Characteristics Analysis Of Coupling Vibration Of Rotor Bending And Torsion Under Rubbing Fault

The rubbing of the rotor is a common fault.The rubbing may cause the torsional vibration of the shaft and the coupled vibration of the bending and torsion.The bending and torsion coupled vibration may cause the vibration response to be bifurcated,chaotic or even unstable.Therefore,the study of the bending-torsional coupled vibration of the rubbing rotor can provide theoretical guidance and application reference for the rotor bending and torsion coupled vibration analysis and fault diagnosis.In this paper,the dynamic characteristics of coupled bending and torsion caused by rotor rubbing are studied.The main research contents and results as follows:(1)Based on the five-degree-of-freedom model of beam element joints,the differential equations of beam element joints of bending and torsion coupled vibrations of rubbing rotors are derived.The dynamic analysis model of rotor rubbing and bending-torsion coupled vibration is established by using node motion differential equations.The mechanism and physical meaning of the coupled bending and torsion vibration of the rotor are expounded.(2)Through the numerical integration method,the dynamic characteristics of the response of bending and torsional vibration caused by rubbing under the influence of different parameters of the single-disc rotor are solved and the mutual influence analysis is carried out.The results show that the bending vibration of the rotor is the influence of the amplitude of the torsional vibration is more obvious.Once the rubbing occurs,even if the rubbing disappears quickly,the torsional vibration will continue for a long period of time;(3)Compared with the bending vibration,the torsional vibration is less damped,and under the excitation of the intermittent friction force of the rotor,the amplitude of the torsional vibration changes randomly and irregularly,and a lateral chaotic vibration phenomenon similar to the rotor occurs.(4)An early warning method for rotor instability under full-cycle rubbing is proposed.The diameter ratio of the inner and outer circle of the petal-like axis trajectory is used as the basis for determination.The smaller the ratio of the inner and outer diameters,the more likely the instability is.The simulation results show that: The bending vibration spectrum of the full-cycle rubbing will have a spectral component slightly higher than the fundamental frequency,which can be used as one of the characteristics for judging whether the rotor is rubbed or not;(5)Using the simple rotor model,the verification experiment of single point rubbing is carried out.The results show that the experimental results of the axial trajectory are consistent with the theoretical calculation results and trends,which verifies the accuracy of the theoretical model and numerical simulation.(6)Improved a test scheme for verifying the rotor rubbing and bending-torsional coupling vibration.The scheme uses the bending and torsional vibration(grating)test system to obtain the bending-torsional coupled vibration characteristics.The thesis analyzes and experimentally studies the bending-torsional coupled vibration caused by rubbing.The research results provide a theoretical and characteristic analysis reference for rotor-bending bending-torsional coupled vibration,and have practical reference significance for rotor rubbing fault diagnosis.