CO₂ Emissions Benefits of Alternative Diesel Engine Architectures

Autoren

Alok Warey, Peter Andruskiewicz, Russell Durrett, Venkatesh Gopalakrishnan, Michael Potter, Paul Najt,
General Motors Global Research and Development, Pontiac, Michigan, USA

Zusammenfassung

Alternative diesel engine architectures could be a promising solution for reducing carbon dioxide (CO₂) emissions from light-duty vehicles. The main objective of this study was to assess the potential of three alternative diesel engine concepts in achieving a substantial reduction in CO₂ emissions compared to four-stroke diesel baselines. As part of this study 1-D models were developed for a loop scavenged twostroke diesel engine, an opposed piston two-stroke diesel engine and a diesel exhaust compounded engine.

Based on the engine models and an in-house vehicle model, projections were made for the CO₂ emissions from a representative light-duty vehicle over the Worldwide Harmonized Light Vehicles Test Procedure (WLTP). The loop scavenged two-stroke engine had about 5 % lower CO₂ emissions compared to a state of the art four-stroke diesel engine, while the opposed piston two-stroke diesel engine had about 7 % potential benefit. The efficiency advantages of the opposed piston two-stroke engine are mainly because of lower in-cylinder heat losses due to elimination of the cylinder
head and lower surface area to volume ratio.

The diesel exhaust compounded engine had about 8 % lower CO₂ emissions compared to the four-stroke diesel baseline. The most significant contributor to the fuel efficiency advantage of the diesel exhaust compounded engine was recovery and conversion of a portion of the exhaust energy to mechanical work. Below 10kW engine brake power level, where the engine spends a significant amount of operating time over the WLTP cycle, additional fuel consumption benefit was achieved due to declutching the supercharger.

Whether the theoretical benefit translates to actual CO₂ emissions reduction will have to be verified experimentally.

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