Impact of nano-lubricants on the dynamic performance of journal bearings with surface waviness

Abstract

Journal bearing performance can be enhanced by the addition of nanoparticles, i.e., copper oxide (CuO), aluminium oxide (Al2O3), and cerium oxide (CeO2) in the lubricant along with providing waviness on the bearing liner inner surface. The plain circular bearing when operated under a low load with an iso-viscous lubricant without nanoparticles in the lubricant has unstable motion due to whirl action, which influences the bearing’s dynamic performance. The performance is improved when nanoparticles are added to the lubricant, thereby enhancing viscosity that varies with temperature and by providing waviness to the bearing liner surface in either the circumferential, axial, or both directions. The performance of the bearing with surface waviness and nano-lubricants can be analyzed by using the Reynolds equation and the finite element analysis by the superposition of a sinusoidal waviness profile on the smooth surface of a bearing bush operating with variable viscosities of lubricants with nanoparticles using the viscosity model. The viscosity model presented in this chapter forms an equation that forms the relationship between the relative viscosity, temperature, and percentage weight fraction of nanoparticles in lubricants by using the experimental results. The wave bearing with nanoparticles in lubricants provides better stability as compared with the rigid circular journal bearing operating under the same conditions without nanoparticles. By considering various geometrical parameters of waviness such as wavenumber and wavelengths and variable viscosity due to nanoparticles in lubricants, the performance parameters of the bearing, such as stiffness and damping coefficients, whirl frequency ratio, and the threshold speed, can be calculated at various eccentricity ratios. The circumferential waviness enhances the bearing system’s stability. However, the presence of axial waviness harms the performance of the bearing. The increase in the wave amplitude and use of nano-lubricants improve the stability of the journal bearing.