An Experimental Investigation into the Lubrication of Piston Rings in an Internal Combustion Engine-Oil Film Thickness Trends, Film Stability and Cavitation

Transducers based on capacitance and inductance measurement techniques have been used to make extensive measurements of the lubricant film thickness between the piston rings and liner of an I.C. engine.

It was found that ring operating film thicknesses were not stable but suffered both gradual and abrupt changes, even under apparently stable engine operating conditions. It is postulated that these effects arise as a result of two effects; ring spin and secondary piston motion.

The paper also presents evidence for cavitation effects. However this evidence is inconclusive and further work is planned to examine the effects more rigorously.