A Comparative Morphological Study of Primary and Aged Particles Emitted from a Biodiesel (B20) vis-a-vis Diesel Fuelled CRDI Engine

A comparative morphological analysis was performed on the exhaust particles emitted from a common rail direct injection (CRDI) sports utility vehicle (SUV) engine for primary and aged particulates. In this study, soot particles were collected from the CRDI engine fuelled with mineral diesel and 20% biodiesel blend (B20). The engine was operated at a constant speed of 1800 rpm for five different loads (0%, 25%, 50%, 75%, 100% rated load) for primary and aged particulate collection. Primary particulate samples were collected on pre-conditioned quartz filter papers from the exhaust stream after partial dilution. For collection of aged particles, the diluted exhaust was passed through a customized photochemical chamber with 2 hour retention time. This allowed photochemical reactions to proceed in presence of ultraviolet light leading to particulate aging in simulated daylight conditions and particulates were collected downstream of the photochemical chamber. Particulate laden filters were observed by scanning electron microscopy (SEM). It was observed that B20 emitted significantly lower primary particulates in comparison to mineral diesel for all the loads. B20 emitted lower particulates at lower load conditions for aged samples. At higher engine loads (75% and 100%), this reduction in aged particulates for B20 compared to mineral diesel was quite significant.