The Effects of Trapezoidal Groove on a Self-Acting Fluid-Lubricated Herringbone Grooves Journal Bearing

As a self-acting fluid-lubricated herringbone grooves journal bearing, a trapezoidal cross-sectional shape of grooves is considered. Trapezoidal groove shape effects on its bearing characteristics such as variations of load capacity, attitude, and friction torque for various trapezoidal angle of groove are determined. 1. Introduction Since a herringbone grooves journal bearing has high stability at half whirl speed, it is equipped in miniature rotating machines. Performances of herringbone-grooved journal bearing are investigated by many researchers, for example, Vohr and Pan [1], Hamrock and Fleming [2], Murata et al. [3], Bonneau and Absi [4], Jang and Chang [5], as well as Liu and Yoshihiro [6]. In many cases numerical methods are applied to solve a pressure distribution equation (viz., a Reynolds equation of fluid thin film), evaluating fluid-lubricated herringbone-grooved journal bearing performance for load capacity and attitude angle. In this paper, attention is focused on trapezoidal groove shape of a self-acting fluid-lubricated herringbone grooves journal-bearing to investigate influences of a variation of trapezoidal angle of groove change on characteristics. 2. Analytical Model Consider a fluid-lubricated journal bearing equipped with herringbone grooves as shown in Figure 1. Let bearing length be and groove be symmetric with respect to its center of bearing. The shaft itself rotates around its center with an angular velocity ω in the counter-clockwise direction and revolves around the center of the bearing with an angular velocity Ω in the counter-clockwise direction. The eccentricity of the shaft is given by , and the outer bearing is fixed. Figure 1: Herringbone-grooved journal bearing. The inner radius of the bearing is , the radius of the shaft corresponding to the plane without grooves is , the bearing clearance is defined as？？ , and the groove depth, the groove width, ridge width, and grooves angle are denoted by？？？ , and ,？？respectively. For a trapezoidal type of grooves, the trapezoidal angle is defined as shown in Figure 2. Figure 2: Cross-section perpendicular to the trapezoidal surface of groove. Here, two coordinate systems are used, that is, S (r, θ, z), an inertial cylinder coordinate system, is fixed at the center of the outer bearing, and , noninertial cylinder coordinate system is fixed at the rotation shaft Relationship between the coordinates is given by Hereafter, the superscript * is meant for the noninertial coordinate system. The radial component or at the surface of the shaft is denoted by in or in . 3. Local