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

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.