Abstract
Research and/or Engineering Questions/Objective
Tough regulations for emission reduction force OEMs to develop and introduce high-efficient vehicles concepts. Drivetrain electrification represents one of the main measures for reducing the fuel consumption of passenger vehicles. Mild-hybridization based on a voltage level below 60 V is a promising alternative to cost-intensive high voltage powertrains. The objective of this study was to investigate the belt-driven starter/generator architecture for its CO2 emission reduction potential within different driving cycles.
Methodology
In order to evaluate the CO2 emission reduction potential resulting from 48 V Mild-Hybridization, a complete vehicle simulation model was built-up. Key components like internal combustion engine and electric motor were parameterized with characteristic diagrams, representing the efficiency under each operating point. The remaining parameters were selected to correlate with a typical C-segment vehicle. Different hybrid functions were implemented in the simulation model. The superior operation strategy was designed in dependence of the battery state of charge. By performing a parameter study, the influence of different driving cycles and electric motors on the CO2 emissions was worked out. The identical vehicle without drivetrain electrification was selected as comparison base.
Results
In this paper, the CO2 emission reduction potential of a P0 hybrid will be presented. The impacts of different hybrid functions on the emissions are shown. The main findings are the influence of individual functions on the fuel consumption / CO2 emissions. The contribution of stop/start and regenerative braking and torque assist functions was quantified. Furthermore, it was shown that load shifting can have negative effects on the cumulated fuel consumption over a driving cycle, depending on the given loss chain.
Limitations of this study
The performed sensitivity study with different power levels of the electric machine was carried out with simplified, constant efficiency characteristic diagrams. W
hat does the paper offer that is new in the field including in comparison to other work by the authors?
The provided comparison between different driving cycles, as well as the function individual influence on the CO2 emissions of a P0 mild-hybrid represents a different approach than has been shown so far.
Conclusions
The results show a significant potential for CO2 emission reduction in the elaborated vehicle segment. Even higher potentials can be expected in lower vehicle segments and with increasing system power.
Key Words: Mild-Hybrid; Hybridization; 48V; Electrification; Energy Management; Operation Strategy