Analysis Of Coupling Vibration Of Multi-stage Gear-Bearing-Rotor Systems With Finite Element Method

This dissertation mainly deals with the dynamic behaviors of the multi-stage gear-rotor-bearing system and its application. The whole thesis consists of the following parts:(1) The first is on the study of the modeling of the multi-stage gear-rotor-bearing system using FEM (Finite Element Method), the establishment and solution of kinetic equations. In this part, the multi-stage gear-rotor-bearing system is divided into different element types, the functions and uses of the elements are given; the kinetic equations are derived; the vibration modes and harmonic response of the system are also solved.(2) The second is on the modeling of a two-stage gear-rotor-bearing system by using three-dimensional solid elements. Based on the model, the dynamics of a spur-geared and helical-geared system is analyzed, the vibrations of the modes of the systems are also simulated. The result shows that the helical angle must be considered in the calculation. Using this model, the example in Kahraman's paper is analyzed and calculated, and the vibrations of the modes are also simulated .(3) The third is on the modeling of a real rotor system in type DH of turbine compressor unit by using three-dimensional solid elements. Based on the model, the modes of the system are gained, and the vibrations of the modes are simulated. By comparing the modes of the single shaft system with the coupling system, it isfound that the vibrations of new modes are more complex.(4) The forth is on the experiment. The coupling vibration table is designed and manufactured. The frequencies of the table are measured by using precise instruments. The modes are calculated by FEM. The experimental and theoretical results are in good agreement.(5) The fifth is on the engineering application. The model of a two-stage gear-rotor-bearing system is given by using solid elements and linear elements. This model can reduce the number of the nodes, and save the calculating time. The harmonic response of the system is calculated by this model. It is found that the amplitude of unbalance response of the system is larger than that of the single shaft system. When the system is designed, the harmonic response of the whole system must be considered. In this part, the model of a system is given by using matrix elements, beam elements and mass elements. The behaviors of the rotor system with different contact stiffness, rotating speed, the ratio of B/D and clearance rate are studied. It is found that the performance of the system can be improved by properly increasing the gear modulus, helix angle and gear-width/gear-height. The performance of the system can also be improved by properly modifying the ratio of B/D and clearance rate of the bearings.(6) The last is on the modeling of the system supported by thrust bearings and journal bearings, and an example of its application is given.