Stability Threshold of Flexibly Supported Hybrid Gas Journal Bearings

1979 ◽  
Vol 101 (4) ◽  
pp. 451-457 ◽  
Author(s):  
Zbyszko Kazimierski ◽  
Krzysztof Jarzecki
Keyword(s):  
Dynamic Properties ◽  
Theoretical Calculations ◽  
Journal Bearings ◽  
Experimental Investigations ◽  
Elastic Supports ◽  
Stability Threshold ◽  
The Stability ◽  
Elastically Supported ◽  
Gas Bearing ◽  
Bearing System

Results of experimental investigations of the dynamic properties of elastic supports for gas bearings having the form of rubber O-rings are presented. Theoretical calculations of the stability threshold of an externally pressurized gas bearing system elastically supported by means of O-rings were performed. An experimental investigation of the stability threshold of this gas bearing system was made. Comparisons between theoretical and experimental results verify the theoretical model and illustrate the possibility of its application to design purposes.

Stability of Multirecess Hybrid-Operating Oil Journal Bearings

1985 ◽  
Vol 107 (1) ◽  
pp. 116-121 ◽  
Author(s):  
Y. S. Chen ◽  
H. Y. Wu ◽  
P. L. Xie
Keyword(s):  
Finite Difference Method ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Design Parameters ◽  
Stability Threshold ◽  
Damping Coefficients ◽  
Hybrid Bearing ◽  
The Stability ◽  
Stiffness And Damping ◽  
Bearing System

An analysis and a numerical solution using finite difference method to predict the dynamic performance of multirecess hybrid-operating oil journal bearings are presented. The linearized stiffness and damping coefficients of a typical capillary-compensated bearing with four recesses are computed for various design parameters. The corresponding stiffness and the stability threshold of the bearing are then obtained, and the opposite influences of the hydrodynamic action on them are demonstrated. The effect of rotor flexibility on the onset of self-excited whirl is discussed, and a method is given to determine the stability threshold of a rotor-hybrid bearing system.

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.

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.

Non-linear stability analysis of micropolar fluid lubricated journal bearings with turbulent effect

2019 ◽  
Vol 71 (1) ◽  
pp. 31-39
Author(s):  
Subrata Das ◽  
Sisir Kumar Guha
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Micropolar Fluid ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Turbulent Regime ◽  
Content Type ◽  
Non Linear ◽  
The Stability ◽  
Bearing System

Purpose The purpose of this paper is to investigate the effect of turbulence on the stability characteristics of finite hydrodynamic journal bearing lubricated with micropolar fluid. Design/methodology/approach The non-dimensional transient Reynolds equation has been solved to obtain the non-dimensional pressure field which in turn used to obtain the load carrying capacity of the bearing. The second-order equations of motion applicable for journal bearing system have been solved using fourth-order Runge–Kutta method to obtain the stability characteristics. Findings It has been observed that turbulence has adverse effect on stability and the whirl ratio at laminar flow condition has the lowest value. Practical implications The paper provides the stability characteristics of the finite journal bearing lubricated with micropolar fluid operating in turbulent regime which is very common in practical applications. Originality/value Non-linear stability analysis of micropolar fluid lubricated journal bearing operating in turbulent regime has not been reported in literatures so far. This paper is an effort to address the problem of non-linear stability of journal bearings under micropolar lubrication with turbulent effect. The results obtained provide useful information for designing the journal bearing system for high speed applications.

Experimental Study on Journal Gas Bearing with Axial Slot for a Miniature Air Turboexpander

2012 ◽  
Vol 220-223 ◽  
pp. 611-614
Author(s):  
Ru Gang Chen ◽  
Ya Jun Nie ◽  
Quan Zhou ◽  
Chao Gong ◽  
Tao Chen
Keyword(s):  
Experimental Study ◽  
Instability Threshold ◽  
Radial Clearance ◽  
Experimental Investigations ◽  
New Type ◽  
The Stability ◽  
The Relationship ◽  
Gas Bearing

A new type of hydrostatic journal gas bearing with axial slot of tangential gas entry for miniature air turboexpander is firstly developed in this paper. This bearing configuration is presented and constructed to fit manufacture simplicity. The experimental investigations are carried out to reveal the relationship between bearing parameters and instability threshold speed. It is feasible to increase the stability of hydrostatic journal gas bearing by adopting this kind of configuration with axial slot of tangential gas entry. Some valuable tested results are obtained to reveal the optimum slot height and radial clearance for this miniature air turboexpander.

