Oil whirl, oil whip and whirl/whip synchronization occurring in rotor systems with full-floating ring bearings

Journal Bearings are excellent bearings due to their large load carrying capacity and favorable damping characteristics. However, Journal bearings are known to be prone to instabilities. The oil whirl and oil whip instabilities limit the rotor maximum rotating speed. In this paper, a novel approach is used to control the Journal bearing (JB) instability. An Active Magnetic Bearing (AMB) is used to overcome the JB instability and to increase its range of operation. The concept is quite simple: rather than using the AMB as a load carrying element, the AMB is used as a controller only, resulting in a much smaller and more efficient AMB. The load carrying is done by the Journal bearings, exploiting their excellent load carrying capabilities, and the JB instability is overcome with the AMB. This results in a combined AMB/JB that exploits the advantages of each device, and eliminates the deficiencies of each bearing. Different controllers for the AMB to control the JB instability are examined and compared theoretically and numerically. The possibility of collocating the JB and the AMB is also examined. The results illustrate the effectiveness of the concept.

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Sub-Synchronous Shaft Oscillations due to Oil Supply

Volume 8: 30th Conference on Mechanical Vibration and Noise ◽

10.1115/detc2018-86029 ◽

2018 ◽

Author(s):

Luboš Smolík ◽

Jan Rendl ◽

Jan Stifter ◽

Milan Omasta

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Computational Analysis ◽

The Finite Element Method ◽

Test Rig ◽

Oil Supply ◽

Oil Whip ◽

Oil Whirl ◽

Multi Body ◽

Element Method

This paper aims at the modelling and investigation of unstable journal bearing with an emphasis on instabilities such as oil-whirl or further induced oil-whip. For this reason, a test rig for the investigation of these phenomena was built. Geometry, parameters and operating cases of the rig are described in detail in the presented paper. Computational analysis of the test rig was performed using two methods — the finite element method and a multi-body approach. The calculations of pressure distribution in journal bearings were also performed applying two methods — the finite difference method and the finite element method. The results of the analysis are properly introduced and discussed at the end of this paper. The results suggest that a yet unknown sub-synchronous component may appear under specific conditions. The component typically appears at frequency 0.9–0.98 of shaft speed and is likely caused by a location of a bore for oil supply.

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Theoretical and Experimental Study on Stability of Rotor System With Cylindrical Bearing and Elliptical Bearing

Volume 6: Structures and Dynamics, Parts A and B ◽

10.1115/gt2010-23120 ◽

2010 ◽

Author(s):

Yongliang Wang ◽

Zhansheng Liu ◽

Guanghui Zhang ◽

Liquan Sun

Keyword(s):

Turbine Rotor ◽

Group Model ◽

Dynamic Tests ◽

Test Rig ◽

Turbine Generator ◽

Nonlinear Characteristics ◽

Rotor Systems ◽

Oil Whirl ◽

Different Types ◽

Rotor Model

Dynamic characteristics of a 600MW steam turbine rotor model supported by cylindrical bearings and elliptical bearings were investigated respectively. Differences between the linear and nonlinear characteristics of rotor-bearing systems were studied by numerical simulations, and the performances of rotor systems using different bearings were also presented. Dynamic tests were performed on the 600MW turbine generator group model test rig, while sustained by different types of bearings, to study the oil whirl and whip phenomenon. Comparisons of the numerical results with experimental data show that the nonlinear model is more accurate than the linear model, and the elliptical bearing has the advantage of better dynamic stability over cylindrical bearings.

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Influence of Lubricant Film Cavitation On the Vibration Behaviour of a Semi-Floating Ring Supported Turbocharger Rotor with Thrust Bearing

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4053266 ◽

2021 ◽

Author(s):

Christian Ziese ◽

Cornelius Irmscher ◽

Steffen Nitzschke ◽

Christian Daniel ◽

Elmar Woschke ◽

...

Keyword(s):

Squeeze Film ◽

Two Phase ◽

Hydrodynamic Bearing ◽

Lubricating Film ◽

Oil Whip ◽

Oil Whirl ◽

Bearing Stiffness ◽

Run Up ◽

Stiffness And Damping ◽

The Impact

Abstract This contribution investigates the influence of outgassing processes on the vibration behaviour of a hydrodynamic bearing supported turbocharger rotor. The examined rotor is supported radially by floating rings with outer squeeze-film damping and axially by thrust bearings. Due to the highly non-linear bearing properties, the rotor can be excited via the lubricating film, which results in sub-synchronous vibrations known as oil-whirl and oil-whip phenomena. A significant influence on the occurrence of oil-whip phenomena is attributed to the bearing stiffness and damping, which depend both on the kinematic state of the supporting elements and the thermal condition as well as the occurrence of outgassing processes. For modelling the bearing behaviour, the Reynolds equation with mass-conserving cavitation regarding the two-phase model and the 3D energy as well as heat conduction equation is solved. To evaluate the impact of cavitation, run-up simulations are carried out assuming a fully (Half-Sommerfeld) or partially filled lubrication gap. The resulting rotor responses are compared with the shaft motion measurement. Also, the normalized eccentricity, the minimum lubricant fraction and the thermal bearing condition are discussed.

