Diesel Engine Biofuelling: Effects of Ash on the Behavior of the Diesel Particulate Filter

The use of biodiesels is an effective way to limit greenhouse emissions and partly limit the dependence on fossil primary sources. Biodiesel fuels also show interesting features in terms of PM-NOx emissions trade-off that appears more favorable toward an optimized control of the Diesel Particulate Filter (DPF). In fact, the DPF, which is the assessed aftertreatment technology to reduce PM emissions below the limits, suffers from fuel consumption penalization or excessive exhaust system backpressure, as a function of the frequency of the regeneration process. On the other side, issues such as the impact of the higher ash content of biodiesel on the DPF performance have also to be better understood. In the given scenario, an experimental study on a DEUTZ 4L off-road Diesel engine coupled to a DOC-DPF (Diesel Oxidation Catalyst-Diesel Particulate Filter) system is proposed in this paper. Experimental data have been gathered at the engine test bench of the University of Rome Tor Vergata to validate a model of the DPF, including ash related effects, and by adding a special sampling unit to collect particles. To that final aim, collected particulate has been examined via an experimental TGA (Thermo-Gravimetric Analysis) to measure ash content of particles emitted with B30 distilled biodiesel blend from Waste Cooking Oil (WCO), and compare it with a commercially available fossil fuel (B06). The multiple effects, in terms of lower regeneration activation energy, lower PM emissions and higher ash content, have been analyzed under repeated equivalent Non Road Transient Cycles (NRTCs), proving that the positive effects more than counterbalance the negative ones while using the B30 fuel.