Research On Bending And Torsional Vibration Simulation For Turbo-generator Shafts With Power Network Impact

With the development of electric power, the problem of vibration on turbo generator shafts stands out. The electric faults and operation can bring the impact which makes network oscillate and shaft torsional vibration. Shaft torsional vibration can produce serious mechanical damages to the unit, even a mechanical failure in the shaft. On the other hand, flexural vibration and torsional vibration have relation, and they are interactional and influencing. Because of on-line limit and danger, turbine generator simulated test is studied. Therefore, the dissertation has focused on several crucial problems in this field, the main outcome of our research includes:This paper based on Finite Element Method (FEM) analyses the characteristic of torsion vibration for turbine generator simulator shafts. The result of computeration is close to that of torsional vibration responsed test. The test results show that network faults or operations can stimulate torsional vibration of the shafts in different degree, and three-phase short-circuit fault makes the strongest torsional vibration.Based on a Jeffcott rotor system in imbalance and misalignment with rigid support, the differential equations of coupled vibrations are established. Mass unbalance is necessary condition of coupling. The analysis of bending and torsion characteristics of the test shows that the shaft flexural vibration and torsional vibration are interaction with each other, and torsional vibration can inhibit the complex rotor exercise.The test of flexural vibration and torsional vibration on simulator shafts during network impacts is finished. The important datas have been acquired. The result of test analysis is in the followling: Because of interaction of flexural vibration and torsion vibration, it is discovered that 1X, 2X and N/3X frequencie components exist in spectral diagram of torsion vibration and the amplitudes of 1X and 2X frequency in spectral diagram of flexural vibration have changed.Subsynchronous Resonance is tested on the line which has series compensating capacitance. The test discovered that torsion vibration can restrain the complex motion of flexural vibration. When mechatronics coupling Subsynchronous Resonance (SSR) happens, the 1X, 2X and N/3X frequencie components are disappeared. The first natural frequency of tosion vibration which is complementary with the resonance frequency is found. From frequency diagram of flexural vibration, it is revealed that the vibration amplitude of 1X frequency decreases and that of 2X frequency disappears. The relation between flexural vibration and torsional vibration is revealed in this paper. And it is diacovered that the motion characteristic of torsion is similar with that of flexural vibration. Useful information for fault diagnosis is provided by the coupled characteristics.The characteristics of flexural vibration and torsional vibration are significant to diagnosis of the rotor system.The Hilbert-Huang Transform (HHT) method is studied, and the HHT is used to analyse flexural vibration and torsional vibration signals in high compensation degree. The Hilbert-Huang time-frequency analysis has more true and distinct time-frequency distribution. From HHT analysis of the experimental data, it is concluded that the HHT time-frequency analysis is more accurately showing the essential characteristics of signals which provides a basis for flexural vibration and torsional vibration fault diagnosis.