Continuously Variable Compression Ratio for Downsizing Diesel Engines – Approach to Improve Efficiency, Emissions and Performance

Authors

Dr.-Ing. M. Brauer, Dipl.-Ing. C. Schramm,
Dipl.-Ing. A. Werler, Dipl.-Ing. M. Diezemann,
Dr.-Ing. C. Severin, Dipl.-Ing. M. Kratzsch,
Dr.-Ing. H. Neukirchner, Dipl.-Ing. G. Buschmann, Dipl.-Ing. K. Blumenröder, IAV GmbH, Berlin

Year

2015

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 783

Summary

This paper describes the potential of a variable compression ratio (VCR) for diesel engines in passenger cars. Simulation studies and engine tests describe the CO₂ and emission-reducing potential at part load together with the potential for further improving performance in downsizing engines. Variability of the compression ratio is realized by a variable quench gap height at top dead center. The increased compression ratio for the part-load points must be achieved by combining a normal quench gap height of approx. 0.5 mm with a smaller compression volume in the piston. The shape of the piston bowl was developed using 3D combustion computations and validation measurements on a single-cylinder engine. Both computations and tests showed that increasing the geometric compression ratio from CR = 16.2 to CR = 20.0 leads to a 5% reduction in the indicated fuel consumption. However, an increase in NOx engine-out emission must be tolerated in order to reduce particulate-matter emissions to an acceptable level.