Showing papers on "Fluid bearing published in 2000"

Load Capacity Estimation of Foil Air Journal Bearings for Oil-Free Turbomachinery Applications

Abstract: This paper introduces a simple “Rule of Thumb” (ROT) method to estimate the load capacity of foil air journal bearings, which are self-acting compliant-surface hydrodynamic bearings being considere...

Performance and Durability of High Temperature Foil Air Bearings for Oil-Free Turbomachinery

Abstract: The performance and durability of advanced, high temperature foil air bearings are evaluated under a wide range (10 to 50 kPa) of loads at temperatures from 25° to 650 °C. The bearings are made from uncoated nickel based superalloy foils. The foil surface experiences sliding contact with the shaft during initial start/stop operation. To reduce friction and wear, the solid lubricant coating, PS304, is applied to the shaft by plasma spraying. PS304 is a NiCr based Cr2O3 coating with silver and barium fluoride/calcium fluoride solid lubricant additions. The results show that the bearings provide lives well in excess of 30,000 cycles under all of the conditions tested. Several bearings exhibited lives in excess of 100,000 cycles. Wear is a linear function of the bearing load. The excellent performance measured in this study suggests that these bearings and the PS304 coating are well suited for advanced high temperature, oil-free turbomachinery applications. Presented at the 55th Annual Meeting Nashville, Tenn...

Analysis of Gas Lubricated Foil Thrust Bearings Using Coupled Finite Element and Finite Difference Methods

Abstract: Load performance of gas lubricated, compliant surface foil thrust bearings has an interlocking relationship with the compliance of the bearing and hydrodynamics of convergent wedge surface. Compliance of the bearing consists of supporting spring elements (elastic foundation) and a smooth elastic top foil. In this paper, a class of gas lubricated foil thrust bearings has been investigated analytically utilizing a novel approach which combines Finite Difference (FD) and Finite Element (FE) methods. Solution of the governing hydrodynamic equations dealing with compressible fluid is coupled with the structural resiliency of the foil bearing surfaces. FD method is utilized for hydrodynamic analysis while FE is used to model structural resiliency. Influence coefficients were generated to address the elasticity effects of combined top foil and elastic foundation on the hydrodynamics of thrust bearing, and were used to expedite the numerical solution. Within 2 to 3 iterations the convergence criterion was reached. The overall program logic proved to be an efficient technique to deal with the complex structural compliance of various foil bearing. Case study has been conducted and sample solutions are provided. Unlike prior analytical investigations, the essential effect of the top foil on the performance of the bearing has been elucidated.

Oil-Free Turbocharger Demonstration Paves Way to Gas Turbine Engine Applications

Abstract: An oil-free, 150 Hp turbocharger was successfully operated to 100% speed (95,000 rpm), with turbine inlet temperatures to 650°C on a turbocharger gas test stand. Development of this high speed turbomachine included bearing and lubricant component development tests, rotor-bearing dynamic simulator qualification and gas stand tests of the assembled turbocharger. Self acting, compliant foil hydrodynamic air bearings capable of sustained operation at 650°C and maximum loads to 750 N were used in conjunction with a newly designed shaft and system center housing. Gas stand and simulator test results revealed stable bearing temperatures, low rotor vibrations, good shock tolerance and the ability of the rotor bearing system to sustain overspeed conditions to 121,500 rpm. Bearing component development tests demonstrated 100,000 start stop cycles at 650°C with a newly developed solid film lubricant coating. In a separate demonstration of a 100 mm compliant foil bearing, loads approaching 4,500 N were supported by a compliant foil bearing. This combination of component and integrated rotor-bearing system technology demonstrations addresses many of the issues associated with application of compliant foil bearings to gas turbine engines.Copyright © 2000 by ASME

Joint Clearances With Lubricated Long Bearings in Multibody Mechanical Systems

Abstract: Proper modeling of joint clearance is of great importance in the analysis and design of multibody mechanical systems. The clearance may be due to wear or imperfection in manufacturing. When there is no lubricant in the clearance solid-to-solid contact occurs. The impulse due to contact between the links is transmitted throughout the system. The presence of a lubricant avoids such contact, as the hydrodynamic forces developed by the lubricant film support the loads acting on the bodies and prevent the bodies from coming into contact. In this paper, an analysis of revolute joint clearances in multibody mechanical systems with and without lubricant is presented. Squeeze as well as viscous effects are considered utilizing the hydrodynamic theory of lubrication in long bearings. Unlike the traditional machine design approach, the instantaneous lubricant forces are the unknown and evaluated in terms of the known geometrical position and velocity of the journal and bearing. In the case of analysis of a joint clearance with no lubricant, a modified Hertzian relation is used to model the impact or contact between the journal and bearing, which includes a hysteresis damping term to account for the energy dissipation during impact. The methodology is applied for the analysis of a slider-crank mechanism having a clearance in the piston pin. The simulations are carried out with and without lubricant and the results are compared, It is shown that the lubricant results in a steady motion with fewer peaks in the required cranking moment for the system.

