Finding a replacement for fossil fuels is critical for the
future of automotive transportation. The compression ignition (CI)
engine is an important aspect of everyday life by means of
transportation and shipping of materials. Biodiesel is a viable
augmentation for conventional diesel fuel in compression ignition
engines. Biodiesel-fuelled diesel engines produce less particulate
matter (PM) relative to conventional diesel and biodiesel has the
ability to be a carbon dioxide (CO₂) neutral fuel, which may come
under government regulation as a greenhouse gas. Although biodiesel
is a viable diesel replacement and has certain emissions benefits,
it typically also has a known characteristic of higher oxides of
nitrogen (NOx) emissions relative to petroleum diesel.
Advanced modes of combustion such as low temperature combustion
(LTC) have attained much attention due to ever-increasing emission
standards, and could also help reduce NOx in biodiesel.
LTC has the ability to simultaneously reduce soot and nitric oxide
(NO) emissions by having lower local equivalence ratios and
combustion temperatures in order to significantly reduce soot and
NO formation.
Results in this study - taken from a medium-duty diesel engine
using 100% petroleum diesel, 100% palm olein biodiesel, and a 20%-v
blend of biodiesel into petroleum diesel - demonstrate the
attainment of later-phased low temperature combustion and the
ability of biodiesel to sustain near-similar torque levels as of
conventional combustion. The shorter ignition delay and combustion
duration of B100, the latter of which is relatively shorter than
petroleum diesel because of the burn characteristic of the studied
biodiesel, allow biodiesel low temperature combustion to take place
earlier in the combustion stroke than if petroleum diesel were
used. Comparatively, the 20%-v blend also shows improved sustained
torque, but less so than the 100% biodiesel. The biodiesel fuels
also show improved combustion efficiency relative to the petroleum
diesel at the low temperature combustion condition, further
improving the engine's torque. Results of nitric oxide and soot
concentrations are compared; differences in combustion phasing,
exhaust gas recirculation level, and initial temperatures, however,
render a direct comparison in these exhaust species among the fuels
invalid.