Advances in Rotordynamics

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Mechanical Engineering".

Deadline for manuscript submissions: closed (20 October 2019) | Viewed by 11237

Special Issue Editor

Special Issue Information

Dear Colleagues,

The dynamics of rotating machinery have been extensively investigated during the past century. To date, longer rotating shafts, higher rotating velocity, higher fluid pressure, and generally high performances are required. For this purpose, a deep understanding and a more accurate modeling of the rotating machinery dynamical behavior is needed, especially in terms of the resultant vibrations and stability issues.

The presence of fluid-lubricated journal bearings, squeeze-film dampers, rolling element bearings, fluid seals, impeller blades, or, in general, of destabilizing nonlinear forces requires more and more detailed theoretical models validated by using good-concept test rigs in order to provide a correct machine design and maintenance.

This Special Issue focuses on the latest advances in rotordynamics with particular reference to the modeling of nonlinear effects rising up with shaft rotation. The Editor welcome research and reviews on the nonlinear phenomena in rotordynamics, dynamic analysis and stability, fluid–structure interactions in rotordynamics, rotor vibration control using active and semi-active methods, condition monitoring, diagnostics and prognostics of rotors, fluid film bearings, magnetic bearings, rolling bearings, seals, and dampers.

Prof. Alessandro Ruggiero
Guest Editor

Manuscript Submission Information

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Keywords

  • Nonlinear dynamics
  • Stability
  • Fluid–structure interactions
  • Vibration control
  • Diagnostic
  • Fluid film bearings
  • Magnetic bearings
  • Rolling bearings
  • Seals
  • Dampers

Published Papers (3 papers)

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Research

29 pages, 8580 KiB  
Article
Application of Non-Symmetric Bending Principles on Modelling Fatigue Crack Behaviour and Vibration of a Cracked Rotor
by Joseph Spagnol, Helen Wu and Chunhui Yang
Appl. Sci. 2020, 10(2), 717; https://doi.org/10.3390/app10020717 - 20 Jan 2020
Cited by 13 | Viewed by 2698
Abstract
Many studies on cracked rotors developed crack breathing models that assume that the neutral axis of bending always remains horizontal for simplification. These models may generate significant discrepancies and thus there is a need to develop more sophisticated models to look into the [...] Read more.
Many studies on cracked rotors developed crack breathing models that assume that the neutral axis of bending always remains horizontal for simplification. These models may generate significant discrepancies and thus there is a need to develop more sophisticated models to look into the shifting of the neutral axis for a cracked rotor. Herein, a case study on the shifting of the neutral axis for a cracked rotor is firstly performed by using a three-dimensional finite element model to confirm that the neutral axis becomes inclined as the cracked rotor rotates. In response to this finding, non-symmetric bending principles are used to develop a new crack breathing model which has the advantage of being able to numerically calculate the inclination angle of the neutral axis. When compared to an existing crack model in the literature that assumes that the neutral axis remains horizontal (HNA model), the proposed model is relatively less stiff in bending as a result of an overall lower area moment of inertia. Using the harmonic balance method, a two-dimensional finite element vibration model of a cracked rotor was devised by employing the proposed crack breathing model and the HNA model for validation. It can be found that the vibration amplitudes of the first three frequency components are similar between the two models for shallow cracks and significantly differed for deep cracks. This result highlights the potential of the proposed model for modelling and detecting mid-to-late-stage cracks in rotors. Full article
(This article belongs to the Special Issue Advances in Rotordynamics)
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13 pages, 6049 KiB  
Article
Experimental Analysis on Skid Damage of Roller Bearing with the Time-Varying Slip and Temperature Distribution
by Junning Li, Jiafan Xue, Ka Han, Qian Wang and Wuge Chen
Appl. Sci. 2020, 10(1), 9; https://doi.org/10.3390/app10010009 - 18 Dec 2019
Cited by 8 | Viewed by 3163
Abstract
Skid damage affects the performance of aviation bearing, which covers different disciplines in tribology, thermology, materials science, dynamics, et al. In this manuscript, a novel horizontal skid damage test rig of a rolling bearing with higher rotation accuracy and better linear contact was [...] Read more.
Skid damage affects the performance of aviation bearing, which covers different disciplines in tribology, thermology, materials science, dynamics, et al. In this manuscript, a novel horizontal skid damage test rig of a rolling bearing with higher rotation accuracy and better linear contact was built, which can simulate the rolling/sliding contact between the roller and inner ring. Combining with temperature, load, speed, slip, and surface microscopy, the skid damage mechanism of roller bearings was analyzed from a multi-information perspective. Meanwhile, the dynamic lubrication failure process of the contact pair in rolling bearings with the time-varying slip and temperature distribution was revealed. The effect of different radial loads, inner ring speeds, lubricating oil quantities, and states of cleanliness on the time-varying characteristics of the temperature and the slip of the rolling bearing were obtained. Among them, the radial load has the greatest influence on the slip rate of rolling bearing. In addition, the test results show that the skid damage under extremely light load is the comprehensive effect of adhesive wear and thermal failure. Full article
(This article belongs to the Special Issue Advances in Rotordynamics)
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19 pages, 8141 KiB  
Article
Numerical Study on the Critical Frequency Response of Jet Engine Rotors for Blade-Off Conditions against Bird Strike
by Saeed Badshah, Ahsan Naeem, Amer Farhan Rafique, Ihsan Ul Haq and Suheel Abdullah Malik
Appl. Sci. 2019, 9(24), 5568; https://doi.org/10.3390/app9245568 - 17 Dec 2019
Cited by 11 | Viewed by 3984
Abstract
Vibrations are usually induced in aero engines under their normal operating conditions. Therefore, it is necessary to predict the critical frequencies of the rotating components carefully. Blade deformation of a jet engine under its normal operating conditions due to fatigue or bird strike [...] Read more.
Vibrations are usually induced in aero engines under their normal operating conditions. Therefore, it is necessary to predict the critical frequencies of the rotating components carefully. Blade deformation of a jet engine under its normal operating conditions due to fatigue or bird strike is a realistic possibility. This puts the deformed blade as one of the major safety concerns in commercially operating civil aviation. A bird strike introduces unbalanced forces and non-linearities into the engine rotor system. Such dynamic behavior is a primary cause of catastrophic failures. The introduction of unbalanced forces due to a deformed blade, as a result of a bird strike, can change the critical frequency behavior of engine rotor systems. Therefore, it is necessary to predict their critical frequencies and dynamic behavior carefully. The simplified approach of the one-dimensional and two-dimensional elements can be used to predict critical frequencies and critical mode shapes in many cases, but the use of three-dimensional elements is the best method to achieve the goals of a modal analysis. This research explores the effect of a bird strike on the critical frequencies of an engine rotor. The changes in critical mode shapes and critical frequencies as a result of a bird strike on an engine blade are studied in this research. Commercially available analysis software ANSYS version 18.2 is used in this study. In order to account for the material nonlinearities, a Johnson Cook material model is used for the fan blades and an isotropic–elastic–plastic–hydrodynamic material model is used for modeling the bird. The bird strike event is analyzed using Eularian and smoothed particle hydrodynamics (SPH) techniques. A difference of 0.1% is noted in the results of both techniques. In the modal analysis simulation of the engine rotor before and after the bird strike event, the critical failure modes remain same. However, a change in the critical frequencies of the modes is observed. An increase in the critical frequencies and excitation RPMs (revolution per minute) of each mode are observed. As the mode order is increased, the higher the rise in critical frequency and excitation RPMs. Also, a change in the whirl direction of the different modes is noted. Full article
(This article belongs to the Special Issue Advances in Rotordynamics)
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