Rotordynamics of a rotor radially and axially supported by active bump-type foil bearings and bump-type thrust foil bearings

The rotordynamics of a rotor supported by gas foil bearings (GFBs) has been studied, focusing mainly on the relation between radial loads and lateral vibration. Nevertheless, the various axial loads occurring during operation must be compensated by thrust GFBs. Their effect on lateral and axial vibrations of the rotor must be addressed. This research studied the effect of axial load on the rotordynamics of a rotor supported by active bump-type foil bearings (ABFBs). Two ABFBs and a pair of bump-type thrust foil bearings (BTFBs) supported a rigid rotor along the radial and axial directions, respectively. The 5 degree of freedom nonlinear dynamic model for the rigid rotor is shown in this paper and was validated through experimental measurements. The study considered the coupling of the time-variant nonlinear bearing forces of ABFBs and BTFBs. The rotordynamic behaviors of a rotor under various axial loads, rotor unbalances, and voltages are predicted. Moreover, the effects of various disk misalignments on the minimum gas film thickness of the BTFBs are discussed.