Theoretical investigations on the performance of an externally adjustable fluid-film bearing including misalignment and turbulence effects

An externally adjustable fluid-film bearing has been devised whereby the hydrodynamic conditions can be changed as required in a continuously controlled manner. Principal feature of the externally adjustable pad bearing is the facility to control the bearing clearance and film thickness gradient in circumferential direction, irrespective of the operating conditions. Unlike a tilting pad bearing, this bearing can have both radial and tilt adjustments. A single pad externally adjustable pad bearing will perform as a conventional partial arc bearing when the adjustments are set to zero.The paper deals with the effect of turbulence and misalignment on steady state characteristics of a centrally loaded 120° single pad externally adjustable bearing. The bearing has an aspect ratio of one and operates over a wide range of eccentricity ratios with adjustments and degrees of misalignment. Reynolds equation incorporated with linearized turbulent lubrication model of Ng and Pan is solved using a finite difference method. Static performance characteristics calculated are presented in terms of attitude angle, Sommerfeld number, friction variable, misalignment moment and oil flow. A study with various adjustments predicts that negative radial and negative tilt adjustment configuration results in superior static characteristics as compared to a conventional fluid-film bearing.