Diesel hybrid powertrains – enabling lowest emissions, minimum CO2 and fun-to-drive

Continuously tightened exhaust emission standards along with very challenging CO₂ fleet emission limits represent major challenges for the automotive industry. Electrified powertrain concepts are considered as a major enabler to reduce CO₂ emissions and to improve especially inner-city air quality. In this context, the combination of a modern Diesel engine, featuring a high thermal efficiency, with an electric machine represents a very appropriate, but also costly powertrain concept.In this paper, different Diesel Hybrid powertrain configurations are analysed with regards to added customer value, such as e.g. fun-to-drive by reduced time to torque, lowered fuel consumption, robust low emission behaviour to ensure city operation and attractive overall system costs. The powertrain concepts are investigated for a typical, currently very popular, medium SUV application, covering a wide range of different configurations, starting from a 48V Mild Hybrid up to a high voltage Plug-In Hybrid. In a first step, the base Diesel engine and the exhaust gas aftertreatment system are optimized for each Hybrid configuration in order to minimize the cost impact of the electrical components. Afterwards, the different configurations are evaluated in an extensive simulation study, assessing the functional performance in the WLTC and various RDE cycles. The impacts of different powertrain operating strategies are finally discussed and analysed individually for each of the proposed configurations. Besides pollutant- and CO₂ emissions, customer relevant key attributes, such as transient acceleration potential and general driveability, are assessed as well for the final conclusion.