Showing papers on "Fluid bearing published in 1993"

Experimental Versus Theoretical Characteristics of a High-Speed Hybrid (Combination Hydrostatic and Hydrodynamic) Bearing

Abstract: The high-speed test facility designed and installed at Texas A&M to study water lubricated journal bearings has been successfully used to test statically an orifice compensated five-recess-hybrid (combination hydrostatic and hydrodynamic) bearing for two radial clearance configurations. Measurements of relative-bearing position, torque, recess pressure, flow rate, and temperature were made at speeds from 10,000 to 25,000 rpm and supply pressures of 6.89 MPa (1,000 psi), 5.52 MPa (800 psi), and 4.14 MPa (600 psi)

Tilt pad variable geometry bearings having tilting bearing pads and methods of making same.

Abstract: A one piece hydrodynamic bearing which replicates the function and performance of more costly tilt pad bearings. The pads (12) are supported on a single thin web (37) for pivoting on a support structure which can include one or more beam-like members (14). The support structure preferably includes a primary support portion, a secondary support portion and a tertiary support portion. The beams (14) allow deflection of the pad (12) by either deflecting or twisting in a torsional mode. The bearing pad support structure may include portions which are fluid dampened.

Lubrication With Binary Mixtures: Bubbly Oil

Abstract: Mixtures do not exhibit Newtonian behavior even when their individual components themselves are Newtonian, and thus classical lubrication theory is not applicable to bearings lubricated with mixtures. Our objective is to extend hydrodynamic lubrication theory to lubrication with mixtures of a Newtonian liquid and an ideal gas. To this end, we make use of the theory of interacting continua and derive two coupled non-linear equations in component densities. The extended theory is tested on finite journal bearings: our results of pressure distribution show good qualitative agreement with the experimental data of Braun et al

Pad type hydrodynamic thrust bearings having a modular construction

Abstract: A hydrodynamic bearing which includes a carrier (10) and a plurality of bearing pads (23) circumferentially spaced about the carrier. The pads may have a modular construction whereby pad portions are secured to support portions (72). The pads may also be releasably secured to the carrier (10). Various bearing pad constructions are contemplated.

A Hydrodynamic Journal Bearing Test Rig with Dynamic Measurement Capabilities

Abstract: A bearing lest rig was developed to characterize the static and dynamic properties of hydrodynamic journal bearings. Static measurement capabilities include operating eccentricity, pressure and thermal boundary conditions, and continuous circumferential pressure and film thickness profiles at multiple axial planes. Dynamic stiffness and damping coefficient measurements are achieved using steady state harmonic excitations generated by a two-axis shaker system. All essential data for a complete understanding of one particular bearing can be collected simultaneously. To ensure high quality results, the rig was designed to minimize the influence of measurement uncertainties on the derived dynamic coefficients. Complete details are described. The rig is configured to lest bearings with 70 mm bore diameters at speeds up to 2500 rpm and loads up to 6000 N. The data reduction technique is presented along with typical results at one steady operating position for a three-lobe bearing which demonstrate the reproduci...

Limitations of the Short Bearing Approximation in Dynamically Loaded Narrow Hydrodynamic Bearings

Abstract: Transient solutions are still widely used for evaluating the vibrational behavior of rotor bearing systems containing dynamically loaded journal bearings with large unbalance, or noncircular orbit type squeeze film dampers, such as dampers without centralizing springs. For parametric design studies, such transient analyses need rapid means for evaluating the motion dependent fluid film forces and for narrow bearings or dampers (aspect ratios less than 0.5) the short bearing approximation (SBA) to the Reynolds equation has generally been assumed. Comparisons with exact numerical solutions under conditions of static loading and pure squeezing show that the SBA pressure profile predictions are significantly in error for aspect ratios as low as 0.25 at eccentricities around 0.9, whereas the optimal parabolic axial profile approximation (MSBA), while retaining all the rapid calculation features of the SBA, is accurate to within 1 percent under the same conditions and to within 3 percent for aspect ratios around 1.0. Using the MSBA as a yardstick under transient solution conditions, the SBA, while satisfactory for aspect ratios of 0.05, was found to be inadequate in predicting transient and steady state orbits and transmitted forces at aspect ratios of 0.5. At these aspect ratios, jump speeds and instability threshold speeds were also found to be erroneously predicted, with speed overestimates of 30 percent possible for practical unbalance situations. In view of the vastly improved accuracy obtainable by the MSBA, its use is to be preferred to the SBA under dynamic loading conditions for aspect ratios around 0.5, and probably around 0.25 or lower.

