CNG-Specific Downsizing – Potentials and Challenges

Authors

Dipl.-Ing. C. Weber, Dr.-Ing. U. Kramer,
Dipl.-Ing. R. Klein, Dipl.-Ing. C. Hofmann,
Dipl.-Ing. M.Sc. O. Berkemeier,
Dipl.-Ing. J. Dunstheimer,
Ford Werke GmbH, Köln;
Dr.-Ing. H. Baumgarten,
Dr.-Ing. T Uhlmann, Dr.-Ing. M. Thewes,
Dr.-Ing. J. Scharf, Dr.-Ing. J. Ewald,
FEV GmbH, Aachen

Year

2015

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 783

Summary

Downsizing the SI engine is a mega trend aiming at reduction of CO₂ emissions and fuel consumption while providing fun to drive at attractive cost of ownership. It offers increased potential when combined with alternative fuels. This paper focuses on Compressed Natural Gas (CNG) specific issues with downsizing the SI engine. Potentials as well as challenges are elaborated in detail. The paper quantifies the performance characteristics of a downsized CNG engine considering reduced knock sensitivity, adaptation of compression ratio potential and combustion efficiency. Insight is given into the charge motion layout and injection strategy of the CNG direct injection (DI) process. CNG DI in combination with a CNG-specific turbocharger (TC) matching compensates lower energy density and can even account for a competitive low end response in transient operation. In order to be able to exploit the high knock resistance of CNG under real world conditions it is essential to ensure a sufficient CNG quality by appropriate automotive fuel standardization.