Analysis of Dynamic Behavior of a Non-Nominal Five-Pad Tilting Pad Journal Bearing

Because tilting-pad journal bearings (TPJB) are more stable and efficient than conventional bearings, they have been commonly applied to many rotating machinery applications. Most of the studies about steady state and dynamic characteristics of TPJBs are usually evaluated by means of thermo hydrodynamic (THD) models assuming nominal dimensions for the bearing. However machining errors could lead to actual bearing geometry and dimensions different from the nominal ones. In particular for TPJB the asymmetry of the bearing geometry is the principal cause of unexpected behavior. In this paper a theoretical analysis on dynamic characteristics of a five-pad TPJB is investigated with non-nominal geometry, that is, different thickness for each pad. The dynamic coefficients of a five-pad TPJB with a nominal diameter of 100mm, length-todiameter ratio (L/D) of 0.7 are evaluated versus rotor rotational speed, load direction and static load. Then, the analytical results of the non-nominal bearing are compared to those of the nominal one.