Analysis of Hydrodynamic Journal Bearings Considering Lubricant Supply Conditions

Abstract: A method of analysis of steadily loaded hydrodynamic journal bearings with a single axial groove (either on the load line or at 90° to the load line) or two diametrically opposed axial grooves is d...

Miniature air bearings

Abstract: A miniature air bearing for supporting and guiding parts has a bearing surface of monocrystalline silicon. Nozzles are formed on the bearing surface by means of anisotropic etching for feeding air.

Compact high power turbopump for a rocket engine

Abstract: A compact high power turbopump for feeding liquid propellant to a rocket engine comprises: a short, large diameter shaft that is capable of rotating; a single impeller providing a large pressure rise at a large flow rate, the impeller being mounted on the short shaft so as to constitute a single pump stage; a ball bearing for supporting the short shaft in a small section zone thereof situated in front of the impeller; a fluid bearing dimensioned so as to withstand a high speed of rotation N and having a large diameter D, the fluid bearing serving to support the short shaft in a large section zone situated behind the impeller; a turbine cantilevered out on the short shaft behind the fluid bearing; an inducer of the high pressure type disposed upstream from the ball bearing on the suction pipe; and metal casing elements for the pump and for the turbine that are of simplified shape.

Air bearing control system

Abstract: The invention comprises a machine having air bearings (60) and a control apparatus (62) for turning off one or more of the air bearings when the machine has been idle for a specified time period.

Angular-compliant hydrodynamic bearing performance under dynamic loads

Abstract: The study is focused on a dynamically loaded composite bearing, consisting of a hydrodynamic journal bearing inside the internal race of a rolling-element bearing. In this combination, the hydrodynamic bearing has an angular-compliant sleeve with a restricted freedom of rotation around its axis. Under static loads, the improvement is primarily in a significant reduction of friction and wear during the starting and stopping. Under periodical loads, our analysis shaws that the performance depends on two dimensionless design parameters. Below particular critical values of these parameters, the results show a considerable improvement, demonstrated by a reduction of the maximum eccentricity. However, above the critical values, the bearing becomes unstable

Design Optimization of Spirally Grooved Thrust Air Bearings for Polygon Mirror Laser Scanners

Abstract: Polygon mirror laser scanners have been widely used in computer peripheral equipment and office automation systems, and improvement in scanning quality has been desired. In light of this, the use of self-acting air bearings has been recommended in spindle design to realize superior performance in terms of rotational speed and rotational errors. This study concerns the analysis of characteristics of spirally grooved thrust air bearings. Namely, it reports the rigidity, load capacity, power loss and critical damping factors. Employed in this study are the finite element method (FEM) and the computer simulation method in order to obtain a numerical solution to the Reynolds equation. Based on calculation results, the load characteristics and the effects of various design parameters of the bearing are discussed, and optimization principles for designing the bearing are proposed. The proposal may be summarized as follows. ( 1 ) The bearing rigidity and load capacity are closely related to the spiral groove width, depth, length in the radial direction and spiral groove pump-in angle, and the number of grooves should be as large as possible. ( 2 ) Decrease in the bearing clearance and increase in the bearing outer radius together achieve the best damping characteristics.

Design of gas bearing systems for precision applications

Abstract: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers.

Nonlinear Study of a Misaligned Hydrodynamic Journal Bearing

Abstract: Hydrodynamic/hydrostatic journal bearings have been widely used in various types of high speed rotating machinery. For space applications, the issue of using cryogenic fluids as working lubricants has steadily gained in significance. The main objective of this paper is to study the nonlinear effects in a hydrodynamic journal bearing with special attention to the effects of journal axial misalignment. The numerical model that couples the Reynolds equation with the dynamics of the rotor is solved by means of a finite difference solution technique. Fluid film pressures that resulted from an iterative scheme are integrated to generate bearing supporting forces. A two-dimensional Newton-Raphson iteration method is used to locate the journal equlibrium position from which both linear and nonlinear bearing stiffness are evaluated by means of the small perturbation technique. The effects of axial misalignment on bearing equilibrium position, lubricant fluid film thickness, pressure distribution, and stiffness cha...

