Potential of Pre-Turbo Exhaust Gas Aftertreatment Systems in Electrified Powertrains 2021-01-0579

In order to operate effectively, exhaust gas aftertreatment (EAT) systems require a certain temperature level. The trend towards higher grades of hybridisation causes longer switch-off phases of the internal combustion engine (ICE) during which the EAT components cool down. Additionally, efficiency enhancements of the ICE result in lower exhaust gas temperatures. In combination with further strengthening of the legal requirements regarding tailpipe emissions, new approaches are desired to ensure reliable emission reductions under all conditions. One possibility to achieve a faster warm-up of the EAT system is to place it upstream of the turbine, where temperatures are higher. Although, the extra thermal inertia and larger volume upstream of the turbine delay the throttle response, even a light hybridisation is sufficient for compensating the dynamic loss. This work deals with the examination of various combinations of a diesel oxidation catalyst (DOC), a coated diesel particulate filter (cDPF) and a selective catalytic reduction (SCR) system upstream of the turbine with 0-D/1-D-simulation. The pre-turbo systems (PTS) have been analysed and evaluated during steady state operation, load steps and cold starts. In this work, the focus is set on driving cycles. Besides the emission control and the shortening of catalyst’s light-off time, the fuel consumption and the interaction between pre-turbo EAT and the turbocharger are part of investigation. Thereby the required electrical energy for compensating the dynamic disadvantages of various hybrid types are studied. Among a P2-hybrid, systems to support the boost pressure provision are investigated, such as an electrically assisted turbocharger. The conditions before the turbine are harsher due to higher temperature and pressure fluctuations, for which reason a failure risk analysis is conducted for all PTS.