Theoretical Analysis of the Vibrations in Gas Turbine Rotor

Abstract

Vibration analysis plays an important role in the dynamics of rotors, which can be afflicted by unbalancing forces that, over the long term, can lead to the initiation and growth of cracks at the rotor shaft. To predict cracking, it is necessary to study the vibration parameters of the rotor and existence of expected cracks. In this study, rotor vibration was studied analytically and numerically using a developed ANSYS code. The rotor under consideration is supported by journal bearings, the stiffness and damping coefficients were calculated analytically and then applied to the vibration model of the rotor. The results of the numerical analysis were compared with those obtained analytically. Good agreement was obtained between both solutions, with maximum error of 7.31% for the critical speed. These results show that when the depth of the crack is increased, the orbit size and the response are also increased while the critical speed is reduced.