Linear electrostatic actuators: Gap maintenance via fluid bearings

Abstract: This paper addresses a novel actuator for manufacturing applications, the “electrostatic artificial muscle.” Artificial muscle is composed of a dense array of small linear actuators. Its promise lies in the prospect of high performance (e.g. higher force-to-weight ratio and peak acceleration than a comparable magnetic motor), clean, quiet operation, and design versatility (especially the elimination of transmissions in many applications). The characteristics of artificial muscle are particularly appealing for applications in robotics and high-speed automation. A model of a linear electrostatic induction motor is presented to illustrate the potential for high performance as well as the difficulty of “gap maintenance.” Gap maintenance refers to the demanding task of preserving a uniform, narrow gap between “slider” and stator in the presence of destabilizing electrostatic forces. A novel approach to gap maintenance, the use of dielectric fluid bearings, is presented. Analysis of a simple, 2-D motor model shows that gap maintenance and motor efficiency may be characterized by two nondimensional parameters: a levitation number, and a gap aspect ratio. It is shown that achieving both low-speed levitation and high efficiency requires long, narrow gaps (high aspect ratio). The results of this analysis are extended to a more complex model featuring an unconstrained, rigid slider. An experimental study of fluid bearings is also presented.

Variable speed fluid bearing and method of use

Abstract: A fluid bearing assembly for rotatably supporting a rotary-driven spindle having smooth bearing surfaces. Each bearing has a stationary housing holding an annular bearing race that presents a smooth continuous bearing surface facing a complementary bearing surface of the spindle; together the race and spindle define a continuous, thin, uniform crevice space. The smooth race bearing surface is interrupted by a plurality of circumferentially spaced pressure generating zones, each capable of dynamically compressing a fluid body contained in the zone into the crevice in either direction of rotation of the spindle at higher speeds. Pressurized fluid is supplied to flow through each zone and out of the crevice while exerting a predetermined hydrostatic force against the spindle at lower rotational speeds.

Static pressure fluid bearing

Abstract: PURPOSE:To improve the bearing rigidity and adapt to high-speed rotation by setting both ends of a radial bearing to the opened state to the outside air, and setting only one side of a thrust bearing to the opened state to the outside air. CONSTITUTION:When the pressure gas is guided to an intake hole 5, the pressure gas is squeezed by a cylindrical porous member 2 and a circular porous member 3, flows into a bearing gap Cr between a rotary shaft 1 and a bearing, and rotatably supports the rotary shaft 1 in no contact. The pressure gas of a radial bearing is discharged to the outside from a center discharge hole 6 and a radial bearing end section discharge hole 7, the pressure gas of a thrust bearing on the opposite side to a gas sump 8 is discharged to the outside as it is, the pressure gas on the gas sump 8 side is partially discharged from the radial bearing end section discharge hole 7 because the seal section 2a of the cylindrical porous member 2 has the same gap as the bearing gap Cr and serves as discharge resistance, and the gas sump 8 is kept at the pressure Pm higher than the external pressure Pa. The thrust rigidity can be improved without reducing the radial rigidity, and high bearing rigidity is obtained. This device can be miniaturized, and it can be used at a high speed.

Fluid bearing device

Abstract: PROBLEM TO BE SOLVED: To provide a fluid bearing device having a high bearing rigidity even when a self-excited vibration measure is taken so as to reduce a groove volume. SOLUTION: This fluid bearing device 1 consists of a track base 2 having a guide surface 21 and a movable base 3 having a bearing pad 31. The bearing pad 31 is formed with an air supplying hole 32 for ejecting the fluid and a circular groove 33 communicated with the air supplying hole 32. A hollow chamber 37 is formed in the upper part of the bearing pad 31 with a pressure receiving plate 36 disposed as an upper wall. The bearing pad 31 is communicated with the chamber 37 through a vent hole 35 provided with a fluid passage 34. A vent hole 35 is disposed on both sides of the air supplying hole 32 at an angle distance of 1/5 to 1/3.5 of the angle pitch of the air supplying hole 32. Accordingly a high bearing rigidity is obtained even when a self-excited vibration measure is taken so as to reduce a groove volume.

