Three-dimensional Simulation Of Shafting Vibration Characteristic And Unbalance Response

Rotor string vibration is the most familiar fault in the operation of the rotary machines. It can cause fatal accident. So, the analysis of the rotor system vibration and unbalance response is very important. With the science technology development, simulation emerges as the times require based on computer technology which has been widely used. It is a multidisciplinary synthetical application. Simulation has much more advantage in the aspect of security and convenience. Its essential is modeling based on comparability principle. So, the more analogical the modal is, the more credible the result is. Compare with one-dimensional and two-dimensional modeling, the three-dimensional modeling can reflect the structure of rotor string and the vibration better. So, the analysis of three-dimensional simulation of the rotor string vibration is valuable and significative.Taking nonlinear finite element software Msc.Marc as developing platform, three-dimensional modeling method is analyzed. Properly modeling the parts and boundary conditions of the rotor system, finite element model is built. Some suggestions are put forward to provide the instruction for the next research of three-dimensional finite element analysis. The calculated results of mode and unbalance response analysis are validated by theory which taking Jeffcott rotor as object, the result indicates that the calculated data agree well with the theory.Taking 600 MW steam-turbine generator shaft system test rig as object, mode and unbalance response are analyzed. The result indicates that the calculated data agree well with the experimental data, which prove the validity of this modeling method. Taking the 600 MW steam-turbine generator shaft system test rig and a nine-span long rotor system as object, the effect of bearing position variation on the vibration mode is analyzed. The calculated results show that bearing position variation (elevation variation) has effect both on the natural frequency and the mode shape of the rotor system. The effect is mostly on the rotors which include or near the position variation bearing. It has little effect on torsional vibration. The effect of the bearing which is on the middle rotor is larger than that of the bearing which is on the end rotor. Large effect on mode shape could be caused by the horizontal position variation of bearing, which could also exacerbate the vibration.