Effects of a diesel oxidation catalyst on gaseous pollutants and fine particles from an engine operating on diesel and biodiesel

Abstract

The effects of a diesel oxidation catalytic (DOC) converter on diesel engine emissions were investigated on a diesel bench at various loads for two steady-state speeds using diesel fuel and B20. The DOC was very effective in hydrocarbon (HC) and CO oxidation. Approximately 90%–95% reduction in CO and 36%–70% reduction in HC were realized using the DOC. Special attention was focused on the effects of the DOC on elemental carbon (EC) and organic carbon (OC) fractions in fine particles (PM_2.5) emitted from the diesel engine. The carbonaceous compositions of PM_2.5 were analyzed by the method of thermal/optical reflectance (TOR). The results showed that total carbon (TC), OC and EC emissions for PM_2.5 from diesel fuel were generally reduced by the DOC. For diesel fuel, TC emissions decreased 22%–32% after the DOC depending on operating modes. The decrease in TC was attributed to 35%–97% decrease in OC and 3%–65% decrease in EC emissions. At low load, a significant increase in the OC/EC ratio of PM_2.5 was observed after the DOC. The effect of the DOC on the carbonaceous compositions in PM_2.5 from B20 showed different trends compared to diesel fuel. At low load, a slight increase in EC emissions and a significant decrease in OC/EC ratio of PM_2.5 after DOC were observed for B20.

Keywords

diesel oxidation catalyst (DOC) / diesel particulate matters / elemental carbon (EC) / organic carbon (OC) / biodiesel

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Acknowledgements

This work was financially supported by the National Science Fund for Distinguished Young Scholars of China (No. 20625722) and the National Natural Science Foundation of China (Grant No. 20807025). We would also like to thank Prof. Yunshan Ge from Beijing Institute of Technology for the significant in-kind support on the engine test and thank Mr. Charles N. Freed for useful comments on this work.

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg