Optimum Groove Location of Hydrodynamic Journal Bearing Using Genetic Algorithm

This paper presents the various arrangements of grooving location of two-groove oil journal bearing for optimum performance. An attempt has been made to find out the effect of different configurations of two groove oil journal bearing by changing groove locations. Various groove angles that have been considered are 10°, 20°, and 30°. The Reynolds equation is solved numerically in a finite difference grid satisfying the appropriate boundary conditions. Determination of optimum performance is based on maximization of nondimensional load, flow coefficient, and mass parameter and minimization of friction variable using genetic algorithm. The results using genetic algorithm are compared with sequential quadratic programming (SQP). The two grooved bearings in general have grooves placed at diametrically opposite directions. However, the optimum groove locations, arrived at in the present work, are not diametrically opposite. 1. Introduction Journal bearings are used extensively in rotating machines because of their low wear and good damping characteristics. Fluid-film journal bearings are available to support a rotating shaft in a turbo machinery system. A full circular journal bearing has a much simple configuration but exhibits instability at higher rotational speeds. It is relatively less expensive compared to the multilobe bearings. It is well known that whirl instability occurs at high speed in oil journal bearing. Present day bearings, at over increasing speeds and loads, confront the engineer with many new problems. Excessive power losses reduce the efficiency of the engine, and high bearing temperature poses a danger to material of the bearing as well as the lubricant. Instability arising mainly in the form of oil whip may ruin not only the bearing but the machine itself. New bearing designs are sought to meet the new requirements. A journal bearing fed by two axial grooves has a wide practical application due to its good load carrying capacity and ability to operate when reversal of shaft rotation occurs [1]. These bearing usually have the grooves positioned orthogonal to the predominant load direction. Among the previous works on two axial groove oil journal bearings; Klit and Lund [2] used finite element method to find dynamic coefficients of plain circular bearing with two 20° axial grooves. Gethin and Deihi [3] studied the effect of loading direction on the performance of a twin-axial groove cylindrical bore bearing. It has been anticipated that, if the bearing is loaded into the groove, its load carrying ability will be diminished, but the