Abstract
The effect of diesel fuel quality on exhaust emissions was studied using 6 diesel fuels. Both regulated and unregulated emissions of a high pressure distributing pump Renault Megane DI EURO II vehicle with an oxidation catalyst and EGR were measured according to the year 2000 European Type I emission test cycle.
Four reformulated fuel grades, Paraffin fuel and a 1997 European EN590 specification fuel containing 500 mg/kg sulfur were tested. Sulfur contents of the reformulated grades were extremely low ranging from 2 to 15 mg/kg. Only two fuel grades reached the Euro III particulate emission limit (0.05 g/km), one of them being the paraffin fuel. When these two fuels showed lowest particulate emission, they concurrently showed the highest NOx emission (0.53 g/km). Three fuels out of 6 reached the Euro III NOx emission limit (0.5 g/km). Particulate emission of the EN590/97 fuel was 0.067 g/km and NOx-emission 0.48 g/km. Fuel reformulation decreased particulate emission by at least 15 and up to 45 %.
The paraffin fuel produced the lowest regulated emissions, but on the other hand, the fuel showed the highest volumetric fuel consumption. Both the density and the volumetric net energy of the paraffin fuel were lower in comparison with the reference fuel and the measured power loss became noticeable (10 %). The engine calibration was not modified accordingly.
Effect of fuel reformulation on the unregulated emissions - including aldehyde emission, composition of particulate matter including soluble organic fraction (SOF), fuel and lube derived hydrocarbons and polyaromatic hydrocarbons (PAHs) and particulate size distribution analysis - were an important research subject in this study. Reformulation reduced total aldehyde emission 15 % in comparison with the EN590/97 fuel. Paraffin reduced aldehyde emission by 50 %, respectively. The major aldehydes found in the gaseous exhaust were formaldehyde and acetaldehyde. Total aldehyde emission was 50% of the total hydrocarbon emission.
From the thirteen PAHs, analyzed from the particulate matter, six were those defined in the US EPA list of Mobile Source Air Toxic PAHs. The present study showed very low total PAH(13) emissions, 4 to 13  2 µg/km. Fuel reformulation reduced the total particulate PAH emission significantly by 55 to 70 % and bentso(a)pyrene emission by 65 to 80 %. Paraffin fuel did not differ from the reformulated grades. Phenanthrene, pyrene and fluoranthene dominated the 3-4 ring PAHs and bentso(b)fluoranthene the 5-6 ring PAHs. Under the selected and limited testing and sampling conditions, the particle size number and mass distributions showed only minor differences between the fuels. The particle size distributions peaked at 90 to 100 nm.
The very positive effect of the reformulated fuel grades on the non-regulated emissions has to be noticed and emphasized in comparison with the results achieved with the standard EN590/97 fuel. In addition the contribution of the lubricant on the PM emissions must be highlighted.