A numerical model to study the role of surface textures at top dead center reversal in the piston ring to cylinder liner contact

Abstract

Minimisation of parasitic losses in the internal combustion engine is essential for improved fuel efficiency and reduced emissions. Surface texturing has emerged as a method palliating these losses in instances where thin lubricant films lead to mixed or boundary regimes of lubrication. Such thin films are prevalent in contact of compression ring to cylinder liner at piston motion reversals because of momentary cessation of entraining motion. The paper provides combined solution of Reynolds equation, boundary interactions and a gas flow model to predict tribological conditions, particularly at piston reversals. The results of the analyses are validated against measurements using a floating liner for determination of in-situ friction of an engine under motored condition. Very good agreement is obtained. The validated model is then modified to include the effect of surface texturing which can be applied to the surface of the liner at compression ring reversals under fired engine conditions. The predictions show that some marginal gains in engine performance can be expected with laser textured chevron features of shallow depth under certain operating conditions.