Optimal Clearance Configuration of Fluid-Film Journal Bearings for Stability Improvement

2004 ◽  
Vol 126 (1) ◽  
pp. 125-131 ◽  
Author(s):  
Koichi Matsuda ◽  
Yoichi Kanemitsu ◽  
Shinya Kijimoto
Keyword(s):  
Performance Index ◽  
Fourier Coefficients ◽  
Journal Bearings ◽  
Rotating Machinery ◽  
Fluid Film ◽  
System Stability ◽  
Rigid Rotor ◽  
System A ◽  
Improve Stability ◽  
Machinery System

This paper aims to optimize a clearance configuration of fluid-film journal bearings. In order to improve stability of a rotating-machinery system, a performance index is given by summing the squared values of the attitude-angles over a region of eccentricity. A Fourier series is used to represent an arbitrary clearance configuration of a bearing, and the problem is to find the Fourier coefficients to minimize the performance index. The problem is numerically solved by a kind of the conjugate gradient method to yield a unique clearance configuration. The optimal clearance configuration is computed for various ratios of length to diameter of a bearing. A rigid-rotor system is used to verify that the designed bearing improves the system stability compared with that of a full circular bearing and to show that this optimization is more effective for shorter bearings.

An experimental investigation of a microturbine simulated rotor supported on multileaf gas foil bearings with backing bump foils

2017 ◽  
Vol 232 (9) ◽  
pp. 1169-1180 ◽  
Author(s):  
Bo Zhang ◽  
Shemiao Qi ◽  
Sheng Feng ◽  
Haipeng Geng ◽  
Yanhua Sun ◽  
...  
Keyword(s):  
High Speed ◽  
Preliminary Test ◽  
Journal Bearings ◽  
Rotating Machinery ◽  
System Stability ◽  
Test Rig ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Simulated System ◽  
First Time

Two multileaf gas foil journal bearings with backing bump foils and one set of gas foil thrust bearings were designed, fabricated, and used in a 100 kW class microturbine simulated rotor system to ensure stability of the system. Meanwhile, a preliminary test rig had been built to verify the simulated system stability. The rotor synchronous and subsynchronous responses were well controlled by using of the gas foil bearings. It is on the multileaf gas foil bearings with backing bump foils that the test was conducted and verified for the first time in open literatures. The success in the experiments shows that the design and fabrication of the rotor and the gas foil bearings can provide a useful guide to the development of the advanced high speed rotating machinery.

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.

Chaos of a Flexible Rotor in Journal Bearings

1995 ◽  
Author(s):  
R. D. Brown ◽  
G. Drummond
Keyword(s):  
Theoretical Models ◽  
Journal Bearings ◽  
Rotating Machinery ◽  
Rigid Rotor ◽  
Flexible Rotor ◽  
Hydrodynamic Bearings ◽  
Stress Reversals ◽  
Oil Films ◽  
Rigid Rotors ◽  
Rotor Model

Abstract Nonlinear systems can give rise to chaotic behaviour, essentially unpredictable. Oil film forces arising from hydrodynamic bearings in rotating machinery can be extremely nonlinear under conditions of large unbalance. Chaotic response has been demonstrated in theoretical models of rigid rotors supported in hydrodynamic bearings. The behaviour of a rigid rotor can be extended by looking at a flexible rotor model supported on journal bearings and subject to large unbalance levels. The introduction of a flexible shaft yields chaotic regions which are less extensive than those obtained from a rigid rotor model. This is not surprising as the nonlinearity in the model is confined to the oil films at the end of the shaft. However if this level of unbalance is experienced in service then shaft fatigue could occur because of the sustained nature of the non-synchronous response and the effect of the resulting stress reversals.

Stability analysis of a rigid rotor on tilting-pad journal bearings

2000 ◽  
Vol 214 (3) ◽  
pp. 243-251 ◽  
Author(s):  
J. M. M. Guijosa ◽  
Z. C. Feng
Keyword(s):  
Previous Analysis ◽  
Journal Bearings ◽  
Rotating Machinery ◽  
Superior Performance ◽  
Limiting Factor ◽  
Loss Of Stability ◽  
Rigid Rotor ◽  
Tilting Pad ◽  
Tilting Pad Journal Bearings ◽  
Insight Into

Tilting-pad journal bearings are used in many rotating machinery applications. They are known to have superior performance in comparison with fixed geometry cylindrical bearings. Previous analysis by other investigators on the rotor stability has shown that the pad inertia is the main limiting factor on the bearing performance. In this paper, that analysis is extended to examine the bifurcation types that are associated with the loss of stability in order to gain insight into whether the linear stable regions are robust under finite perturbations. The effect of pad friction force on the rotor stability is also examined. Furthermore, the analysis is extended to bearings with four pads.

