Dynamic analysis of rotor's radial rub-impact in full degrees of freedom accounting for turborotor's non-linear clearance-excitation force

Abstract

Dynamic behaviours of rotor's radial rub-impact in the presence of turborotor's non-linear clearance-excitation force are analysed by numerical simulations in all the six degrees of freedom of a rotor, which represent all the three kinds of vibrations: lateral, axial, and torsional vibrations. Results are displayed by bifurcation diagrams, waveforms, frequency spectrums, orbits, Poincare maps, and frequency waterfalls. Much more complicated dynamic behaviours are represented in these results. Compared with the case of pure rub-impact that does not involve any other non-linear elements, the stable motion regime is largely reduced, correspondingly the rotating speed threshold of rub-impact is also reduced slightly, and the complicated motion patterns appear in the early stage of rub-impact. Thick superharmonics and subharmonics emerge in axial and torsional vibrations, respectively, which are the typical characteristics of a chaotic motion. This indicates that the main motion pattern of the system is chaos. In the full range of investigated speed, the lateral vibrations nearly take on a sole synchronous component, and the axial vibration shows very rich superharmonic components, which mainly scatter in three thick superharmonic bands that approach to three fixed frequency components with their amplitudes growing as the rotating speed increases. The torsional vibration demonstrates rich subharmonics near half-time-frequency components, and the amplitudes of which increase with rotating speed. These conclusions are of great significance to the rotordynamic design and fault diagnostics of turborotor systems.

Vibration analysis of coupled bending-torsional rotor-bearing system for hydraulic generating set with rub-impact under electromagnetic excitation

“…The fourth-order Runge-Kutta method is used for the integration of Eq. (19), due to the strong nonlinear characteristics of the system presented in this paper. In order to eliminate the influence of free vibration, the results of former 1000 periods are abandoned, and the last 100 periods are reserved for analysis.…”

“…Furthermore, the research object has also been developed from single bending vibration [2][3][4][5][6][7][8][9][10][11][12][13][14][15] to coupled bending-torsional oscillation [16][17][18][19][20][21][22][23], gradually. Edwards et al [16] were treated as the first scholar introducing the torsional degree of freedom (DOF) into the vibration analysis of rotor system with rub-impact.…”

“…Sun et al [18] selected single Jeffcott rotor model as the object and discussed the effect of considering or not considering bending-torsional coupling vibration on the dynamic characteristics of impact-rub rotor system, by means of chaos and bifurcation theory. Also built upon the Jeffcott rotor model, the six DOFs model including lateral, axial and torsional vibrations was adopted by Yuan et al [19] to investigate the dynamic behavior of coupled lateral-torsional rotor system with rub-impact, in the presence of turbo rotor's nonlinear clearance-excitation force. Patel et al [20] set up a mathematical model consisting of interacting vibratory systems of rigid rotor and viscoelastically suspended stator considering coupled bending-torsional vibration, and meanwhile, the stator motion was brought into the system differential equation.…”

“…However, whether the single bending oscillation or coupled bending-torsional vibration is chosen as the starting point of study, the basic objects of model establishment among the literatures described above were mainly focused on the high-speed, horizontal rotor structure and single rubbing fault [1][2][3][4][5][6][7][8][9][15][16][17][18][19][20][21][22][23], while the reports about low-speed, vertical systems such as hydraulic generating set were insufficient, and the nonlinear dynamic analyses of corresponding rub-impact rotor systems accompanied by other faults were more limited [10][11][12][13][14].…”

Rotordynamic Analysis of Asymmetric Turbofan Rotor Due to Fan Blade-out Event with Contact-Impact Rub Loads

“…In the past, researchers have studied the dynamic stability of a typical rotor shaft in many different forms by varying parameters such as internal damping, torque, tip-rub, pulsating axial force etc [10][11][12][13][14][15][16][17][18][19][20][21][22] . However in general, these studies invariably consider the bladed-disk American Institute of Aeronautics and Astronautics assembly as rigid with entire flexibility of the dynamical system limited to the shaft material only.…”