Abstract
Mechanical failures of a complex machine such as rotor widely used in severe conditions often require specialized knowledge, technical expertise, and imagination to prevent its rupture. In this paper, a model for analyzing excitation of a coupled lateral-torsional vibrations of a shaft system in an inviscid fluid is proposed. The model considers the recurrent contact of the vibrating shaft to a fixed stator. The simplified mathematical model of the rotor-stator system is established based on the energy principle. The dynamic characteristics of the fluid-rotor system are studied, and the features of rub-impact are extracted numerically and validated experimentally under the effects of the unbalance and the hydrodynamic forces. The main contribution of this article is in extraction and identification of the rub features in an inviscid medium which proved to be complex by the obstruction of the fluid and required the use of appropriate signal processing tools. The results through a synchrosqueezing wavelet transform indicated that the exciting fluid force could significantly attenuate the instability and amplitude of rubbing rotor. The experimental results demonstrated that for half the first critical speed, the subharmonic 1 / 2 × Ω and the irregular orbit patterns provide good indices for rub detection in an inviscid fluid of the rotating shafts. Finally, it is revealed that the instantaneous frequency extraction based on wavelet synchrosqueezing is a useful tool to identify the weak and hidden peak harmonics localised in the time-frequency maps of the fluid-rotor system.
Highlights
Science and technology have encountered complex problems with fluid-structure interaction
In a fluid-shaft interaction problem, where one solid structure interacts with a surrounding fluid; the extraction of specific features requires an excellent comprehension of the concerned fundamental physics
This paper proposed a coupled fluid-rotor interaction model to analyse the influences of hydrodynamic forces on the rotor-stator-rubbing defect in rotating machine by numerical and experimental methods
Summary
Science and technology have encountered complex problems with fluid-structure interaction. Kadyrov et al [3] studied the oscillations of a rigid cylinder in a cylindrical duct filled with an incompressible viscous fluid They used theoretical mathematical analysis results for the frequency subjected to different fluid parameters. Tchomeni and Alugongo [5] identified a complex rotor vibration system, induced by the oscillation of an International Journal of Rotating Machinery unbalanced rigid rotor in a viscous fluid under the parametric excitations, namely, rub and crack. They adopted a new algorithm called wavelet denoising technique to denoise the corrupted signal in extracting the feature of the damaged rotor system in a viscous fluid medium. Since the unbalance and rubbing faults are widely observed in the rotor system, distinguishing them is becoming more attractive
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