Study of lubricant compressibility effect on hydrodynamic characteristics of heavily loaded journal bearings

By means of numerical techniques, the effect of lubricant compressibility on hydrodynamic behavior of heavily loaded journal bearings is studied in the present work. To reach this goal, the set of continuity and momentum equations for compressible two-dimensional lubricant flow in journal bearings are solved numerically by CFD method. The journal bearing under consideration has infinite length and the lubricant flow is assumed to be laminar and isoviscous. Although the lubricant is liquid, in the cases of high bearing loads, the variation of density with pressure may be important. Therefore, in the computations, the lubricant density is considered variable as a function of pressure. Considering the complex geometry in the physical domain, an attempt is made to transfer the set of governing equations into computational plane by means of conformal mapping. The transformed forms of equations are discretized by the control volume method and are solved using the SIMPLE Algorithm. Results show that the compressibility effect causes an increase in the generated hydrodynamic pressure, such that this effect is enhanced under the condition of high shaft rotational speed, small clearance and high eccentricity ratio.