Vibration analysis of continuous rotor-bearing system under various defects of unbalances

A system including a flexible rotor, a number of bearings and several mass unbalances whose axial positions, phase angles and radius are arbitrary is modeled in order to study the performance of all common unbalances. In this study, the effect of this position and phase angle of unbalances on the rotor-bearing system is synthesized. For this, a rotor model with arbitrary condition is introduced at first. Then, based on Riley theory, potential and kinetic energy terms are written and stiffness, gyroscopic, damping and mass matrices are derived using assumed mode method. Next, these governing equations are solved numerically. Some examples with various combinations of disc numbers, unbalances and their phase are synthesized. The examples verify the model and its proposed technique of solution. The results show the accuracy of modeling various kind of unbalances and the ability of this model to predicting the vibration behavior of the rotor in a complex combination of disc number and unbalances. The results also show the phase angle of the unbalances affect the vibration pattern while disc numbers and mass of unbalances affect on its amplitude.