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Fluid-lubricated thrust bearing technology comprises two structural components, a rotor and stator separated by a thin fluid film experiencing relative rotational motion. The fluid film is employed to maintain a clearance between rotating and stationary elements when subjected to external axial loads. The fluid film lubrication mechanism is designed to provide an improved performance for applications characterized by high differential speed and requiring low frictional losses. An incompressible fluid flow model is derived for a parallel and coned thrust bearing using a modified Reynolds equation for the thin film dynamics of a stator and rapidly rotating rotor. Initially a no-slip boundary condition is imposed on the bearing faces. For high speed operation the lubrication approximation to the incompressible Navier-Stokes equations leads to a modified Reynolds equation incorporating rotational effects. The bearing dynamics are examined by coupling the fluid flow and axial motion of the rotor and stator; the rotor has prescribed periodic axial oscillations and the stator is modelled as a spring-mass-damper system, having axial motion in response to the film dynamics. To solve the modified Reynolds equation and stator equation simultaneously the time dependent minimum face clearance (MFC) variable is introduced, leading to the derivation of a non-linear second-order non-autonomous ordinary differential equation for the MFC. Applying a transient solver gives solutions of the MFC settling down to a stable periodic behaviour, motivating the derivation of a Fourier spectral collocation scheme. |
