Effects of ethanol-biodiesel blends and diesel oxidation catalyst (DOC) on particulate and unregulated emissions

Experiments were conducted on a diesel engine operating on Euro V diesel fuel, pure biodiesel and biodiesel blended with ethanol (BE blends) to assess the particulate and unregulated emissions with and without diesel oxidation catalyst (DOC). The results indicate an increase of particle number concentration, formaldehyde emission and acetaldehyde emission while a decrease of particulate mass concentration, when the diesel engine is operated with biodiesel, compared with the diesel fuel. Adding ethanol in biodiesel can help to control particulate emissions, especially particle number concentration. However, the unregulated emissions, such as formaldehyde, acetaldehyde and unburned ethanol are worsened with BE blended fuels. The diesel oxidation catalyst (DOC) can effectively reduce particulate mass concentration, particle number concentration and unregulated emissions for all different fuels, while the conversion efficiency of DOC is different for each fuel. The oxidation catalyst is not equally active for different hydrocarbon species. The oxidation catalyst is most active for unburned ethanol, then formaldehyde and benzene emissions. The effects of DOC on particulate and unregulated emissions are more obvious for BE blends than those for Euro V diesel fuel and biodiesel, indicating that application of biodiesel-ethanol blends together with DOC has the potential to reduce particulate emission and unregulated emissions of diesel engine. (C) 2013 Elsevier Ltd. All rights reserved.