Oil Consumption Measurements for a Modern Opposed-Piston Two-Stroke Diesel Engine

Opposed-piston two-stroke diesel engines have an inherent thermodynamic efficiency advantage and, by virtue of having double the firing frequency, allow for increased power density and lower NO_X emissions while improving fuel efficiency, when compared to a four-stroke engine of equivalent power. However, opposed-piston two-stroke engines are piston-ported and, as such, are often erroneously dismissed for use in emissions compliant, on-highway vehicle applications over oil control concerns. The results presented in this paper show that oil control at levels acceptable for combustion and emissions control purposes is attainable with crankcase-lubricated, piston-ported opposed-piston diesel engines. Lubricant oil consumption was measured for the 13 test modes of the European Stationary Cycle using a real-time Da Vinci lubricant oil consumption measurement system. Repeatability of the measurement process was demonstrated. Oil consumption was measured during engine warm-up and shown to be reduced 30% compared to the fully warm condition. Furthermore, an increase of the oil control ring tension resulted in 16% lower oil consumption compared to the baseline. An optimization involving measurements with different cylinder kits resulted in a weighted average fuel-specific lubricant oil consumption of 0.18%. These data represent the first measured lubricant oil consumption maps for any contemporary two-stroke diesel engine ever reported.