Numerical study of the effect of ZnO/MWCNT lubricant additives on density and piston ring lubrication under cylinder liner distortions

This study aims to model the actual shape of an internal combustion engine cylinder liner and investigate how its axial and radial deformations, coupled with emerging lubricants containing nano-particle additives, impact the design parameters governing piston compression ring tribological behavior. The viscosity behavior of non-Newtonian lubricants with nano-particle additives is obtained by using the Power Law model. The effect of oil additives and tribofilm formation is not included in the lubricant viscosity, its variation with pressure, or the wear coefficient. The study focuses on a SAE10W40 lubricant oil with ZnO/MWCNT nano-particles additives, based on data from current literature. Analysis using Archard's model with non-Gaussian surface distribution, reveals the combined deformations effect on compression ring wear in terms of wear depth and material volume loss. Additionally, a blow-by model is incorporated to approximate real engine operating conditions. Predictions for compression ring friction and minimum lubricant film thickness are generated. The findings underscore the significant impact of cylinder deformation profiles on compression ring friction behavior, particularly with respect to the number of sine waves, across all lubricant cases. Notably, the study shows a 21 % drop in friction force with nanoparticle-enhanced lubricant, highlighting their importance.