Date of Award

Spring 2004

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical & Computer Engineering

Committee Director

Karl Schoenbach

Committee Member

Dennis Manos

Committee Member

Ravindra Joshi

Committee Member

Linda Vahala

Abstract

A microhollow cathode discharge was used as a plasma cathode to sustain a stable direct current glow discharge in atmospheric pressure air. The volumetric scale of glow discharge increased from the millimeter to the centimeter range by extending the plasma in lateral and axial directions. In the axial direction, the length of the glow discharge column was varied from 1 mm to 2 cm, with the sustaining voltage increasing linearly with the glow discharge column length. Extension in the lateral direction was obtained by operating discharges in parallel. The glow discharge plasma of the parallel discharge columns was found to merge when either the discharge current or the electrode gap was increased. For a glow discharge with a current on the order of 10 mA, the electron density in the glow discharge exceeded 1011 cm−3, with a peak value of 1013 cm−3 near the plasma cathode. The electron temperature in the positive column of the glow discharge was found to be in the range of 1.14 eV. The glow discharge axial gas temperature was found to have a maximum value of 2200 K close to the plasma cathode, and to decrease toward the third electrode to about 1400 K. The application of a 10 ns pulse to the glow discharge increased the electron density to 1015 cm−3 and reduced the power density by a factor of three compared to the dc discharge. The effect is assumed to be due to the nonequilibrium electron heating of the electrons without causing changes in gas temperature. The gas temperature was found to increase by only 200 K within 15 ns after the pulse, which indicated the time of energy transfer from electrons to the neutral particles.

Flowing air through the hole of the microhollow cathode discharge generated a stable micro-plasma jet. The power consumption in the jet was 1 to 10 W depending on the micro-plasma discharge current. The gas temperature in the jet was controllable between 300 K to 1000 K by varying the discharge current and the flow rate. The jet changed from a laminar to a turbulent mode with an increase of the flow rate. The transition from laminar to turbulent correlated to a significant decrease in its gas temperature.

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DOI

10.25777/tjd1-wt32

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