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Nonlinear Analysis of Rotor-Stator-Bearing System Unsteady Oil Film Force

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.341-342.395 ◽

2013 ◽

Vol 341-342 ◽

pp. 395-399

Author(s):

Gui Zhen Liu ◽

Ying Yu ◽

Bang Chun Wen

Keyword(s):

Dynamics Model ◽

Oil Film ◽

Oil Whip ◽

Film Instability ◽

Oil Whirl ◽

Amplitude Spectra ◽

Axis Orbit ◽

Speed Change ◽

Effective Diagnosis ◽

Bearing System

According to the LaGrange energy equation, the establishment of the unsteady oil film force of the rotor - stator - bearing system dynamics model, the application of numerical method, the system with the speed change time domain waveforms, amplitude spectra and Axis Orbit, the results show that: the unsteady oil film force and speed of change is closely related to changes in the process of oil film force oil whirl Oil Whip. Provide a theoretical basis for effective diagnosis of rotor - stator - bearing oil film instability fault research.

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A New Approach to Solve for Oil-Whirl and Oil-Whip Limit-Cycle Response

Proceedings of the 9th IFToMM International Conference on Rotor Dynamics - Mechanisms and Machine Science ◽

10.1007/978-3-319-06590-8_81 ◽

2015 ◽

pp. 995-1008

Author(s):

Min Zhang

Keyword(s):

Limit Cycle ◽

New Approach ◽

Oil Whip ◽

Oil Whirl

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Analysis and Experimental Study on Stability of Nonlinear Rotor-Bearing System

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.236-238.2626 ◽

2011 ◽

Vol 236-238 ◽

pp. 2626-2629

Author(s):

Wei Dong Gu ◽

Yong Liang Wang ◽

Bo Fang ◽

Zhan Sheng Liu ◽

Wen Hu Huang

Keyword(s):

Finite Element Method ◽

Experimental Study ◽

Test Rig ◽

Model Simulations ◽

Oil Whip ◽

Film Instability ◽

Oil Whirl ◽

Rotor Bearing ◽

Practical Model ◽

Bearing System

The paper established the model of the practical Model test rig rotor-bearing system using finite element method, and discusses the phenomena of oil whirl and oil whip occurred in fluid lubricated bearing. The characteristics of stability of the nonlinear rotor-bearing system were numerically studied under different unbalance and different parameter of bearings, the model simulations are compared with measurements at the test rig, which can provide the theoretical reference for forecasting malfunction of oil film instability.

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Reliability Analysis for Rotor System with Oil Whip and Resonance Based on Frequency

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.544.110 ◽

2012 ◽

Vol 544 ◽

pp. 110-114

Author(s):

Chang Qing Su ◽

Yi Min Zhang

Keyword(s):

Failure Probability ◽

Integration Method ◽

Random Perturbation ◽

Rotor System ◽

Reliability Design ◽

Rotor Systems ◽

System A ◽

Oil Whip ◽

General Systems ◽

Engineering Problems

Parameter uncertainty of general systems is inherent in most engineering problems. Based on the regularity of oil whip and resonance for rotor system, the reliability problem of rotor system with oil whip and resonance is studied by applying random perturbation technology and reliability theory considering the correlation of the multi-order natural frequency. The reliability mode and the failure probability of rotor systems are defined. The second-order joint failure probability is obtained by using the numerical integration method. The presented method provided the theoretic basis for the reliability design of the rotor system. A numerical example demonstrated that the proposed method is effective.

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Oil Whip and Unstable Whirling in Anisotropic Rotors on Lubricated Bearings

Volume 3: Dynamic Systems and Controls, Symposium on Design and Analysis of Advanced Structures, and Tribology ◽

10.1115/esda2006-95337 ◽

2006 ◽

Cited By ~ 1

Author(s):

Giancarlo Genta ◽

Nicola Amati

Keyword(s):

Time Domain ◽

Real World ◽

Chaotic Motion ◽

Dynamic Behaviour ◽

Simplified Models ◽

Complex Behaviour ◽

Oil Whip ◽

Oil Whirl ◽

The Stability ◽

Rotor Model

The dynamics of rotors running on lubricated bearings is complex. While the linearized analysis allows to study the stability in the small and phenomena like oil whirl and oil whip, more complex behaviour, that may include chaotic motion, requires a fully nonlinear analysis. Since lubricated bearings behave like anisotropic supports, complex whirling pattern can be expected when the rotor is anisotropic. The aim of the present paper is to investigate to what extent the anisotropy of the rotor affects its dynamic behaviour. In particular, the interactions between the instability ranges due to rotating anisotropy and to oil whip are searched. The rotor models are built using DYNROT FEM code to build the basic rotor model and to obtain linearized solutions. The linear model of the rotor is then mated to nonlinerar bearing models and integrated numerically in time. Time domain results allow to draw some general conclusions applicable to simplified models as well as to real-world rotors.

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Some Experiments on Oil Whirl and Oil Whip

Volume 6: Turbo Expo 2004 ◽

10.1115/gt2004-53644 ◽

2004 ◽

Author(s):

A. El-Shafei ◽

S. H. Tawfick ◽

M. S. Raafat ◽

G. M. Aziz

Keyword(s):

Twentieth Century ◽

Critical Speed ◽

Journal Bearings ◽

Flexible Rotor ◽

Angular Misalignment ◽

Oil Whip ◽

Early Twentieth Century ◽

Oil Whirl

The oil whirl and oil whip phenomena are well known since the early twentieth century. However, there is a lot of confusion on the parameters that affect the onset of instability. In this study, we investigate the onset of instability on a flexible rotor mounted on two plain cylindrical journal bearings. The rotor is run through the first critical speed, the instability, and the second critical speed. Tests are conducted at various unbalance levels, pressures, and misalignment conditions on the coupling. It is shown that, by far, the misalignment of the coupling is the parameter that is most effective on the onset of instability. In particular angular misalignment resulted in the smoothest rotor response.

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