Experimental test on the feasibility of passive regeneration in a catalytic DPF at the exhaust of a light-duty diesel engine

Diesel engines are attractive thanks to good performance in terms of fuel consumption, drivability, power output and efficiency. Nevertheless in the last years, increasing restrictions have been imposed to particulate emissions, concerning both mass (PM) and number (PN). Different technologies have been proposed to meet emissions standards and the wall-flow Diesel Particulate Filter (DPF) is currently the most common after-treatment system used to trap PM from the exhaust gases. This technology exhibits good features such that it can be regenerated to remove any accumulation of PM. However, this process involves oxidation of the filtered PM at a high temperature through after and post fuel injection strategies, which results in an increase of fuel consumption and may lead to physical damages of the filter in the long term. This work deals with the experimental testing of a catalytic silicon carbide (SiC) wall flow DPF, aiming at decreasing the soot oxidation temperature. The catalyst (CuFe2O4) was deposited on the filter by means of an optimized procedure based on a preliminary controlled chemical erosion of the SiC porous structure. In this way, a uniform distribution of the catalyst on the surface of the filter and in its internal porosities can be obtained. The experimental tests were performed at the exhaust of a EURO V light duty Diesel engine, operating at different speed/load conditions. The results evidence a filtration efficiency higher than 96%, throughout the soot accumulation phase, and, more importantly, a constant value of pressure drop (meaning that the soot oxidation rate equals its deposition rate) at the temperature of 320°C. A further increase of the temperature up to 340 °C, achievable by a small adjustment of engine load, a decrease of the pressure drop is observed, thus evidencing the occurrence of passive regeneration.