Journal of Mechanics, Vol. 31, No. 4, August 2015 391 A REVIEW ON APPLICATION OF DYNAMIC PARAMETERS OF JOURNAL BEARING FOR VIBRATION AND CONDITION MONITORING T. Narendiranath Babu  T. Manvel Raj Mechanical Engineering Department Sri Krishna Engineering College Anna University Chennai, India Chennai, India T. Lakshmanan Mechanical Engineering Department R.M.K. Engineering College Chennai, India ABSTRACT The journal bearings are used to support high-speed rotors in turbo machinery which often operate above the rotor first bending critical speed. This bearing provide both lateral support and dynamic coef- ficients: Stiffness, damping, and mass terms, related to machine vibrations. The various methods of identifying journal bearing dynamic characteristics, from measured data, obtained from different meas- urement systems, are reviewed. The various approaches to the bearing identification problem are dis- cussed. The various data processing methods in the time and frequency domains are presented. Also, vibration and condition monitoring techniques are presented. In this review, the relative strengths and weaknesses of bearing are presented and developments and trends in improving bearing measurements are documented. Future trends of journal bearing are discussed. Keywords: Journal bearing, Dynamic characteristics, Vibration and condition monitoring. 1. INTRODUCTION The journal bearings used to provide support and rela- tive motion between rotor systems. They are also the source of bearing stiffness, damping, and mass proper- ties in rotor bearing systems. The proper design of these bearings is required for the successful industrial operation of rotating machinery. As machine speeds and loads and instability drivers increase, there is an increasing need for more accurate fluid film bearing identification carried out for the high surface speeds of today’s machines. The support forces and dynamic properties in fluid film bearings arise from the fluid-structure interaction forces between the rotor and the bearing fluid film. These properties were originally described by Reynolds using a laminar, isoviscous fluid model. More advanced, modern bearing theories have been developed, including THD and TEHD bearing models which describe bearing hydrodynamics with significant heating of the lubricant and elastic deformations of the bearing solid compo- nents [1]. Lubricant starvation effects and turbulence must be accurately modeled [1]. The models with increased complexity are required to provide more ac- curate theoretical bearing parameters, as test data is quite limited. The stiffness, damping, and mass coef- ficients arise from a perturbation solution to the elas- tohydrodynamic and thermal equations of the model used. However, there is model sensitivity to design parameters such as bearing clearances, changes in vis- cosity, manufacturing tolerances, thermal growth, and elastic deformation. The experimental validation of the bearing models is vital. Generally, two distinct approaches to exciting the rotor-bearing system for dynamic coefficient identifica- tion have been used. One approach, that resembles real machine operation, involves holding the bearing housing rigidly while exciting a moving shaft. The other approach, referred in this work as the inverse method, holds the shaft rigidly while exciting the mov- ing bearing housing. For lubricant flows in fluid film bearings, the approaches are dynamically equivalent and either is valid in measuring bearing coefficients when performed properly. Many of the older published reports describing bearing identification experiments have not presented confidence intervals for the measured coefficients, but more recent experimenters have included them in their published work [2,3]. * Corresponding author (tnarendiranath@gmail.com) DOI : 10.1017/jmech.2015.6 Copyright © 2015 The Society of Theoretical and Applied Mechanics, R.O.C. Downloaded from https://academic.oup.com/jom/article/31/4/391/5948420 by guest on 17 December 2023