On the Performance of Hybrid Foil-Magnetic Bearings

Abstract: Recent technological advancements make hybridization of the magnetic and foil bearing both possible and extremely attractive. Operation of the foil/magnetic bearings takes advantage of the strengths of each individual bearing while minimizing each others weaknesses. In this paper one possible hybrid foil and magnetic bearing arrangement is investigated and sample design and operating parameters are presented. One of the weaknesses of the foil bearings, like any hydrodynamic bearing, is that contact between the foil bearing and the shaft occurs at rest or at very low speeds and it has low load carrying capacity at low speed. For high speed applications, AMBs are, however, vulnerable to rotor-bending or structural resonances that can easily saturate power amplifiers and make the control system unstable. Since the foil bearing is advantageous for high speed operation with a higher load carrying capacity, and the magnetic bearing is so in low speed range, it is a natural evolution to combine them into a hybrid bearing system thus utilizing the advantages of both. To take full advantage of the foil and magnetic elements comprising a hybrid bearing, it is imperative that the static and dynamic characteristics of each bearing be understood. This paper describes the development ofmore » a new analysis technique that was used to evaluate the performance of a class of gas-lubricated journal bearing. Unlike conventional approaches, the solution of the governing hydrodynamic equations dealing with compressible fluid is coupled with the structural resiliency of the bearing surface. The distribution of the fluid film thickness and pressures, as well as the shear stresses in a finite-width journal bearing, are computed. Using the Finite Element (FE) method, the membrane effect of an elastic top foil was evaluated and included in the overall analytical procedure. Influence coefficients were generated to address the elasticity effects of combined top foil and elastic foundation on the hydrodynamics of journal bearings, and were used to expedite the numerical solution. The overall program logic proved to be an efficient technique to deal with the complex structural compliance of various foil bearings. Parametric analysis was conducted to establish tabulated data for use in a hybrid foil/magnetic bearing design analysis. A load sharing control algorithm between the foil and magnetic elements is also discussed.« less

A new 3-DOF Z-tilts micropositioning system using electromagnetic actuators and air bearings

Abstract: A new 3-DOF Z-tilts (z, pitch, and roll motion) micropositioning system has been developed. It uses electromagnetic actuators and air bearings. An electromagnetic actuator produces an attraction force between the air bearing and the base plate. An air bearing has the role of suspension and guidance, with a clearance of several tens of micrometers in the z-direction. Therefore, this system has design features of guiding 3-DOF XYθ motion without limiting the plane motion and playing the role of a z-directional position actuator. With the control of current, the equilibrium position between magnetic attraction force and air bearing thrust force can be controlled with inherently infinite resolutions. The theoretical background of an electromagnetic actuator is explained. Then, an air bearing is analyzed in the point of z-directional positioning mechanism. The air bearing can be modeled as a second-order system with parameter variation—stiffness and damping vary with respect to the z-directional displacement. Therefore, a simple robust control algorithm is applied to improve the control performance. With the aid of robust control, this system provides 25 nm positioning resolution over the total range of 40 μm along the z-direction and, accordingly, 0.29 μrad resolution over the total range of 460 μrad in pitch and roll motion.

Squeeze Film Air Bearings Using Piezoelectric Bending Elements

Abstract: Reference LSA-CONF-2000-016 Conference Web Site: http://server.woomeranet.com.au/~movic2000/default.html Record created on 2006-12-07, modified on 2016-08-08

Parametric study of spiral groove gas face seals

Abstract: A finite element analysis for the isothermal flow in spiral groove gas face seals is detailed along with a successive approximation method for the iterative solution of the nonlinear Reynolds equation. Zeroth- and first-order pressure fields are calculated for evaluation of the seal opening force and leakage and the axial stiffness and damping force coefficients, respectively. A parametric study shows the static and dynamic force behavior of a baseline SGFS operating with a large pressure ratio. The recommended geometric parameters presented ensure large static stiffness and damping force coefficients while still allowing for low seal leakage rates. A reduction in the power loss and a significant increase in the seal static stiffness coefficient are unique features of thin seal dams. Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in Orlando, Florida, October 11–13, 1999

