Vibration Analysis And Experiment Research On Misalignment Of Rotor System

The rotating machineries, such as aero-engine, turbine, aero-generator and pumps, are widely used and playing important roles in the fields of national defense, power and traffic industry. Rotor system is a crucial part of rotating machinery; its dynamic characteristics determine the performance and structural safety of the machinery. There are many factors, especially faults, may lead acute vibration to the complex and important machinery. In the engineering industry, the misalignment fault is the most common fault and it accounts above60%of the rotor system faults. The misalignment of the rotor system may cause axial and radial alternating force, and then cause axial and radial vibration. The vibration will increase with the rise of misalignment degree. When the degree of misalignment beyond a certain range, the vibration will do great harm to the stability of the system, even lead to disastrous accident.The research emphasis of this paper is the vibration analysis of the rotor system with misalignment fault. Base on the theory of rotor dynamic and finite element method, the dynamic differential equations are established for the single rotor system, tandem dual-rotor system and parallel dual-rotor system. The vibration characteristics of rotor system are obtained by numerical simulation and experiment in this paper. The main research contents of this paper are as following:1. The basic theories of the rotor dynamic and finite element method are introduced, and the numerical calculation methods involved in the paper are also introduced.2. The dynamic model and finite element model of the single rotor system are established, and the simulation analyses are processed under different misalignment degree and different rotating speed by finite element method. The test rig of single rotor system with misalignment is set up, and the experiment research is done. The correctness of the simulation results is proved by the experimental results.3. The finite element model of tandem dual-rotor system is introduced, and the dynamic equation of the rotor system with misalignment is established. The misalignment exciting fore of the tandem dual-rotor system is deduced in detail. Base on this, the numerical simulation is processed, and the vibration responses are obtained under the condition of different misalignment cases and different rotating speeds.4. The dynamic characteristics are analyzed focused on the parallel dual-rotor system. The modeling progress of the rotor system is introduced by finite element method, and the calculation of the coupling stiffness and damp of the bearings are introduced. Finally, the dynamic equation of parallel dual-rotor system is established. The nature frequency and vibration mode of three kinds of parallel dual-rotor with different supporting form are calculated by MATLAB and ANSYS, and the correctness of the simulation model is proved by the comparison of the MATLAB and ANSYS results.5. The dynamic model of parallel dual-rotor system with supporting bearing misalignment fault and intermediate bearing misalignment fault is deduced. The misalignment exciting force is calculated for the two kinds of bearing misalignment fault, and the vibration responses are analyzed under different misalignment cases and different rotating speeds.Finally, the vibration characteristics of the rotor system with misalignment faults are obtainded as following:there is not only rotating frequency but also multiple frequencies appearing in the spectrum, and the ratio of the multiple frequencies increase with the rise of the degress of misalignment. Under the condition of misalignment, the shaft center orbit presents a "banana" shape or "8" shape.