White Eco Diesel Powertrain with Pre‐Turbine Exhaust Aftertreatment and Mild‐Hybrid Concept for Lowest NOₓ Emission under Urban Driving Condition

Authors

Dipl.-Ing. B. Lindemann, Dr.-Ing. M. Schönen, Dr.-Ing. J. Schaub, L. Robb PhD, Dr.-Ing. M. Fiebig, H. Sankhla MSc, R. Klein MSc, FEV Europe GmbH, Aachen

Year

2019

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 811

Summary

The potential to achieve a positive effect on both pollutant and CO₂ emissions with the fitting of a Pre-Turbine exhaust aftertreatment system in combination with a mild hybrid concept was investigated via simulation. A vehicle demonstrator was set up in parallel which contained an electric turbocharger, with an 11 kW electric motor sized using GT-Power. An operating strategy to determine where recuperation is performed via BSG instead of e-TC was created. Although an HP-EGR only strategy was deemed possible via VGT position control, the base vehicle LP-EGR circuit was retained for optimal fuel consumption. A Euro 7 scenario for emissions, with limit values of 35 mg/km for NO_x, 50 mg/km for HC, 500 mg/km for CO together with a CF of 1 were assumed as the main boundary conditions. The EATS structure, system components and operating strategy were optimised using the FEV SimEx software. Extensive representative real driving conditions were covered through simulating many driving profiles, including short & long driving distances, low & high load operation, stop & go sections and urban driving. The optimal EATS layout was found to be a 1.0 l DOC with HP-EGR take off downstream of the DOC, a 1.0 l LT-SCR followed by a 2.0 l SDPF and a 5.0 l UF-SCR. This system can achieve the target emissions in all cycles, except the BAB-160. The fuel consumption penalties for engine heating are in the range of 2-4%. This fuel consumption penalty can be potentially offset or negated by recuperation via the 48-Volt system with savings potentials of up to 7% possible for low load cycles. Furthermore, the corresponding reduction can provide savings of up to 3% for high load cycles. In both cases, savings are accomplished whilst fulfilling the emission targets. Compared to the conventional system, which can also be brought to emissions compliance via extensive heating measures, the pre-turbine system shows a potential CO₂ saving of up to 19%. Additionally, there is less clogging observed in the high pressure exhaust recirculation line and a benefit for passive DPF regeneration in normal mode. Compared to the conventional system, the pre-turbine system shows similar low emission levels but at a significant CO₂ saving thus enable both a low-emission concept and a low-CO₂ concept.