Hydrostatic Gas Bearings

1960 ◽  
Vol 82 (2) ◽  
pp. 276-285 ◽  
Author(s):  
John H. Laub
Keyword(s):  
Gas Flow ◽  
Pressure Profile ◽  
Load Carrying Capacity ◽  
Air Bearing ◽  
Gas Flow Rate ◽  
Test Fixture ◽  
Gas Bearings ◽  
Load Carrying ◽  
Gap Height ◽  
Starting Torque

Orifice-regulated hydrostatic gas bearings offer significant advantages for instrument applications. In particular, gimbal bearings for inertial guidance systems can be designed with negligible starting torque and high stiffness, and for operation at extreme temperatures. A literature search revealed the lack of convenient and accurate data for the design of hydrostatic gas bearings of various configurations, taking into consideration the effects of compressibility, which cannot be neglected at higher pressures. Based on Euler’s equation, expressions for the significant parameters, i.e., pressure profile, gas-flow rate, gap height, and load-carrying capacity of pad and step bearings, are developed. These parameters yield results which are in excellent agreement with experimental data. The test fixture incorporates pneumatic loading by means of a bellows-suspended piston which is prevented from cocking by an air bearing.

Deformation Effects on the Load Carrying Capacity of the Barrel Bearing in Axial Piston Pumps and Motors

2006 ◽  
Author(s):  
Peter A. J. Achten ◽  
Marc P. A. Schellekens
Keyword(s):  
Elastic Deformation ◽  
Carrying Capacity ◽  
Thrust Bearing ◽  
Pressure Profile ◽  
Load Carrying Capacity ◽  
Axial Piston Pumps ◽  
Load Carrying ◽  
Face Seals ◽  
Axial Piston Machine ◽  
Axial Piston

Most hydrostatic pumps and motors apply mechanical face seals, often also acting as a thrust bearing. The load carrying capacity of these bearings is very much dependent on the pressure profile generated in the sealing gap. Previous research, outside pumps and motors, has already shown that the gap pressure profile is largely influenced by small radial deformations of the seal lands. This paper discusses the elastic deformation of pump components and the effects of these deformations on the load carrying capacity of a barrel in an axial piston machine.

The Effect of Centrifugal Stretching in High-Speed, Self-Acting Gas Bearings Operating under Steady-State Conditions

1974 ◽  
Vol 16 (3) ◽  
pp. 139-146
Author(s):  
K. S. H. Sadek ◽  
B. N. Cole ◽  
D. Dowson
Keyword(s):  
Radial Growth ◽  
High Speed ◽  
Load Carrying Capacity ◽  
Gas Bearings ◽  
Rotary Machine ◽  
Lubricating Film ◽  
Pressure Distributions ◽  
High Speeds ◽  
Load Carrying ◽  
Very High

The study reported in this paper arose from an investigation of methods of achieving oil-free compression of refrigerant vapours. One part of the investigation included a feasibility study of a high-speed rotary machine running in self-acting gas bearings lubricated by the refrigerant. In certain designs of very high-speed rotor-bearing arrangements, centrifugal or radial growth of the journal might disturb the shape and magnitude of the nominal clearance space and thus affect the performance characteristics of the bearing. The nature and magnitude of these changes in bearing performance for uniform and for two forms of non-uniform centrifugal growth have been examined theoretically. Typical gas-film pressure distributions are presented together with design charts showing how attitude angle and load carrying capacity vary with speed. Comparisons are made with the performance of bearings having the same eccentricity ratio on the mid-plane, and guidance is given on the calculation of uniform radial growth at high speeds. It is concluded that changes in lubricating film geometry resulting from centrigual stretching might have a significant effect upon the performance of certain high-speed, self-acting gas-lubricated bearings.

Improvement of Punch Profiles for Elastic Circular Contacts

2006 ◽  
Vol 128 (3) ◽  
pp. 486-492 ◽  
Author(s):  
Marilena Glovnea ◽  
Emanuel Diaconescu
Keyword(s):  
Carrying Capacity ◽  
Numerical Evaluation ◽  
Pressure Profile ◽  
Electrical Contacts ◽  
Machine Design ◽  
Load Carrying Capacity ◽  
Uniform Pressure ◽  
Pressure Distributions ◽  
Load Carrying ◽  
Double Integrals

Machine design and electrical contacts involve frequently elastic circular contacts subjected to normal loads. Depending on geometry, these may be Hertzian or surface contacts. Both possess highly nonuniform pressure distributions which diminish contact load carrying capacity. The achievement of a uniform pressure distribution would be ideal to improve the situation, but this violates stress continuity. Instead, the generation of a uniform pressure over most of contact area can be sought. Generally, equivalent punch profile which generates this pressure is found by numerical evaluation of double integrals. This paper simplifies the derivation of punch profile by using an existing correspondence between a polynomial punch surface and elastically generated pressure. First, an improved pressure profile is proposed seeking to avoid high Huber-Mises-Hencky stresses near contact surface. Then, this is approximated by the product between typical Hertz square root and an even polynomial, which yields directly the punch profile. Formulas for normal approach and central pressure are derived.

Elastohydrodynamic Lubrication by Powder Slurries

1996 ◽  
Vol 118 (1) ◽  
pp. 67-73 ◽  
Author(s):  
D. