Influence of fluid film nonlinearity on the experimental determination of dynamic stiffness and damping coefficients for three-lobe journal bearings© Article

Müller-Karger, CM, Barrett, LE, Flack, RD. (1997). Influence of fluid film nonlinearity on the experimental determination of dynamic stiffness and damping coefficients for three-lobe journal bearings© . TRIBOLOGY TRANSACTIONS, 40(1), 49-56. 10.1080/10402009708983627

cited authors

  • Müller-Karger, CM; Barrett, LE; Flack, RD

authors

abstract

  • Recently, several papers have been published reporting measured journal bearing characteristics including the linear dynamic force coefficients. In some instances, analyses were performed to give confidence levels for the data based on uncertainties in the measured data. However, the effect of fluid film nonlinearity on the measured data used to calculate the dynamic coefficients has not previously been reported. This paper presents results of a nonlinear simulation to assess these effects for one particular bearing test rig previously documented. The nonlinearity arises from the finite size orbital motion imposed on the journal or housing during the measurement process to obtain response data used to extract the dynamic coefficients from a linear model of the journal bearing dynamic system. The orbit size may be large enough to introduce nonlinearity in the fluid film forces which may in turn affect the resulting calculation of the linearized force coefficients. The nonlinear simulation includes a time-transient solution of the Reynolds equation for a three-lobe bearing and replicates the testing procedure used in an experimental journal bearing test rig previously reported upon. Comparisons of orbital motion and dynamic force coefficients to data obtained from that rig are reported herein. The fluid film nonlinearity was found to produce an uncertainty in the coefficients of up to 20 percent compared to the linearized coefficients obtained from a small perturbation solution of the Reynolds equation which are commonly used in rotating machinery design and analysis. A further objective of the simulation is to evaluate the effect of different external forcing functions to assist guiding the test procedure in the actual test rig to reduce the influence of fluid film nonlinearity on the test results. © 1997 Taylor & Francis Group, LLC.

publication date

  • January 1, 1997

published in

Digital Object Identifier (DOI)

start page

  • 49

end page

  • 56

volume

  • 40

issue

  • 1