Experimental Investigation on the Influence of Boost on Emissions and Combustion in an SGDI-Engine Operated in Stratified Mode

Artikel i vetenskaplig tidskrift, 2015

Among many techniques used for increasing fuel efficiency of a modern Gasoline Direct-Injected (GDI) engine are boosting and stratified operation. In modern downsized GDI engines, boosting is standard in order to achieve a high power output. Boosted GDI-engines have however mostly been operated in homogenous mode and little is known on the effects of operating a boosted GDI-engine in stratified mode. This paper presents the influence on combustion , standard emissions and particulate size distribution in a Spray-Guided, Gasoline, Direct-Injected (SGDI), single cylinder, research engine operated with various levels of boost . The engine was operated in steady state mode at five engine operating points of various load and speed. The engine was boosted with a Roots blower and operated at four levels of boost as well as atmospheric pressure for comparison. The engine was fueled with market gasoline (95 RON) blended with 10% ethanol. The gas motion induced by the engine head was primarily tumble motion but a small amount of swirl. The spark plug and injector was mounted in parallel with the intake valves. Results indicate that exhaust temperature and NOx emissions decrease with increasing boost . Hydrocarbon emissions increase with increasing boost . The results on particulate emissions indicate that nucleation mode particulates increase with increasing boost . The opposite trend was observed for agglomeration mode particulates which decreased with increasing boost pressure.