Investigation of an Extended-Expansion Engine with Variable Compression Ratio

Authors

Dr. Justin Ketterer, Ryan Heinbuch, General Motors, Warren, Michigan, USA

Summary

To achieve high efficiency and high power density, extended-expansion has been coupled with variable compression ratio. This produces high expansion ratios for efficient part-load operation and low compression ratios to minimize knock. A 6-bar linkage with a driven and phased eccentric shaft was selected as the most promising implementation of an engine achieving both extended-expansion and variable compression ratio. The proposed system generates a geometrically-extended expansion stroke. Though coupled, compression and expansion ratios can be varied by phasing a rotating eccentric shaft. Software was developed to specify linkage geometries achieving piston motion targets within known constraints. A single cylinder prototype engine was built and part-load dynamometer testing was completed.

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