Impact of Varying Biodiesel Blends on Direct-Injection Light-Duty Diesel Engine Emissions 2012-01-1313
A 1.9L turbocharged direct-injection engine representing a model
year 1998-2003 Volkswagen vehicle, equipped with the OEM diesel
oxidation catalyst (DOC) and exhaust gas recirculation (EGR), was
tested on an eddy-current engine dynamometer with a critical flow
venturi-constant volume sampling system (CFV-CVS). The engine was
operated over three steady-state modes: 1600 rev/min at 54 Nm; 1800
rev/min at 81 Nm; and 2000 rev/min at 98 Nm.
Commercially available ultra-low sulfur diesel fuel (≺15 ppm S)
was splash-blended with fatty acid methyl ester biodiesels derived
from three different feedstocks: canola, soy, and tallow/waste fry
oil. Test blend levels included: 0%, 2%, 5%, 20%, 50%, and 100%
biodiesel for each feedstock.
Detailed emissions characterization included: carbon monoxide
(CO), total hydrocarbons (THC), oxides of nitrogen
(NOx), nitrogen dioxide (NO₂), total particulate matter
(TPM), organic and elemental carbon (OC/EC), carbon dioxide (CO₂),
nitrous oxide (N₂O), methane (CH₄) and brake-specific fuel
consumption (BSFC). Although this study did not investigate engine
performance or the long-term effects of biodiesel operability,
engine temperatures, speed, torque and power were monitored
throughout the test program.
Decreases in TPM as well as OC/EC were noted with increasing
bioblend levels. With the test engine fuelled with 100%
tallow/waste fry oil, a decrease in TPM as high as 62% was
measured. Changes in NOx and NO₂ varied; at higher
engine loads, the NOx levels were increased with
increasing biodiesel content, but NOx levels decreased
with increasing biodiesel content at lower engine loads. The NO₂
levels were unchanged with biodiesel. Changes in GHG and BSFC
varied with the different bioblends and test modes. Emissions of CO
and HC were found to be at or near ambient background levels.