Centrifugal Effects in Misaligned Hydrostatic Thrust Bearings

1983 ◽  
Vol 105 (4) ◽  
pp. 621-624 ◽  
Author(s):  
Z. S. Safar
Keyword(s):  
Flow Rate ◽  
Load Capacity ◽  
Friction Torque ◽  
Centrifugal Forces ◽  
Thrust Bearings ◽  
Lubricant Flow

An analysis is conducted and solutions are provided for the effect of centrifugal forces on hydrostatic misaligned thrust bearings. The results show that centrifugal forces reduce considerably the load capacity, the friction torque and increase the lubricant flow rate. It is found that the effect of centrifugal forces is decreased as tilting of the bearing is increased.

An Experimental and Theoretical study of Lubricant flow rate in Static, Grooved, Rectangular Thrust Bearings

1982 ◽  
Vol 24 (1) ◽  
pp. 21-29 ◽  
Author(s):  
D. J. Hargreaves ◽  
C. M. Taylor
Keyword(s):  
Liquid Film ◽  
Flow Rate ◽  
Theoretical Study ◽  
Film Formation ◽  
Research Programme ◽  
Journal Bearings ◽  
Thrust Bearings ◽  
Rate Prediction ◽  
Lubricant Flow ◽  
Lubricant Films

The work to be described here was undertaken in the preliminary stages of a research programme designed to study the true extent of lubricant films in non-stationary, grooved, rectangular thrust bearings. In such externally pressurized bearings an air-lubricant interface may be formed. The study of this interface was seen as a useful step in a consideration of film formation and flow rate prediction in liquid film journal bearings.

A Comparison Study on the Performance of Four Types of Oil Lubricated Hydrodynamic Thrust Bearings for Hard Disk Spindles

1999 ◽  
Vol 121 (1) ◽  
pp. 114-120 ◽  
Author(s):  
Jiasheng Zhu ◽  
Kyosuke Ono
Keyword(s):  
Load Capacity ◽  
Dynamic Performance ◽  
Hard Disk ◽  
Friction Torque ◽  
The Other ◽  
Design Parameters ◽  
Axial Stiffness ◽  
Comparison Study ◽  
Thrust Bearings ◽  
Optimal Values

In this paper, the static and dynamic performance of herringbone, step-pocket, taper-pocket, and taper-flat thrust bearings were numerically analyzed. Optimal values for the design parameters of each type of bearing were analyzed in terms of both maximum axial stiffness (kzz) and maximum ratio of axial stiffness to friction torque (kzz/T) and bearing performance for both cases was calculated. The optimal performance characteristics of these bearings were compared in terms of application to hard disk spindles. Step-pocket and taper-pocket thrust bearings are superior to herringbone and taper-flat thrust bearings with respect to both the maximum kkk and the maximum kzz/T conditions. It was found that the dams of thrust bearings with pockets play an important part in improving the hearing performance. It was made clear that the taper-pocket and the taper-flat thrust bearings have a much larger load capacity than the other two types of thrust bearings in the proximity of zero clearance.

The Influence of Surface Patterning on the Thermal Properties of Textured Thrust Bearings

2017 ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu
Keyword(s):  
Surrogate Model ◽  
Load Capacity ◽  
Computing Time ◽  
Friction Torque ◽  
Fluid Film ◽  
Design Parameters ◽  
Textured Surface ◽  
Textured Surfaces ◽  
Thrust Bearings ◽  
Lubricated Contacts

Contact performance can be enhanced by using textured surfaces. These are also found to have influences on lubricated contacts. The effects of textured surface on lubricated contacts has been widely investigated over the past twenty years. The property of lubricated contacts has been found to play an important role on the performance of fluid film bearings. According to the previous study, the introduction of dimples on the inner surfaces of parallel thrust bearings can improve the load capacity and reduce the friction. Since the friction loss is mostly converted to thermal energy and then increase the temperature, textured surface is expected to have a positive effect on the thermal property of the thrust bearings. A procedure to find the optimal partially texture geometry, which minimize the temperature inside the bearing film, is presented in this study. A parallel sector-pad thrust bearing is simulated by a 3D computational fluid dynamics model. The stationary surface of the bearing is textured with dimples while the rotor surface is flat. The results of the baseline model have been validated by the experimental data from the literature. The temperature and pressure distribution on the bearing pad are presented. In this study, two types of dimples, including rectangular and elliptical, are compared together. A parametric study is conducted to investigate the influence of the texture geometries. In this study, the length of the major axis (width), the length of the minor axis (length), dimple depth, circumferential space between two dimples, radial space between two dimples, radial extend and circumferential extend are selected as design parameters. A surrogate model is used to reduce the computing time of CFD analysis. Based on the surrogate model, a multi-objective optimization scheme is used to navigate the design space and find the optimal texture structure that provides a lower maximal temperature inside the fluid film, higher load capacity, and lower friction torque. The optimal radial extent of the texture is around 80% of the pad radial length for both cases. The optimal length of the elliptical dimples in the circumferential direction is about 30% larger than the value of the rectangular dimples. In the final optimal design, the maximal temperature reduces 1.1% and 1.3% for rectangular and elliptical dimples while the load capacities are maintained at the same level.

Optimum Design of Porous Gas Bearings With Maximum Load Carrying Capacity and Static Stiffness

2005 ◽  
Author(s):  
V. I. Grabovskii
Keyword(s):  
Flow Rate ◽  
Carrying Capacity ◽  
Load Capacity ◽  
Maximum Load ◽  
Optimum Shape ◽  
Load Carrying Capacity ◽  
Static Stiffness ◽  
Lubricant Flow ◽  
Load Carrying ◽  
Gap Height

The problem of optimum porous infinite sliding bearings design with isothermal compressed lubricant is solved. The sliders and journal bearings with maximum load carrying capacity or maximum a lubricant film static stiffness in conditions of restriction on the lubricant flow rate through a pored insert are examined. The found optimum shapes of bearings depend on problem parameters, determining property of lubricant and insert, conditions of feed and lubricant flow rate through an insert. Besides the bearings shape a size and position of insert are determined. The optimum shape features are the discontinuity of their gap height function and insert arrangement in the vicinity of this function breaking. In the case of journal bearing at fixed gap height only the best sizes of bushing and their positions from a point of view of maximum load capacity are founded. The method of calculus of variations is used.

An Optimum Design Approach for Textured Thrust Bearing With Elliptical-Shape Dimples Using Computational Fluid Dynamics and Design of Experiments Including Cavitation

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Design Of Experiments ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Friction Torque ◽  
Load Force ◽  
Optimization Approach ◽  
Thrust Bearings ◽  
Design Variables

Textured thrust bearings are capable of providing higher load capacity and lower friction torque compared to nontextured bearings. However, most previous optimization efforts for texturing geometry were focused on rectangular dimples and employed Reynolds equation. Limited studies have been done to investigate the effects of partially textured thrust bearings with elliptical dimples. This study proposes a new optimization approach to find the optimal partially texture geometry with elliptical dimples, which maximize the loading capacity and minimize the friction torque. In this study, a 3D computational fluid dynamics (CFD) model for a parallel sector-pad thrust bearing is built using ANSYS cfx. Mass conserving cavitation model is used to simulate the cavitation regions. Energy equation for Newtonian flow is also solved. The results of the model are validated by the experimental data from the literature. Based on this model, the flow pattern and pressure distribution inside the dimples are analyzed. The geometry of elliptical dimple is parameterized and analyzed using design of experiments (DOE). The selected geometry parameters include the length of major and minor axes, dimple depth, radial and circumferential space between two dimples, and the radial and circumferential extend. A multi-objective optimization scheme is used to find the optimal texture structure with the load force and friction torque set as objective functions. The results show that the shape of dimples has a crucial effect on the performance of the textured thrust bearings. Searching the design space for a proper combination among the design variables satisfying the constraints has the advantage of capturing the codependence among design variables and leads to a surface patterning of the bearing, which showed a 42.7% improvement on the load capacity.

An Experimental Study on Externally Pressurized Supersonic Gas Thrust Bearings

1985 ◽  
Vol 107 (1) ◽  
pp. 122-127 ◽  
Author(s):  
Yutaka Miyake ◽  
Takehiko Inaba ◽  
Naoshige Kubo ◽  
Jun-ichi Takeoka
Keyword(s):  
Experimental Study ◽  
Flow Rate ◽  
Load Capacity ◽  
Experimental Results ◽  
Static Characteristics ◽  
Thrust Bearings ◽  
Pressure Distributions ◽  
Theoretical Predictions ◽  
New Type ◽  
Good Agreement

Externally pressurized supersonic gas thrust bearings whose generation of load capacity is substantially independent of the viscosity of working fluids, have been proposed and analyzed by the authors. This report presents the experimental results of the static characteristics of this new type of bearings. The experimental results including load capacity, stiffness, mass flow rate, and pressure distributions in the bearing clearance, generally show a good agreement with the theoretical predictions and verify the validity of this new bearing. The effect of an orifice to improve the stiffness is also examined. Some problems which should be solved to put the bearing in practical use are pointed out.

Centrifugal Effects in Thrust Bearings and Seals Under Laminar Conditions

1981 ◽  
Vol 103 (1) ◽  
pp. 126-136 ◽  
Author(s):  
Oscar Pinkus ◽  
J. W. Lund
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Load Capacity ◽  
Finite Difference Methods ◽  
Navier Stokes ◽  
Negative Consequences ◽  
Centrifugal Forces ◽  
Thrust Bearings ◽  
Dominant Component ◽  
The Individual

An analysis is conducted and solutions are provided for the effect of centrifugal forces on the hydrodynamics of high-speed thrust bearings and seals. First, a scrutiny of the individual inertia terms of the Navier-Stokes equations delineates the circumstances under which the centrifugal term (u2/r) becomes the dominant component. A Reynolds equation incorporating centrifugal forces is then derived for finite sectorial configurations operating under incompressible laminar conditions. Thermal effects are included. The equation is solved by finite difference methods. The results show that at the upper limits of laminar operation centrifugal forces reduce considerably the load capacity and alter the pattern of lubricant flow. As a result, at sufficiently high velocities the inflow of lubricant at the inner radius of a sectorial configuration may bring about the scavenging of lubricant from wide portions of the bearing surface, producing a form of thrust bearing cavitation. Design features which would reduce the negative consequences of centrifugal action are outlined, including the introduction of radial tapers.

Turbulent Lubrication of Tilting-Pad Thrust Bearings With Thermal and Elastic Deformations

1985 ◽  
Vol 107 (1) ◽  
pp. 82-86 ◽  
Author(s):  
H. Hashimoto ◽  
S. Wada
Keyword(s):  
Friction Torque ◽  
Shaft Speed ◽  
Centrifugal Forces ◽  
Balance Equations ◽  
Elastic Deformations ◽  
Film Pressure ◽  
Thrust Bearings ◽  
Temperature Distributions ◽  
Tilting Pad ◽  
Energy Equations

Pad deformations of sector-shaped, tilting-pad thrust bearings affecting turbulent lubrication are discussed theoretically. Solving the lubrication and energy equations with turbulence and centrifugal forces and the elastic and moment balance equations of a pad simultaneously, film pressure and temperature distributions, thermal and elastic deformations and inclinations of a pad are obtained. Film thicknesses at a pivot under a constant shaft speed become larger due to pad deformations, whereby pad inclinations increase and friction torque coefficients decrease outstandingly. It is important to introduce the effects of pad deformations when analysing performances of such bearings running in the turbulent conditions.

scholarly journals Optimization of Conical Hydrostatic Bearing for Minimum Friction

1972 ◽  
Vol 94 (2) ◽  
pp. 136-142 ◽  
Author(s):  
L. J. Nypan ◽  
B. J. Hamrock ◽  
H. W. Scibbe ◽  
W. J. Anderson
Keyword(s):  
Laminar Flow ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Flow Rate ◽  
Load Capacity ◽  
Friction Torque ◽  
Radius Ratio ◽  
Hydrostatic Bearing ◽  
Laminar And Turbulent Flow

