CFD analysis of journal bearing hydrodynamic lubrication by Bingham lubricant

Design of smart journal-bearing systems is an important issue that opens up the possibility for semi-active dynamic control of bearing behavior. Recent studies show that there is an increasing interest in designing hydrodynamically lubricated bearings using electro-rheological fluids (ERFs) or magneto-rheological fluids (MRFs). Both smart fluids behave like Bingham fluids, and thus the Bingham plastic model is used to describe the grease and the electro-rheological (ER) and magneto-rheological (MR) fluids behavior of the non-Newtonian fluid flow. The performance characteristics of a hydrodynamic journal bearing lubricated with a Bingham fluid are derived by means of three-dimensional computational fluid dynamics (3-D CFD) analysis. The FLUENT software package is used to calculate the hydrodynamic balance of the journal using the so-called “dynamic mesh” technique. The results obtained from the developed 3-D CFD model are found to be in very good agreement with experimental and analytical data from previous investigations on Bingham fluids.Journal-bearing performance characteristics, such as relative eccentricity, attitude angle, pressure distribution, friction coefficient, lubricant flow rate, and the angle of maximum pressure, are derived and presented for several length over diameter (L/D) bearing ratios and dimensionless shear numbers T₀ of the Bingham fluid. The above diagrams are presented in the form of Raimondi and Boyd charts, and can easily be used in the design and analysis of journal bearings lubricated with Bingham fluids. The core profile formed in the bearing is also calculated and presented for various bearing eccentricities, L/D ratios, and shear numbers T₀, and found to be in very good agreement with previous experimental and theoretical investigations. The analysis presented here leads to charts that could be used by the designer engineer to design smart journal bearings.