In order to meet the CO2 emission reduction targets, downsizing coupled with turbocharging has been proven as an effective way in reducing CO2 emissions while maintaining and improving vehicle driveability. As the downsizing becomes widely exploited, the increased boost levels entail the exploration of dual stage boosting systems. In a context of increasing electrification, the usage of electrified boosting systems can be effective in the improvement of vehicle performances. The aim of this work is therefore to evaluate, through numerical simulation, the impact of different voltage (12 V or 48 V) electric superchargers (eSC) on an extremely downsized 1.0L engine on vehicle performance and fuel consumption over different transient manoeuvres. The virtual test rig employed for the analysis integrates a 1D CFD Fast Running Model (FRM) engine representative of a 1.0L state-of-the-art gasoline engine featuring an eSC in series with the main turbocharger, an electric network (12 V or 48 V), a six speed manual transmission and a vehicle representative of a B-SUV segment car. A preliminary assessment of the steady state performances of the 1.0L engine with the electrified dual boosting system with both 12 V and 48 V electric supercharger was performed. Then, the vehicle performances were evaluated by means of, on the one hand, vehicle elasticity manoeuvres for the performance assessment and, on the other hand, type approval and RDE driving cycles, for the fuel economy assessment. An evaluation of possible engine and vehicle hardware modifications was also carried out. In particular, the effect of a variation of the final drive ratio, the increase of the turbine size and the usage of a high efficiency engine concept (featuring an increased compression ratio from 10 to 12 and a late intake valve closing, exploiting the advantages of a Miller cycle) were investigated.
