Optical Investigation of Postinjection Strategy Effect at the Exhaust Line of a Light-Duty Diesel Engine Supplied with Diesel/Butanol and Biodiesel Blends

Abstract

Ultraviolet (UV)-visible-near infrared (IR) multiwavelength extinction spectroscopy was applied in the exhaust line of an automotive common rail diesel engine to investigate the postinjection strategy impact on the fuel vapor. Four fuels were tested: a baseline diesel and three blends of diesel with 20% by volume of rapeseed methyl ester (RME), 20% of n-butanol and 20% of RME along with 20% of n-butanol. Experiments were performed at the engine speed of 2,750 rpm and 1.2 MPa of brake mean effective pressure. Preliminary engine tests were carried out to explore the postinjection activation aptitude to produce hydrocarbons at the exhaust, needed for the diesel oxidation catalyst (DOC) and the regeneration of the diesel particulate filter (DPF). Results of hydrocarbon and smoke emissions at the exhaust, with and without postactivation, are presented for the different blends. The optical diagnostic allowed to evaluate, during the postinjection activation, the evolution of the fuel vapor in the engine exhaust line. The spectroscopic investigation was focused on evaluation of the postinjection aptitude and fuel composition to produce hydrocarbon-rich exhaust gaseous. The main results showed that the butanol blended with diesel and/or biodiesel induced a higher concentration of fuel vapor within the exhaust manifold and consequently a lower tendency to lubrication oil dilution.