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.

Theoretical Condition for the Cxy=Cyx Relation in Fluid Film Journal Bearings

1989 ◽  
Vol 111 (3) ◽  
pp. 426-429 ◽  
Author(s):  
T. Kato ◽  
Y. Hori
Keyword(s):  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Fluid Film ◽  
Finite Width ◽  
Damping Coefficients ◽  
Dynamic Coefficients ◽  
Cross Terms ◽  
Linear Damping ◽  
Theoretical Condition

A computer program for calculating dynamic coefficients of journal bearings is necessary in designing fluid film journal bearings and an accuracy of the program is sometimes checked by the relation that the cross terms of linear damping coefficients of journal bearings are equal to each other, namely “Cxy = Cyx”. However, the condition for this relation has not been clear. This paper shows that the relation “Cxy = Cyx” holds in any type of finite width journal bearing when these are calculated under the following condition: (I) The governing Reynolds equation is linear in pressure or regarded as linear in numerical calculations; (II) Film thickness is given by h = c (1 + κcosθ); and (III) Boundary condition is homogeneous such as p=0 or dp/dn=0, where n denotes a normal to the boundary.

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.

Threshold Speed of Instability of a Herringbone-Grooved Rigid Rotor With a Bearing Bush Flexibly Supported by Straight Spring Wires

2015 ◽  
Author(s):  
Kei Somaya ◽  
Koki Okubo ◽  
Masaaki Miyatake ◽  
Shigeka Yoshimoto
Keyword(s):  
Support System ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
Foil Bearings ◽  
High Speeds ◽  
Hexagonal Shape ◽  
Temperature Environment ◽  
Manufacturing Accuracy ◽  
Excellent Stability

In recent years, small-size aerodynamic bearings for turbomachines such as blowers and compressors have attracted considerable attention for increasing rotational speed. These kinds of bearings require excellent stability at high speeds and durability in a high-temperature environment. Foil bearings are one of the most suitable candidates that can satisfy these requirements but their structure is very complicated, and it is difficult to control their manufacturing accuracy. It is well known that flexibly supported herringbone-grooved aerodynamic journal bearings have excellent stability at high speeds and they are relatively easy to manufacture compared with foil bearings. Moreover, their dynamic characteristics can be easily solved numerically. In this paper, a flexibly supported herringbone-grooved aerodynamic journal bearing using straight spring wires made of stainless steel is proposed to provide a simple and reliable support system for a bearing bush. Six straight spring wires were assembled into a hexagonal shape into which the bearing bush was inserted. The threshold speed of instability of the proposed aerodynamic bearing was investigated numerically and experimentally. For this investigation, the nonlinear orbit method was adopted in numerical calculations. This investigation found that straight spring wires could steadily support the bearing bush and provide a simple and reliable support system for the bearing bush and that a 6-mm-diameter rigid rotor with a mass of 4.8 g supported by the proposed aerodynamic journal bearings could stably rotate at speeds of more than 0.7 million rpm.

Combined Influence of Misalignment and Orifice Diameter on the Static Performances of Hydrostatic, Water-Lubricated Journal Bearings

2014 ◽  
Vol 607 ◽  
pp. 608-611
Author(s):  
Hui Hui Feng ◽  
Chun Dong Xu ◽  
Feng Feng Wang
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Film Thickness ◽  
Power Loss ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Orifice Diameter ◽  
Rigid Rotor ◽  
Static Performance

The water-lubricated bearings have gained an increasing focus to overcome the disadvantages of the oil film bearings and gas bearings. In this paper, the influences of orifice diameter in aligned and misaligned conditions on the static performance of two hydrostatic, four-recess, water-lubricated journal bearings used to support a rigid rotor, are investigated. The steady Reynolds equation for the journal bearing for the turbulent bulk flow and the film thickness expression considering tilting angles are used and numerically solved by finite difference method. Results demonstrate that the static performances, such as the quality, power loss and temperature rise are affected by the tilting angles, orifice diameter to some degree.

