Light Duty Diesel Particulate Emissions -Fuel and Vehicle Effects

The potential effect of fuel composition on total particulates and particulate character were measured on a variety of production vehicles, which are representative of different combustion system types, using commercial and laboratory fuel blends. Tests were made with a CVS dilution tunnel, primarily using the EPA CVS-CH test procedure. Particulate emissions were found to be a function of both fuel and vehicle parameters. Both the particle bound organic and the carbonaceous fractions of diesel particulates showed linear relationships with the fuel’s aromatic content and backend volatility (as measured by the fraction of the fuel boiling above 640°F). Emission rates were strongly affected by vehicle type. The regression models for each car indicated that the back-end volatility contributed primarily to the particle bound organic fraction, while the aromatic content of the fuel influenced the carbonaceous fraction. Very large differences were found in the intrinsic capability of different vehicles to limit the emissions of extractable or sooty fraction of particulates. One vehicle emitted very low levels of extractables but high levels of soot. Another emitted high levels of extractables, but low levels of soot. This suggests the possibility for improved particulate control by combination of the vehicle design changes minimizing both particulate fractions.