Vehicles with electric drive train offer a good compromise between conventional drive concepts and all-electric vehicles regarding fuel consumption and range. They use the advantages of electrification (recuperation, electric propulsion) without being limited by the short range of today’s electric vehicles. Thus, the usage of the internal combustion engine is changed toward the combined propulsion with the electric motor or the charging of the battery. The waste heat of the engine can be used for heating the interior, which is essential for electrified vehicles.
These complex structures require appropriate tools to develop a customized engine concept.
The aim of the project was therefore to develop a numerical model for the optimization of combustion engines in serial hybrid drives.
For this purpose, a longitudinal dynamics model of the Chevrolet Volt and the Opel Ampera has been created in the simulation environment GT–SUITE. The vehicle model included the internal combustion engine, the cooling water circuit, the driver's cab and the electrified powertrain.
The model has been adjusted and calibrated to reflect the real vehicle as good as possible. As a result, there was a detailed vehicle model available, which can reflect the complex interaction of the engine with the rest of the vehicle.
Finally, the drive train was optimized with the help of an optimization algorithm, which was developed within the project. Compared to the measured fuel consumption of different driving cycles at the test bench, potentials for fuel savings could be detected. As an example, the drive system was optimized for the driving cycle US06, which simulates a demand for interior heating due to ambient temperatures of -10 degrees. It could be shown that the fuel consumption can be lowered by an improved battery charging strategy and a punctual heating of the cooling water. Significant influences were avoiding multiple energy conversion and the ability to operate the engine under better conditions regarding the energy conversion efficiency. A resizing of the engine was not effective due to the strict performance requirements