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.

The paper describes the importance of reducing frictional losses in internal combustion (IC) engines, thereby improving engine efficiency. One of the main sources contributing significantly to engine friction is the interaction between the piston compression and oil rings and the cylinder bore/liner. Improving the tribological performance in these conjunctions has the greatest potential for performance improvement in the IC engine. Traditionally, the approaches used to tackle this problem have relied heavily on empirical engineering judgement. These have resulted in many inconclusive studies, involving a large number of alternatives, including the introduction of cylinder liners with surface modification work and/or with special coatings. This paper highlights a fundamental investigation of surface modification and coating and its impact on frictional performance. The study combines numerical and experimental approaches. Very good agreement is found between the conclusions of numerical predictions and those of engine test bed work.

No abstract

The paper describes the combined axial, lateral and tilting motions of piston within the confine of cylinder bore, with sliding and normally approaching and separating contacts between the piston skirt and the cylinder wall on both the major and minor thrust sides. The methodology developed undertakes combined solution for inertial dynamics of the piston, together with transient elastohydrodynamic analysis of both contacts. It also includes important practical features of the contacting surfaces, such as the axial form relieving of the piston skirt profile. The space–time solver uses Newmark β-type time marching integrator, as well as the effective influence Newton–Raphson method for space-domain solution of the elastohydrodynamic conjunctions in each step of time. This approach, not hitherto reported for this type of conforming contacts yields accurate predictions of lubricant film thickness and pressure distribution within computationally acceptable times, given the inclusion of level of detail in the model.

No abstract