Journal bearings are widely used for supporting high speed rotating machinery, such as turbine and compressor, because of their high load carrying capacity stability and durability. In recent trends, engineers are oriented towards higher speed and smaller sizes of the rotating machinery, for which the only alternative is noncircular journal bearings. The present paper focuses on one of the noncircular bearings called spiral bearing. A study was done on the static and dynamic performance of hydrodynamic short spiral bearing. Out of the two forms of spiral bearings, i.e., convergent and divergent types, Divergent Spiral Journal Bearing (DSJB) is considered in the present paper. A geometric study of different spirals and analysis of film thickness is carried out for the determination of pressure function from Reynolds equation. A discussion is presented concerning the various pressure boundary conditions used in the calculation of the static characteristics parameter of short spiral journal bearing. To simplify the problem, short bearing analysis is made. The dimensionless load, attitude angle and friction parameters are graphically compared with the circular bearing. The paper analyzes frequency effects by theoretical investigation into the DSJB’s stiffness and damping characteristics.

Fluid film journal bearings are widely used to support a rotating machinery system, and those bearings often have a clearance configuration of a full circle. However, the circular bearings have the disadvantage of destabilizing the support system at high speeds, which is called the whirl instability. The whirl instability occurs due to the presence of skew-symmetric stiffness coefficients. To solve the whirl instability many configurations are proposed, for example elliptical bearings, pressure dam and multilobe bearings. These configurations are only to improve the stability of the system.

In this paper, a new configuration of film thickness of spiral journal bearing is introduced to improve the stability aspects. The study of the hydrodynamic behaviors of journal bearings is based on the Reynolds equation which is derived from Navier-Stokes and continuity equations using many assumptions (Oscar and Beno, 1961; and Alastair, 1981). The pressure distribution in fluid in the clearance of journal bearing was first found by Tower (Majumdar, 1999), and the friction torque of oil lubricated sliding bearings was measured by Petroff (Pradanta, 2005). In the Reynolds equation, two general simplifications are infinitely long bearing and the short bearing. Sommerfeld solved the Reynolds equation making special boundary conditions for pressure distribution.

Two solution techniques with algorithms, namely the Gauss-Siedel iterative scheme and the linear complementarily problem approach, for finding the positive pressure region in a hydrodynamic journal bearing are presented by Chandrawat and Sinhasan (1990). Prabakar et al. (2005) presented the effect of deformation of the bearing liner on the static and dynamic performance characteristics of an elliptical (twolobe) journal bearing operating with micropolar lubricant.

Mechanical Engineering Journal, Dynamic Performance Characteristics, Hydrodynamic Short Divergent Spiral Journal Bearing, Fluid Film Journal Bearings, Rotating Machinery System, Experimental Data, Nonlinear Orbit, Eccentricity Ratio, Micropolar Lubricant, Multilobe Bearings, Lubricated Sliding Bearings.