The influence of piston ring geometry and topography on friction

Abstract

This article provides solution for isothermal mixed hydrodynamic conjunction of the compression ring to cylinder liner. This is obtained using the average flow model representation of Reynolds equation based on pressure- and shear-induced flow factors. In particular, the effects of compression ring axial profile along its face-width and surface topography of contiguous solids are investigated. It is shown that ring geometry may be optimized to improve lubrication, whilst care should be taken in order to avoid oil loss or degradation resulting from any loss of sealing. In predicting friction, it is shown that appropriate surface parameters should be used in-line with the state of wear of the ring. For a new ring against a plateau honed liner, boundary friction contribution during the initial running-in wear phase should be predicted according to the average asperity peak heights protruding above the plateau, whilst the plateau height also takes into account the valleys within the surface roughness or grooves created by any cross-hatch honing would be the appropriate measure of topography for worn rings. The main contributions of the article are in providing an analytic solution as well investigation of ring face-width geometry and effect of wear upon friction. However, it is acknowledged that generated heat, inlet boundary starvation and circumferential non-conformity of ring to the bore surface would affect the film thickness and exacerbate generated friction accordingly. These further considerations would require a numerical solution, rather than an analytical one presented here.

In-cycle and life-time friction transience in piston ring–liner conjunction under mixed regime of lubrication

“…Furthermore, the inlet wedge effect varies with the state of wear of the ring edge profiles. The effect of inlet wedge height is discussed in detail in Morris et al [22]. Briefly, a larger inlet wedge causes a higher pressure gradient and can lead to greater pressure-induced shear.…”

“…Wear of ring coatings yields transient boundary friction throughout the useful life of the ring which is also affected by changes in the ring face-width geometry [11,22]. Therefore, the surface characteristics and overall geometry of new and worn top compression rings are studied ( Figure 1).…”

A hydrodynamic flow analysis for optimal positioning of surface textures

“…More comprehensive solutions, including 2-dimesional analysis with thermal effects, sideleakage flow and surface roughness are provided elsewhere [3,11,28,29].…”

Design approach for optimization of a piston ring profile considering mixed lubrication

“…Their results showed that using this method can significantly reduce friction power loss. Morris et al [27] and Wu et al [28] carried out a simulation study on the influence of piston ring geometry and topography on piston ring and cylinder liner friction. Singh et al [29] used an experimental study to investigate the effect of modified profiles of the piston ring face on the performance of a diesel engine.…”