The use of biomass fuels such as biodiesel as an alternative
fuel for petroleum diesel in automotive sector is of great
importance today, as it reduces global warming. Previous research
has pointed out that biodiesel/diesel blends can be used in diesel
engines with little or no modification. It is estimated that the
differences on the characteristics of diesel engines exhaust
emissions are due to the different molecule composition of
conventional diesel and biodiesel fuels.
The scope of this work was to compare the exhaust gas emissions
from the use of mixtures of biodiesel and diesel and their effect
on the performance of a passenger car engine. The blends B10, B50
and neat biodiesel, B100, were used in an old technology 1600 cc
diesel car, equipped with a retrofit catalytic diesel particulate
filter. While the car was running on a chassis dynamometer with
wide open throttle and under full engine load, measurements of
torque, speed and fuel consumption were taken for three different
vehicle speeds and gear ratios. Regarding the emissions, the
concentrations in the exhaust gases of CO₂, CO, HC, NOX and soot
opacity values were recorded. The results clearly showed that
increasing the percentage of biodiesel in the fuel, adversely
affected the emissions of NOX as compared with neat biodiesel.
Diesel engines always run "lean," thus the emissions of
CO and HC were very low and practically negligible. On the other
hand, CO₂ emissions primarily depend on the raw materials and the
processes that are used for the production of biodiesel. Soot
emissions decreased when blends with higher biodiesel content were
used. The engine performance, as measured on the chassis
dynamometer, increased slightly by the use of B10, B50 and B100
fuels. On average, the torque increased by 4.6% and the power by
3.1%, but these results were obtained along with an 11.5% higher
fuel consumption. The best overall results, at all speeds, were
obtained using the B100 fuel, with a remarkable average reduction
of 26% in soot emission.