ENGINE COMBUSTION AT LARGE BORE-TO-STROKE RATIOS

With the greater premium placed on reducing fuel comsumption today, another type of engine is being reevaluated -- the variable stroke engine (VSE). The VSE modulates its output power without inlet charge throttling. Rather, the stroke length is shortened to reduce engine displacement and power output. As a result, engine operation at light load occurs at much larger B/S than is typical for throttled engines. For the VSE to offer better fuel consumption that its throttled counterpart, it must operate a significant amount of time in the uncharted regions above 1.5 B/S. The effect of bore-to-stroke ratio (B/S) on indicated specific fuel consumption (ISFC) and emissions of a gasoline-fueled, spark-ignited, single-cylinder engine was studied while holding compression ratio and bore diameter constant. As B/S was increased from 1.1 to 3.3, both ISFC and hydrocarbon emissions increased significantly. Increased cylinder heat loss and, to a lesser extent, increased combustion duration were the principal causes of the ISFC increase. Increased surface-to-volume ratio was the principal cause of the increase in hydrocarbon emissions. The influence of combustion chamber modifications on these effects was investigated.

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  • Accession Number: 00195292
  • Record Type: Publication
  • Source Agency: Engineering Index
  • Report/Paper Numbers: SAE 780968
  • Files: TRIS
  • Created Date: Sep 29 1979 12:00AM