Impact of biodiesel use on soot particle emission andudregeneration particulate filter process of a modernuddiesel engine

摘要

It is well know that from an environmental point of view, the use of biofuels can contribute to a significantudwell-to-wheel (WTW) reduction of greenhouse gas (GHG) emissions.udBiofuels can be classified in first generation and second generation biofuels. First generation biodieseluddesignates a wide range of methyl-esters blends (generally indicated with the acronym FAME, Fatty-AcidudMethyl Esters) characterized by a lower LHV and higher oxygen content. They are obtained from vegetableudoils and animal fat by means of a transesterification process, and interfere with the human chain.udThe second generation biofuels have minor interferences with the human chain and present a better stabilityudin the chemical properties. These fuels can be obtained from biomass, gas, etc… by means of a Fisher-udTropsh synthesis process. They are usually indicated with XTL, where X denotes the specific sourceudfeedstock and TL (to Liquid) highlights the final liquid state of the fuel.udSeveral studies showed that biodiesels can have a remarkable impact on engine performance, such as FueludConsumption (FC) and full torque/power performance, and even more significant on pollutant emissions,udmainly for the modern electronically controlled diesel engines [1, 2, 3, 4, 5].udGeneral Motors is one of the largest producers of diesel engines for passenger cars and light-trucksudapplication in EU, Asia-Pacific and US markets and considers of high importance the test on biodiesels toudanalyse their effect on engine performances and emissions.udGreat attention was devoted also to the interaction between biofuels and aftertreatment devices, such asuddiesel particulate filter (DPF). To this aim, a cooperative project between GM Europe and Istituto Motori ofudCNR was established. The particles emission in terms of mass, number concentration and size wasudinvestigated during the regeneration of a DPF with either a conventional diesel fuel that biofuels. Inudparticular, measurements were performed with a fresh and aged Rapeseed- and palm-oil-based methyl-esterud(RME). The measurements were carried out at the exhaust of a CR Diesel engine equipped with a CloseudCoupled DPF. The soot particles characterization was performed by means of a Microsoot Sensor, for sootudmass concentration measurement, and a differential mobility spectrometer for particles sizing and counting.