A Dedicated Hybrid Engine Concept with BTE > 45 %

Authors

J. Li, Dr. Y. Liu, L. Han, X. Li, C. Zhao, CHINA FAW Group Co. Ltd., Changchun; Dr.-lng. M. Hunger, Dr.-Ing. M. Kleinen, Dipl.-Ing. M. Riess, Dipl.-Ing. M. Sens, IAV GmbH, Berlin:

Year

2023

Print Info

Production/Publication ÖVK

Summary

Hybrid powertrains, along with pure battery electric and fuel cell powertrains, are being considered as a building block of future fleet scenarios in many markets around the world. However, as the efficiencies of these powertrains lag significantly behind those of pure BEVs or FCEVs, technologies need to be introduced to help raise the powertrain efficiency of hybrid powertrains. To this end, the electrical components such as the inverter, e-machine and battery are being optimized, even if the potential is no longer very great due to already high efficiency values. The focus here must be placed more on the combustion engine, because it usually performs a significant proportion of the work required to propel the vehicle and is by far the weakest link in the efficiency chain of the powertrain. Even if its operating scenarios and proportions vary depending on the hybrid topology, it deteriorates the efficiency chain.

In this respect, the planned paper will deal with the development of an internal combustion engine concept for hybrid applications that is consequently geared to high brake thermal efficiency. The aim of the development was to achieve brake thermal efficiencies of significantly more than 40 % in a considerable map range and a BTE peak efficiency of 45 %.

The special feature of the concept is that the engine can achieve this high efficiency in both lean and stoichiometric operation. For this purpose, a completely new combustion process was developed with an extremely high residual gas tolerance of EGR rates up to 40 % - 45 %. Building blocks used here are a compression ratio of 17.5:1, a long stroke cranktrain design and specially developed intake and exhaust ports. Last, but not least an active Pre-Chamber spark plug is used, which operates with an air/fuel mixture injection for stoichiometric operation with high residual gas rates. The engine achieves this potential without any electrified powertrain components, i.e., without an electrically driven fuel pump or an electric camshaft drive, etc. All are part of the mechanical setup of the concept engine.

In the paper to be submitted, all development steps of the fully virtually developed engine will be described and the validation on the engine test bench will be presented. In addition to the high efficiency, the engine achieves a specific power output of 55 kW/l.

Building on what has been achieved, an outlook will be given on what would be technologically possible to increase the efficiency even further beyond 45 %.

ISBN

978-3-9504969-2-5