Fuel Impact on Exhaust Emissions - Comparison of Two Diesel Fuels 2012-01-1702
In the EU regulations, specification's for diesel fuel quality is regulated in the standard EN590. Sweden has however for many years used an “Environmental Class 1” (EC1) diesel fuel. In addition to fulfilling the EN590 standard, the main difference today between the Swedish EC1 and the EN590 fuel specifications is that higher levels of aromatics and polyaromatics (PAH) are allowed in the EN590 standard. Aromatics are considered to be potentially mutagenic, and the higher levels of aromatics also lead to increased particle emissions.
Earlier studies of the exhaust emissions from engines using the different fuel qualities have shown significant differences, both regarding regulated emissions and health effects. In these studies, vehicles from emission standard Euro III and older have been used. The scope of this study was to investigate whether the differences persist for a modern Euro V vehicle or not.
Emission results from tests performed on a heavy duty vehicle fuelled with the two different diesel qualities are presented. The tests were carried out on a chassis dynamometer and the vehicle was driven according to the WHVC test cycle. Both regulated and several unregulated components were measured, along with CO2 and fuel consumption. The gaseous components were sampled in bags and measured second-by-second. Particulate matter was collected on filter and also measured second-by-second with a TEOM instrument.
In addition to the particulate mass, the particle size distribution was measured with an ELPI instrument. The unregulated components includes olefins, PAH and aldehydes. Extract of the particulate and semivolatile phase was used to carry out the Ames' bio assay to analyze the level of mutagenicity in the exhausts.
This study has shown that there were significant differences between these two fuel qualities for a modern Euro V vehicle. The emission tests performed with EN590 show higher levels of the regulated components NOx, PM and CO - all of which have shown direct and indirect effects on both health and environment. For the unregulated components, aldehydes are emitted to a greater extent when the vehicle is fuelled with the EN590 fuel. The higher levels of PAH in the EN590 fuel is reflected in the emissions, and the PAH extracts used for the Ames' bio assay show higher levels of mutagenicity for the EN590 fuel.
The WHVC driving cycle can be divided into three subcycles, each representing different driving patterns (urban, rural and motorway). This enables an analysis of emissions relative to the driving pattern, and a comparison of the two fuels. Since HDVs are designed to operate on various conditions such as urban, rural and motorway, the exhausts from all of those conditions have been analyzed. NOx and PM emissions have especially been highlighted as problems in urban areas and the high levels are probably caused by diesel fuelled HDVs and LDVs. Previous studies of real driving emissions have shown that some Euro IV and V HDV emit as much as Euro III vehicles during urban driving.