Stability Analysis of Non-Circular Hydrodynamic Journal Bearing with Micropolar Fluids

Stability Analysis of Non-Circular Hydrodynamic Journal Bearing with Micropolar Fluids

In this work steady state and stability performance characteristics of circular and two lobe noncircular journal bearings with micropolar fluids are presented. Lubricating oil containing additives and contaminants is modeled as micropolar fluid. The modified Reynolds equation is obtained using the micropolar lubrication theory and solving it by using finite element method (FEM) as a simple and efficient numerical technique. The static and dynamic performance characteristics in terms of load carrying capacity, coefficient of friction, attitude angle and side leakage flow, whirl frequency and critical mass are determined for various values of size of material characteristic length, coupling number, aspect and eccentricity ratio. The results show compared with Newtonian fluids, that micropolar fluid exhibits better efficiency. Also results show that micropolar fluids exhibit increase in critical mass, load carrying capacity but decrease in whirl frequency ratio, coefficient of friction, attitude angle and side leakage flow. It is observed that the effect of micropolar fluids is more pronounced at high coupling numbers. Results show that though noncircularity of journal bearings can have certain advantages in bearing operation, however, the magnitude of pressure distribution developed in bearings decreases with increasing in noncircularity or decreasing of preload factor in bearing.