Lubrication characteristics of shear-thinning Non-Newtonian lubricants in aero-engine high-speed ball bearings

Aero-engines commonly employ low-viscosity lubricants to enhance low-temperature fluidity and cooling efficiency while reducing friction losses. However, the shear-thinning behavior of lubricants at high rotational speeds diminishes film thickness and load-carrying capacity, leading to mixed lubrication. This study proposes a power-law elastohydrodynamic lubrication (EHL) model to investigate the lubrication characteristics of aero-engine high-speed ball bearings. The rheological properties of lubricants are analyzed under isothermal conditions. A composite iterative scheme is proposed to enhance computational efficiency, and the mesh size and computational domain are carefully determined through surface deformation analysis. Finally, the effects of operating parameters and model parameters on film thickness and pressure distribution are examined through numerical simulations. The results show that shear-thinning reduces film thickness but stabilizes oil-film pressure. A decrease in the power-law index from 1.00 to 0.95 reduces the film thickness by approximately 30%. Raising lubricant viscosity is more effective at improving film thickness than increasing speed or reducing load. Increasing vertical load from 1900 N to 5000 N reduces the minimum film thickness by 2 × 10 − 5 μ mN − 1 , whereas increasing dynamic viscosity from 3.5 cP to 5.5 cP increases it by 0.15 μ m · cP − 1 . Shear-thinning lubricants retain high viscosity at the inlet while exhibiting low viscosity and reduced shear stress at the outlet. This self-adjusting viscosity benefits film formation and alleviates viscous heating, thereby enhancing lubrication under high-speed, light-load conditions.