scholarly journals On Error Torques of Squeeze-Film Cylindrical Journal Bearings

1968 ◽  
Vol 90 (1) ◽  
pp. 191-198
Author(s):  
C. H. T. Pan ◽  
T. Chiang
Keyword(s):  
Radial Displacement ◽  
High Performance ◽  
Journal Bearing ◽  
Rotational Symmetry ◽  
Mathematical Problem ◽  
Journal Bearings ◽  
Squeeze Film

The squeeze-film bearing has been considered for the output axis of high performance gyroscopes. Viewing this application, it is important that the parasitic torque of the bearing be very small. In the case of a squeeze-film journal bearing, parasitic torque can result from tolerance effects which disrupt rotational symmetry of the bearing. This problem has been studied by assuming ellipses for the tolerances of the journal and bearing surfaces as well as the squeeze motion, respectively. Each tolerance effect is assumed to be axially uniform. The mathematical problem is linearized with respect to each of the tolerances and the radial displacement of the journal. It was found that the parasitic torques do not depend on the radial displacement of the journal. The parasitic torques result from interactions among the three types of tolerance effects while each of the tolerances alone will not lead to any torque. Numerical estimates based on the geometry of a typical gyroscope and current fabrication practice shows such parasitic torques can seriously impair the accuracy of the gyroscope.

A Review of Journal Bearing Induced Nonlinear Rotordynamic Vibrations

2021 ◽  
Vol 143 (11) ◽  
Author(s):  
Sitae Kim ◽  
Dongil Shin ◽  
Alan B. Palazzolo
Keyword(s):  
High Performance ◽  
Journal Bearing ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Thermally Induced ◽  
Frequency Domain Methods ◽  
Vibration Responses ◽  
Numerical Tools ◽  
Rotordynamic Forces ◽  
Solution Methodology

Abstract Nonlinear elements found in fluid film journal bearings and their surrounding structures are known to induce sub- and super-synchronous, chaos and thermally induced instability responses in rotor-bearing systems. The current review summarizes the literature on journal bearing induced nonlinear, rotordynamic forces, and responses. Nonlinear, thermo-elasto-hydrodynamic (TEHD) aspects of journal bearings has become increasingly important in high-performance turbomachines. These have significant influence on bearing dynamic performance and thermally induced, rotordynamic instability problems. Techniques for developing TEHD bearing models are discussed in the second section. Nonlinear solution methodology, including bifurcation determination and time and frequency domain methods such as harmonic balance, shooting and continuation, etc., is presented in the third section. Numerical tools to determine nonlinear vibration responses, including chaos, along with examples of bearing induced nonlinear vibrations are presented in the fourth and fifth sections, respectively.

Rotordynamic Evaluation of a Large High-Speed Rotor Equipped With Flexure Pivot Journal Bearings and Integral Squeeze Film Damper

2021 ◽  
Author(s):  
Giuseppe Vannini ◽  
Alice Innocenti ◽  
Filippo Cangioli ◽  
Kim Jongsoo
Keyword(s):  
High Speed ◽  
Oil And Gas ◽  
Journal Bearing ◽  
Journal Bearings ◽  
System Level ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Process Gas ◽  
Gas Market ◽  
High Flexibility

Abstract The current oil and gas market trends lead the compressor OEMs to increase the rotational speed and maximize the efficiency given a target power output. Especially when applied to large process gas centrifugal compressors, characterized by high-flexibility ratio, the achievement of these targets pushes the rotordynamic design towards its limit in terms of API requirements. Tiling pad journal bearings (TPJBs) are commonly adopted in high-speed applications for their inherent stability characteristics that permit to ensure the rotordynamic stability and eliminate self-induced sub-synchronous vibrations. The experimental activities subject of this paper aim to assess, for the first time, the rotordynamic behaviour of a large dummy rotor (6 meter long and total weight of 8 tons) equipped with Flexure Pivot tilting-pad journal bearing and Integral squeeze film damper (ISFD). This system level testing program has been performed in the Authors’ high-speed balancing bunker properly equipped with special instrumentation such as: flow meters and pad temperature probes to monitor journal bearing behaviour, displacement probes to measure rotor vibrations relative to the bearings. The main objective of the experimental activity is the full assessment of the rotordynamic response and the selection of the best configuration to target the design requirements (e.g. FPJB and “Active ISFD” vs. FPJB and “Inactive ISFD”).

