A Study on Diesel Emission Reduction using a High-frequency Dielectric Barrier Discharge Plasma 2003-01-1879
The aim of this study is to develop a plasma-assisted after-treatment system for simultaneous reduction of NOx and PM in diesel exhaust, which is less sensitive to the fuel sulfur. The work presented focuses on development of a high-frequency dielectric barrier discharge reactor for oxidation of NO to NO2 in diesel exhaust and low-temperature oxidation of diesel soot with NO2. The first part of this paper describes the combustion characteristics of carbonaceous matters with pure NO2 and discusses the difference when oxygen is used as oxidation agent. The second part focuses on the development of a high-frequency dielectric barrier plasma reactor and describes the effects of plasma reactor configuration, energy density and gas composition on the NO conversion into NO2, and last part describes the soot oxidation with the plasma gas. The results reveal that NO can be efficiently oxidized into NO2 using the developed plasma reactor. NO2 formation is greatly affected by the energy density, gas composition and temperature. Hydrocarbons show positive effects on NO conversion into NO2 by increasing the conversion rate, lowering the required electrical energy and preventing the formation of byproducts. Diesel soot oxidation experiments reveal that oxidation of soot with NO2 begins at temperature of about 270°C that is 200°C lower than that of O2. This result show that NO2, which is produced by the plasma assisted conversion of NO can be used for continuous regeneration of PM filter at low temperature range, which is usually available in diesel exhaust.