Experimental analysis and 1D simulation of an advanced hybrid boosting system for automotive applications in transient operation

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 paper an advanced turbocharging system is analyzed, 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. 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 modeled 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 analyzed. Secondly, the transient response of the two layouts was compared, removing the constraints imposed by the experimental activity. The practical significance of the results is outlined, with reference to the transient response of the turbocharger. The adoption of the boosting system presented here allows a fast and stable transient response. Moreover, a reduction in the engine back pressure could be achieved through an optimization of the boosting systemengine matching calculation.