Tribology of compression ring-to-cylinder contact at reversal

Abstract

Piston ring-pack-to-cylinder contact accounts for one of the major sources of frictional losses in internal combustion engines. The regime of lubrication alters during the piston cycle because of the transient nature of applied load and kinematic contact conditions. Ring geometry, surface topography, and lubricant rheology also play an important role. The aim is to attain full fluid film lubrication, thus reducing friction because of boundary interactions. Therefore, accurate prediction of lubricant film thickness and pressure distribution constitutes the first step in a proper analysis of piston ring-cylinder conjunction. The creation of a gap through elastic deformation is sought in order to inhibit asperity tip interactions. The generated contact pressures in the lubricant film are due to combined entraining motion and squeeze film effect. The integrated pressure distribution balances the elastic force due to ring tension and the applied combustion pressure acting behind the ring. The article highlights a detailed analysis, which forms the basis for its future expansion to include the study of mixed regime of lubrication, which may be prevalent in some real engines.

Tribology of the ring—bore conjunction subject to a mixed regime of lubrication

“…Okamoto and Sakai [5] and Mishra et al [8] estimated the generated elastic contact pressures when a ring is fitted into the cylinder bore. The ring is considered as a beam element, fixed at one end and subjected to an applied bending moment.…”

Wear Analysis of Top Piston Ring to Reduce Top Ring Reversal Bore Wear

“…Study was experimentally validated with analytical results showed good correlation. Mishra [19] found that in the engine cycle at the dead centres, motion reversals take place resulting in a mixed regime of lubrication. In the vicinity of the top dead centre a higher combustion force can contribute to an increased contact force and reduction in lubricant viscosity.…”

Effect of Compression Ring Elastodynamics Behaviour upon Blowby and Power Loss

“…From these reports, further studies on various aspects of the ring-liner conjunction have been carried out. Ma et al [16] and Mishra et al [17] examined ring-bore conformability. Ma concluded that bore distortion may reduce the power loss; however oil consumption would increase as a result.…”