Showing papers on "Fluid bearing published in 1988"

Lubrication by a Smectic Liquid Crystal

Abstract: The hydrodynamic aspects of lubrication by the smectic A liquid crystal octylcyanobiphenyl (8CB) were investigated in a thrust bearing and in the concentrated ball-on-flat contact. Both bearings were run with a Newtonian mineral basestock for comparison and performed as expected; friction followed the Stribeck curve in the thrust bearing and the film thickness increased with (velocity)2/3 in the elastohydrodynamic lubrication of the point contact. The lubricating behavior of the smectic liquid crystal is qualitatively different from that of the Newtonian fluid. Curves of friction coefficient vs velocity × viscosity/load cannot be superimposed to form a Stribeck curve. The higher the load, the lower the velocity at which low friction is maintained, which is opposite to the behavior of Newtonian fluids. In concentrated contact (EHD lubrication) the smectic gives a friction coefficient that is constant with velocity and lower than the minimum value with the Newtonian fluid. The fluid film thickness varies wi...

Beam mounted bearing pad and methods of making same

Abstract: A hydrodynamic bearing and methods of manufacturing the same. The bearing includes a bearing pad structure that may change shape and move in any direction (six degrees of freedom) to form a converging wedge for hydrodynamic operation, and to adjust for any shaft (5) misalignment. The pad (12) is separated from the support member by one or more beam-like members. The beams (14) extend substantially parallel to the plane of the face of the pad (12). The beams (14) allow defection of the pad (12) by either deflecting or twisting in a torsional mode. The bearings may be made of a wide variety of materials including plastics, ceramics, powdered metals, composites and metals. The bearings may be manufactured by injection molding, casting, powdered metal die casting, extrusion, electric discharge or laser cutting.

The Eigenvalue Dependence of Reduced Tilting Pad Bearing Stiffness and Damping Coefficients

Abstract: A method is presented for calculating reduced tilting pad bearing stiffness and damping coefficients eliminating the explicit dependence of the pad degrees of freedom. Previous analyses are extended to include the real part of the system eigenvalues, so the present analysis is applicable to general free damped vibratory motion as well as synchronous and nonsynchronous steady state response previously considered. The number of coefficients is reduced from a total of 2(5n + 4), when the pad rotational degrees of freedom are retained, to eight, the number required to describe the translational dynamics of a rotor in fixed pad hydrodynamic bearings. The eight coefficients are especially suited for we in bearing optimization schemes for optimizing the stability of rotor-bearing system. Calculations are presented for five pad bearings with the static load directed between pads and with negligible pad inertia for a range of bearing preload and operating Sommerfeld number. Presented as a Society of Tribologists a...

Thermohydrodynamic Analysis of Journal Bearings Considering Cavitation and Reverse Flow

Abstract: Analyse thermohydrodynamique d'un palier de glissement tenant compte de la cavitation et des ecoulements inverses

Equalizing hydrodynamic bearing

Abstract: The hydrodynamic bearing assembly may be either a journal bearing or a thrust bearing. Bearing pads are located adjacent a shaft when a journal bearing or adjacent a collar on a shaft when a thrust bearing. The bearing pads are located on equalizing pads, two bearing pads for each equalizing pad. An elastomeric layer is disposed between the bearing pads and the equalizing pads.

Self-aligning fluid bearing

Abstract: A self-aligning fluid bearing for supporting a moving part, and allowing that part to move along at least one flat support surface substantially without friction, includes a body with at least one planar face having at least one spheroidal concave depression therein, channels within the body for directing pressurized fluid to each depression, and one planoconvex disk for each depression. Each disk includes a convex spheroidal surface with a spherical radius which is approximately equal to that of the corresponding concave depression and an oppositely facing planar surface so that the convex surface of the disk is located in spaced relation to the depression surface when pressurized fluid is directed into the depression. Each disk furthermore has a passageway between the convex surface and the planar surface through which pressurized fluid can pass to the planar surface of that disk so that the disk is supported in spaced relation to the flat support surface when pressurized fluid is directed through that passageway. Each planoconvex disk is slightly rotatable with respect to its corresponding depression so that the disks can move to compensate for imperfections in the flat support surface without upsetting the bearing. The bearing may include one or more magnets which bias the bearing toward a ferromagnetic flat support surface.

Thermohydrodynamic Analysis of Solid-Liquid Lubricated Journal Bearings

Abstract: Analyse thermohydrodynamique d'un palier dans le cas ou le lubrifiant liquide contient des particules solides

A Three Dimensional Thermohydrodynamic Finite Element Scheme for Fluid Film Bearings

Abstract: A finite element procedure is presented for the solution of fluid film lubrication problem that allows for a temperature dependent viscosity. The major concern is with the solution of the three dimensional fluid film and pad energy equations. A major advantage of the method developed here over previous finite element schemes is that the system of equations for the temperature field may be solved by iterative methods. This is because the discrete equations are formulated using either the parabolic form of the energy equation along with appropriate backwards differencing, or using upwinding with the elliptic form of the energy equation. The method is powerful in that it can treat bearing film with reverse flow. A convenience of the method is that the film and pad are treated as a single continuum and their temperature fields solved for simultaneously. Presented at the 42nd Annual Meeting in Anaheim, California May 11–14, 1987

Self-filtering apparatus for hydrodynamic bearing gas

Abstract: Gas bearing of the hydrodynamic self-acting type in which replenishment gas for the support film is drawn by the operating bearing through filter means as required to assure entrapment of potentially damaging particles before they can enter the gas film in the narrow clearance between the rotating and stationary bearing members. To further increase the flow of filtered gas, the bearing elements may optionally be equipped with supplemental gas pumping apparatus.

