Methods for improving transient response of diesel engines – influences of different electrically assisted turbocharging topologies

Abstract

The paper presents a comprehensive study on engine performance improvement attributable to application of different electrically assisted turbocharger topologies. Performance of a baseline turbocharged high-speed direct-injection (HSDI) diesel engine is compared to the performance of an engine utilizing an electrically assisted turbocharger, an engine utilizing a turbocharger with an additional electrically driven compressor, and an engine utilizing an electrically split turbocharger. Analyses are performed based on a validated physically based engine and vehicle model comprising detailed models of all vehicle components, thus ensuring adequacy of results. Analyses are performed for various driving conditions, including tip-in in the fixed gears and the new European drive cycle (NEDC). Results reveal that electrically assisted turbocharger topologies improve transient response of the engine and thus driveability of the vehicle. Additionally, over a limited period of time, electrically assisted turbocharger topologies are able to improve steady-state torque output of the engine with retained fuelling, which is made possible by the availability of energy in electric storage devices. It was also revealed that the utilization of electrically split turbocharger enables considerable reduction in fuel consumption when driven according to urban drive cycles.