Motor including hydrodynamic bearings with pair of thrust plates

Abstract: Disk-drive motor having two hydrodynamnic bearing sections separated with respect to the shaft by an air intervention, each composed of a radial and a thrust dynamic-pressure bearing portion, and in each of which lubricant is retained continuously throughout the radial and thrust bearing portions At least one communicating pathway is formed in the sleeve, axially communicating the thrust faces that are constituents of, and retaining lubricant continuously with, the pair of thrust bearing portions. Via the communicating pathway, the lubricant retained in the two hydrodynamic bearing sections shifts mutually from the one section to the other, such that the radii of curvature of the meniscuses forming the respective boundaries arc equalized. The amount of lubricant held in the bearing sections is accordingly equalized and lubricant leaking out of the radial bearing portions is taken up and re-circulated.

Both ends open fluid dynamic bearing having a journal in combination with a conical bearing

Abstract: A method of creating an improved hydrodynamic fluid bearing is provided which is relatively insensitive to shock vibration changes in load and rotational speed. The hydrodynamic bearing motor in which the bearing is open at both the upper and lower ends, and in which the balance of fluid flow within the bearings is maintained. The assembly of the hydrodynamic bearing is more easily assembled, and the gaps are easily adjusted. In the design of the hydrodynamic bearing, the tolerances for assembly of the various components is minimized; that is, the critical nature of many of the gaps is diminished.

THD Analysis of Tilting Pad Thrust Bearings—Comparison Between Theory and Experiments

Abstract: The objective of the present research is to verify a THD model of hydrodynamic thrust bearings. The developed model of a pivoted pad bearing, which can tilt both radially and circumferentially, allows for three-dimensional temperature distribution in the oil film and in the pad, as well as two-dimensional temperature variation in the runner. Viscosity and density are treated as functions of both temperature and pressure. Experiments have been performed on a test rig, containing two identical equalizing pivoted pad thrust bearings. Power loss, runner temperature, and pressure profiles as a function of load and rotational speed are compared for both theoretical and experimental investigations. Fairly good agreement has been found when the oil inlet temperature and heat transfer coefficients have been estimated in order to get the same runner temperature in both theory and experiment.

Characteristic analysis of hydrodynamic bearings for HDDs

Abstract: In this paper we describe the application of Hydrodynamic Bearings (HDBs) to conventional products and discuss the technical distinctions of HDBs between HDD applications and another applications. We also report on numerical analytical and experiments aimed at solving the characteristic problems of high-speed HDDs.

Bearings and mechanical seals enhanced with microstructures

Abstract: Properties of mechanical bearings and mechanical seals can be significantly improved by covering the load-bearing surfaces with fields of high aspect ratio microstructures (HARMs), such as microchannels or microposts. The HARMs can substantially enhance heat transfer capability and lubricant flow. The present invention uses microstructures and micro-channels manufactured by a modified LIGA process to enhance the performance of load bearing surfaces. Benefits include reduced operating temperatures, precise metering of lubricant flow to all affected surfaces, increased reliability, increased life, higher maximum rotational speed, and the ability of the seal or bearing to run “dry,” that is, without periodic re-application of lubricant. The invention may be used with a variety of bearings and mechanical seals, including for example ball bearings, roller bearings, journal bearings, air bearings, magnetic bearings, single mechanical seals, double mechanical seals, tandem mechanical seals, bellows, pusher mechanical seals, and all types of rotating and reciprocating machines. Improved cooling jackets are also disclosed, for use with bearings, seals, or other applications.

Bulk-Flow Analysis of Hybrid Thrust Bearings for Process Fluid Applications

Abstract: Advanced cryogenic fluid turbopumps are very compact, operate at extremely high shaft speeds, and require hybrid (hydrostatic/hydrodynamic) radial and thrust fluid film bearings for accurate rotor positioning. Sound design and reliable operation of fluid film thrust bearings also allows for unshrouded impellers with a significant increase in the turbopump mechanical efficiency. A bulk-flow analysis for prediction of the static load performance and dynamic force coefficients of high speed, angled injection orifice-compensated, hybrid (hydrostatic/hydrodynamic) thrust bearings is presented. The model accounts for the bulk-flow mass, momentum and thermal energy transport, and includes flow turbulence and fluid inertia (advection and centrifugal) effects on the bearing film lands and recesses. The performance of a refrigerant hybrid thrust bearing for an oil-free air conditioning equipment is evaluated at two operating speeds and pressure differentials. The computed results are presented in dimensionless form to evidence consistent trends in the bearing performance characteristics. As the applied axial load increases, the bearing film thickness and flow rate decrease while the recess pressure increases. The axial stiffness coefficient shows a maximum for a certain intermediate load while the damping coefficient steadily increases with load. The computed results show the significance of centrifugal fluid inertia at low recess pressures (i.e. low loads) and high rotational speeds, and which can lead to film starvation at the bearing inner radius and subambient pressures just downstream of the bearing recess edge.

