Impact of High-Voltage Discharge After-Treatment Technology on Diesel Engine Particulate Matter Composition and Gaseous Emissions

Diesel particulate matter (DPM) and oxides of nitrogen (NOx) are the emissions from diesel engines (compres-sion ignition engines) of the most concern and are currently strictly regulated. In this work, we present an alternative diesel emission control technique to assist in further emission reduction. An experiment-oriented study on diesel engine emission abatement using low-power, low-frequency, high-voltage discharge (HVD) treatment was carried out in a laboratory-scale reactor with whole diesel engine exhaust gas. A dielectric barrier discharge (DBD) reactor was used in direct contact with diesel exhaust gas at atmospheric temperature with an input energy density between 200 and 400 J/L. An investigation of the direct effect of the high-voltage discharge reactor on the diesel exhaust gas treatment was carried out to characterize both diesel particle and gaseous emissions. The proposed HVD system demonstrated up to 95% particulate matter reduction by mass or 64% reduction by number, and 63% reduction of the diesel soot particle geometrical mean diameter by HVD-generated O-3 oxidation. Thermogravimetric analysis revealed the significant change in the diesel soot compositions and oxidation characteristics. HVD-treated particulate matter demonstrated a lower reactivity in comparison to untreated soot. Gas composition analysis indicated the generation of free radicals (e, O, OH, O-3, and N) by the FWD system, as mainly indicated by the increase of the NO2/NO ratio and concentration of CO and O-2. The pattern of CO2 reduction while CO and O-2 increased indicated the dissociation of CO2 by HVD. Free radicals generated by FWD directly affected DeNO, DeNOx, NO2/NO ratio, and CO and CO2 selectivities.

Automated summary

Diesel particulate matter (DPM) and oxides of nitrogen (NOx) from diesel engines are strictly regulated due to environmental concerns. This study introduces an alternative diesel emission control technique using low-power, low-frequency, high-voltage discharge (HVD) treatment to significantly reduce particulate matter emissions. Experimental results show up to 95% reduction in particulate matter mass or 64% reduction by number, and a 63% reduction in diesel soot particle geometrical mean diameter through HVD-generated O-3 oxidation.