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Studies on the oxidation of diesel particulates characteristically showed that the particle number concentration for a particle size of about 30 nm can be reduced by more than 90% when the characteristics of the particulates are adapted to the oxidation potential of the catalyst employed. This corresponds to a total PM emission reduction of about 70% and demonstrates the high oxidation potential for other partial load operating points of a light-duty truck EURO 3 engine. It was found that the impact of modified engine adjustments on the particle contribution of smaller particles meets the technical requirements for an optimized reduction using an SCR catalyst based on V 2 O 5 /WO 3 /TiO 2 . Although the number concentration of particles with a size of <50 nm increases excessively, this results in a much higher efficiency of reduction of the particle number concentration by the catalyst, observed over the complete measurement range of the SMPS system used. The same result was also observed when EGR was used. The unavoidable NO x emission can be reduced, as usual, by running the catalyst in urea SCR, if necessary. In this context, the generation of particulates and their components was studied in the presence of urea SCR for selected stationary operating points depending on the urea dosage and fuel sulfur content to investigate the mechanisms of PM generation with the intention of optimizing emission control.

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This article describes the first development phase of a centrifugal compressor with variable geometry which is designed to match the needs of future heavy-duty engines. Requirements of truck engines are analyzed, and their impact on the properties of the compressor map is evaluated in order to identify the most suitable kind of variable geometry. Our approach utilizes the transformation of engine data into pressure ratio and mass flow coordinates that can be displayed and interpreted using compressor maps. One-dimensional and three-dimensional computational fluid dynamics fluid flow calculations are used to identify loss mechanisms and constraints of fixed geometry compressors. Linking engine goals and aerodynamic objectives yields specific recommendations on the implementation of the variable geometry compressor.