Fatty Acid Methyl Ester (FAME) products derived from vegetable
oils and animal fats are now widely used in European diesel fuels
and their use will increase in order to meet mandated targets for
the use of renewable products in road fuels. As more FAME enters
the diesel pool, understanding the impact of higher FAME levels on
the performance and emissions of modern light-duty diesel vehicles
is increasingly important. Of special significance to
Well-to-Wheels (WTW) calculations is the potential impact that
higher FAME levels may have on the vehicle's volumetric fuel
consumption.
The primary objective of this study was to generate
statistically robust fuel consumption data on three light-duty
diesel vehicles complying with Euro 4 emissions regulations. These
vehicles were evaluated on a chassis dynamometer using four fuels:
a hydrocarbon-only diesel fuel and three FAME/diesel fuel blends
containing up to 50% v/v FAME. One FAME type, a Rapeseed Methyl
Ester (RME), was used throughout. One vehicle was equipped only
with an oxidation catalyst while the other two were also equipped
with two types of Diesel Particulate Filters (DPFs). In addition to
CO₂ emissions, regulated tailpipe emissions (NOx, HC, CO, PM, and
PN) were collected in order to evaluate the impact of higher RME
contents on emissions performance.
The results obtained over the New European Driving Cycle (NEDC)
indicate that the volumetric fuel consumption systematically
increases with increasing RME content for all three vehicles.
Within the statistical precision, the vehicles were not able to
compensate for the lower energy content of the RME/diesel blends
and consumed more fuel in direct proportion to the lower energy
content of the RME/diesel blends.
As the RME content of the fuel increased, the particulate mass
(PM) and solid particle number (PN) were generally found to
decrease over the NEDC while the NOx, CO, and HC emissions
increased. The overall impact of RME on regulated tailpipe
emissions is much smaller, however, compared to the variations in
emissions seen over the NEDC sub-cycles.
