Influence of Soot Particles and Electrode Forms of Barrier Discharge on Treatment of Diesel Exhaust

The influence of soot particles on treatment of diesel exhaust using barrier discharge has been experimentally investigated. A diesel fuel and air diffusion flame burner system is used for simulation of diesel exhaust gas. It produces particulate, NOx and HC emissions similar to diesel exhaust. Barrier discharge plasma reactor consists of double coaxial cylinders. Different design electrode forms have been tested, with results indicating the importance of testing devices with soot. 1500 ppmC1 of C3H6 were added to burner gas to increase HC concentration. NO conversion efficiency increases with increasing specific energy density in both uniform field reactor and non-uniform field reactor. In the case of non-uniform field reactor, NO conversion efficiency is low, ; current waveform of discharge varies with soot, surface discharge occurs outside reactor due to soot fouling and barrier discharge decrease to resulting in relaxation of the electric field. In the case of uniform field reactor, NO conversion efficiency is high, and the conversion improves drastically with high HC concentration. Concentration of C3H6 decreases with increasing specific energy density. Soot deposits on the surface of reactor and the presence of soot in gas decrease the NO conversions. Therefore, it is suggested that soot in diesel exhaust gas influenced both the occurrence of discharge and the plasma reaction as for conversion of NO to NO2.