An Evaluation of Eight-Node Quadrilateral Finite Elements for the Analysis of a Dynamically Loaded Hydrodynamic Journal Bearing

Abstract: A comparative study is presented for the finite element analysis of a dynamically loaded journal bearing showing the improvement in solution accuracy and decrease in computer time achieved when using eight-node quadilateral, rather than three-node triangular, elements. Results are presented for medium size diesel engine big end bearings using a wide variety of mesh gradings.

An Interior Collocation Method for Static and Dynamic Analysis of Finite Length Gas Journal Bearings

Abstract: Analyse statique et dynamique d'un palier a gaz de longueur finie par une methode de collocation interne

Dynamic pressure type field bearing device

Abstract: PURPOSE:To obtain a dynamic pressure type fluid bearing device which prevents air from its inflow to the inside of a lubricant, by providing a ventilating hole, in parallel with a shaft, on a thrust member mounting surface in a thrust bearing part. CONSTITUTION:If a shaft 12 rotates, a lubricant 21 in a thrust bearing part increases the pressure by the pumping action of a dynamic pressure generating groove 14A and a helical groove 18A, and the shaft 12 floats rotating. A ventilating hole 11H, when the thrust bearing part is excessively heated by generated heat of a motor and a bearing causing thermal expansion of air inside, releases this air to the outside of a base member 11 preventing the pressure by this thermal expansion from extruding the lubricant 21 in herringbone grooves 11B, 11C of the radial bearing. While a device, in which this ventilating hole 11H can be easily machined by a drill, is excellent in productivity.

Protective system for a device rotatably supported by air bearings.

Abstract: A protective air control system for an air turbine (73) motor having air bearings (72) ensures pressurized air is supplied to the air bearings (72) whenever the air turbine (73) is being driven. In one embodiment, a sensing device (81) monitors the air pressure supplied to the air bearings, and is operative to open a valve (78) for supplying air to the turbine (73) only when the bearing air pressure exceeds a predetermined amount. In another embodiment, a check valve (88) is mounted to divert a portion of the turbine air to the bearings (72) when the bearing air pressure is below the turbine air pressure. The protective system can be used with an electrostatic rotary atomizer coater (10).

Influence of Feed Groove Pressure and Related Lubricant Flow on Journal Bearing Performance

Abstract: The existence of feed groove pressure is significant to the control of journal bearing temperatures when operating at low eccentricities. A study of the effects of feed groove pressures on journal bearings having axial lubricant feed grooves has included preparation of a PC-operational finite difference code including specifiable feed groove boundary pressures as part of non-dimensional solutions. While capable of handling superlaminar variable viscosity cases, it is exercised herein on laminar isoviscous solutions. These, together with results from a similar zero speed code, are used to test the hypothesis that zero-feed flow solutions can be superimposed on zero-pressure hydrodynamic solutions to obtain combined lubricant flow rates. The superposition method is found to indicate flow rates that are high by 10 to 20 percent. Other effects of feed groove pressures on load capacity, power loss, temperature rise and stiffness and damping are discussed. Presented as a Society of Tribologists and Lubrication ...

The analysis of dynamically loaded flexible journal bearings using higher-order finite elements

Abstract: An efficient and robust predictive technique has been developed for the analysis of dynamically loaded, flexible journal bearings using the finite element method. The work is in two parts. In the first part a fast predictive technique is developed for the analysis of dynamically loaded, rigid journal bearings. The finite element formulation of Reynolds equation is presented using both 3-node triangular and 8-node isoparamteric elements to model the lubricant film. The latter are shown to approximate the problem more closely using fewer nodal points and hence requiring fewer equations. The Gauss-Seidel over-relaxation method is used to solve the resulting system equations and the sparseness of these equations is exploited. Comprehensive results are presented for the Ruston and Hornsby 6VEB Mk ifi marine diesel engine connecting rod bearing. Two different time stepping methods are considered and the effects of incorporating various oil feed features in the analysis are also presented. The second part of the work deals with the flexible bearing problem. The method of carrying out the structural modelling and the way in which the structural compliance relationships are obtained is described. A fast matrix inversion technique used to obtain these relationships is also described. Based on the rigid bearing work 8-node isoparametric elements are used to model the lubricant film. Two methods are presented for coupling the structural and lubrication analysis. The first method, the under-relaxation method, although proving straightforward to implement is shown to be unsatisfactory for this particular problem due to to convegnence problems. The second method is the Newton-Raphson method which is shown to be highly convergent. The Newton-Raphson method is subsequently highly modified to produce a fast solution method. This is shown to be several orders of magnitude faster than any previously developed method making this technique viable as a general design tool rather than just providing benchmarks against which to compare simpler analysis techniques. Again results are presented for the Ruston bearing showing the effect upon the predicted performance of incorporating elasticity into the analysis.

