Stability and Transient Characteristics of Four Multilobe Journal Bearing Configurations

1980 ◽  
Vol 102 (3) ◽  
pp. 291-298 ◽  
Author(s):  
D. F. Li ◽  
K. C. Choy ◽  
P. E. Allaire
Keyword(s):  
Transient Analysis ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
Frequency Content ◽  
Stability Threshold ◽  
Fast Fourier Transform Analysis ◽  
Linearized Stability ◽  
Nonlinear Transient ◽  
The Stability

Multilobe journal bearings are often used to improve the stability response of rotating machinery. Such machines operate near the stability threshold of the bearing-rotor system. This work determines the linearized stability threshold of four multilobe journal bearings: elliptical, offset elliptical, three lobe, and four lobe. A nonlinear transient analysis of a rigid rotor in each of these bearings is carried out above and below the threshold speed. Shaft orbits and bearing forces are calculated. A numerical fast Fourier transform analysis is used to obtain the frequency content of the nonlinear orbit.

Comparison Between Linear and Nonlinear Transient Analysis Techniques to Find the Stability of a Rigid Rotor

1999 ◽  
Vol 121 (1) ◽  
pp. 198-201 ◽  
Author(s):  
Ram Turaga ◽  
A. S. Sekhar ◽  
B. C. Majumdar
Keyword(s):  
Transient Analysis ◽  
Stability Limit ◽  
Journal Bearings ◽  
Quantitative Comparison ◽  
Rigid Rotor ◽  
Analysis Techniques ◽  
Analysis Technique ◽  
Nonlinear Transient ◽  
Nonlinear Transient Analysis ◽  
The Stability

The subsynchronous whirl stability limit of a rigid rotor supported on two symmetrical finite journal bearings has been studied using the linearised perturbation method and the nonlinear transient analysis technique. A quantitative comparison for journal bearings with different l/d ratios has been provided.

Stability Analysis of Two-Layered Finite Hydrodynamic Porous Journal Bearing Using Linear and Nonlinear Transient Method

2007 ◽  
Author(s):  
S. K. Kakoty ◽  
S. K. Laha ◽  
P. Mallik
Keyword(s):  
Journal Bearing ◽  
Journal Bearings ◽  
Operating Conditions ◽  
System Stability ◽  
Rigid Rotor ◽  
Transient Method ◽  
Porous Bearing ◽  
Nonlinear Transient ◽  
Linear And Nonlinear ◽  
The Stability

A theoretical analysis has been carried out to determine the stability of rigid rotor supported on two symmetrical finite two-layered porous oil journal bearings. The stability curves have been drawn for different eccentricity ratios and Sommerfeld numbers. The effect of bearing feeding parameter, L/D ratio on the stability is also investigated. This paper also deals with a theoretical investigation of stability using a non-linear transient method. This analysis gives the journal centre locus and from this the system stability can be determined. With the help of graphics, several trajectories of the journal centre have been obtained for different operating conditions. Finally a comparison between single-layered porous bearing and the two-layered porous bearing is presented here.

Transient Unbalance Response of Four Multilobe Journal Bearings

1980 ◽  
Vol 102 (3) ◽  
pp. 300-306 ◽  
Author(s):  
P. E. Allaire ◽  
D. F. Li ◽  
K. C. Choy
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Transient Response ◽  
Journal Bearings ◽  
Stability Threshold ◽  
Unbalance Response ◽  
Fast Fourier Transform Analysis ◽  
Linearized Stability ◽  
The Stability

This work carries out an analysis of the transient response of four multilobe journal bearings (elliptical, offset, three-lobe, and four-lobe) subject to unbalance both below and above the linearized stability thresholds for the bearings. It extends the work of a previous paper on a balanced rotor in the same four bearing types. Transient orbits, bearing forces, and a numerical fast Fourier transform analysis of the orbits are presented. A comparison of bearing forces above the stability threshold for each bearing indicates that the elliptical bearing has the most violent whirl vibration amplitudes, while the offset bearing exhibits the least amount of subsynchronous vibration.

Comparison study of misalignment effect along two perpendicular directions on the stability of rigid rotor-aerostatic journal bearing system

2020 ◽  
Vol 234 (10) ◽  
pp. 1618-1634
Author(s):  
Jianbo Zhang ◽  
Han Zhao ◽  
Donglin Zou ◽  
Na Ta ◽  
Zhushi Rao
Keyword(s):  
Journal Bearing ◽  
Thickness Distribution ◽  
Vertical Direction ◽  
Inertial Force ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
Stability Threshold ◽  
Dynamic Coefficients ◽  
The Stability ◽  
Bearing System

Under misalignment condition, the film thickness distribution of aerostatic journal bearings is changed comparing with condition without misalignment, which results in the change of performances of aerostatic journal bearings. In the paper, the effects of misalignment along two perpendicular directions (along the vertical direction θ y and along the horizontal direction θ x) on the dynamic coefficients and stability thresholds of both critical whirl ratio and critical inertial force calculated by the motion equation of rigid rotor-aerostatic journal bearing system are studied comparatively. The results indicate that the dynamic coefficients, critical whirl ratio, and critical inertial force are more sensitive to θ x compared with θ y. Moreover, the stability threshold of whirl ratio reduces with increasing the misalignment degree, while stability threshold of inertial force increases with increasing the misalignment degree.

