Showing papers on "Fluid bearing published in 2001"

Applied Tribology: Bearing Design and Lubrication

Abstract: Series Preface. Preface. Part I: General Considerations. 1 Tribology - Friction, Wear, and Lubrication. 2 Lubricants and Lubrication. 3 Surface Texture and Interactions. 4 Bearing Materials. Part II: Fluid-Film Bearings. 5 Fundamentals of Viscous Flow. 6 Reynolds Equation and Applications. 7 Thrust Bearings. 8 Journal Bearings. 9 Squeeze-Film Bearings. 10 Hydrostatic Bearings. 11 Gas Bearings. 12 Dry and Starved Bearings. Part III: Rolling Element Bearings. 13 Selecting Bearing Type and Size. 14 Principles and Operating Limits. 15 Friction, Wear and Lubrication. Part IV: Seals and Monitoring. 16 Seal Fundamentals. 17 Condition Monitoring and Failure Analysis. Appendix A Unit Conversion Factors. Appendix B Viscosity Conversions. Index.

Thermal Features of Compliant Foil Bearings—Theory and Experiments

Abstract: The paper presents an analytical and experimental investigation aimed at eliciting the thermal characteristics of air lubricated compliant foil bearings. A Couette Approximation to the energy equation is used in conjunction with the compressible Reynolds equation to obtain a theoretical temperature distribution in the air used as a lubricant. The effect of temperature on the thermal properties of the working fluid is included. In parallel, an experimental program was run on a 100 mm diameter foil bearing operating at speeds up to 30,000 rpm employing cooling air across the bearing. The temperature rise of the cooling air provided an indication of the amount of heat energy conducted across the top foil of the bearing from the hydrodynamic film. The temperatures resulted from some tests are compared with the temperatures predicted by the analysis, and maximum over-prediction of about 19 percent was obtained. This simplified approach provides us with reasonably predicted temperatures. By comparing the theoretical heat dissipation obtained from the analytical predicted temperatures with the amount of heat carried away by the cooling air it was possible to arrive at the relative quantities of heat transferred from the bearing by convection via side leakage and by conduction via the top foil. From these comparisons it was deduced that about an average of 80 percent of the heat energy is carried away by conduction. The transient temperatures of the foil bearing in conducted tests for various speeds and loads are also presented.

Fluid bearing device

Abstract: A fluid bearing device achieves superior in wear resistance in starting and stopping and in manufacturing ability The fluid bearing device includes a shaft having a flange portion, a sleeve opposing to the shaft across a fluid bearing clearance of a radial fluid bearing, a counterpart member opposing to at least one of plane of the flange portion across a fluid bearing clearance of a thrust bearing The flange portion and the sleeve portion being formed of copper alloy of mutually difference composition

Groove Effects on Thrust Washer Lubrication

Abstract: A numerical model was developed to investigate the effects of groove geometry on the hydrodynamic lubrication mechanism of thrust washers. In order to achieve the objectives the isothermal, time-dependent, polar-coordinate Reynolds equation, including the cavitation and centrifugal effects, was solved numerically to determine the pressure distribution for various groove geometries and operating conditions. The polar coordinate Reynolds equation was discretized using the control volume finite difference approach. The results indicate that thrust washers are capable of supporting a significant amount of load with proper groove geometries. Design curves were generated for load support and other operating parameters as a function of each of the groove geometrical parameters (i.e., depth, width, number of grooves, and shape) as well as the operating conditions so that thrust washers performance can be predicted and optimized.

Effect of Surface Roughness on Hydrodynamic Lubrication of Slider Bearings

Abstract: The effect of surface roughness on the performance of hydrodynamic slider bearings is studied. A generalized form of surface roughness characterized by a stochastic random variable with non-zero mean, variance and skewness is assumed to define the bearing surface topography. Various film shapes such as: plane slider, exponential, secant and hyperbolic are considered. The results are obtained for the general lubricant film shape in integral form which are numerically computed for the shapes under consideration. The results are presented both graphically as well as in tabular form. The performance of a rough bearing can be considered in terms of an identical smooth bearing with an equivalent film thickness. It is observed, for the lubricant film shapes under consideration, that the increasing positive values of α, σ and e decrease the load carrying capacity, frictional force and temperature rise while it increases the coefficient of friction. Increasing positive values of α and e shift the center of pressur...

