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Influence of the exhaust gas turbocharger on nano-scale particulate matter emissions from a GDI spark ignition engine

“…Two different dilution ratios were studied: DR of 5 (DR1 = 5, DR2 = 1) and DR of 100 (DR1 = 5, DR2 = 20), in addition from the original experiment at DR = 125 (DR1 = 5, DR2 = 25). Repeatability, expressed as CoV on total emissions from three independent repeats, has an average value of 25.4%, indicating that dispersion in total number emissions under these test conditions is well within one order of magnitude, in line with results obtained from other researchers in the recent years [3,21,24]. The first hypothesis test on differences is now implemented in order to check whether the use of different dilution ratios induces variations in the PM number emission levels that are measured at the same sampling location.…”

“…Repeatability for the fixed dilution experiments is expressed as the CoV on the total PM number count from three independent repetitions of every point of the matrix and for both sampling locations. On average for fixed dilution experiments, CoV of 17.7% is obtained, well in line with results from other researchers in the recent years [3,21,24]. The hypothesis test on differences between particle size distributions measured before and after the turbocharger for all operating conditions at fixed dilution aimed at understanding whether it is possible to reject the null hypothesis of equal emission spectra at the two sampling locations.…”

“…In an attempt to improve the efficiency, to increase the performance and to limit the fuel consumption and emissions of modern automobiles, the use of an exhaust gas turbocharger in Gasoline Direct Injected (GDI) engines has become a popular solution that has been adopted by numerous automotive manufacturers [1]. On the other hand, though, direct injection leaves a much shorter time for thorough fuel vaporisation and for mixture preparation, which results in higher Particulate Matter (PM) emissions [2,3]. Given this substantial increment, and considering the impact of PM on human health [4], PM emissions from GDI engines need to be studied closely.…”

“…For GDI engines in particular, the catalytic converter was shown to have a profound influence on the particle size distributions of PM measured at its inlet and outlet. Research by Whelan et al [5] proved that particle agglomeration and growth are phenomena which can alter the PM population balance in devices which handle particle-laden gases. These considerations acquire even further significance if the Euro-VI Emission Regulations for the European Market are accounted for.…”