Electric torque assist and supercharging of a downsized gasoline engine in a 48V mild hybrid powertrain

Abstract

48V systems enable not only mild hybrid functionalities such as recuperation or torque assist by a belt-driven starter generator (BSG), but also electrification of accessories and the engine boosting system. To maximize the powertrain efficiency, a proper layout of the electrified system and an optimized distribution of the electric power during transient operation is essential. In this study, a vehicle co-simulation of a conventional powertrain with a downsized turbocharged gasoline engine is extended by a 48V system with an electric compressor (eC) and a BSG. The control functions of the eC and BSG are based on a state-of-the-art vehicle application and calibrated for transient operating conditions. The engine model, which is built using a one-dimensional crank angle resolved approach in GT-POWER, has been validated with measurement data and is used to predict the interaction between the eC and the engine air path. The investigations using the simulation platform show that the 48V eC and the BSG can significantly improve the fuel effïciency if the electric energy consumption is initially neglected. However, when considering the electric energy consumption within the vehicle co-simulation, efficient operation is particularly depending on driver torque demand, the battery state-of-charge and charging effïciency. Hence, intelligent operating strategies are necessary to take advantage of the better torque response and improve fuel consumption at the same time.

Enabling off-highway diesel engine downsizing and performance improvement using electrically assisted turbocharging

“…In effect, this 6.5:1 power ratio of engine brake power increase to eBooster ® power means that for the same increase in engine power, 6.5X less power would be required from an eBooster ® than if the same brake power was sought from an alternative source external to the air system, such as a crank-mounted motor generator unit in many mild hybrid architectures. In 48 V mild hybrid powertrain block load torque performance simulation studies by Xia et al, 32 this trend is echoed by the finding that under low electrical power constraints where electrical power has a high utility expense, electric supercharging provides improved energy efficiency over direct electromechanical torque addition. This is because the eBooster ® helps access the high energy density of diesel fuel which was limited by desired combustion and emissions characteristics.…”

Simulation of the Performance of an Electrically Turbocharged Engine Over an Urban Driving Cycle

“…According to this study, an electrified turbocharged diesel engine should have a two-level energy management system that is coherent. In a study to improve the electric power distribution under transient conditions in a hybrid system, Xia et al [23] suggested an electric system architecture. According to the study, using a belt-driven starter generator (BSG) with an electric supercharger improves the engine's fuel efficiency.…”

The effects of combustion phasing induced by water injection on deNOx performance of GDI engine at MBT ignition timing

“…The EU emission legislation has enforced the CO2 emission limitation per distance travelled [10,11] which aims to reduce CO2 emissions from passenger vehicles by 25% within 2025 (to 81 g/km). This influences GDI engines to have smaller displacement and operate at higher indicated mean effective pressure (IMEP) and at lower RPM in order to attain low brake specific fuel consumption (BSFC) [12][13][14] . Increasing IMEP can be achieved by turbocharging which significantly increases intake air pressure and temperature.…”