Holistic View on a Dedicated Hybrid Drivetrain – Thermodynamics, Thermal Management and Controls

Authors

Dr. P. Kapus, Dipl.-Ing. L. Leonhartsberger, Dipl.-Ing. (FH) F. Hoelbling, A. Eckart MSc, Dr. A. Huss, AVL List GmbH, Graz:

Year

2023

Print Info

Production/Publication ÖVK

Summary

Upcoming, increasingly stringent greenhouse gas (GHG) as well as pollutant emission limits demand for powertrain electrification throughout all vehicle applications. Demanding vehicle efficiency targets increase the requirements on the combustion engine in hybrid powertrains. Next-generation hybrid engines, with brake thermal efficiency (BTE) targets reaching up to 45%, require a re-thinking of the engine’s thermodynamics, the thermal management and the controls considering the whole vehicle. This paper describes the development of a dedicated hybrid engine with 45% peak efficiency and its integration into a series / parallel hybrid drivetrain in a SUV demo car. An engine with an extremely high efficiency requires a very high compression ratio – in this case 16,5:1. To control knocking a combustion moderator is required. Low pressure cooled EGR is used for this purpose. A new triple spark combustion system allows stable operation of the engine even at highest EGR rates. A complete thermal management system of engine and vehicle ensures safe operation at lowest and highest ambient temperatures. This includes controllable cooling circuits for EGR and charge air cooling, a specific introduction of EGR to the compressor, avoiding any accumulation of condensate as well as a complete separation of the engine bay from ambient by insulation and radiator shutters. To achieve the desired high efficiency also in the vehicle under all conditions a novel closed loop combustion controller was developed that only uses sensors available on the engine. Boosting is performed by an electrified turbocharger that enables extremely precise charging control as well as providing secondary air for the distribution of heat from the electrically heated catalyst to the rest of the aftertreatment system. A specific city detection allows automatic pure electric driving in inner city zones as a step towards “The Connected Powertrain”.

ISBN

978-3-9504969-2-5