Basic study of atmospheric microplasma
effect on the pressure loss
Yuta NOMA, Marius BLAJAN and Kazuo SHIMIZU
Innovation and Joint Research Center, Shizuoka University,Johoku, Hamamatsu, 432-8561, Japan
E-mail：shimizu@cjr.shizuoka.ac.jp

INTRODUCTION
Fluidic control is an important factor for improving
efficiency for various machines. To control a fluid,
many mechanical actuators were already proposed
and used effectively. The mehcanical actuators havesome disadvantages such as secondary flow orcomplicated mechanism. Recenty, actuators which areused plasma are investigated actively to control
flows. Comparing with the mechanical actuators,
plasma actuator has some advantages due to its
simple structure. Fig. 1 shows the principle of theplasma actuator.

Fig. 4 shouws a current-voltage characteristic
at discharge voltage of 1.4 kV. Spike current
occured at rise and decay points of discharge
voltage. This is a typical waveform of dielectricbarrier discharge.
Discharge voltage

A relationship between pressure loss and discharge
voltage at 1.5 m/s is shown in Fig. 7 and at 3.5
m/s is shown in Fig. 8.

Discharge voltage
1.0 kV/div
10 μs/div

GNDGND

1.0 kV/div
250 ns/div

GNDGND

100 mA/div

Discharge current
200 mA/div

10 μs/div

Discharge current

250 ns/div

Fig. 4 Current-voltage characteristic.

Fig. 7 A relationship between pressure loss
and discharge voltage at 1.5 m/s.

(2) Experimental setup
Vinyl chloride flange

124

Air flow
3Fig. 1 Principle of the plasma actuator.
For applying to industries, atmospheric pressureplasma is required to minimize cost or size.
Microplasma is atmospheric pressure nonthermal
plasma which requires relatively low discharge
voltage, and a type of dielectric barrier discharge
which has micro meter gap. The effect of gas flow byatmosphericmicroplasma
wasexperimentallyinvestigated.

METHODS(1) Microplasma Electrodes
A schematic image of microplasma electrodes is shown in
Fig. 2. Microplasma was generated with a pair of electrodes
which covered with dielectric layer and faced each otherwith a spacer (thickness 100 μm) in between.

Measuring point
Acrylic pipe①～④Fig. 5 Experimental setup.
A neon transformer was used as a power supply for
microplasma generation. An AC high volatageenergized the electrodes and could generate
microplasma and ionic wind between electrodes.
That ionic wind could impact the air flow in theacrylic pipe. A manometer was used to measure thepressure difference and observe how the flow waschanged by passing through electrodes.
Table 1 Experimental conditions.
Discharge voltage [kV]

1.0 ～1.4

Gas velocity [m/s]

1.5 (Re num. : 5,000)
3.5 (Re num. : 13,000)

Hole size of electrodes[mm]

1.3 (aperture ratio : 45.7 %)
2.6 (aperture ratio : 41.0 %)Discharge gap [µm]100Frequency [kHz]27Fig. 8 A relationship between pressure loss
and discharge voltage at 3.5 m/s.
A decrease of the pressure difference was
equivalent to a decrease of the pressure loss atelectrodes . A higher value was measured at 3.5m/s comparing with 1.5 m/s. The maximum
decrease of pressure difference (1.2 Pa) wasobserved for the electrodes with 1.3 mm holes
diameter at 3.5 m/s. This was about 5% of totalpressure loss. There were no significant
differences of pressure change for both 1.3 mm
and 2.6 mm holes electrodes.
Table 3 shows the reducing rate of pressure loss
each hole size of electrode and flow rates.
Table 3 Reducing rate of pressure loss
by atmospheric microplasma.
Hole size Gas velocity Pressure difference
[mm]
[m/s]
at 1.4 kV [Pa]

Reducing rate ofpressure loss [%]

1.5

0.5

8.6

3.5

1.2

3.9

1.5

0.6

17.7

3.5

1.0

5.7

1.3

2.6

RESULT

Fig. 2 Microplasma electrodes.

Fig. 6 shows the pressure loss of electrodesitselves. The pressure loss of each hole size
electrode was increased with increacing flow
velocity.

CONCLUSIONSIn this study, the following conclusions wereobtained.
1. Decrease of pressure loss was observed at theback and at the forth electrode for each holesize of electrode and air flow rates. Effect andpossibility of fluidic control by atmosphericmicroplasma was confirmed at a relatively low
discharge voltage.

Fig. 6 A relationship between flow rate andpressure loss.
Table 2 The pressure loss of electrodes.
Fig. 3 An image of microplasma duringdischarge (about 1.2 kV).

Hole size [mm]Gas velocity [m/s]

Pressure loss [Pa]

1.5

5.8

3.5

25.8

1.5

3.4

3.5

20.9

1.3

Dependingonthiselectrodes
constitution,
microplasma which used this experiment could be
suppressed to a relatively low discharge voltage(around 1 kV) and cut down its power consumption
and size.

2.6

2. A higher value of rate change of pressure
difference was measured at 3.5 m/s for eachhole size electrode. This result suggested a
possibility of fluidic control by atmosphericmicroplasma for a fuild which has a relatively
high Reynolds number.
3. The reducing rate of pressure loss with 2.6 mm
hole size of electrode was higher than that of
1.3 mm hole size of belectrode. It could beconsidered that configuration of electrode isalso one of important factors for fluidic control.
4. The reducing rate of pressure loss with 1.5 m/s
was higher than that of 3.5 m/s for each holesize of electrode. This could be considered that asmaller Reynolds number is more effective thana higher Reynolds number.