Prediction of oil whirl initiation in journal bearings using multi-sensors data fusion

An analysis of the self-excited oscillations of a rotor supported in fluid film journal bearings is presented. It is shown that Hopf bifurcation theory may be used to investigate small-amplitude periodic solutions of the nonlinear equations of motion for rotor speeds close to the speed at which the steady-state equilibrium position becomes unstable. A numerical investigation supports the findings of the analytic work.

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Controlling Journal Bearing Instability Using Active Magnetic Bearings

Volume 5: Turbo Expo 2007 ◽

10.1115/gt2007-28059 ◽

2007 ◽

Cited By ~ 5

Author(s):

A. El-Shafei ◽

A. S. Dimitri

Keyword(s):

Journal Bearing ◽

Magnetic Bearing ◽

Journal Bearings ◽

Active Magnetic Bearing ◽

Rotating Speed ◽

Damping Characteristics ◽

Oil Whip ◽

Novel Approach ◽

Oil Whirl ◽

Load Carrying

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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Oil whirl in journal bearings under no load conditions

Wear ◽

10.1016/0043-1648(73)90135-x ◽

1973 ◽

Vol 26 (2) ◽

pp. 207-217 ◽

Cited By ~ 9

Author(s):

E. Capone

Keyword(s):

Journal Bearings ◽

Oil Whirl ◽

Load Conditions

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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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Active Self-Excited Vibration Elimination of Rotating Machine With an Electromagnetic Exciter

Volume 1: 22nd Biennial Conference on Mechanical Vibration and Noise, Parts A and B ◽

10.1115/detc2009-86405 ◽

2009 ◽

Cited By ~ 1

Author(s):

Chen-Chao Fan ◽

Min-Chun Pan

Keyword(s):

Journal Bearings ◽

Rotor System ◽

Stable Method ◽

Rotating Machine ◽

Oil Whip ◽

Control Scheme ◽

Oil Whirl ◽

Excited Vibration ◽

Load Carrying ◽

Auxiliary Device

Journal bearings are commonly used in large rotary machineries because they have excellent mechanical and geometric properties as well as large load-carrying capacities. Nevertheless, the oil whirl and oil whip instabilities limit their applications due to their insufficient stiffness at high running speeds. This paper presents a method to increase the stiffness of a rotating machine using an electromagnetic exciter (EE), which can raise the threshold of instability of the rotating machine and eliminate fluid-induced instability. The EE is a controllable auxiliary device that can provide additional stiffness to the bearings to increase the operating ranges of a rotating machine, while the journal bearings act as load-carrying devices. Together, the EE complements the JB to stiffen the rotor system and raise the threshold of instability. A simple control scheme is used to calculate the amount of supplemental stiffness supplied by the EE. The experimental results demonstrate that the oil whirl and oil whip instabilities of the rotating machine can be eliminated effectively, even at higher running speeds. The advantage of the EE is to offer a faster, more stable method to eliminate fluid-induced instability.

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Investigations of Cylindrical and Conical Whirl Instabilities on Hydrodynamic Journal Bearings

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.656-657.688 ◽

2015 ◽

Vol 656-657 ◽

pp. 688-693

Author(s):

Norifumi Miyanaga ◽

Jun Tomioka

Keyword(s):

Vibration Mode ◽

Mechanical Systems ◽

Journal Bearings ◽

Span Length ◽

Transitional State ◽

Conical Whirl ◽

Oil Whirl ◽

Bearing Design

Hydrodynamic journal bearings induced serious shaft vibrations called oil whirl. Since they often give severe damages to the mechanical systems, it is important to fully understand the phenomenon to avoid the occurrence by the proper bearing design. This study theoretically and experimentally investigated both cylindrical and conical whirl instabilities, which can be appeared in journal bearings, and their relation was discussed. As the result, the span length of the bearings had a significant effect on the vibration mode. The transitional state in which the cylindrical and conical whirl instabilities alternately appeared was observed.

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Experimental Investigation of the Effect of Angular Misalignment on the Instability of Plain Journal Bearings

ASME/STLE 2009 International Joint Tribology Conference ◽

10.1115/ijtc2009-15057 ◽

2009 ◽

Cited By ~ 1

Author(s):

Aly El-Shafei ◽

Sameh H. Tawfick ◽

Mokhtar O. A. Mokhtar

Keyword(s):

Journal Bearings ◽

Displacement Sensor ◽

Maximum Speed ◽

Test Rig ◽

Angular Misalignment ◽

Vibration Displacement ◽

Oil Whip ◽

Fluid Film Bearings ◽

Oil Whirl ◽

Overall Stability

The effect of angular misalignment of plain journal bearings on the oil whirl and oil whip phenomena was investigated using a test rig comprising a flexible one inch diameter shaft supported on two cylindrical fluid film bearings. A matrix of experiments was designed where a precisely controlled angular misalignment between the shaft and the drive end, the non-drive end, or both bearings was induced. In each case we measure the onset of oil whirl and/or the onset of oil whip and the maximum speed that the test rig can reach before reaching a maximum vibration displacement of 1 mm at the location of the displacement sensor. The results show clearly that the angular misalignment of the bearings with respect to the shaft help delay the onset of oil whip from 3200 rpm to 4500 rpm in some cases. An interesting and new observation was the effect of the configuration of the misalignment on the overall stability characteristics. In particular, when the two bearings were misaligned in the same direction such that the two misaligned bearing planes were parallel to each other the onset of instability was more delayed and the overall operation was smoother.

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Lubrication and Wear Group: Oil-Whirl Characteristics of a Rigid Rotor in 360° Journal Bearings

Proceedings of the Institution of Mechanical Engineers ◽

10.1243/pime_proc_1963_177_026_02 ◽

1963 ◽

Vol 177 (1) ◽

pp. 291-307 ◽

Cited By ~ 19

Author(s):

R. Holmes

Keyword(s):

Journal Bearings ◽

Rigid Rotor ◽

Oil Whirl

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Some Experiments on Oil Whirl and Oil Whip

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2181185 ◽

2004 ◽

Vol 129 (1) ◽

pp. 144-153 ◽

Cited By ~ 25

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 have been 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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Geared Rotordynamic Systems on Hydrodynamic Bearings

Volume 6A: 18th Biennial Conference on Mechanical Vibration and Noise ◽

10.1115/detc2001/vib-21432 ◽

2001 ◽

Author(s):

S. Theodossiades ◽

S. Natsiavas

Keyword(s):

Journal Bearings ◽

Gear Pair ◽

Nonlinear Characteristics ◽

Time Dynamics ◽

Strongly Nonlinear ◽

Gear Mesh ◽

Oil Whirl ◽

Long Time ◽

Mechanical Models ◽

Long Time Dynamics

Abstract The present study investigates response and stability characteristics of gear-pair systems supported on oil journal bearings. The systems examined are driven by a motor providing a known torque, which is transferred to a load element through shafts and a gear-box. Here, the emphasis is placed on the gear-pair action, by assuming that the interconnecting shafts are rigid. This results in mechanical models with strongly nonlinear characteristics, whose long time dynamics are then effectively studied by applying appropriate numerical methodologies. In this way, useful information is obtained for the influence of the loading, the gear mesh and the journal parameters on the system dynamic behavior, including periodic, quasiperiodic and chaotic response. Efforts are also directed towards predicting the onset of oil whirl instability and investigating its effects on the gear-pair dynamics.

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