THEORETICAL ANALYSIS FOR FRICTION LOSSES MINIMIZATION IN PISTON RINGS

A significant share of the total power loss in a modern automotive engine is due to the friction interaction between the upper compression ring (the “top ring”) and the cylinder wall. This paper presents the results of simulations on the friction interaction top ring/cylinder wall in a SI engine taking into account the mixed lubrication (ML) regime and considering different engine operating conditions, lubricant viscosity, surface roughness. The oil film thickness prediction describes a sensible different behaviour in the case of the entire stroke in ML regime while the plots confirm bigger portions of the four strokes in hydrodynamic regime for high speed/low load operating conditions. A quite insensible response of the friction coefficient is observed for ring roughness in the neighbour of 1.00 μm, while an effective gain on the mechanical efficiency is achievable only below 0.40 μm