Elastic Bearings Lubricated With Non-Newtonian Power Law Fluids—A Boundary Element Approach

Abstract: This paper discusses the influence of two material property effects on the hydrodynamic lubrication of large-slenderness-ratio, plane slider bearings. Bearing surfaces are covered with an elastic material. This uniformly thick elastic material deforms under the hydrodynamic fluid film pressure. The elastic layer is incompressible (i.e. Poisson ratio is ½). The lubricant is a power-law, non-Newtonian fluid with shear thinning properties. A boundary element method is wed to determine the elastic solid deformation. The important dimensionless parameter coupling the elastic deformation and hydrodynamic pressure is the deformation number. A comparison of bearing pressure profiles and bearing gap-geometries for different fluids is shown. Results reveal increased bearing gaps due to deformation, gap geometries that are more uniform in thickness due to fluid film pressure, pressure peaks moving rearward with increased bearing deformation, sharper converging gaps formed near the bearing trailing edge, and effectiv...

Improved resiliently mounted fluid bearing assembly

Abstract: The bearing assembly (10) is of the hydrodynamic type, for use as a spindle. It includes spaced journals mounted on a shaft (12) for rotation therewith. The housing (20) includes spaced support bearings (16, 18) cooperating with the journals to form a gas gap (16c, 18c) therebetween. The support bearings (16, 18) are resiliently mounted by flexible spring seal elements (23) in the housing for axial, radial and angular movement. The elements (23) are self-energizing and comprised of relatively low coefficient of friction materials to reduce the friction of the system thus allowing rapid adjustment of the bearing (16 or 18) in response to loads on the shaft (12). Various details are described with respect to the various structures illustrated, including the details of an air bearing spindle assembly of relatively light weight and capable of operating at speeds in excess of 100,000 RPM.

The Effect of Thermal Distortion on the Characteristics of Large Hydrodynamic Bearings

Abstract: An experimental investigation has been carried out on a 350 mm partial arc journal bearing to determine the steady state characteristics and the stiffness and damping coefficients. The bearing was ...

Spindle bearing structure

Abstract: PURPOSE:To make it possible to rotate a spindle at a high speed, and to increase the rigidity of the same at a low speed, by supporting the spindle by static fluid bearings during high rotational speed operation, but by rolling bearings which are arranged in a part other than the part where the static fluid bearings are arranged, during low rotational speed operation. CONSTITUTION:During low rotational speed operation of a tool spindle 1, pressure oil flows into oil passages 23, 24 so that sleeves 9, 10 are pressed in the directions (a), (b), and when the front or rear ends of the sleeves 9, 10 are detected by detectors 30, 31, a pressure line is closed. Thereby, the outer races and balls of angular ball bearings 2, 3 are coupled to the inner races thereof, and the spindle 1 is supported by the angular ball bearings 2, 3. During speed change rotation, no pressure oil is effected, and therefore, the sleeves 9, 10 are pressed in the directions (a'), (b') so that the outer races and balls of the angular ball bearings 2, 3 are separated from the inner races thereof. Then, compressed air is jetted from passages 17a, 17b to enable radial load support by air bearings 8a, 8b, and air is jetted from a passage 19 to enable thrust load support by an air bearing 15.

Dynamic pressure type fluid bearing device

Abstract: PURPOSE:To facilitate machining a dynamic pressure type thrust bearing by setting the thrust load supported by a thrust fluid bearing only in one direction to provide only one dynamic pressure type thrust bearing. CONSTITUTION:A disc 40 is disposed opposite to a sleeve 11 in such a manner as to be suitably spaced therefrom in the axial direction, and attraction type permanent magnets 50, 51 are fixed to the opposite axial sides 46, 16 of both. A flange portion 21 is attracted to an annular member 12 by the attraction force of the permanent magnet 50 mounted on the disc for the permanent magnet 51 and by the weight of a shaft 20. Accordingly the attraction force produced by the permanent magnets 50, 51 works to attract the shaft 20 in the axial direction to the annular member side of a housing through the disc 40, whereby the thrust load only in one direction is supported, so that a thrust bearing can be easily machined.

Hydrodynamic bearing or thrust bearing, especially a foil bearing

Abstract: Hydrodynamic bearing, in particular a foil bearing, the shaft of which is intended to rotate at high speed, at least 30,000 revolutions per minute. The outer surface of the shaft (10) is dry-lubricated by an encrustation of molybdenum or graphite disulphide.

Instability analysis of groove compensated journal air bearings

Abstract: The whirl instability of groove compensated journal air bearing is analyzed. The finite element method is used to obtain the numerical solution of the Reynolds equation and the computer simulation method is used to obtain the locus of the shaft center after a step displacement disturbance. From the shaft loci, the effects of various design parameters on the stability of the bearings are discussed.