Short Bearing Analysis Applied to Rotor Dynamics—Part 2: Results of Journal Bearing Response

1976 ◽  
Vol 98 (2) ◽  
pp. 319-329 ◽  
Author(s):  
R. G. Kirk ◽  
E. J. Gunter
Keyword(s):  
Transient Response ◽  
Journal Bearing ◽  
Rotor Dynamics ◽  
Journal Bearings ◽  
Radius Of Curvature ◽  
Extensive Investigation ◽  
Stability Threshold ◽  
Stability Maps ◽  
And Performance ◽  
The Stability

The results of an extensive investigation of the transient response of rotors supported in fluid-film journal bearings is presented in the form of computer generated orbits of rotor motion. The stability of the rotor-bearing system was determined by examination of the system characteristic equation in Part 1. Rotor transient response orbits demonstrate the rotor behavior below and above the stability threshold. The results show the effect of imbalance, steady loading, cyclic unidirectional and rotating loads upon the stability and performance of a short journal bearing. The results are compared to previous investigations and modified stability maps are deduced from the results obtained. The concept of whirl is examined and several plots presented of the instantaneous whirl ratio and radius of curvature versus cycles of motion (of the journal) for the various cases considered. Bearing forces are analyzed and the resulting plots of force versus cycles of motion are presented for selected cases.

Stability of a Rigid Rotor Supported by Aerostatic Journal Bearings With Circular Slot Restrictors (On the Double-Row Admission Bearing)

1988 ◽  
Vol 110 (2) ◽  
pp. 228-234 ◽  
Author(s):  
S. Yoshimoto ◽  
Y. Anno ◽  
T. Ohashi
Keyword(s):  
Theoretical Analysis ◽  
Energy Loss ◽  
Point Source ◽  
Gas Flow ◽  
Journal Bearing ◽  
Rapid Change ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
Double Row ◽  
The Stability

This paper discusses the stability of a rigid rotor supported by double-row admission journal bearings with circular slot restrictors. In the theoretical analysis, the energy loss at the outlet of the slot is taken into account because the gas flow is subject to a rapid change in direction, and here, the energy loss coefficient is determined experimentally. It is found that a better agreement between the theoretical and experimental results for the threshold of instability can be obtained by considering the energy loss. Furthermore, in this paper, it is shown experimentally that an aerostatic journal bearing with circular slot restrictors has higher stiffness and higher stability than a conventional point source bearing with inherently compensated feeding holes.

scholarly journals Stability analysis of long hydrodynamic journal bearings based on the journal center trajectory

Friction ◽  
2020 ◽  
Author(s):  
Yu Huang ◽  
Haiyin Cao ◽  
Zhuxin Tian
Keyword(s):  
Stability Analysis ◽  
Equilibrium Point ◽  
Journal Bearing ◽  
Stability Boundary ◽  
Initial Point ◽  
Journal Bearings ◽  
Bearing Surface ◽  
Rotating Speed ◽  
Stability Threshold ◽  
The Stability

AbstractIn this study, we observe that there are two threshold speeds (stability threshold speed and second threshold speed) for the long journal bearing, which is different for the short bearing. When the rotating speed is below the stability threshold speed, the stability boundary nearly coincides with the clearance circle, and the journal center gradually returns to the equilibrium point after being released at an initial point. If the rotating speed is between the stability threshold speed and the second threshold speed, after being released at an initial point, the journal center converges to a contour containing the equilibrium point. In this situation, for a higher rotating speed, the corresponding contour is also larger. When the rotating speed exceeds the second threshold speed, the journal gradually moves towards the bearing surface after being released at an initial point.

Effect of Unbalance on a Journal Bearing Undergoing Oil Whirl

1976 ◽  
Vol 190 (1) ◽  
pp. 535-543 ◽  
Author(s):  
L. E. Barrett ◽  
A. Akers ◽  
E. J. Gunter
Keyword(s):  
Nonlinear Analysis ◽  
Limit Cycle ◽  
Journal Bearing ◽  
Ambient Pressure ◽  
Displacement Velocity ◽  
Stability Threshold ◽  
Linearized Stability ◽  
Oil Whirl ◽  
Instantaneous Values ◽  
The Stability

SYNOPSIS A time-transient nonlinear analysis has been developed to examine the dynamical limit cycle motion of a plain journal bearing. The effect of unbalance and ambient pressure on the journal limit cycle motion below and above the linearized stability threshold speed is examined. The short bearing approximation is used, and the assumption of a 180° oil film has been relaxed. An arbitrary film extent based upon the instantaneous values of journal displacement, velocity, and ambient pressure is used. It has been found possible to optimize the unbalance to minimize the amplitude and the force transmitted for limit cycle operation above the stability threshold speed. Below this optimum value the whirl is fractional frequency and above this value it is synchronous. It has been found that when the journal is operating above the stability threshold speed, rotor unbalance may result in a smaller limit cycle than the balanced rotor. The effect of a non-zero ambient pressure at the optimum value of unbalance is to increase the size of the limit cycle and make the motion nonsynchronous.

Dynamic Behaviour of Tilting-Pad Journal Bearings

1995 ◽  
Vol 209 (4) ◽  
pp. 275-285 ◽  
Author(s):  
S Pagano ◽  
E Rocca ◽  
M Russo ◽  
R Russo
Keyword(s):  
Dynamic Behaviour ◽  
Static Load ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
Tilting Pad ◽  
Non Linear ◽  
The Stability ◽  
Tilting Pad Journal Bearings

The dynamic behaviour of a rigid rotor on tilting-pad journal bearings system is analysed for balanced and unbalanced rotors. The study mainly regards a two-pad journal bearing symmetric with respect to the external static load. Both linear and non-linear behaviours have been analysed, with particular reference to the stability of the journal and pads equilibrium positions in the case of balanced or slightly unbalanced rotors, and to the stability of their synchronous motions in the case of considerable unbalance.

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