Multivariate analysis of exhaust emissions from heavy-duty diesel fuels

Particulate and gaseous exhaust emission phases from running 10 diesel fuels on two makes of heavy-duty diesel engines were analyzed with respect to 63 chemical descriptors. Measurements for one of the fuels were also made in the presence of an exhaust aftertreatment device. The variables included 28 polycyclic aromatic compounds (PAC), regulated pollutants (CO, HC, NOx, particles), and 19 other organic and inorganic exhaust emission components. Principal components analysis (PCA) was applied for the statistical exploration of the obtained data. In addition, relationships between chemical (12 variables) and physical (12 variables) parameters of the fuels to the exhaust emissions were derived using partial least squares (PLS) regression. Both PCA and PLS models were derived for the engine makes separately. The PCA showed that the most descriptive exhaust emission factors from these diesel fuels included Fluoranthene as a representative of PAC, the regulated pollutants, sulfates, methylated pyrenes, and monoaromatics. Exhaust emissions were significantly decreased in the presence of an exhaust aftertreatment device. Both engine makes exhibited similar patterns of exhaust emissions. Discrepancies were observed for the exhaust emissions of CO2 and oil-derived soluble organic fractions, owing to differences in engine design. The PLS analysis showed a good correlation of exhaust emission of the regulated pollutants and PAC with the contents of PAC in the fuels and the fuel aromaticity. Also, the emission of soluble sulfate was directly related to the contents of sulfur in the fuels. In conclusion, the PCA clearly indicates that emissions of PAC, particulates, and sulfates are the most descriptive exhaust emission factors. These exhaust emissions can, as shown from the PLS analysis, be much reduced by a decrease of aromatics, PAC, and sulfur in the fuels.