The Load Capacity of Short Journal Bearings With Oscillating Effective Speed

1964 ◽  
Vol 86 (2) ◽  
pp. 348-353 ◽  
Author(s):  
B. K. Gupta ◽  
R. M. Phelan
Keyword(s):  
Significant Contribution ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Numerical Solutions ◽  
Load Capacity ◽  
Journal Bearings ◽  
Squeeze Film ◽  
Major Conclusion ◽  
Angular Velocities ◽  
Effective Speed

The development of the Reynolds equation for the general case of dynamically loaded journal bearings is extended to include the concept of an effective speed that combines in one term the angular velocities of the journal, bearing, and load. Numerical solutions for the short-bearing approximation are presented for the case of an oscillating effective speed and a load that is constant or varying sinusoidally. Results are compared with available experimental data. The major conclusion is that for those cases involving an oscillating effective speed and a reversing load, the only significant contribution to load capacity comes from the squeeze film and the wedge film can safely be ignored when designing such bearings.

An Augmented, Small-Parameter Equation for the Squeeze-Film Journal Bearing

1970 ◽  
Vol 92 (3) ◽  
pp. 442-449 ◽  
Author(s):  
C. L. Strodtman
Keyword(s):  
Small Parameter ◽  
Shape Factor ◽  
Radial Displacement ◽  
Journal Bearing ◽  
Numerical Procedure ◽  
Squeeze Film ◽  
Mean Square ◽  
Root Mean Square Amplitude ◽  
Parameter Equation ◽  
Good Agreement

The asymptotic gas film equation for the squeeze-film journal bearing is solved for the quadratic and cubic terms in the series expansion in terms of the radial displacement. The load support calculated from this augmented, small parameter equation is compared to calculations from an all numerical procedure. Good agreement is shown to exist for large values of the radial displacement. A method of treating nonuniform excursion of the driving member by a root-mean-square amplitude and a shape factor is also given.

Stability Characteristics of a Journal Bearing Mounted in an Uncentralized Squeeze Film Damper

1991 ◽  
Vol 113 (3) ◽  
pp. 584-589
Author(s):  
Yuichi Sato ◽  
H. Fujino ◽  
H. Sakakida ◽  
S. Hisa
Keyword(s):  
Steam Turbine ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
The Stability ◽  
Bearing Analysis

This paper describes the stability of a journal bearing mounted in an uncentralized squeeze film damper. It is known that mounting a journal bearing in a centralized squeeze film damper improves the bearing stability. From a practical viewpoint, however, it is difficult to centralize journal bearings which support a heavy rotor, such as a steam turbine. Experimentally, we show that a journal bearing can be stabilized by mounting in an uncentralized squeeze film damper. The effect of clearance of a squeeze film damper is investigated. By using short bearing analysis, rotor trajectories are calculated. Calculated results also shows stability improvement.

Determination of the Integration Constant for Squeeze Films in Infinitely Long Journal Bearings

1970 ◽  
Vol 92 (1) ◽  
pp. 179-180
Author(s):  
D. C. Kuzma
Keyword(s):  
Arbitrary Constant ◽  
Journal Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Integration Constant ◽  
Squeeze Film ◽  
Positive Pressure ◽  
Limiting Case

The complete film solution for the squeeze film in an infinitely long journal bearing contains an arbitrary constant. When only positive pressure regions are retained, this constant influences the load capacity. Several different values have been used for this constant. Its value is determined here so that the infinitely long journal bearing is the limiting case of the finite journal bearing.

Design and Test of Hydrostatic Gas Bearings for a Hybrid Cryogenic Refrigerator

2003 ◽  
Author(s):  
Jonathan C. Evans ◽  
Gregory F. Nellis
Keyword(s):  
Mass Flow ◽  
High Performance ◽  
Journal Bearing ◽  
High Reliability ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Pulse Tube ◽  
Gas Bearings ◽  
Lower Stage ◽  
Upper Stage

A hybrid pulse-tube/reverse-Brayton cryocooler is being developed that integrates a regenerative, pulse-tube upper stage with a recuperative, reverse-Brayton lower stage using a flow rectification system consisting of check-valves and buffer volumes. This system shows the potential for high performance with high reliability and low mass, and simple electrical, mechanical, and thermal integration. The turbine in the reverse-Brayton stage will be supported on hydrostatic gas bearings. The performance of the hybrid cryocooler system is strongly dependent upon the performance of these bearings; in particular their stiffness and mass flow consumption. This is a unique application of hydrostatic bearings; the miniature bearings are operating at cryogenic temperatures using high pressure helium. This paper describes the theoretical model that was developed to predict journal bearing performance as geometry and operating conditions change. The model is verified against experimental measurements of stiffness and mass flow consumption for a prototypical set of journal bearings. The model is subsequently used to optimize a set of journal bearings for the cryogenic turbine and parametrically investigate the effect of journal bearing clearance on system performance.