CFD Analysis of Hydrodynamic Pressure Distribution in Non-Newtonian Oil in Journal Bearing Lubrication Gap

2015 ◽  
Vol 220-221 ◽  
pp. 37-42 ◽  
Author(s):  
Adam Czaban
Keyword(s):  
Shear Stress ◽  
Pressure Distribution ◽  
Journal Bearing ◽  
Hydrodynamic Pressure ◽  
Journal Bearings ◽  
Lubricating Oil ◽  
Cfd Analysis ◽  
Relationship Power ◽  
Lift Capacity ◽  
Relative Eccentricity

This paper presents the results of CFD analysis of the hydrodynamic pressure distribution in slide journal bearings lubricated by non-Newtonian oil. It was assumed that the oil shear stress varies from shear rate according to the Ostwald–de Waele relationship (power law lubricant). The comparison was related to bearings differences only in properties of lubricating oil – Newtonian and non-Newtonian properties; other parameters for both in each case were the same. The Tables show relative decrease of the maximum hydrodynamic pressure value and bearing lift capacity according to the bearing lubricated with Newtonian oil, for different values of bearing relative eccentricity.

scholarly journals Study on the performance of journal bearings in different lubricants by CFD and FSI method with thermal effect and cavitation

2018 ◽  
Vol 249 ◽  
pp. 03006 ◽  
Author(s):  
Hulin Li ◽  
Yanzhen Wang ◽  
Ning Zhong ◽  
Yonghong Chen ◽  
Zhongwei Yin
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Thermal Effect ◽  
Journal Bearing ◽  
Fluid Structure Interaction ◽  
Journal Bearings ◽  
Lubricating Oil ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Load Carrying

This paper used a new transient computational fluid dynamics and fluid–structure interaction method to investigate the journal bearing performance with the effect of thermal and cavitation, to reveal the performance of journal bearing in different lubricants and to provide substitution references for bearings in different lubricants. Considering thermal effect, elastic deformation and cavitation, a detailed discussion was conducted to show the performance of plain journal bearings lubricated by water, seawater, and lubricating oil by computational fluid dynamics (CFD) and fluid structure interaction (FSI) method. And the results in this work are compared with the published results. The variation of dimensionless load carrying capacity, maximum film pressure and temperature with eccentricity ratio are presented, which can provide reference for the design of bearings. Furthermore, a diagram is presented for journal bearings with different diameter, length-diameter ratio and lubricants, which can be used as a reference for the equivalent substitutions of bearings. The present research provides references as to the design of bearings and the substitutions of bearings by different lubricants.

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.

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.

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.

Influence of Fluid Film Boundary Migration on Dynamic Coefficients of Journal Bearings and Behavior of Rotor System

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Changmin Chen ◽  
Jianping Jing ◽  
Jiqing Cong ◽  
Zezeng Dai ◽  
Jianhua Cheng
Keyword(s):  
Journal Bearing ◽  
Boundary Migration ◽  
Dynamical Behavior ◽  
Journal Bearings ◽  
Rotor System ◽  
Fluid Film ◽  
Dynamic Coefficients ◽  
Film Boundary ◽  
Rotor Bearing ◽  
Stiffness And Damping

Abstract The position of fluid film in journal bearing will change while the journal moving in bearing, which can be named fluid film boundary migration (FFBM). It is usually ignored in the calculation of linear dynamic coefficients. While, the errors brought by this neglection was not ever investigated in detail. In this paper, the influence of FFBM on bearing dynamic coefficients and rotor system dynamic behaviors are investigated. A new perturbation-based model is proposed to take the FFBM into account by modifying the boundary conditions of governing equations. It is then verified by the experimental results and analytical results from previous research. Furthermore, the effects of FFBM on stiffness and damping in two typical journal bearings are investigated. The result indicates that the FFBM has a significant influence on dynamic coefficients of full circular journal bearing but little impact on journal bearing with axial grooves. Moreover, it affects the stiffness and damping more significantly in the cases of large length-to-diameter ratios or small eccentricity ratios in full circle bearing. Finally, the dynamical behavior of a rotor-bearing system with considering the FFBM is also investigated. The result shows that the FFBM of oil film has remarkable influences on the instability threshold and imbalance responses of the rotor system, which should not be ignored. The conclusions obtained in this research are expected to be helpful for the design of full circular journal bearings or rotor-bearing systems.

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