Ozone generation using electrical discharges : a comparative study between pulsed streamer discharge and atmospheric pressure glow discharge

This thesis deals with an investigation into atmospheric pressure glow discharge and pulsed streamer discharge techniques of ozone generation, in an attempt to compare their performances in the generation of a high concentration and high yield of ozone. It is motivated by the desire to exploit further the ability and potential possessed by both techniques for ozone generation and to provide support to the increased demand for ozone in many areas of application. Chapter 1 of the thesis provides a brief history into the application of ozone. In Chapter 2, a basic understanding of the gas discharge is given for both thermal and non-thermal plasm as, and the theory 0 f non-thermal plasma is presented. The different types of electric discharges commonly used for ozone generation are explained. A review of the effect of both the physical configuration and the electrical parameters on the ozone yield and concentration is presented in Chapter 3, with the three main parameters that limit the efficiency of the production being highlighted. The second part of the thesis describes a thorough experimental investigation. In Chapter 4, a study is made of the stability of the atmospheric pressure glow discharge (APGD) which is found to be more stable when perforated electrodes are used rather than a fine steel wire mesh. Following this, a comparative study between APGD and pulsed streamer discharge (PSD) is presented in Chapter 5. A detailed investigation into both APGD and PSD in air is described. The effects of varying the input voltage, gap distance, chamber length, air flow rate and gas residence time are all used to evaluate the performance of both techniques. The PSD is found to generate a higher concentration but with a lower ozone yield. On the other hand, the APGD generates a lower concentration but with a higher yield. Chapter 6 presents the effect of a cross magnetic field on an AC corona and the PSD techniques and its influence on ozone generation. Results show no apparent effect of the magnetic field in either technique. Chapter 7 describes the use of dimensional analysis in investigating the effect of the electrical and the discharge configuration parameters on ozone production in oxygen by means of a PSD. Ozone destruction factors are taken into account in the model, and predicted results are shown to be in good agreement with experimental findings.