A study of two lobe non recessed worn journal bearing operating with non-Newtonian lubricant

The present paper is aimed to investigate theoretically the effect of non-linear behavior of the lubricant on the performance of an orifice compensated two lobe non recessed worn hybrid journal bearing. A non-linear behavior of lubricating oil is modeled by using the cubic shear stress law. Dufrane's abrasive model has been used for the analysis of wear damage on the bearing surface. A modified form of Reynolds' equation is solved by using finite element method (FEM) taking into account the relation between shear stress and shear strain rate. The influence of non-linearity factor (K) and the wear depth parameter on the bearing performance of a two lobe non recessed hybrid journal bearing is presented for the different values of the offset factor (=0.80, 1.0 and 1.20). The numerically simulated results indicate that the direct fluid-film stiffness coefficients S11 and 22 of worn symmetric bearing configuration (=1.20) operated with non-Newtonian lubricant are reduced about 30% and 18%, respectively, vis-a-vis the circular unworn hole entry journal bearing lubricated with Newtonian lubricant. Further, it is also noticed that two lobe non recessed worn hybrid journal bearing with offset factor greater than one results in an enhancement by the order of 11% in the value of S22 and 6% in the value of th as compared to circular worn symmetric hybrid journal bearing operated with non-Newtonian lubricant. The bearing with offset factor less than one is prevailingly suffering by the non-linear behavior of lubricant and wear defect.