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

Abstract

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 NOX 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.