Effect of Fluid Inertia on Stability of Oil Journal Bearings

Abstract: In the analysis of hydrodynamic journal bearings the effect of fluid inertia is generally neglected in view of its negligible contribution compared to viscous forces. However, the fluid inertia effect is to he taken in the analysis when modified Reynolds number is around one. Though there are a few attempts to analyse steady-state and dynamic characteristics of finite journal bearings, stability of the journal under the effect of fluid inertia is yet to he investigated. An attempt has been made to evaluate the mass parameter (a measure of stability) besides finding out the steady-state characteristics of finite journal bearings considering the effects of fluid inertia. The analysis is carried out for modified Reynolds number ∼O(l.), which is assumed to be laminar. A nonlinear time transient analysis is carried out for the stability analysis.

Viscous fluid charging method of fluid bearing, and motor

Abstract: PROBLEM TO BE SOLVED: To provide a viscous fluid charging method of a fluid bearing generating no irregulality in generating of dynamic pressure, by certainly removing bubble in lubricating oil 25, viscous fluid generating the dynamic pressure, and certainly charging the lubricating oil in a predetermined space. SOLUTION: In this charging method, pressure of environment around an assembly body into which the lubricating oil 25 has been injected is reduced to previously exhaust air inside the bearing (process shown in Fig. 1 (B)), and then the pressure of the environment around the assembly body is returned to a normal value to press and charge the viscous fluid into the predetermined space (process shown in Fig. 1 (C)). COPYRIGHT: (C)2002,JPO

Frequency characteristics of stiffness and damping effect of magnetic fluid bearing

Abstract: In this study, we measured damping characteristics and frequency characteristics of magnetic fluid bearing spindles using a high-frequency vibration base by a piezo actuator. Using the high-frequency vibration base, high frequency excitation was added to magnetic fluid bearing spindles mounted on the vibration base, and we proved that magnetic fluid bearing spindles have effective damping. Also the damping effect became larger with higher spindle rotational speed.

Thermoelastohydrodynamic Analysis of Tilting Pad Journal Bearing—Theory and Experiments

Abstract: Thermal and elastic effects play a very important role in lubrication of tilting pad journal bearings. This paper presents both theoretical and experimental analysis of tilting pad journal bearing. Theoretical analysis includes the simultaneous solution of Reynolds equation, energy equation and deformation equation. The computer code has been developed based on FEM which will work for large number of pads. Experimental study has been carried out on a four-pad tilting pad journal bearing, load between pad configuration and load on pad configurations with the rotational speed varied from 500-4000 rpm. Twelve thermocouples are used to measure pad temperatures. Coastdown time analysis results are presented in the form of Stribeck diagram of friction and compared with theoretical ones. Theoretical results are presented for steady-state and dynamic-state conditions of a four-pad tilting pad journal bearing. Presented as a Society of Tribologists and Lubrication Engineers paper at the World Tribology Congress in...

Zero static-friction actuator pivot bearing for production disk drives

Abstract: A hydrostatic bearing assembly, with an integral rotating-shaft hydrodynamic pump, adapted for use as a stiff zero static-friction actuator pivot bearing for the head-stack assembly of a disk drive data storage apparatus. The zero static-friction pivot bearing avoids all “limit cycling” and “sticking” problems arising from static bearing friction during micro-tracking operations. The motor-driven hydrodynamic pumping element is disposed coaxially to the zero static-friction hydrostatic bearing element in a single assembly adapted for use as an actuator pivot bearing. The hydrodynamic pumping element and the hydrostatic bearing element both use a plurality of spaced-apart radial journal-bearing layers and a plurality of axial thrust-bearing layers to provide stiffness in all directions at any rotational velocity. The lubricating fluid pressure within the hydrodynamic pumping element is controlled on both sides of every bearing layer by coupling all radial journal-bearing layers and axial thrust-bearing layers to a circumferential undercut (or overcut) and by coupling these circumferential undercuts to ambient pressure through a plurality of fluid-filled passages in the several rotating and stationary elements. The fluid bearing layers are coupled to form a continuous pressure-controlled fluid film sealed at three ends by surface tension. In an actuator pivot bearing for a disk drive data storage apparatus, the hydrodynamic pump motor can be operated under the control of a dual phase-locked motor drive controller to synchronize it with a spindle motor element in a manner that cancels vibrations arising from both motors.

