An experimental apparatus and an analytical model have been developed to investigate and determine the lubrication condition and frictional losses at the interface between a piston ring and cylinder liner. The experimental apparatus features twin fiber optic displacement sensors to accurately measure the lubricant film thickness and a tri-axial piezoelectric force transducer to simultaneously measure frictional force. An analytical mixed lubrication model featuring Elrod cavitation and a stochastic/deterministic approach for asperity contact was used to investigate the effects of boundary and mixed lubrication conditions at the ends-of-stroke. A comparison between experimental and analytical results indicated that they are in good agreement. The results illustrate the transition through all of the different lubrication regimes (i.e. boundary, mixed and hydrodynamic lubrication) the piston ring and liner experience during a stroke. The twin displacement sensor arrangement is capable of producing accurate, repeatable measurements of lubricant film thickness that are in agreement with the analytical predictions. The analytical model developed for this study can capture the different lubrication regimes that the piston ring and liner experience.

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