The Effect Of OH Radicals On Formaldehyde Removal And Investigation Of Diffuse Discharge At Atmospheric Pressure

The removal of formaldehyde in dielectric barrier discharge in nitrogen has been studied, and the plasma characteristics of bi-directional diffuse nanosecond pulsed discharge have been investigated at atmospheric pressure. The main results presented in the dissertation have been summarized as follows:1. The emission spectra of OH (A2Σ→X2п,0-0) emitted from dielectric barrier discharge are successfully recorded. The relationship between formaldehyde removal efficiency and the emission intensity of OH (A2Σ→X2п,0-0) has been investigated at different applied voltages, driving frequencies, the concentrations of argon and oxygen. It is found that the removal efficiency of HCHO increases when the emission intensity of OH (A2Σ→X2п,0-0) increases with rising applied voltage, driving frequency and the concentration of argon. However, the removal efficiency decreases when the emission intensity of OH (A2Σ→X2п,0-0) decreases with increasing the concentration of oxygen. The removal efficiency of HCHO is 93.8%in N2+HCHO mixed gas at 11.5 kV applied voltage and 9 kHz driving frequency.2. A high voltage bi-directional pulse with 20 ns rising time is employed to generate an atmospheric pressure diffuse dielectric barrier discharge using wire-plate electrode configuration in nitrogen. The gas temperature of the nitrogen plasma is determined by measuring the optical emission spectra of the first negative band of N2+(B2Σu+→X2Σ+,0-0, 391.4 nm). The effects of pulse peak voltage, pulse repetition rate, and the concentrations of argon and oxygen on the emission intensities of N2(C3пu+→B3пg,0-0,337.1 nm) and N2+(B2Σu+→X2Σg+,0-0,391.4 nm) are investigated. It is shown that the plasma volume increases with the rising of pulse peak voltage but keeps almost constant with the increasing of pulse repetition rate. The emission intensities of N2(C3пu→B3пg,0-0,337.1 nm) and N2+(B2Σu+→X2Σg+,0-0,391.4 nm) rise with an increase in the pulse peak voltage, the pulse repetition rate and the concentration of argon, but decrease with increasing the concentration of oxygen.