Relevance of exhaust aftertreatment degradation for EU7 gasoline engine applications 2020-01-0382
Exhaust aftertreatment systems must function sufficiently over the full useful life of a vehicle. In Europe this is currently defined as 160.000 km, but it is expected that with introduction of EU7, the required mileage will be extended to 240.000 km. This will then be consistent with the US legislation.
While emission limits are tightened, additional engine operation areas become relevant for certification. This results in new challenges in terms of limiting the deterioration of the conversion efficiencies of the exhaust aftertreatment system during the life of the vehicle.
Before this backdrop, three-way catalyst aging and gasoline particulate filter ash accumulation are investigated in this paper. An advanced gasoline exhaust aftertreatment system with high platinum group metals loading, as expected necessary for the EU7, is evaluated. The system is aged using different cycles, such as the Standard Bench Cycle, the ZDAKW cycle for gasoline exhaust systems (a cycle developed by the German Exhaust Center for the Automotive Industry) and supplemented with borderline catalyst aging as well as a novel ash loading method. All aging operations are carried out on a gasoline burner test bench.
In order to rate the degradation effects, several emission relevant parameters are included in the analyses. Very low temperatures down to -30 °C strongly increase the hydrocarbon emissions. Switching to a sporty vehicle operation mode increases the fuel consumption as well as carbon monoxide emissions. Passive particulate filter regeneration slightly increases fuel consumption, while an active regeneration with lean lambda increases the nitrogen oxide emissions.
It will be demonstrated that all emission relevant parameters require thorough investigation. However, only a minor number of the whole vehicle fleet is operated under lowest temperatures or requires active particulate filter regenerations. With respect to statistical relevance, the exhaust aftertreatment degradation is identified as a crucial factor regarding environmental protection and needs to be considered for each application individually. The paper concludes with an outlook towards EU7 aftertreatment enhancements, such as electrical heated catalysts or exhaust burners.
Stefan Sterlepper, Johannes Claßen, Stefan Pischinger, Michael Görgen, Jim Cox, Martin Nijs, Johannes Scharf
RWTH Aachen University, FEV Europe GmbH