Post-resonance backward whirl in accelerating cracked rotor systems

AL-Shudeifat, Mohammad A.; Shiryayev, Oleg; Hammadi, Fatima Al; Alzarooni, Tariq; Nataraj, C.

doi:10.1016/j.euromechsol.2020.104039

Cited by 12 publications

(4 citation statements)

References 27 publications

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“…In Fig. 9 a it can be observed that Po-BW precession takes place immediately following the FW resonance curve and the minima of subsequent local transient peaks (similar findings were obtained in earlier works 45 , 57 for single and double-disk systems with an open crack model) at the frequency range of . By applying the wavelet transform to the whirl response, it is interesting to note that the wavelet spectrum indicates that the frequency content of Po-BW nearly overlaps with the shaft rotational frequency as shown in Fig.…”

Section: Simulation Results and Discussionsupporting

confidence: 86%

Post-resonance backward whirl analysis in cracked overhung rotors

Alzarooni

AL-Shudeifat

Shiryayev

et al. 2022

Sci Rep

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Overhung rotors usually exhibit recurrent transitions through critical whirl rotational speeds during startup and coast down operations, which significantly differ from their steady-state whirl responses. The presence of angular acceleration results in a linear-time-varying (LTV) system, which, although technically linear, still presents complexities often evinced by a nonlinear system. In general, backward whirl zones can either precede the critical forward whirl speed (termed as pre-resonance backward whirl, Pr-BW), or immediately follow the critical forward whirl speed (termed as post-resonance backward whirl, Po-BW). The Po-BW in the whirl response of a cracked overhung rotor with a breathing crack is studied here as distinct from that of geometrically symmetric configurations of other rotor systems. The equations of motion from the finite element (FE) model of an overhung rotor system with a breathing crack are numerically integrated to obtain the whirl response. The transient whirl responses with different bearing conditions are thoroughly investigated for excitation of Po-BW. The Po-BW zones of rotational speeds are determined via the wavelet transform method and full spectrum analysis (FSA) and applied to signals with added noise. The results of this work confirm the excitation of the Po-BW in cracked overhung rotors and confirm the robustness of the employed methods.

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Section: Simulation Results and Discussionsupporting

confidence: 86%

Post-resonance backward whirl analysis in cracked overhung rotors

Alzarooni

AL-Shudeifat

Shiryayev

et al. 2022

Sci Rep

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“…the offset disk in the present paper) and the bearing is both primary sources of rotor nonlinear vibration, which may provoke the intricate dynamics behavior of the rotor system. [10][11][12][13] Hence, further study of the dynamic properties of bolted joint rotor-bearing systems with an unbalanced offset disk is of great guiding significance to the structure design, dynamic response prediction, as well as health detection of aero-engine rotor systems.…”

Section: Introductionmentioning

confidence: 99%

A parametric study of a bolted joint rotor-bearing system with an unbalanced offset disk

Zhu,

Li,

Wen

et al. 2024

Proceedings of the Institution of Mechanical Engineers, Part C:

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The turbine disk is the core component of an aero-engine whose position and unbalanced force seriously affect the vibration stability of the rotor system. Ignoring the influence of the offset disk may result in discrepancies between real-world scenarios and numerical simulation results. The present work aims to explore the nonlinear dynamic characteristics of rotor systems under the coupling of bolted joint and offset disk effect, as well as the influence of offset disk position and its unbalanced force on the system dynamic behavior and bending stiffness of bolted joint also investigated. The governing equations of a bolted joint rotor-bearing system with an offset disk were established based on the finite element method and derived as a dimensionless expression in the first. Then, the Newmark method was employed for the numerical solution of the motion equations, and then a bifurcation analysis of the rotor system and the evolution of bending stiffness for the bolted joint was studied. Next, by comparing the frequency-amplitude diagrams, bifurcation diagrams, time history, shaft obits, and bending stiffness diagrams of the bolted joint, the effect of the offset disk position and its unbalanced force on the nonlinear system dynamic was revealed. Finally, an experimental study was carried out to verify the numerical result using the bolted joint rotor test rig with an offset disk. The analysis result of the present work can provide theoretical guidance for structure design and stability analysis on the aero-engine.

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“…In several studies, the transient whirl response during startup operations in which angular acceleration rate was considered in the equations of motion has been well-studied for cracked rotor systems with open and breathing crack models in [9][10][11][12][13][14][15][16]. In [9], experimental investigations have been conducted for analyzing the transient vibrational whirl behavior during the passage through the critical rotational speed.…”

Section: Introductionmentioning

confidence: 99%

“…The transient whirl response was investigated to distinguish between the effect of the transverse and slant crack models in [10,11] and between the responses of transverse crack and the shaft misalignment in rotor systems in [12]. Recently, a new backward whirl phenomena named as a post-resonance backward whirl has been captured in the transient response of accelerated cracked rotor systems immediately after the passage through the critical forward whirl speeds [13][14][15]. This post-resonance backward whirl was found to be associated with an abrupt reduction in whirl amplitudes in the vicinity of local minima of whirl amplitudes.…”

Section: Introductionmentioning

confidence: 99%

Negative Potential Energy Content Analysis in Cracked Rotors Whirl Response

AL-Shudeifat

Alhammadi

2021

Preprint

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Appearance of fatigue cracks in rotor systems mainly affects their stiffness content. The stability of such systems at steady-state running is usually analyzed by using the Floquet’s theory. Accordingly, the instability zones of rotational speeds are dominated by negative stiffness content in the whirl response in the vicinity of critical rotational speeds. Consequently, an effective stiffness measure is introduced here to analyze the effect of the crack and the unbalance force vector orientation on the intensity of negative potential and stiffness content in the whirl response. The effective stiffness expression is obtained from the direct integration of the equations of motion of the considered cracked rotor system. The proposed effective stiffness measure is applied for steady-state and transient operations using the Jeffcott rotor model with open and breathing crack models. The intensity of negative potential and stiffness content in the numerical and experimental whirl responses is found to be critically depending on the propagation level of the crack and the unbalance force vector orientation. Therefore, this can be proposed as a crack detection tool in cracked rotor systems that either exhibit recurrent passage through the critical rotational speeds or steady-state running.

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Post-resonance backward whirl in accelerating cracked rotor systems

Cited by 12 publications

References 27 publications

Post-resonance backward whirl analysis in cracked overhung rotors

Post-resonance backward whirl analysis in cracked overhung rotors

A parametric study of a bolted joint rotor-bearing system with an unbalanced offset disk

Negative Potential Energy Content Analysis in Cracked Rotors Whirl Response

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