Stability of rotors supported by tilting pad journal bearings

Rotor instability, a self-excited vibration phenomenon, remains a serious and costly problem with turbomachinery. Avoidance is attempted through rotordynamic modeling as well as testing. However, large modeling uncertainties exist, and common shop testing methods provide no correlation with predictions. For tilting pad journal bearings, the central uncertainty lies in whether or not they should be represented with frequency dependent dynamics. The two existing representations, one being a simplification of the other, can produce very different stability predictions. Such predicted differences suggest that stability testing should be an effective platform for distinguishing between the two representations. A method for stability measurement of rotor systems is developed in this investigation.