Pulsed Electrical Excitation of Dielectric Barrier Discharge Reactors using Semiconductor Power Supplies 2000-01-2894
For practical application of non-thermal plasma enhanced selective catalytic reduction of NOx for Diesel cars compact low cost power supplies are necessary, which enable efficient plasma generation. The influence of pulsed electrical excitation of dielectric barrier discharges (DBD) on the conversion of NO to NO2 was investigated for various discharge gaps and exhaust gas temperatures: Using a thyratron switched HV power supply with a voltage pulse duration of about 100 ns, DBDs with discharge gaps up to 8 mm could be excited. Plasma energies of up to 50 mJ per pulse were obtained. At 220 °C the energy requirements for an NO-conversion of 50 % were determined to be 9.2 Wh/g NO. Up to 80 % plasma enhanced selective catalytic reduction of NO were obtained at an energy requirement of less than 6 Wh/g NOx.
Further experimental work was done using a compact semiconductor switched power supply with a voltage pulse duration of about 500 ns. Compared to the short pulse voltage source much lower peak current amplitudes were measured, but due to a longer current pulse duration plasma energies of up to 20 mJ per pulse were obtained, too. Maximum peak current amplitudes and maximum plasma energies per pulse increased significantly with increasing exhaust gas temperature. At 235 °C energy requirements of 9.2 Wh/g NO were determined for a 50 % DBD-induced NO-conversion.