Two-Stage Turbocharging with Electrical Boosting – An Enabler for Further Downsizing in Gasoline Engines

Authors

Dr.-Ing. H. Breitbach, Dipl.-Ing. D. Metz, Dr. sc. techn. J. Adam, Dipl.-Ing. D. Alt, Dr.-Ing. S. Dönitz, BorgWarner Turbo Systems GmbH, Kirchheimbolanden; Dipl.-Ing. H. Weckenmann, Dipl.-Ing. U. Schellenbauer, Dipl.-Ing. J. Janitschka, Daimler AG, Stuttgart

Year

2017

Print Info

Fortschritt-Berichte VDI, Series 12, No 802

Summary

In 2017, the BorgWarner eBooster^®, an electrically driven compressor, will make its world premiere as it enters series production on a gasoline engine by Mercedes-Benz. Vehicle customers and legislators worldwide demand further reductions in fuel consumption in new engines. Electrically powered turbocharging systems, made possible by increasing electrification of vehicles, allow new options in downsizing and downspeeding concepts. Higher torque and engine power can be achieved without compromising transient behavior at low speed. Technical features of the eBooster and its integration on the M 256 3l six-cylinder engine by Mercedes-Benz are explained, challenges during series development are addressed. The eBooster is combined with a conventional turbocharger to realize a two-stage turbocharging system. The eBooster operates independently from the exhaust gas flow, and the response even at lowest engine speeds is outstanding. Compared to conventional two-stage systems, no second turbine is needed, which is positive for the gas exchange and especially for gas engines beneficial for consumption and robustness against engine knock. The eBooster is decoupled from the exhaust side and, compared to typical two stage systems, offers both more flexibility to position the second compressor and advantages in the warm up of the exhaust system. Excellent electrical and thermodynamic efficiencies ensure the high overall system efficiency. The combination of the eBooster with the exceptional engine concept results in a very attractive and efficient powertrain.