Equations for the flow rate, load capacity, and friction torque for a conical hydrostatic bearing were developed. These equations were solved by a digital computer program to determine bearing configurations for minimum friction torque. Design curves are presented that show optimal bearing dimensions for minimum friction torque as a function of dimensionless flow rate for a range of dimensionless load capacity. Results are shown for both laminar and turbulent flow conditions. The results indicate the hydrostatic pocket friction is a significant portion of the total friction torque. However, the bearing dimensions for a minimum friction design are affected very little by inclusion of pocket friction in the analysis. For laminar flow the values of the outerland radius ratio X3 and outer bearing radius ratio X4 did not change significantly with increasing friction factor. For turbulent flow, the outer bearing radius ratio X4 did not change with increasing friction factor; therefore, the value determined for X4 in the laminar flow case is valid for all turbulent flows.

Identification of Dynamic Characteristics of Gas Foil Thrust Bearings Using Base Excitation

2016 ◽  
Author(s):  
Tae Ho Kim ◽  
Moon Sung Park ◽  
Jongsung Lee ◽  
Young Min Kim ◽  
Kyoung-Ku Ha ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Load ◽  
Loss Factor ◽  
Load Capacity ◽  
Excitation Frequency ◽  
Vibrational Amplitude ◽  
Test Rig ◽  
Thrust Bearings ◽  
Bearing Plate ◽  
Bearing Stiffness

Gas foil bearings (GFBs) have clear advantages over oil-lubricated and rolling element bearings, by virtue of low power loss, oil-free operation in compact units, and rotordynamic stability at high speeds. However, because of the inherent low gas viscosity, GFBs have lower load capacity than the other bearings. In particular, accurate measurement of load capacity and dynamic characteristics of gas foil thrust bearings (GFTBs) is utmost important to widening their applications to high performance turbomachinery. In this study, a series of excitation tests were performed on a small oil-free turbomachinery with base excitations in the rotor axial direction to measure the dynamic load characteristics of a pair of six-pad, bump-type GFTBs, which support the thrust collar. An electromagnetic shaker provided dynamic sine sweep loads to the test bench (shaking table), which held rigidly the turbomachinery test rig for increasing excitation frequency from 10 Hz to 200 Hz. The magnitude of the shaker dynamic load, represented as an acceleration measured on the test rig, was increased up to 9 G (gravity). An eddy current sensor installed on the test rig housing measured the axial displacement (or vibrational amplitude) of the rotor thrust collar during the excitation tests. The axial acceleration of the rotor relative to the test rig was calculated using the measured displacement. A single degree-of-freedom base excitation model identified the frequency-dependent dynamic load capacity, stiffness, damping, and loss factor of the test GFTB for increasing shaker dynamic loads and increasing bearing clearances. The test results show that, for a constant shaker force and the test GFTB with a clearance of 155 μm, an increasing excitation frequency increases the dynamic load carried by the test GFTB, i.e., bearing reaction force, until a certain value of the frequency where it jumps down suddenly because of the influence from Duffing’s vibrations of the rotor. The bearing stiffness increases and the damping decreases dramatically as the excitation frequency increases. Generally, the bearing loss factor ranges from 0.5 to 1.5 independent of the frequency. As the shaker force increases, the bearing dynamic load, stiffness, damping, and loss factor increase depending on the excitation frequency. Interestingly, the agreements between the measured GFTB dynamic load versus the thrust runner displacement, the measured GFTB static load versus the structural deflection, and the predicted static load versus the thrust runner displacement are remarkable. Further tests with increasing GFTB clearances of 155, 180, 205, and 225 μm revealed that the vibrational amplitude increases and the jump-down frequency decreases with increasing clearances. The bearing load increases, but the bearing stiffness, damping, and loss factor decrease slightly as the clearance increases. The test results after a modification of the GFTB by rotating one side bearing plate by 30° relative to the other side bearing plate revealed insignificant changes in the dynamic characteristics. The present dynamic performance measurements provide a useful database of GFTBs for use in microturbomachinery.

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