Hydrodynamic bearing device

Abstract: A pair of thrust hydrodynamic bearing portions are made to communicate with each other to form fluid circulating passages for equalizing a pressure imbalance between both thrust hydrodynamic bearing portions Even in a case where a pressure imbalance has occurred in a lubricating fluid inside the thrust hydrodynamic bearing portions due to such a cause as the deformation of a thrust plate, the lubricating fluid is allowed to move between the pair of upper and lower thrust hydrodynamic bearing portions through the fluid circulating passages so as to overcome the pressure imbalance, thereby making it possible to stably obtain the amount of floatation in the thrust hydrodynamic bearing portions

Effect of Using Current-Carrying-Wire Models in the Design of Hydrodynamic Journal Bearings Lubricated with Ferrofluid

Abstract: Based on the momentum and continuity equations for ferrofluid under an applied magnetic field, a modified Reynolds equation has been obtained. Assuming linear behavior for the magnetic material of the ferrofluid, the magnetic force was calculated. The magnetic pressure resulting from the magnetic force was incorporated into the Reynolds equation and it was not separately treated. The derived Reynolds equation can be applied for any magnetic field distribution model. Using different magnetic field models, the equation has been solved numerically by the finite difference technique with an appropriate iterative technique and pressure distributions have been obtained. The boundary shapes of the load-carrying active regions and cavitation regions could be then determined. The solution gives the bearing performance characteristics, namely; load-carrying capacity, attitude angle of the journal center, friction coefficient and bearing side leakage. The displaced current-carrying infinitely long wire gives a field distribution with a gradient in the circumferential direction. Two novel field models are introduced. The concentric finite current-carrying-wire model gives an axially symmetric magnetic field with a gradient in the axial direction. Axial and circumferential gradients are obtained using displaced finite wire model. The effect of these magnetic models and their design parameters on the overall bearing performance characteristics has been studied. The results concluded that the magnetic lubrication provides a higher load capacity and a reduced friction coefficient, compared with a conventional lubricated bearing. The other bearing characteristics depends on the applied field model. An axially symmetric applied field, with its sealing magnetic force, leads to a decrease in the side leakage, such that the bearing may operate without side leakage by appropriate design of the field.

Analysis of Bouncing Vibrations of a 2-DOF Model of Tripad Contact Slider Over a Random Wavy Disk Surface

Abstract: We numerically analyzed the bouncing vibrations of a two-degree-of-freedom (2-DOF) model of a tri-pad contact slider with air bearing pads over a random wavy surface and manifested the design conditions of a contact slider. The effects of the design parameters such as air bearing stiffness, contact damping ratio, the coefficient of friction, and the characteristics of the disk surface waviness on dynamic behavior and the contact sliding ability of the slider have been investigated. As a result, we found that friction force decreases the contact sliding ability at the boundary of the intermittent and continuous contact sliding. We also found that the distance between the rear air bearing center and the contact pad has a significant effect on the contact sliding ability. If the contact pad is apart from the rear air bearing center, the contact pad tends to separate from the disk. Based on this analytical study, we have proposed two design concepts: (1) Make the distance between the rear air bearing center and the contact pad as small as possible; in this case, the larger the rear air bearing stiffness results are, the better the contact ability is; (2) If some distance between the rear air bearing center and the contact pad is inevitable, then make the rear air bearing stiffness much smaller than the contact stiffness.