Hydrodynamic bearing, hydrodynamic bearing apparatus

Abstract: In a hydrodynamic bearing apparatus for rotatably supporting a rotor by a hydrodynamic bearing, wear of the apparatus caused by sliding contact of dynamic pressure bearing faces in starting and stopping thereof is prevented to thereby promote durability, working of a dynamic pressure generating groove is facilitated and the bearing faces are prevented from being adsorbed to each other. By providing a low friction metal layer having water repellency at dynamic pressure bearing portions of a hydrodynamic bearing apparatus, friction can be reduced, wear or dust formation can effectively be restrained and the bearing faces can be prevented from being adsorbed to each other by dew condensation.

Vibration analysis of fluid dynamic bearing spindles with rotating-shaft design

Abstract: This paper is to present theoretical and experimental vibration analysis of fluid dynamic bearing (FDB) spindles with rotating-shaft design. In the theoretical analysis, a mathematical model is developed to predict half-speed whirls, rocking modes, frequency response functions (FRF), and transient responses. In the experimental studies, a FDB spindle with rotating-shaft design carrying four identical disks is tested. An impact hammer applies an impact force to the top disk in the out-of-plane direction and a capacitance probe measures the transverse vibration of the top disk. FRF and impulse response are obtained to verify the mathematical model.

Conductive lubricant for fluid dynamic bearing

Abstract: There is provided is a conductive lubricant for a fluid dynamic bearing being able to ground static electricity occurring at the fluid dynamic bearing without impairing the performance of the fluid dynamic bearing. This conductive lubricant for a fluid dynamic bearing is provided by an ester base oil such as dioctyl sebacate that concurrently has heat resistance, a small quantity of evaporation, low cost and wettability to metal, which are necessary for a fluid dynamic bearing. The conductive lubricant contains 0.1 to 5 percent by weight of antistatic additive such as alkyl aryl sulfonate having an affinity for this ester base oil. Therefore, this antistatic additive imparts conductivity to the base oil, by which the static electricity occurring at the fluid dynamic bearing can be grounded without impairing the lubrication performance.

Bearing structure for turbo charger

Abstract: PROBLEM TO BE SOLVED: To reduce the vibration generated in rotating a turbine shaft of a turbo charger and to suppress the generation of the sound by reducing the weight of oil film dampers supported from the circumferences of ball bearings of the turbine shaft in a turbine shaft penetration part of a bearing housing. SOLUTION: This bearing structure for the turbo charger is formed by integrally connecting a turbine housing 1 with a compressor housing 2 via the bearing housing 3. This bearing structure is provided with the ball bearings 25 and 26 fitted in the axial both ends of the turbine shaft penetration part of the bearing housing 3 as journal bearings 3a and the oil film dampers 27 inserted in the outside diameter parts of the respective bearings 25 and 26 for absorbing the vibration of the ball bearings 25 and 26 and composed of an approximately cylindrical heat-resistant synthetic resin material. COPYRIGHT: (C)2001,JPO

Surface Roughness Evolution of Ball Bearing Components

Abstract: An accurate knowledge of the expected life is essential to the proper selection of ball bearings. Bearings principally fail owing to fatigue if they are properly lubricated, mounted and sealed against the entrance of dirt. Fatigue life is strongly correlated to the surface roughness. Experiments were performed to evaluate the effects of different ball bearings materials on the surface roughness, the bearing temperature and the power consumption of a high speed spindle. The use of hybrid or pseudo-hybrid ball bearings show competitive tribologic characteristics and a slower increase in surface roughness with reference to steel, which makes them very attractive for high speed spindle systems. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference In Toronto, Ontario, Canada, October 26–28, 1998

Spindle motor and magnetic disc device with hydrodynamic bearing

Abstract: A rotary shaft is rotatably supported by a hydrodynamic fluid radial bearing and a hydrodynamic fluid thrust bearing which are excellent in shock resistance, an bearing arrangement in which vibration in a translation mode of the shaft, among vibration components caused by unbalance force exerted to the rotary shaft, is supported by the radial bearing, and vibration in conical mode is supported by the thrust bearing, magnetic fluid is used as lubrication oil, and a permanent magnet is located between the radial bearing and the thrust bearing so as to apply a magnetic attracting force between the rotary shaft and the thrust bearing so as to carry out axial positioning in order to use the magnetic disc device in an arbitrary attaching posture. With this arrangement, the magnetic disc device using such a bearing arrangement can enhance portability, thinning and antishock ability, and reduce noise and power consumption, thereby it is possible to provide a note-type personal computer with a high degree of reliability.