Experimental Analysis and 1D Model Simulation of an Advanced Twin Stage Hybrid Boosting System

Due to the increasingly restrictive limits of pollutant emissions, electrification of automotive engines is now mandatory. For this reason, adopting hybrid boosting systems to improve brake specific fuel consumption and time-to-boost is becoming common practice. In this thesis an innovative turbocharging system is analysed, consisting in an electrically assisted radial compressor and a traditional turbocharger. As a first step, the steady-state performance of each component was measured at the University of Genoa test rig. Due to problems related to over temperature, the working time of the e-compressor coupled to the electric motor is limited avoiding an accurate evaluation of compressor efficiency. For this reason a driving system (instead of the electric machine) was designed to provide a more accurate evaluation of the compressor map. Subsequently another experimental campaign was carried out to evaluate the transient response of the entire turbocharging system. Two different layouts were compared: upstream and downstream. In the upstream configuration the electrically assisted compressor was placed in front of the traditional turbocharger, in the downstream configuration the e-compressor was positioned after the traditional turbocharger. The two different coupling configurations, upstream and downstream, were then modelled in 1-D simulation software following the dimensions and characteristics of the experimental line from which the exploited data originates. The models were first validated by emulating the steady-state condition and subsequently the transient response was simulated and analysed. Secondly, the transient response of the two layouts was compared, removing the constraints imposed by the experimental activity.