Analysis of lubrication and friction for a complete piston-ring pack with an improved oil availability model: Part 2: Circumferentially variable film

Abstract

A model of piston-ring pack lubrication and friction which is capable of analysing non-axisymmetric conditions has been developed by the authors. Part 1 of this paper describes how the influences of relative ring locations, oil accumulation and mixed/boundary lubrication are modelled in a ring pack. An attempt has been made to validate the model by comparing its predictions with measurements from Hamilton and Moore's experiments. Results obtained from a computer simulation of a modern automotive ring pack in a circular bore, based on this model, have also been presented and discussed. In this part of the paper, a description of a bore geometry model and an approximate approach for evaluating the ring conformability are presented. In addition, two methods for determining the oil availability in a distorted bore are described. Finally, the results obtained from simulating the operation of a full ring pack in a non-circular bore under a range of conditions are presented and discussed. The results show that bore distortion can considerably reduce the power loss, but will also dramatically increase the net quantity of oil transported into the combustion chamber, when the bore out-of-roundness is excessively large.