Abstract
A nonlinear coupled dynamic model of a rod fastening rotor under rub-impact and initial permanent deflection was developed in this paper. The governing motion equation was derived by the D’Alembert principle considering the contact characteristic between disks, nonlinear oil-film force, rub-impact force, unbalance mass, etc. The contact effects between disks was modeled as a flexural spring with cubical nonlinear stiffness. The coupled nonlinear dynamic phenomena of the rub-impact rod fastening rotor bearing system with initial permanent deflection were investigated by the fourth-order Runge-Kutta method. Bifurcation diagram, vibration waveform, frequency spectrum, shaft orbit and Poincaré map are used to illustrate the rich diversity of the system response with complicated dynamics. The studies indicate that the coupled dynamic responses of the rod fastening rotor bearing system under rub-impact and initial permanent deflection exhibit a rich nonlinear dynamic diversity, synchronous periodic-1 motion, multiple periodic motion, quasi-periodic motion and chaotic motion can be observed under certain conditions. Larger radial stiffness of the stator will simplify the system motion and make the oil whirl weaker or even disappear at a certain rotating speed. With the increase of initial permanent deflection length, the instability speed of the system gradually rises, and the chaotic motion region gets smaller and smaller. The corresponding results can provide guidance for the fault diagnosis of a rub-impact rod fastening rotor with initial permanent deflection and contribute to the further understanding of the nonlinear dynamic characteristics of the rod fastening rotor bearing system.
Highlights
The rotor-stator rub-impact is one of the most typical faults in rotor bearing systems, and it will result in strong vibration and even catastrophic accidents of the machines if not caught quickly.the clearance between rotor and stator is inevitable in rotating machines
The results indicated that the dynamic responses were quite different from those of radial ones
The period of the dimensionless system is 2π; the integral step length of each period is 1/100; the calculation is 200 periods; we of the effective data pointsas is the Bifurcation diagram, vibration waveform, frequency spectrum, choose the last 100 periods effective analysis data; and the number of the effective data points orbitBifurcation and Poincaré map are presented to illustrate the nonlinear dynamic of system isshaft diagram, vibration waveform, frequency spectrum, shaftphenomena orbit and Poincaré as follows
Summary
The rotor-stator rub-impact is one of the most typical faults in rotor bearing systems, and it will result in strong vibration and even catastrophic accidents of the machines if not caught quickly. It is essential to analyze the nonlinear coupled dynamic behavior of the rod fastening rotor under rub-impact and initial permanent deflection. Xiang et al [7] modeled an asymmetric double-disc rotor-bearing system under rub-impact and oil-film forces and studied the coupled nonlinear dynamics of the system. Wang et al [8] investigated the dynamic response of rotor systems with sudden unbalance and rub-impact caused by blade loss using theoretical and experimental methods. Sun et al [14] modeled a bending-torsional coupling rub-impact rotor system and analyzed the nonlinear dynamic characteristics of the system. The existence of fiction force during rotor-stator rub-impact will generate the coupled effect on lateral and torsional motion. The effect of force on the critical speeds of a rod fastening rotor was studied through experimental methods [22].
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