International Journal of Rotating Machinery
Volume 10 (2004), Issue 6, Pages 507-513
doi:10.1155/S1023621X04000508
A Nonlinear Model for Prediction of Dynamic Coefficients in a Hydrodynamic Journal Bearing
1Rotor–Bearing Dynamics & Diagnostics Laboratory, Department of Mechanical Engineering, Cleveland State University, 2121 Euclid Ave., SH 245, Cleveland 44115-2214, OH, USA
2Birla Institute of Technology and Science, Pilani, India
Abstract
This paper investigates the variation of nonlinear stiffness
and damping coefficients in a journal orbit with respect
to equilibrium position. The journal orbit is obtained by
the combined solution of equations of motion and Reynolds
equation. In the linearized dynamic analysis, dynamic pressure
is written as a perturbation of static pressure and pressure
gradients at equilibrium position. However, in order
to obtain nonlinear dynamic coefficients about equilibrium
position, the dynamic pressure gradients in the orbit are
also written as the first order perturbation of static pressure
gradients and higher order pressure gradients for displacement
and velocity perturbations. The dynamic coefficients
are functions of bearing displacement and velocity perturbations.
The higher order pressure gradients at equilibrium
position are evaluated at various eccentricity ratios and L/D
ratios of 0.5 and 1.0. The variation of nonlinear dynamic
coefficients is analyzed for three Sommerfeld numbers of
a two-axial groove journal bearing under the action of an
external synchronous load along and perpendicular to the
radial journal load. Results indicate that the oil film nonlinearities
affect the journal motion at lower eccentricity ratios
(higher Sommerfeld numbers) with wide variation in stiffness
and damping coefficients.