| With the development of science and technology, rotating machine is widely used in various kinds of machinery, such as compressor, steam turbine, generator, aviation engine, etc. Due to the complexities of the motion of the rotor system, the particularity of support boundary conditions and various nonlinear factors, it will produce various faults inevitably in the process of the operation of the rotating machinery. The main reason for the faults is the vibration of rotor system. The reason for inducing the faults of the rotor system varies for the diversities and complexities of the rotating machinery working environment. There are various common rotating mechanical faults, such as rubbing, crack, oil whip, misalignment, loose, etc. In the process of the operation of the rotating machinery, in addition to the single fault, there are usually two or more of the coupling faults.This paper mainly researches the dynamic characteristics of rubbing, crack and coupling fault of crack and rubbing. Based on the finite element method, the finite element model of foundation-bearing-rotor system is established. The dynamic characteristics of simple rotor system are studied under the different rubbing factors. And crack, coupling fault of crack and rubbing are analyzed. The main contents are as follows:(1) Finite element model (FEM) of foundation-bearing-rotor system is established. The single point rubbing model, local rubbing model and full annular rubbing based on the contact theory are introduced. Based on the theory of fracture mechanics and strain energy, the local flexibility matrix of crack was deduced. Then the breathing crack model is presented.(2) Based on the theory of contact, the rotor-stator single point rubbing rotor finite element model is established. The simulation parameters, load conditions and three cases of the disc installation location are determined. The influences of three cases of the disc installation location on natural frequencies are analyzed. Then, under two loading condtions, the effects of rotating speeds and three disc installation locations on dynamic characteristics of rotor systems are analysed. (3) FEM considering rotor-stator misalignment and rubbing, and FEM considering the rubbing beween rotor and elliptical stator are established. Under two loading conditions, we analyze the effects of offsets, the stator stiffness and rubbing damp on dynamic characteristics of misalignment local rubbing rotor system and the effects of ellipticity, stator stiffness and rubbing damp on dynamic characteristics of the elliptical stator rubbing rotor finite element model. Compared with single point rubbing, it also has a periodic motion, but exercise forms are more complex; rubbing is more serious; nonlinear characteristics are more prominent.(4) The FEM of full-annular rubbing is established. Respectively in the two load cases, we analyze the effects of rotating speed and three cases of the disc installation location on dynamic characteristics of full-annular rubbing rotor system.(5) The FEM of breathing crack rotor finite element model is established. The flexibility of breathing crack as the change of crack depth curve is compared with the result of literature. The validity of local flexibility matrix is verified. And the main stiffness of the stiffness matrix of crack as changing in the breathing process is analyzed. And the conclusion agreed with the rule of breathing crack stiffness. From two aspects of natural frequency and response curve, the simulation method of breathing crack is verified. Respectively in the two loading cases, the effects of rotating speeds, crack depths and crack positions on the breathing crack rotor system are analyzed. And respectively for the model of coupling faults of crack and single point rubbing and the model of coupling faults of crack and local rubbing, we study the crack, rubbing and coupling faults of crack and rubbing comparatively. In the end, we analyze the effects of ellipticity, rubbing damping and crack depth on the model of coupling faults of crack and rubbing. |
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