Investigation On Characteristics Of The Bipolar Nanosecond Pulse Plasma And The Removal Of HCHO At Atmospheric Pressure

The characteristics of uniform bipolar nanosecond pulse dielectric barrier discharge in atmospheric air have been investigated. And the experiments in removal of HCHO by uniform N₂ bipolar nanosecond pulse dielectric barrier discharge plasma have been done. The main results obtained have been summarized as follows:1. A bipolar nanosecond pulsed power supply which has the 15 ns rising time is applied to generate the uniform dielectric barrier discharge using the wire-cylinder electrode configuration in atmospheric pressure air. The discharge pictures, waveforms of discharge voltage and current, and the optical emission spectra of the discharges have been kept track of. It is found that an uniform plasma with low gas temperature can be obtained, and the emission intensities of N₂ （C³∏u�' B³∏g,0-0） and N₂⁺ （B²∑u+�'>X²Eg⁺,0-0） rise as increasing the pulse peak voltage and pulse repetition rate, whereas recede as the increase of quartz tube diameter. In addition, under the condition of 28 kV pulse peak voltage,150 Hz repetition rate and 7 mm diameter quartz tube, the plasma gas temperature is determined to be 330 K. The result also indicates that the plasma gas temperature keep almost constant as the increase of the pulse peak voltage and pulse repetition rate. However, as increasing the quartz tube diameter, the plasma gas temperature rises.2. The optical emission spectrum of OH （A²∑�' X²∏,0-0） emitted from the uniform atmospheric N₂ dielectric barrier discharge generated by the bipolar nanosecond pulsed power supply with 15 ns rising time has been recorded. It is found that the emission intensity of OH （A²∑�' X²∏,0-0） rises with increasing the input power density. With the increase of input power density and the emission intensity of OH （A²∑�' X²∏,0-0）, the removal rate of formaldehyde rises correspondingly. The results also indicate that when the O2 concentration rises within 0-5%, the removal rate of formaldehyde increases, while the O₂ concentration rises within 5%-20%, the formaldehyde removal rate decreases correspondingly. In addition, at the same conditions the formaldehyde removal rate of dielectric barrier discharge with Al₂O₃ and TiO₂ is higher than the dielectric barrier discharge with Al₂O₃, and the formaldehyde removal rate of dielectric barrier discharge with Al₂O₃ is higher than the dielectric barrier discharge only.