Industrial Lubrication and Tribology

Purpose – The paper aims to devise an externally adjustable fluid film bearing whereby the hydrodynamic conditions can be changed as required in a controlled manner. Unlike a tilting pad bearing, in this bearing film thickness can be varied by providing radial and tilt adjustments to the pad, irrespective of the operating conditions. This variation in film thickness in-turn varies the stiffness and damping coefficients.

Design/methodology/approach – The stability characteristics of a centrally loaded 120° single pad externally adjustable fluid film bearing is studied theoretically. The bearing has an aspect ratio of one and operates over a wide range of eccentricity ratios and adjustments. The time dependent form of Reynolds equation in two dimensions is solved numerically using the finite difference method. Dynamic performance characteristics of the bearing are in terms of film stiffness and damping coefficients, critical mass of the journal and the whirl frequency ratio. Stability is determined using a first-order-linear-perturbation method.

Findings – The paper finds that a study with various adjustments predicts that negative radial and negative tilt adjustment configuration results in superior dynamic characteristics as compared to a conventional fluid film bearing.

Originality/value – It is possible to have a particular set of radial and tilt adjustments that will provide a stable operation of the rotor bearing system. Single pad externally adjustable fluid film bearing will perform as a conventional partial arc bearing when both the adjustments are set to zero.