Pressure Distributions Generated along a Self-Acting Fluid-Lubricated Herringbone-Grooved Journal Bearing with Trapezoidal Groove

Numerical studies are carried out to investigate pressure distributions of a fluid-lubricated herringbone-grooved journal bearing with trapezoidal grooves of various angles. Additionally, the optimal trapezoidal groove geometry is discussed in terms of the radial load capacity and friction torque. 1. Introduction Recently, herringbone-grooved journal bearings have a lot of applications on small rotating mechanisms such as hard disk and turbo machinery. As for a herringbone-grooved gas journal bearing under a narrow groove theory, Vohr and Pan [1] obtained numerical solutions for a special case of small eccentricity. Cheng and Pan [2] gave time-dependent solution of a nonlinear Reynolds equation under stable operation parameters for gas-lubricated bearings. Hamrock and Fleming [3] investigated optimal conditions of radial load capacity for self-acting herringbone-grooved journal bearings. The film in an incompressible fluid was analyzed numerically by Murata et al. [4] based on the potential flow theory. Bonneau and Absi [5] applied a finite element method (FEM) to a compressible Reynolds equation to get aerodynamic characteristics at 4 through 16 grooves with moderate eccentricity. Rondonuwu and Winoto [6] measured pressure distributions along hydrodynamic herringbone-grooved journal bearing for several groove patterns. A fluid-lubricated herringbone-grooved journal bearing with trapezoidal grooves was introduced by Liu and Mochimaru [7], and the influence of viscous trapezoidal grooves on the bearing was evaluated later for various trapezoidal angles [8]. In this paper, the pressure distributions generated along a self-acting fluid-lubricated herringbone-grooved journal bearing with trapezoidal grooves were numerically investigated, using a spectral finite difference scheme. In addition, the optimal trapezoidal groove geometry is discussed in terms of the radial load capacity and friction torque. 2. Analytical Model Consider a fluid-lubricated journal bearing equipped with herringbone groove as shown in Figure 1. The bearing length is and the groove is symmetric with respect to its center of bearing. The shaft itself rotates around its center with an angular velocity in the counterclockwise direction and revolves around the center of the bearing with an angular velocity in the counterclockwise direction. The eccentricity of the shaft is given by , and the outer bearing is fixed. Figure 1: Herringbone-grooved journal bearing. The radius of bearing is , the radius of shaft ignoring grooves is , the bearing clearance is defined as , and the groove depth,