The Use of a Partial Flow Filter to Assist the Diesel Particulate Filter and Reduce Active Regeneration Events

This study investigates the potential of using a partial flow filter (PFF) to assist a wall flow diesel particulate filter (DPF) and reduce the need for active regeneration phases that increase engine fuel consumption. First, the filtration efficiency of the PFF was studied at several engine operating conditions, varying the filter space velocity (SV), through modification of the exhaust gas flow rate, and engine-out particulate matter (PM) concentration. The effects of these parameters were studied for the filtration of different particle size ranges (10-30 nm, 30-200 nm and 200-400 nm). For the various engine operating conditions, the PFF showed filtration efficiency over 25% in terms of PM number and mass. The PFF filtration behaviour was also investigated at idle engine operation producing a high concentration of nuclei particulates for which the filter was able to maintain 60% filtration efficiency. After a 14 hour soot loading phase, the filter trapping efficiency remained over 20% and showed unexpectedly high small PM filtration efficiency. Finally, a system composed of a PFF placed upstream of a DPF was studied and the filtration efficiency, soot mass accumulated, as well as the pressure increase during a loading period of 7 hours were compared to the ones from a standalone DPF, in order to estimate the beneficial effects of using a PFF to assist the main DPF and reduce the regeneration duration and/or frequency.