Gear Dynamics Analysis With Turbulent Journal Bearings Mounted Hybrid Squeeze Film Damper—Chaos and Active Control Analysis

2014 ◽  
Vol 10 (1) ◽  
Author(s):  
Cai-Wan Chang-Jian
Keyword(s):  
Chaotic Motion ◽  
Journal Bearing ◽  
Complex Dynamics ◽  
Journal Bearings ◽  
Squeeze Film ◽  
Maximum Lyapunov Exponent ◽  
Control Analysis ◽  
Bifurcation Diagrams ◽  
Squeeze Film Damper ◽  
Chaotic Vibrations

The hybrid squeeze film damper mounted turbulent journal bearing–gear system is proposed in this paper. The nonlinear dynamics of a gear pair supported by such bearing is studied. Numerical results show that, due to the nonlinear factors of lubricant film force, the trajectory of the pinion demonstrates a complex dynamics with dimensionless unbalance parameters. Poincaré maps and bifurcation diagrams are used to analyze the behavior of the pinion trajectory in the horizontal direction. The maximum Lyapunov exponent is used to determine if the system is in a state of chaotic motion. In order to avoid the nonsynchronous chaotic vibrations, an increased proportional gain kp = 0.1 is applied to control this system. It is shown that the pinion trajectory will leave chaotic motion to periodic motion in the steady state under control action.

scholarly journals Structural Design and Optimization of Herringbone Grooved Journal Bearings Considering Turbulent

2022 ◽  
Vol 12 (1) ◽  
pp. 485
Author(s):  
Xichun Liu ◽  
Wei Chen
Keyword(s):  
Liquid Metal ◽  
High Performance ◽  
Journal Bearing ◽  
Structural Parameters ◽  
Constant Width ◽  
Dynamic Performance ◽  
Helix Angle ◽  
Groove Depth ◽  
Journal Bearings ◽  
Design And Optimization

In order to improve the performance of the traditional constant-width herringbone grooved journal bearing in a computed tomography tube under a high-temperature environment, the present study designed a convergent herringbone grooved journal bearing (HGJB) structure lubricated by liquid metal. The bearing oil film thickness and the Reynolds equation considering the influence of turbulence are established and solved by using the finite difference method in the oblique coordinate system. The performance of the two bearings was compared, and the static and dynamic performance change trends of the two bearing structures under different eccentricities were systematically studied. The results show that the convergent herringbone grooved journal bearings are superior to the constant-width herringbone grooved journal bearings in terms of bearing capacity and stiffness coefficient. At the same time, the influence of structural parameters, such as the number of grooves, helix angle, groove to ridge ratio, groove depth on the performance of the constant-width herringbone grooved journal bearings, and the convergent herringbone grooved journal bearings was studied. Finally, we conclude that the performance of the convergent herringbone grooved journal bearings is optimal when the number of grooves is 15–20, the helix angle is 30–45°, the ratio of the groove to ridge is 1, and the groove depth is 0.02 mm −0.024 mm. This research has provided the thinking and reference basis for the design of liquid metal bearings for high-performance CT equipment.

A Theoretical Investigation of Compliant Surface Journal Bearings

1971 ◽  
Vol 93 (1) ◽  
pp. 191-201 ◽  
Author(s):  
M. K. Benjamin ◽  
V. Castelli
Keyword(s):  
Reynolds Equation ◽  
Journal Bearing ◽  
Mathematical Problem ◽  
Ritz Method ◽  
Newton Iteration ◽  
Journal Bearings ◽  
Elasticity Problem ◽  
Algebraic Equations ◽  
Compliant Surface ◽  
Nonlinear Algebraic Equations

The problem of the compliant surface journal bearing is investigated. The mathematical problem is divided into two parts, the elasticity problem and the fluid problem. The equations of linear elasticity, which represent the elasticity problem, are solved; (a) by expansion of the solution in eigenfunctions (b) by the Raleigh Ritz method, and (c) by a collocation method. Reynolds’ equation, which represents the fluid problem, is then coupled with the solution to the elasticity problem. The corresponding finite difference representation of Reynolds’ equation, which is a set of fourth-order nonlinear algebraic equations, is inverted by Newton iteration. Finally, numerical results are presented.

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