Research On Vibration Characteristics Of Rotor System With Loose Disc

This dissertation was supported by a grant from National Natural Science Foundation of China(No.51675258,51265039,51075372),and The State Key Laboratory of Mechanical Transmissions of Chongqing University(SKLMT-KFKT-201514).Because there are more and more faults of rotors with loose disc in the actual project,lack of theoretical support.This project studied the vibration characteristics of the rotor system with loose disc through dynamic modeling,and experimental methods,and achieved a series of innovative results with applied value.This study contents are mainly as follows:1.The failure of the contact interface of the disk and shaft is the root cause of the faults of rotors with loose disc.The accurate analysis of the interaction force of the disk shaft is the key to establish the rotor system model with loose disc.In this paper,for the different degrees of looseness,a contact model of the clearance-fitting was established based on the Hertz contact theory,a contact model of the lack of interference force was established based on the Hertz contact theory and the GW model.The functional relationships of radial force,tangential force and friction force are analyzed.Lay the foundation for the rotor system dynamic modeling with loose disc.2.When there is a gap between the shaft and the disc,it is already a serious situationt and also a typical situation of the fault of rotors with loose disc.Here,a dynamic model of a rotor system with the clearance between the shaft and the disc is established.The vibration characteristics of the system are discussed and verified by experiments.The results show that the rotation state of the disc is influenced by the shaft speed,the elastic modulus of the disc and shaft,the clearance between the disc and shaft,the damping of the shaft,the damping of the disc,the rotation damping of the disc,and the initial rotation speed of the disc.There may be a vibration phenomenon on the shaft,which may be caused by the vibration of the shaft,or it may be caused by the collision of the shaft.High frequency multiplication occurs in the frequency spectrum chart,and the frequency of high frequency multiplication becomes higher when the speed difference of the shaft and disc is bigger.The distance between the shaft and the disc tends to be stable as the rotation speed of the disc becomes stable.The rubbing of the disc and the shaft causes the sawtooth phenomenon in the trajectory of the disc and the shaft.The sawtooth direction changes with the direction of the rubbing force of the disc and the shaft,and the sawtooth phenomenon is more obvious on the disc.3.The lack of cohesive force of the disc and the shaft is the initial stage of the rotor with loose disc,and the study of the initial stage is more practical.Here,the rotor dynamics model with insufficient coordinating force between the disc and the shaft was established.The vibration characteristics of the system were discussed and verified by experiments.The results show that the rotation state of the disc is influenced by the shaft speed,the contact stiffness,the clearance between the disc and shaft,the damping of the disc,the rotation damping of the disc,and the vibration characteristics is more stable than the rotor system with gap between the shaft and the disc.The frequency chart in the X direction of the disc contains the rotation frequency component of the disc and the rotation frequency component of the shaft,and no disk collision frequency was found.When the rotation speed of the disc and the shaft are same,the collision frequency is mainly composed of one frequency multiplication component and contains tiny high frequency multiplication components.When the rotation speed of the disc and the shaft is close,the vibration of the disc appears a vibration phenomenon,and a periodical similar vibration phenomenon occurs in the waveform of the distance between the disc and the shaft,and the collision frequency is mainly composed of a low frequency and a weak high frequency component.When the rotation speed of the disc and the shaft is differ greatly,the collision frequency is mainly composed of one frequency multiplication,and contains a weak high frequency multiplication component and a low frequency multiplication component.With the reduction of the relative speed of the disc,the trajectory of the turntable changes from "circular" to "inner figure" and then to "circle".The inner circle of "inner figure" gradually becomes smaller and then gradually becomes larger.The outer circle of the "character" has always been smaller.4.When there is a gap between the disc and the shaft,the whirl of the oil film will affect the trajectory of the shaft,thus affecting the rubbing of the disc and the shaft.The rubbing of the disc and the shaft will greatly disturb the whirl of the oil film.Here,rotors with loose disc system model with non-steady-state oil film force is established,and the motion of the disc under two kinds of support conditions including oil film force and no oil film force was comparatively analyzed,the effects of the size of the oil film gap on the trajectory and vibration characteristics at the bearing and the center of the shaft were studied.The results show that when the dimensionless shaft speed of the rotor system irrespective of the film force is 0.8,the speed of the disc enters the high speed state,when the dimensionless shaft speed of the rotor system considering the film force is 1.3.the speed of the disc enters the high speed state.When 0<Det1<8,8?Det1<180,180?Det1?300,the trajectory of the bearing end undergoes a similar periodic motion state,a chaotic state,and a similar periodic motion state,and the shape becomes more and more slender,and the trajectory of the center of the shaft is like a continuously rotating fan,no obvious change.The vibration frequency of the bearing end has the rotation frequency of the disc and the shaft.When the movement trajectory is in a chaotic state,other frequency multiplication components that are weaker will appear.The vibration frequencies at the center of the shaft mainly include the rotating frequency of the disc and the shaft,and the particularly high frequency of collision of the shaft,and sometimes a weak low frequency multiplication occurs.The harmonic amplitude of the rotating frequency of the disc is basically the same at the bearing and the center of the shaft.With the increase of the oil film gap,it first rises rapidly,then drops rapidly,and then gradually becomes stable.The amplitude of the harmonics of the rotation frequency of the shaft at the bearing and the shaft center is reversed,when the oil film gap is small,the amplitude at the bearing rises rapidly,and the amplitude at the center of the rotating shaft drops rapidly,when the oil film gap is large,it gradually becomes stable.High harmonic harmonic amplitude oscillates between 1.6 and 2.5.