The Diesel in the focus of urban air quality – Exhaust concepts to fulfill RDE

Abstract

Despite stricter legislative emission targets, the provisions on nitrous oxides and fine particles are partially violated severely in European cities. Thus, comprehensive regulations are being prepared including the validation of vehicle emissions in real driving conditions by means of portable measurement systems. In contrast to an NEDC based procedure, the extended utilization of the engine operation map as well as the higher dynamics in real driving is leading to inherently higher engine-out emissions which need to be reduced by highly efficient aftertreatment systems.

With a view to fuel consumption, diesel cars provide a distinctively better combustion efficiency compared to gasoline cars and are subsequently an important component to achieve the future European CO₂ fleet emission targets. The further improvements in the overall engine efficiency also induce significant reductions of the exhaust temperature causing additional challenges in the catalyst development.

This paper comprises a comparison of different diesel aftertreatment concepts, focusing on urban NOx emission reduction, taking also account of the engine cold start phase. For that purpose real driving patterns, according to legal provisions, were simulated on an Engine-in-the-Loop test bench which allows a precise back-to-back comparison of the particular catalyst systems. The emission results were broken down in detail with regards to the contribution of each system component and finally conclusions on potentials and limitations were drawn.