| Dielectric barrier discharge (DBD) can produce non-equilibrium plasma at atmospheric pressure. This combination of the advantages of non-equilibrium plasma properties with the ease of atmospheric pressure operation makes it a unique device in many industrial applications ranging from ozone generation, pollution control and removal, surface modification, CO2lasers, ultraviolet excimer lamps to flat large-area plasma displays. Nowadays, the rapid development of new applications in biology and medicine has attracted increasing attention from scholars. However, DBD at atmospheric pressure usually behaves like a large number of streamers or micro-discharges named filamentary discharges, which is not desirable for these applications. To date, it is quite difficult and critical to obtain a large scale uniform discharge and improve the efficiency of the discharge reactor for industrial applications.Investigations on the impact of external conditions on the electrical parameters are of great importance for understanding the DBD processes, because the discharge modes and characteristics of DBD primarily depend on matching degree among this various sensitive parameters, and by adjusting the operating conditions it is possible to observe a discharge modes transition. In this paper, based on atmospheric pressure coaxial electrode configuration DBD reactor, the discharge parameters have been diagnosed by measuring the discharge voltage and current waveforms and Lissajous figures. The influences of the driving voltage and airflow rate on the electrical parameters of discharge reactor have been investigated, and finally the function relationships between breakdown voltage, electrical power consumption, power factor, dielectric equivalent capacitance, gap equivalent capacitance and external conditions were obtained. The results showed that:1) the breakdown onset voltage increases with the rise of flow rate, while decreases with the rise of driving voltage;2) the power law function relationship between electrical power consumption and the difference value resulted from the driving voltage and the breakdown onset voltage was obtained;3) the power factor will increase with increasing the driving voltage, while decrease with increasing the flow rate, and the variation rate of the power factor with external conditions is related to value of discharge power, the maximum power factor in our experimental system is about0.46;4) both the dielectric equivalent capacitance and gap equivalent capacitance will increase with the rise of driving voltage, and decrease with the decline of flow rate, we conclude that the changes of discharge region area and temperature are the underlying reasons for this phenomenon.In order to improve the efficiency of DBD reactor and achieve dynamic impedance matching between the power supply and DBD load, the amplitude-frequency characteristics of the DBD load have been investigated experimentally, and the dynamic variation of load resistance, reactance and impedance with external conditions have been simulated theoretically. Experimental and simulated results consistently indicate that the amplitude-frequency performance of the reactor as the load of the excitation supply is featured with significant RLC circuit resonance; the amplitude-frequency characteristics of DBD load show a significant dynamic feature evidently with the driving voltage and flow rate changed:the resonance frequency of the reactor increases with the rise of gas flow rate, while decreases with the rise of driving voltage, it can be infered that this phenomenon is mainly caused by the change of dielectric equivalent capacitance in DBD reactor. Using the variations of dielectric equivalent capacitance with driving voltage and gas flow rate together with the DBD equivalent electrical circuit model, the dynamic impedance evolution behaviors of DBD reactor can be calculated and analyzed, these technical methods are of great importance for achieving dynamic impedance matching between the power supply and DBD load. |
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