Diagnostic study of atmospheric pressure pulsed arc plasma jets
Date Issued
2009
Date
2009
Author(s)
Wu, Cheng-Yi
Abstract
Diagnostic studies of an arc plasma jet (APJ) sustained by DC pulse power operated at atmospheric pressure were performed. Plasma characteristics studied included electric properties in the discharge region, thermal and optical properties at the jet downstream. A voltage probe and a current probe were used to measure the voltage and current waveforms, respectively, of this APJ in the discharge region. Multiple thermocouples were used to measure the downstream jet temperature. A spectrometer was used to obtain the emission spectrum at the jet downstream. A high speed camera was used to observe the change of the appearance of APJ over the pulse period. he voltage and current waveforms show that the APJ undergoes a glow-to arc transition within each pulse power period. Such a transition is further confirmed by taking images using a high-speed camera, in which the plasma appearance is not uniform in time visually in the time scale of a fraction of a period. Electrical analysis in the discharge region shows that the voltage at which the glow-to-arc transition occurs and the arc current both decreases with the increase in the applied voltage and the decrease in the flow rate. Power consumption of this APJ increases with the applied voltage and remains nearly constant with the change of the flow rate. At a given duty cycle, the power frequency has little effects on the electrical characteristics. hermal analysis of jet downstream showed that the jet temperature decreases with the decrease in the applied voltage and the increase in the flow rate. Optical measurements reveal that the downstream excited state species were controlled by both their initial density in the discharge region and their decay upon formation. High applied voltage results in a high initial density of excited state species while high flow rate gives a smaller decay of excited state species in the axial direction. As a result, the increase of the applied voltage and the flow rate gives a higher downstream excited state species density. The diffusion of the ambient air into the jet downstream causes both a more rapid decay of active species and the formation of NO through the quench by and the reaction with oxygen, respectively. N2, N2+ and NO light emission system were observed in downstream optical emission spectra. At a given duty cycle, the power frequency has only a little effect on the downstream characteristics. xperiment results show that the plasma reactivity increases with the increase in the applied voltage and the flow rate, while jet temperature decreases with the decrease in the applied voltage and the increase in the flow rate. These trends allows for a nearly independent control of the reactive species densities and the temperature by carefully modulating the operating conditions. This allows for the APJ to be operated with a large process window in a controllable manner.
Subjects
Atmospheric pressure
DC pulse power
arc
plasma jet
glow-to-arc
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-98-R96524077-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):bab16e2208ff0d2242e3a7cd890785fd