Performance evaluation of non-thermal plasma on particulate matter, ozone and CO₂ correlation for diesel exhaust emission reduction

This study is seeking to investigate the effect of non-thermal plasma technology in the abatement of particulate matter (PM) from the actual diesel exhaust. Ozone (O₃) strongly promotes PM oxidation, the main product of which is carbon dioxide (CO₂). PM oxidation into the less harmful product (CO₂) is the main objective whiles the correlation between PM, O₃ and CO₂ is considered. A dielectric barrier discharge reactor has been designed with pulsed power technology to produce plasma inside the diesel exhaust. To characterise the system under varied conditions, a range of applied voltages from 11kV_PP to 21kV_PP at repetition rates of 2.5, 5, 7.5 and 10kHz, have been experimentally investigated. The results show that by increasing the applied voltage and repetition rate, higher discharge power and CO₂ dissociation can be obtained. The PM removal efficiency of more than 50% has been achieved during the experiments and high concentrations of ozone on the order of a few hundreds of ppm have been observed at high discharge powers. Furthermore, O₃, CO₂ and PM concentrations at different plasma states have been analysed for time dependence. Based on this analysis, an inverse relationship between ozone concentration and PM removal has been found and the role of ozone in PM removal in plasma treatment of diesel exhaust has been highlighted.