Implementation of an Algorithm to Model the Starved Lubrication of a Piston Ring in Distorted Bores: Prediction of Oil Flow and Onset of Gas Blow-By

Abstract

Experimental evidence suggests that piston rings in internal combustion engines normally experience 'starved' lubrication at some points along their stroke. To take account of lubricant starvation (and hence move towards a full ring pack analysis), a 'flow continuity algorithm' has been incorporated into a non-axisymmetric lubrication model of a single ring. The algorithm allows both inlet and cavitation boundaries of the full film to be located, making it possible to predict the occurrence of gas blow-by through the ring face, particularly for distorted bores. In addition, oil availability has been determined by applying the principle of mass conservation while considering lubricant accumulation. The computational scheme has been tested extensively and, in consequence, its credibility has been confirmed. Using this approach, a piston ring in a non-circular bore has been studied. The results show that, in general, the operating performance of the ring is influenced significantly by lubricant starvation. In particular, as starvation increases, the conditions that could lead to gas blow-by are greatly enhanced.