Performance Of Piston Rings Research Articles

A Three-Dimensional Analysis of Piston Ring Lubrication Part 1: Modelling

The study of piston ring lubrication in internal combustion engines has remained a very active area in tribology. Theoretical analyses have been developed by many researchers to predict the performance characteristics of piston rings, but almost all previous models established were based upon the assumption that ring/cylinder geometry was axisymmetric. This may not be adequate for modern-day engine design since it is well known that cylinder bores are not perfectly circular. They suffer radial distortions which arise for various reasons. In the current work, a three-dimensional model has been developed to account for the effects of bore out-of-roundness. In order to do this, the three-dimensional Reynolds equation was solved cyclically using the finite difference method in fully flooded lubrication conditions. In this part of the paper, the theoretical model is presented and the effect of bore shape on piston ring performance is examined with three proposed types of bore (circular, elliptical and four-lobe). The results have shown that piston ring performance is significantly dependent on the bore shape or bore out-of-roundness.

A Three-Dimensional Analysis of Piston Ring Lubrication Part 2: Sensitivity Analysis

A three-dimensional model, developed by the authors, incorporating axial and circumferential variations in film shape and squeeze effects has been presented in Part 1 (1). In order to verify this model, the minimum film thicknesses predicted by the authors' model are compared with the predictions of an axisymmetric (two-dimensional) theory and with experimental results presented by Brown (2). A sensitivity analysis is then presented. A number of important factors affecting piston ring performance are examined. They include ring lateral location, constant ring twist (or offset of the ring face profile), bore out-of-roundness, liner temperature distribution and barrel height of the ring face profile. The results indicate that most of these factors have a considerable influence on piston ring performance. Notably, it is shown that ring lateral displacement and bore distortion can have a favourable effect on energy consumption provided blow-by and excessive oil consumption are avoided.

Piston Ring Lubrication—Part 1: The Historical Development of Piston Ring Technology

The history of the piston seal may be traced far beyond the Industrial Revolution, for the problems inherent in sealing a moving piston within a cylinder were well known to the early Greek and Roman engineers. Substantial progress in piston sealing technology was not made, however, until the 17th and 18th centuries, and it was the advent of the steam engine that was to spawn the many and elaborate piston packings of the reciprocating engine. The invention of the modern piston ring is generally attributed to John Ramsbottom, who announced his self-tensioning device in the mid-19th Century. In some respects, the piston ring used in current engineering practice is superficially the same as the Ramsbottom ring, but it is important to note that many of the features of piston rings in reciprocating machinery emerged in the steam rather than in the internal combustion engine age. In this paper, we trace the history of the piston ring from the early civilizations to the present day and establish the current state of technology of piston rings in the light of their varied history. It is widely recognized that a substantial proportion of the power loss within a reciprocating engine is attributable to piston-ring-liner interactions, and there is a pressing need for a better understanding of the sealing and lubrication process in order to minimize these losses. Much of the progress in piston ring technology is attributable to materials, but important and recent developments in the field of lubrication analysis have enhanced our understanding of piston ring operation. It is now possible to identify the role of geometrical features of the rings in determining important operating characteristics of a ring pack such as sealing, lubrication and lubricant transport and there are indications that novel design features will further enhance piston ring performance in the future. In addition to providing the historical background to piston ring development, this paper will also serve to introduce some of the basic concepts of piston ring operation developed in recent years which form the basis for the analysis presented in detail in Parts II and III.

Cylinder condensation in steam engines. An experimental investigation

The tribological performance of piston rings in reciprocating internal combustion engines can only be fully understood when both lubrication and wear are considered in combination. To this end, a numerical model has been developed that predicts the dynamics, lubrication and wear of piston rings interactively for the first time. This paper reports the application of this new model to the piston ring pack of a diesel engine. With the overall aim of evaluating the correlation between theory and experiments, this analysis is divided into two discrete parts. First, the model is used to predict the lubrication performance of measured ring packs before and after periods of running, at constant speed and load, in a Caterpillar 1Y73 single-cylinder diesel engine: the objective being to establish the change in tribological behaviour with observed wear in the engine. Secondly, the model is used interactively to predict the lubrication and wear of the top compression ring from the same engine. This research advances the understanding of piston ring profile evolution with time and its dependence on complex interactions between lubrication and wear.