Low-Order Models for Very Short Hybrid Gas Bearings

Abstract: A low-order model was created to analyze a small-scale gas bearing with a diameter of 4.1 mm, designed to spin at 2.4 million rpm. Due to microfabrication constraints, the bearing lies outside the standard operating space and stable operation is a challenge. The model is constructed by reference to Newton's second law for the rotor and employs stiffness and damping coefficients predicted by other models. At any operating point it is able to predict (1) whether the journal can sustain stable operation, and (2) the whirling frequency of the journal. Analysis shows that the best way to operate the bearing is in a hybrid mode where the bearing relies on hydrostatics at low speeds and hydrodynamics at high speeds. However, in transitioning from hydrostatic to hydrodynamic operation, the model shows that the bearing is prone to instability problems and great care must be taken in scheduling the bearing pressurization system in the course of accelerating through low and intermediate rotational speeds.

Spring-Supported Thrust Bearings Used in Hydroelectric Generators: Comparison of Experimental Data with Numerical Predictions

Abstract: Laboratory experiments that simulate the conditions acting on large spring-supported thrust bearings in hydroelectric generators were performed and film thicknesses, temperatures and pressures were measured. A software package provided theoretical predictions of the experimental results. This software used a control volume, numerical formulation to model the three dimensional flow of mass, momentum and energy in the thrust bearing and included thermoelastic deflection of the pad and flow of oil in the groove between the pads. A detailed comparison of the experimental data with the numerical predictions showed quite good overall agreement, particularly with the deformed shape and temperatures of the pad. The agreement provided evidence of the fidelity of the software package and supported its continued use in analysis and design. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Toronto, Ontario, Canada, October 26–28, 1998

Hydrodynamic bearings having strain sensors

Abstract: A hydrodynamic bearing includes a fiber optic sensor for measuring static and dynamic bearing forces or loads during operation. The fiber optic sensor is positioned within the bearing through the most direct load path, which is through the pad support for a tilting pad style bearing. In additional to being positioned in the pad support of a tilting pad bearing, the sensor is also placed 1) inside the pad support or on the pad support structure, and 2) oriented perpendicularly with the shaft centerlines. After the sensor location is chosen and the sensor is properly positioned, a calibration procedure is utilized to determine the relationship between the radial load and measured strain for the specific bearing. Once the calibration factor has been determined, the sensor may be utilized in the bearing to measure load during operation.

An Efficient Journal Bearing Lubrication Analysis For Engine Crankshafts

Abstract: A computationally efficient method is presented for solving the journal bearing lubrication problem in crankshaft-block interaction studies of internal combustion engines. The Reynolds' equation is solved using the finite element method. Four degrees of freedom (vertical and horizontal translations and rotations) are used for each bearing accounting, therefore, for the journal misalignment within the bearing. A bilinear rectangular element with “hourglass control” is used to discretize the two-dimensional oil film domain and develop the element fluidity matrices and load vectors. At each time step, a linear perturbation technique is employed for solving the Reynolds' equation for computational efficiency purposes. The combination of the linear perturbation approach with the “hourglass control” ensure the computational efficiency of the lubrication analysis with minimal loss of accuracy. The accuracy of the developed bilinear oil film element is first demonstrated by comparison with the analytical solution...

Design of high-speed magnetic fluid bearing spindle motor

Abstract: A high-speed magnetic-fluid bearing spindle motor for hard disk drive is introduced. Some design challenges and considerations of its load capacity, stiffness, power consumption, lubricant leakage and shock resistant capability are addressed. The prototypes were fabricated and the test results of the prototypes are presented and discussed. The results show that the magnetic-fluid bearing spindle motor is very promising for use in future hard disk drives.

Influence of Axial Thrust Bearing on the Dynamic Behavior of an Elastic Shaft: Coupling Between the Axial Dynamic Behavior and the Bending Vibrations of a Flexible Shaft

Abstract: This paper presents the nonlinear dynamic behavior of a flexible shaft. The shaft is mounted in two journal bearings and the axial load is supported by a hydrodynamic thrust bearing. The coupling between the axial thrust bearing behavior and the bending vibrations of the shaft is studied in particular. The shaft is modeled with typical beam finite elements. The dynamic behaviors of the fluid supports are considered as nonlinear. The dynamic behavior is analyzed using an unsteady time integration procedure. The paper shows the coupling between the axial dynamic behavior and the bending vibrations of the shaft.

