Influence of non-thermal plasma after-treatment technology on diesel engine particulate matter composition and NOx concentration

The effect of non-thermal plasma technology for particulate matter removal and nitrogen oxide emission reduction from diesel exhaust has been investigated. A sample of exhaust was cooled to the ambient temperature and passed through a dielectric barrier discharge reactor. This reactor was employed for producing plasma inside the diesel exhaust. A range of discharge powers by varying the applied voltage from 7.5 to 13.5 kV (peak–peak) at a frequency of 50 Hz has been evaluated during the experiments. Regarding the NOx emission concentration, the maximum removal efficiency has been achieved at energy density of 27 J/L. Soot, soluble organic fraction and sulphate components of diesel particulate matter have been analysed separately, and the consequence of plasma exposure on particle size distribution on both the nucleation and accumulation modes has been studied. Plasma was found to be very effective for soot removal, and it could approach complete removal efficiency for accumulation mode particles. However, when applied voltage approached 12 kV, the total number of nucleation mode particles increased by a factor of 50 times higher than the total particle numbers at the reactor inlet. This increase in nucleation mode particles increased even more when applied voltage was set at 13.5 kV