Thermal and Inertia Effects in Hydrodynamic Lubrication of Rollers by a Power Law Fluid Considering Cavitation

Abstract: A theoretical aspect of hydrodynamic lubrication of two symmetric rollers by power law fluids is analyzed. The effect of fluid convective inertia, which is significant in case of high speed bearing, is taken into account. The effect of hydrodynamic pressure and temperature on the lubricant consistency m is assumed to vary with pressure and the mean temperature. The squeezing motion of the surfaces is also incorporated along with inertia and thermal effects. The Reynolds equation and the energy equation (with convection and conduction), which are coupled through m, are solved simultaneously. Various bearing characteristics such as pressure, temperature, load and drag etc. are obtained and a comparison between results (with and without inertia) is also made

Magnetic disk device

Abstract: PURPOSE:To reduce the thickness of the magnetic disk device by reducing the size and thickness of a motor and to increase a recording capacity by widening the recording area of a magnetic disk CONSTITUTION:The bearing part of a motor 22 which freely rotatably supports a hard disk 21 via a rotor 23 of the magnetic disk device for which the hard disk having about <=64mm outside diameter is used is constituted of a fluid bearing This fluid bearing consists of a sleeve 30 sliding and rotating with a shaft 29 and a thrust fluid bearing 31 Fish bone-shaped grooves are provided as grooves on either surface of the outer peripheral surface of this shaft 29 and the inner peripheral surface of the thrust fluid bearing 31 and oil or grease is held in the fish bone-shaped grooves

Principles of Design and Classification of Adaptive Bearings

Abstract: The principles of design and classification of adaptive bearings are discussed. According to the given principles, the loading of a system under consideration in the course of its functioning should be definable and controllable. For fluid film bearings, this is effected with the help of a calculated algorithm which effects a change in the thickness of the support layer of lubricant or the inlet pressure in dependence of changes in the velocity of the rotor journal movement. Such bearings differ not only because of their structure, but also in their manner of functioning and may be both auto-adaptive and adaptively controllable. The suggested principles of designing the adaptive bearings are also used for their classification. The classification presented embraces not only the adaptive bearings that the author has created, but also other bearings of this type, in which the supporting surface should be more or less intermittently adjusted in accordance with continuous feedback of the measured position.

Dynamic pressure fluid bearing and polygonal scanner using that bearing

Abstract: PURPOSE:To provide a dynamic pressure fluid bearing having high reliability and polygonal scanner using this bearing by preventing corrosion of bearing members having grooves for generating dynamic pressure CONSTITUTION:In a dynamic pressure fluid bearing provided with a fixed shaft 13, in which radial bearing surfaces 15, 16 having herringbone grooves 14a, 14b for generating dynamic pressure are formed, and a rotary shaft 17, in which a radial bearing surface 18 opposite to the radial bearing surfaces 15, 16 is formed, the radial bearing surfaces 15, 16 are made of the hardened film layer filled with silicon

Magnetic fluid bearing device

Abstract: PURPOSE:To simplify a device, completely prevent the leak of a lubricant from the bearing device, improve reliability, and facilitate maintenance. CONSTITUTION:A bearing housing 57 fitted to a frame body 2 and a bearing section 55 stored in the housing 57 and supporting a rotary shaft 54 are provided. In a bearing device 53 filled with a lubricating fluid MF in a gap S1 between the bearing sides 55, 57 and the rotary shaft side 54, the lubricating fluid MF is made of a magnetic fluid, the rotary shaft 54 is made of a magnetic substance, the bearing section 55 and the bearing housing 57 are made of a nonmagnetic substance respectively, and a magnetic path forming section 56 made of a magnetic substance is provided between the bearing section 55 and the bearing housing 57. A seal section 58 sealing the magnetic fluid MF in the gap S1 is formed by the magnetic path phi1 formed with the magnetic path forming section 56 and the rotary shaft 54.

Static pressure fluid bearing device

Abstract: PURPOSE:To prevent the seizure of a static pressure fluid bearing during high speed rotation and the contact of a thrust plate. CONSTITUTION:The bearing housing 4 of a static pressure fluid bearing 3 is provided with water-cooled jackets 5 so as to hold cylindrical static pressure pads 7 respectively opposed to the cylindrical outer surface of a rotary shaft 1 and a thrust plate 2. The rotary shaft 1 and the thrust plate 2 are made of silicon carbide or silicon nitride small in thermal expansion so as to prevent the generation of seizure caused by the decrease of a bearing clearance due to thermal expansion during high speed rotation. A deformation preventing member 9 is further provided on the face, opposite to the face jointed to the rotary shaft 2, of the thrust plate 2, so that the thrust plate 2 is prevented from coming in contact with the annular static pressure pads 7 because of deformation caused by centrifugal force during high speed rotation.