Dynamic coefficients of tilting-pad journal bearings considering coupling between pads by supporting ring and housing elasticity

A reliable prediction of the dynamic tilting-pad bearing behavior requires an accurate consideration of the structure elasticity that is commonly reduced to pivot support stiffness. For this purpose, analytical descriptions based on Hertzian theory or empirical formulas are often used. On the contrary, measurements of the dynamic coefficients repeatedly indicate that this simplified description of elasticity can lead to large deviations. Furthermore, measurement data of a 120 mm rocker back tilting-pad bearing with four pads show a theoretically not existing anisotropy of the symmetrical four pad bearing in load between pivot configuration. In order to improve the prediction accuracy, the following extensions are made to a thermo-elastohydrodynamic model (TEHD): (I) Implementation of a thermo-mechanical structure model including a contact algorithm for the pad-ring contact and linearization of the structure to calculate the pad support stiffnesses including the coupling of the pads by the ring deformation. (II) Formulation of a full-coefficient model for the radial and angular pad degrees of freedom including the coupling between the pads. The extended TEHD bearing model shows good agreement with the measurement data and provides theoretical understanding of the experimentally observed bearing behavior.