PISTON RING FRICTION IN INTERNAL-COMBUSTION ENGINES

The tribological phenomena of the sliding surfaces between piston rings and cylinder liners may be among the most complex in internal combustion engines, and could become even more severe with an increase of the engine power. The friction between the piston rings and the cylinder liner significantly contributes to the mechanical power losses of the engine. The calculations of friction force for a piston ring pack are conducted based on hydrodynamic lubrication theory. The oil starvation within the piston ring pack is considered in the calculation of oil-film thickness. The friction characteristics of piston rings are evaluated with the frictional mean effective pressure. The instantaneous friction force of a piston assembly under firing engine conditions is measured by an improved floating liner method in which the cylinder liner is supported by means of hydrostatic bearings. The friction characteristics are made clear by analyses and experiments.