Effect of Bearing Profile on the Stability of Statically Indeterminate Rotor Bearing Systems

2007 ◽  
Author(s):  
N. S. Feng ◽  
E. J. Hahn
Keyword(s):  
Dynamic Characteristics ◽  
Rotating Machinery ◽  
Fluid Film ◽  
System Stability ◽  
Fluid Film Bearings ◽  
Flexible Rotors ◽  
Rotor Bearing ◽  
The Stability

The stability of rotating machinery consisting of flexible rotors supported by fluid film bearings is significantly affected by the dynamic characteristics of the bearings and in particular, the bearing profiles as well as the bearing reaction loads, which, in statically indeterminate systems, are in turn strongly influenced by the relative transverse alignment of the bearings. Using a simple four bearing statically indeterminate model, it is shown that relatively simple variants of the circular bearings, viz. elliptic and 2-pad offset bearings display better system stability characteristics systems in aligned situations and are also more likely to be stable in misaligned situations.

Effect of a Biphase Lubricant on Half Frequency Whirl in a Full Journal Bearing

1975 ◽  
Vol 97 (4) ◽  
pp. 1345-1353 ◽  
Author(s):  
G. C. Tolle ◽  
D. Muster
Keyword(s):  
Journal Bearing ◽  
Journal Bearings ◽  
Fluid Film ◽  
Lubricating Oil ◽  
Rigid Rotor ◽  
Uniform Dispersion ◽  
Stabilizing Effect

It is shown that a liquid–solid biphase lubricant can stabilize the motion of a rigid rotor in a full-journal bearing. The biphase lubricant is a uniform dispersion of Teflon particles in an SAE 20 lubricating oil. The stabilizing effect of nine combinations of particles and oil at two rotor speeds are investigated (particles of 25, 32, and 40 micron dia in concentrations of 5, 10, and 15 percent by weight, respectively, at rotor speeds of 1200 and 1800 rpm). These results are compared with the computed and measured orbits of the journal center relative to the bearing center when the same lubricating oil is used alone. In the analysis account is taken of the forces associated with the crushing of the Teflon particles and the usual inertia and fluid-film forces. A rigid-rotor, full-journal bearing apparatus was used to measure the orbits described. Agreement between computed and measured results was generally good. Both support the conclusion that a liquid-solid biphase lubricant can, in fact, stabilize the motion of rotors in full-journal bearings.

PEBB System Stability Margin Monitoring

2002 ◽  
Vol 8 (2) ◽  
pp. 261-276 ◽  
Author(s):  
Xiaogang Feng ◽  
Zhihong Ye ◽  
Fred C. Lee ◽  
Dushan Borojevic
Keyword(s):  
Stability Margin ◽  
System Stability ◽  
Linear Control ◽  
Small Signal ◽  
System A ◽  
Novel Approach ◽  
Implementation Approach ◽  
Dc Bus ◽  
Response Current ◽  
Measurement Approach

PEBB (power electronics building block) systems are typical nonlinear systems. Under the conventional but still popular linear control design, the system stability margin varies from one operating point to another. This paper introduces a novel approach to monitoring the DC bus stability margin of a PEBB system online. At the steady state of the system, a small-signal perturbation current î p is injected into the DC bus, and the load-side response current î L is measured. By checking the validation |î L ( jw)| < |î p ( jw)|, the system stability margin can be examined. Experiments on a 48 V DC DPS demonstrate the proposed measurement approach. An implementation approach is also proposed for an 800 V DC PEBB-based testbed system.

An analytical study of the fluid film force in finite-length journal bearings. Part I

2001 ◽  
Vol 13 (4) ◽  
pp. 329-340 ◽  
Author(s):  
V. D'Agostino ◽  
D. Guida ◽  
A. Ruggiero ◽  
A. Senatore
Keyword(s):  
Finite Length ◽  
Analytical Study ◽  
Journal Bearings ◽  
Fluid Film
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