A performance analysis of hydrodynamic journal bearing lubricated with hybrid MWCNTs-TiO2 nanolubricants considering thermal effects

The new development of nanotechnology proposes cost-effective and upgrading solutions for tribological characteristics of the lubricant. One of these solutions is the coexistence of two or more types of nanoparticles known as hybrid nanoparticles. This work presents useful results of research on the performance features of the circular journal bearings operated with SAE30/TiO₂-MWCNTs (SAE 30-grade base oil blended with titanium dioxide and multi-walled carbon nanotube hybrid nanoparticles) hybrid nanolubricant. In this study, the mathematical model of the lubricant with hybrid nanolubricant is based on the Dowson equation and three-dimensional heat transfer equations. Furthermore, the thermophysical specifications of the hybrid nanoparticle are formulized in terms of characteristics of the base lubricant, TiO₂, and MWCNTs, as well as an empirical formula for the viscosity–temperature relationship. To obtain bearing performance features, a series simulation is conducted under various volume and mass fractions of hybrid nanoparticle and operational conditions (a range of eccentricity ratio from 0.05 to 0.8 and a range of rotating speed from 1000 to 9000 r/min) with a developed algorithm for the iterative solution. The results showed that the effect of the hybrid nanoparticles on the maximum pressure and the load capacity are more visible at high eccentricity ratio, and nanolubricants could increase the load capacity, maximum pressure, and friction force till 11%, 13%, and 15%, respectively. Besides, when the bearing operates with a lubricant containing MWCNTs-TiO₂, the pressure values are higher than the lubricant containing solely MWCNTs nanoparticles by 0.2%, while they are lower than the lubricant containing solely TiO₂ nanoparticles by 1%.