Thermal compensation without creep in a hydrodynamic bearing

Abstract: A hydrodynamic bearing is provided comprising a shaft having a pair of spaced apart conical bearings supporting a surrounding sleeve for rotations. The sleeve comprises a single piece rather than the two-piece design separated by a rubber expansion joint of the prior art. Instead upper and lower slots are cut into the sleeve, and the rings are pressed or otherwise tightly fitted into each slot. The single piece sleeve which also incorporates the bearing seats for the conical bearings on the shaft, is made of aluminum, while each ring is made of steel (as is the shaft and bearing cones). As the temperature rises at which the hydrodynamic bearing is operated, the sleeve expands axially putting the bearing seat closer to the cone, effectively compensating for the thinning of the fluid which supports the bearing seat and sleeve for rotation relative to the cone. Meanwhile, the steel ring, being of the same material as the shaft, prevents the aluminum sleeve from expanding radially away from the cone. Further, the axial length of the interface between the sleeve and ring can be adjusted to control the amount of thermal compensation into any system, allowing for very accurate control of the thermal compensations scheme.

Electric spindle motor with magnetic bearing and hydrodynamic bearing

Abstract: An electric spindle motor for use in precision instruments such as hard disk drives comprises a stationary sub-assembly and a rotary sub-assembly movable relative to the stationary sub-assembly for carrying magnetic disks. The electric spindle motor has an integrated bearing system including a hydrodynamic journal bearing for providing desired radial load and a magnetic bearing for reducing friction resistance during staring/stopping and running of the electric spindle motor. The rotary sub-assembly is suspended from the stationary sub-assembly by the activation of the magnetic bearing during the rotating of the electric spindle motor. The electric spindle motor having integrated hydrodynamic journal bearing and magnetic bearing of the present invention is capable of high speed and high accuracy running, providing increased radial load and stiffness, and reduces the friction resistance therefore improves the performance and power saving.

Influence of Inlet Conditions on the Thermohydrodynamic State of a Fully Circumferentially Grooved Journal Bearing

Abstract: A thermohydrodynamic (THD) analysis of a fully circumferentially grooved hydrodynamic bearing is presented. The pressure distribution is obtained using the short bearing approximation taking into account the viscosity variation in the radial and circumferential coordinates. The axial temperature variation is also included by an axial averaging technique, which incorporates the supply pressure and film entry temperature in the energy equation. It is found that the determination of the lubricant temperature at the entry to the film plays an important role in the overall temperature distribution in the bearing. A simplified approach for determining this temperature is presented. An extensive set of experimental results performed by Maki and Ezzat (1980, ASME J. Lubr. Technol., 102, pp. 8-14) is used for validation purposes. The results show that mixing in the inlet groove may cause the film entry temperature to be significantly different from the nominal supply temperature and hence have a significant influence on the bearing temperature.

Gas turbine device

Abstract: PROBLEM TO BE SOLVED: To provide a gas turbine device capable of increasing the load capacity of thrust air bearings for supporting a rotary shaft. SOLUTION: This gas turbine device is provided with a gas turbine engine 1, a driven equipment having a gas turbine engine and a rotary shaft 53 for common use, and thrust air bearings 69A and 69B for supporting the rotary shaft 53 axially. The gas turbine engine 1 is provided with a compressor 4, combustor 6 and a turbine 5. The thrust air bearings 69A and 69B have a rotary disk 73, which is uniform in thickness and fixed to the rotary shaft 53, and foil elements 75 and 76, which intervene between the external peripheral section of the main face of the rotary disk 73 and a stationary section 74, which opposed to the external peripheral section. Mounting holes 82 are formed at a plurality positions separated from shaft center 1 in the rotary shaft 73, and the rotary shaft 73 is mounted on one end face of the rotary shaft 53 by mounting members 83 which are inserted into these mount ting holes 82. COPYRIGHT: (C)2003,JPO

