In order to fulfill the upcoming LEV III and CAFE regulations, a holistic optimization of engine and aftertreatment system in conjunction with a proper upgrade of the engine management system is required. In the study presented, three different engine calibrations for a new engine, based on FEV's highly efficient combustion system (HECS) engine features have been combined with innovative exhaust aftertreatment configurations. The three engine calibrations are characterized by different NOx raw emission levels, which at the same time represent different levels of fuel economy. As exhaust aftertreatment system, a combination of diesel oxidation catalyst (DOC), close-coupled SCR coated diesel particulate filter (SDPF) and under-floor selective catalytic reduction (SCR) was considered in the first step. System 2 represented the combination of a close-coupled lean NOx trap (LNT) and SDPF featuring a slip coating, and system 3 consists of a close-coupled LNT, coated diesel particulate filter (CDPF) and under-floor SCR. The first obtained results identified, that the tailpipe emission targets cannot be met with the initially determined DOC/SDPF/SCR combination in a robust way, even using the lowest engine emission level without additional heating. Therefore, this engine calibration was combined with a variable valvetrain (VVT) strategy in a second step, in order to further reduce the HC raw emissions and at the same time allow a moderate increase of exhaust temperature. With this new calibration strategy, all three exhaust aftertreatment systems provide the potential to meet the targets. The purely SCR-based system therefore needs a very high SCR-efficiency, which can be realized under ideal conditions, but which is quite challenging to maintain over lifetime. The combinations of LNT and SCR realize an even higher overall NOx-conversion, in which the single performance of LNT and SCR, respectively are lower than for the pure SCR-solution, thus offering increased robustness, but additional challenges for efficiency monitoring. The LNT/SCR combinations provide a good compromise between fuel consumption penalty and AdBlue consumption, with slight fuel consumption advantages for system 3 (LNT/CDPF/SCR) due to the available continuously regenerating trap (CRT)-effect. Under consideration of the above described upgrades in the technology package, consisting of advanced control functionalities, a refined combustion systems and highly capable exhaust aftertreatment systems, modern Diesel aggregates can play a major role for the OEM's to meet upcoming legislative demands in terms of emission and GHG reduction and provide the opportunity to offer affordable mobility solutions for the NAFTA region.
LEV III and CAFE 2025 - Innovative measures for compliance of most stringent legislative demands
2013
25 Seiten, 21 Bilder, 7 Quellen
Aufsatz (Konferenz)
Englisch
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