scholarly journals The stability limits of flexible rotor supported by journal bearings with pressure difference between both ends. (2nd report. Theoretical analysis. Part 2).

1987 ◽  
Vol 53 (492) ◽  
pp. 1691-1696
Author(s):  
Satoru KANEKO
Keyword(s):  
Theoretical Analysis ◽  
Pressure Difference ◽  
Journal Bearings ◽  
Flexible Rotor ◽  
The Stability ◽  
Stability Limits

The Stability of an Elastic Rotor in Journal Bearings With Flexible, Damped Supports

1965 ◽  
Vol 32 (4) ◽  
pp. 911-920 ◽  
Author(s):  
Jorgen W. Lund
Keyword(s):  
Theoretical Analysis ◽  
Dynamic Properties ◽  
Journal Bearings ◽  
Rotor Speed ◽  
Flexible Rotor ◽  
Damping Coefficients ◽  
Oil Whip ◽  
The Stability ◽  
Rotor Stiffness ◽  
Gas Bearing

A theoretical analysis is presented investigating the stability (fractional frequency whirl, “oil whip”) of a symmetrical, flexible rotor supported in journal bearings. The bearings are mounted in flexible, damped supports. The analysis determines the rotor speed at which instability sets in as affected by rotor stiffness, the dynamic properties of the bearing film, and the flexibility and damping of the bearing supports. The analysis is based on the fact that the bearing can be represented by frequency-dependent spring and damping coefficients, and the method by which the coefficients are obtained is described with emphasis on the gas-lubricated bearing. The conclusions are: (a) Rotor and support flexibility by themselves lower the speed at onset of instability; (b) when the bearing support possesses damping in addition to flexibility, the speed at onset of instability can be raised significantly above the threshold speed of a rotor in rigidly mounted bearings. Numerical results are presented in the form of graphs for the plain cylindrical gas bearing.

Nonlinear Simulation Analysis and Experiment of Fluid Plain Journal Bearing With Incompressible Fluid

2003 ◽  
Author(s):  
Katsuhisa Fujita ◽  
Atsuhiko Shintani ◽  
Koji Yoshioka ◽  
Kouhei Okuno ◽  
Hiroaki Tanaka ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Incompressible Fluid ◽  
Journal Bearing ◽  
Simulation Analysis ◽  
Journal Bearings ◽  
Stable Region ◽  
Flexible Rotor ◽  
Nonlinear Simulation ◽  
Fluid Forces ◽  
The Stability

Recently, in many areas such as computers and information equipments etc., the fluid journal bearings are required to rotate at higher speed. To satisfy this requirement, the strictly stability analysis of the journal is indispensable. In this paper, we investigate the stability analysis of the dynamic behavior of the fluid plain journal bearing with an incompressible fluid considering the nonlinear terms of fluid forces. The stability analysis is examined by the numerical simulations on each model of a rigid rotor and a flexible rotor. The stable regions by nonlinear analysis are compared with the regions by classical linear analysis. Performing the nonlinear simulation analysis, it becomes clear that there is rather a stable region which amplitude does not grow up abruptly, and this phenomenon can not only be pointed out, but also is judged to be unstable by linear stable analysis. Finally, the experiment using actual bearings is performed and compared with the numerical results.

The Stability of a Flexible Rotor Supported by Circumferentially Fed Journal Bearings

1977 ◽  
Vol 99 (4) ◽  
pp. 469-477 ◽  
Author(s):  
P. Bar-Yoseph ◽  
J. J. Blech
Keyword(s):  
Journal Bearings ◽  
Asymptotically Stable ◽  
Direct Integration ◽  
Flexible Rotor ◽  
Nonlinear Prediction ◽  
Speed Range ◽  
The Stability

The stability of a flexible rotor, perfectly balanced, was investigated theoretically. The rotor is symmetrically supported by circumferentially fed journal bearings. Short and finite bearings were treated. Stability was checked for small and large disturbances. Two methods were employed to treat large disturbances: Direct integration and the slowly varying technique. The nonlinear prediction was tested concurrently with the prediction of the stability charts. It was observed that in certain cases stability can be obtained in the asymptotic and in the unstable regions. Instability was obtained for regions which presumably are asymptotically stable in the entire speed range.

Stability of Flexible Rotors With a LeBlanc Balancer

2011 ◽  
Author(s):  
Leonardo Urbiola-Soto ◽  
Marcelo Lopez-Parra
Keyword(s):  
High Speed ◽  
Particle Image ◽  
Flexible Rotor ◽  
Rotating System ◽  
Stability Behavior ◽  
Piv Technique ◽  
Flexible Rotors ◽  
Image Velocimetry ◽  
The Stability ◽  
Stability Limits

Although the liquid balancer has nearly a century of having been introduced by LeBlanc, little information is available on the dynamic response and stability behavior of this kind of device. Earlier author’s research using a high-speed camera and a Particle Image Velocimetry (PIV) technique showed the existence of a fluid backward traveling wave inside the balancer cavity. This damping phenomenon helps enhance the unbalance response of the rotating system and also raises the stability limits. This paper shows that a flexible rotor employing a LeBlanc balancer has remarkable increase in the threshold speed of instability for aerodynamic cross-coupling and viscous internal friction damping.

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 and Stability Degree of a Cracked Flexible Rotor Supported on Journal Bearings

1993 ◽  
Author(s):  
Meng Guang ◽  
Robert Gasch
Keyword(s):  
Journal Bearings ◽  
Speed Ratio ◽  
Mass Ratio ◽  
Flexible Rotor ◽  
Cracked Rotor ◽  
Unstable Region ◽  
Stability Degree ◽  
Large Influence ◽  
Crack Stability ◽  
The Stability

Abstract This paper investigates the stability and the stability degree of a flexible cracked rotor supported on different kinds of journal bearings. It is found that no matter what kind of bearings is used, the unstable zones caused by rotor crack locate always within the speed ratio 2N(1-△Kξ4)<Ω<2N when gravity parameter Wg > 1.0; and locate always within the speed ratio 2ΩαN(1-△Kξ4)<Ω<2ΩαN when Wg < 0.1, where ΔKξ is the crack stiffness ratio, N = 1, 2, 3, 4, 5 … and Ωα=(1+2α2α)1/2. When 0.1 < Wg < 1.0, there is a region, where no unstable zones caused by rotor crack exist. Outside the crack ridge zones, the rotor crack has almost no influence on system’s stability and stability degree; while within the crack ridge zones, the stability and stability degree depend both on the crack and system’s parameters. In some cases, the system may still be stable even the crack is very large. For small gravity parameter (Wg < 0.1), the mass ratio α has large influence on the position of unstable region, but its influence on the stability degree is small. The influence of fixed Sommerfeld number So on the crack stability degree is small although So has large influence on the stability degree of uncracked rotor.

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