Effects of Moving Three-Dimensional Nano-Textured Disk Surfaces on Thin Film Gas Lubrication Characteristics for Flying Head Slider Bearings in Magnetic Disk Storage

Abstract: This paper describes the effects of moving three-dimensional nano-textured or patterned disk surfaces on thin film gas lubrication characteristics for flying head slider bearings in magnetic disk storage, In order to perform the most realistic simulation of slider flying characteristics over the textured disk surfaces, the direct numerical simulation method is used, instead of using various averaging techniques. Therefore, a deterministic description of the texture is adopted in this study. A dynamic analysis of the slider responses can be carried out, by solving the air bearing equation based on the linearized Boltzmann equation with the equations of motion of the slider under the excitation of the moving texture simultaneously. The slider's dynamic responses to moving spaced bumps disk surfaces, including both the circumferentially and radially ridged disk surfaces, are computed systematically and basic slider dynamics over patterned disk surfaces is investigated, The effects of the texture area ratios (= texture width/texture pitch) in the circumferential and radial directions on the slider spacing dynamic modulations as well as the slider static flying characteristics are also studied. Furthermore, the effects of three kinds of texture patterns on the slider flying characteristics are investigated. Considering those simulation results, the design optimization for the texture pattern that minimizes not only the slider static flying height increase but also spacing dynamic modulations is discussed in order to achieve ultra-high density proximity magnetic recording.

Apparatus and method for setting bearing gaps in an electric motor

Abstract: An apparatus and method for setting a gap in a hydrodynamic bearing of a disc drive spindle motor. The invention comprises placing an end of the shaft into shaft support apertures in the hub, fitting a thrust bearing counterplate into a recess defined by an annular retaining flange that is proximate the end of the shaft, and deforming the counterplate to form a gap between the end of the shaft and a surface of the counterplate.

Rotation effects on hybrid hydrostatic/hydrodynamic journal bearings

Abstract: Investigates rotation effects on hybrid plain journal bearings with various feeding mechanisms, i.e. orifice, capillary and porous feedings. Employs the numerical method of the finite difference to solve Reynolds equations. Shows that higher speed of rotation induces greater hydrodynamic load capacity, especially with an eccentricity ratio e > 0.85. The porous and orifice feedings also result in higher load capacity than orifice and capillary feedings when the rotation speeds increase. Also analyses the multi‐array of hole‐entry of orifice and capillary feedings and the results show that the bearings with more arrays of feedings produce higher load capacity at low speed. However, the bearings with fewer arrays of feedings produce higher load capacity at high speeds. In other words, the transition from the hydrostatic to hydrodynamic load capacity of the bearing is significant to hybrid plain journal bearings.

Analysis of Gas-Lubricated Bearings with a Coupled Boundary Effect for Micro Gas Turbine ©

Abstract: Due to the limitation of micro-machining technology, the hearing aspect ratio for a micro gas turbine is limited to a small value. Therefore, the load-carrying capacity of such bearing is inherently small. Thus, it is desirable to predict the load-carrying capacity as accurately as possible without being unnecessarily conservative. The direct numerical analysis of bearing characteristics was performed by mass conservation at coupled boundary. Journal bearing was numerically simulated for two cases - 1) an externally pressurized bearing with four feeding holes and 2) a hydrodynamic bearing. Characteristics such as pressure distribution at the bearing surface, load-carrying capacity as a function of aspect ratio with a coupled boundary effects are investigated for micro gas turbine bearings. It is shown that a model of thrust and journal hearings coupled at boundary generally predicts a greater load-carrying capacity than uncoupled models.

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

Abstract: A theoretical study has been carried out to determine an approximate analytical description of the fluid film force of a symmetrical rigid rotor supported on two finite-length lubricated journal bearings. The analysis has been conducted assuming the Warner solution for the pressure field. The analytical approach to studying the behaviour of a system is more effective than numerical investigation, and makes it possible to cover not only an individual system, but also the whole class to which that system belongs. Furthermore, the model proposed allows quick analytical determination of the stiffness and damping coefficients.