On The Finite Element Modeling Of Turbo Machinery Rotors In Rotor Dynamic Analysis

In this study, a program based on finite element method is developed for rotor dynamic analysis of gas turbine rotors. In the FE model of the rotors, various minor and major parts of the rotor are modeled using the cylindrical and tapered Timoshenko beam elements and the lateral vibration behavior of the rotor is evaluated. In the paper, the lateral vibration behavior of a certain gas turbine rotor is analyzed using the developed finite element program and coupled lateral-torsional vibration behavior of the rotor is analyzed using 3D finite element model. A good agreement exists between the results obtained from two FE models. Two design models are used for the rotor one of which has 2 bearings and the other one has 4 bearings with specific locations. The effects of the number of the bearings on the critical speeds, operational deflection shapes and unbalance response of the rotor is investigated. It is found that the number of the bearings has significant effect on the first critical speed but slight effect on the second and third critical speeds. It is demonstrated that the number of the bearings can be used as one of the system design parameters.