Whirling frequencies of rotor systems using ANSYS APDL

Abstract

Abstract Whirling is one important type of vibrations that may cause fatigue failure to a rotor system. The whirling natural frequencies of the system depend very much on the stiffness, damping, mass and constraints imposed to the system. In this study, a modal analysis for whirling type vibration has been conducted on rotor systems using finite element method software of ANSYS APDL to determine the whirling frequencies of the rotor systems. Two cases of rotor system have been considered: a simple shaft with rigid bearing and a disc-shaft system with rigid bearing. Through the second case, the work is validated by comparing the system whirling frequency with past work. Further, through the second case also, parametric studies were conducted to investigate the impact of variation of shaft diameter, bearing and disk parameters on the vibration characteristics of the rotor system. Campbell diagrams have been generated to provide the difference in whirling frequencies of the rotor systems with respect to spin speeds while providing the critical speeds of the rotor system. It was found that in the first case, the Campbell diagram generated followed the supposed theoretical form while the results in the second case agreed well with past results. The parametric studies conducted showed that the several modes of whirling natural frequency depended on the shaft diameter, location of the disc and the mass of the disc.