Stability Analysis of Mechanical Seals With Two Flexibly Mounted Rotors

1998 ◽  
Vol 120 (2) ◽  
pp. 145-151 ◽  
Author(s):  
J. Wileman ◽  
I. Green
Keyword(s):  
Dynamic Properties ◽  
Equations Of Motion ◽  
Closed Form Solution ◽  
Form Solution ◽  
Fluid Film ◽  
Mechanical Seals ◽  
Stability Threshold ◽  
Seal Design ◽  
The Stability ◽  
Gyroscopic Effects

Dynamic stability is investigated for a mechanical seal configuration in which both seal elements are flexibly mounted to independently rotating shafts. The analysis is applicable to systems with both counterrotating and corotating shafts. The fluid film effects are modeled using rotor dynamic coefficients, and the equations of motion are presented including the dynamic properties of the flexible support. A closed-form solution for the stability criteria is presented for the simplifled case in which the support damping is neglected. A method is presented for obtaining the stability threshold of the general case, including support damping. This method allows instant determination of the stability threshold for a fully-defined seal design. A parametric study of an example seal is presented to illustrate the method and to examine the effects of various parameters in the seal design upon the stability threshold. The fluid film properties in the example seal are shown to affect stability much more than the support properties. Rotors having the form of short disks are shown to benefit from gyroscopic effects which give them a larger range of stable operating speeds than long rotors. For seals with one long rotor, counterrotating operation is shown to be superior because the increased fluid stiffness transfers restoring moments from the short rotor to the long.

The Influence of Orifice Restriction on the Stability of Rigid Rotor-Aerostatic Bearing System

2009 ◽  
Author(s):  
Cheng-Hsien Chen ◽  
Ding-Wen Yang ◽  
Yuan Kang ◽  
Ren-Ming Hwang ◽  
Shrh-Shyong Shyr
Keyword(s):  
Reynolds Equation ◽  
Inertial Force ◽  
Adiabatic Process ◽  
Rigid Rotor ◽  
Double Row ◽  
Stability Threshold ◽  
Spindle Rotation ◽  
The Stability ◽  
Air Film ◽  
Bearing System

This paper has studied the influence of the restriction effect on the stability of a rigid rotor in rotation supported by double-row, orifice compensated aerostatic bearings. The air which is assumed to be perfect gas, passes through orifice restrictor into the bearing clearance undergoing the adiabatic process is governed by Reynolds equation including the coupled effects of wedge due to spindle rotation and squeezed film due to journal oscillation. The Ph-method is used to analyze Reynolds equation and which is then solved by the finite difference method and numerical integration to yield static and dynamic characteristics of air film. The motion equation of the rotor-bearing system is obtained by using the perturbation method and the eigensolution method is used to determine the stability threshold and critical whirl ratio. The variations of stability threshold of both critical inertial force and critical whirl ratio with restriction parameters are analyzed for various whirl ratios, speed of journal rotation and eccentricity ratios.

On The Steady State and Dynamic Performance Characteristics of Floating Ring Bearings

1981 ◽  
Vol 103 (3) ◽  
pp. 389-397 ◽  
Author(s):  
Chin-Hsiu Li ◽  
S. M. Rohde
Keyword(s):  
Steady State ◽  
Linear Theory ◽  
High Speed ◽  
Dynamic Performance ◽  
Equations Of Motion ◽  
Nonlinear Behavior ◽  
Journal Bearings ◽  
Transient Problem ◽  
The Stability ◽  
Bearing System

An analysis of the steady state and dynamic characteristics of floating ring journal bearings has been performed. The stability characteristics of the bearing, based on linear theory, are given. The transient problem, in which the equations of motion for the bearing system are integrated in real time was studied. The effect of using finite bearing theory rather than the short bearing assumption was examined. Among the significant findings of this study is the existence of limit cycles in the regions of instability predicted by linear theory. Such results explain the superior stability characteristics of the floating ring bearing in high speed applications. An understanding of this nonlinear behavior, serves as the basis for new and rational criteria for the design of floating ring bearings.

The Stability of Self-Acting Gas Journal Bearings With Noncircular Members and Additional Elements of Flexibility

1969 ◽  
Vol 91 (1) ◽  
pp. 113-119 ◽  
Author(s):  
H. Marsh
Keyword(s):  
Stability Boundary ◽  
Journal Bearings ◽  
Satisfactory Explanation ◽  
Unusual Behavior ◽  
Stability Boundaries ◽  
Linearized Theory ◽  
New Type ◽  
The Stability ◽  
Theory And Experiments ◽  
Bearing System

The linearized theory for the stability of self-acting gas bearings is extended to include bearing systems with noncircular members or additional elements of flexibility and damping. The theory offers a satisfactory explanation for the unusual behavior of a bearing system with a three-lobed rotor, including the whirl at low speeds and the whirl cessation. A comparison between the theory and experiments for a flexibly mounted bearing system shows that the theory can be applied to predict the stability boundaries of bearing systems with additional elements of flexibility. A new type of bearing apparatus is proposed in which it would be possible to obtain information about bearing stability without operating at the stability boundary.

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.

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