative bias
Surface potential, kV
Surface potential, kV
1.0
-0.5
0.5
0.0 -5 0 5 10 15 20
0.0
-5 0 5 10 15 20
Distance, mm
Distance, mm
2.0
Negative pulses Positive bias
Surface potential, V
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
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
Momentum, transfered to the gas
1.4E-08 1.2E-08 Momentum, N*s/m 1.0E-08 8.0E-09 6.0E-09 4.0E-09 2.0E-09 0.0E+00 0.0E+00 4.0E-07 8.0E-07 1.2E-06 1.6E-06 2.0E-06 Time, s High-V neg. pulse High-V pos. pulse Low-V neg. pulse
1600 1400 1200
Surface potential, V
1000 800 600 400 200 0 -200 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
Distance, mm
Surface Charge Build up with 2kV DC bias and 4kV pulses at 20 kHz
1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 0 5 10 15 20 25
1.0 0.5 0.0 -0.5 -1.0 -1.5 -2.0 0 5 10 15 20 25
Distance, mm
Distance, mm
Charge Build-up Rate BuildPositive pulses Positive bias
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.
Pulses efficiently generate plasma
Bias produces the body force on the gas
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
Results
Surface charge experiments Positive pulses
0 kV Bias Voltage +2 kV Bias Voltage 10 s 10 s
20 s
20 s
60 s
60 s
wiped
wiped
First run
0 kV → +2 kV
Results
Predicted Surface Jet Generated Vortex with pulse burst
Schlieren technique
for the DBD plasma actuator induced flow
x
0.5 m/sec at 17 mm 7 m/sec in the plasma region!
NONNON-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.
Charge Build-up Along Surface Buildwith Sinusoidal Applied Voltage 3kHz, 10kV peak-to-peak. peak-toNon-contacting Trek Model 247-3 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.