ANALYSIS OF LUBRICATION AND FRICTION FOR A COMPLETE PISTON-RING PACK WITH AN IMPROVED OIL AVAILABILITY MODEL .2. CIRCUMFERENTIALLY VARIABLEFILM

A model of piston-ring pack lubrication and friction which is capable of analysing nonaxisymmetric conditions has been developed by the auth ors. Part 1 of this paper describes how the influences of relative rin g locations, oil accumulation and mixed/boundary lubrication are model led 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 a utomotive ring pack in a circular bore, based on this model, have also been presented and discussed. In this part of the paper, a descriptio n of a bore geometry model and an approximate approach for evaluating the ring conformability are presented. In addition, two methods for de termining the oil availability in a distorted bore are described. Fina lly 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 qua ntity of oil transported into the combustion chamber, when the bore ou t-of-roundness is excessively large.