Ultrasound and airflow induced thermal instability suppression of DC corona discharge: an experimental study

Abstract

The effect of ultrasound waves, airflow and combined ultrasound with the airflow on the thermal instability suppression of a hollow needle-to-plate electrical discharge was studied experimentally. To evaluate the thermal instability suppression we used the V-A characteristics of the discharge in stationary air, with ultrasound applied in stationary air, and finally when the airflow was supplied into the discharge through the needle without and with ultrasound application. To illustrate the effect of ultrasound, airflow and combined ultrasound with airflow on the discharge thermal instability suppression we also studied the discharge ozone production.We found that in stationary air the application of ultrasound only slightly suppresses thermal instability. A substantial increase of ozone generation was not detected. Application of the airflow through the needle suppressed development of the thermal instability and resulted in a substantial increase of the discharge current. The ozone generation was strongly increased in comparison with the preceding case. The combined application of ultrasound and airflow through the needle caused further instability suppression and consequently an increase of the discharge current. The effect of ultrasound on the current-voltage range of the discharge was, however, smaller than the effect of the airflow through the needle. Nevertheless production of ozone was still substantially increased.

Ozone production by a dc corona discharge in air contaminated byn-heptane

“…The discharge flow enhancement was used because of the fact that the classical needle to mesh dc corona discharge in a stationary medium is a relatively low power discharge not suitable for reasonable ozone production. In order to increase the currentvoltage range of the discharge without discharge transition to spark, a mixture of air with n-heptane was supplied through the needle [8]. In contrast to the stationary medium, the charge transport in this case is given by the sum of a convective term and a drift term.…”

Evaluation of the sensitivity of electro-acoustic measurements for process monitoring and control of an atmospheric pressure plasma jet system

“…In our paper we explore this idea by evaluating the APPJ nozzle using equation 4 A further set of measurement were performed to examine the effect of air gas flow. Draft for submission to PSST 9…”

“…[20] and Rat et al [21] have proposed that the nozzle acoustic can be modelled as a Helmholtz resonator. In our paper we explore this idea by evaluating the APPJ nozzle using equation (4). In this equation the volume of air in the cathode cavity (V o ) has a spring constant that is inversely proportional to its volume (V o ).…”

“…This paper evaluates the use of the electroacoustic technique as a means of achieving this process monitoring of an atmospheric plasma jet system. Since the late 1990s the acoustic emission from laboratory scale atmospheric pressure plasma jet (APPJ) systems [3,4], and optical-acoustic studies of the plasma welding process [5] have been reported. Following these reports acoustic metrology has been used in the monitoring of anomalous arc discharge in plasma processing equipment plasma [6], plasma and laser welding [7][8][9] and plasma anodizing [10].…”

“…Experimental observations with physics-based interpretation [3][4][5][6]; time-series analysis [7][8][9], neural network analysis [10] and multivariate analysis [11][12][13] have been used to investigate the plasma acoustic emission in an attempt to isolate the specific origin of acoustic emission. In all cases it has been observed that the emission signal is complex with parts of the signal associated with specific sources.…”