Axial Subsynchronous Vibration

Abstract

Severe axial subsynchronous vibrations (SSV) can be encountered in turbomachinery. A major concern is the potential for danger from the high levels of vibration acting on the rotor. Longer term implications are fretting and fatigue damage of the rotor components and support structures, which include the thrust bearing pivot contact areas. Although axial SSV is a concern in turbomachinery applications, little published literature can be found on the subject. A series of laboratory tests were therefore designed and performed to investigate the phenomenon in more detail. This paper presents experimental data from a series of pivoted shoe thrust bearing tests investigating the influence of operating conditions and other parameters on axial SSV. Parameters include thrust load, shaft speed, oil flow, inlet temperature, axial clearance, pivot offset, and direct and flooded lubrication. Test results are used to evaluate techniques that have been used when attempting to resolve axial vibration issues. Additional data from thrust shoe load cells and thrust shoe proximity probes provide unique and valuable insight that allowed development of a more robust solution.