980 °C Gasoline Variable Turbine Geometry – The Affordable Upcoming Technology for High-Volume Efficient Engine s

Authors

Dr.-Ing. Claus Glahn, Dr.-Ing. Matthias Kluin, Dr.-Ing. Ingo Hermann, Dipl.-Ing. Achim Koenigstein,
Opel Automobile GmbH, Ruesselsheim

Summary

The requirements on the charging system of gasoline engines regarding charge air pressure availability are more and more challenging with further downsizing and new combustion systems in the future. The trade-off between high low-end torque with fast transient response and low turbine pressure ratios for high engine efficiency therefore becomes critical.

The variable turbine geometry (VTG) is a known measure for solving this issue. VTG has not yet been established in the gasoline mass market due to the challenges related to the higher exhaust gas temperature and system costs. Nevertheless, high-efficiency gasoline combustion concepts like the Miller cycle showed in recent times the strong benefits of VTG technology on gasoline engines. In the past, the compromise between cost and efficiency limited the pre-turbine temperature to below 900 °C, with negative impact on stoichiometric power capability due to hardware protection. The design and material selection of currently available high-temperature VTGs limits the application to the premium segment with high specific engine power output.

Despite all that, newly developed design solutions as well as new material developments enable the beneficial application of this technology even on engines with higher outputs above 90 kW/l and increased exhaust gas temperatures up to 980 °C even for cost sensitive high volume markets. This paper shows the implementation of these approaches and the potential of the 980 °C  VTG for high-efficiency combustion systems.

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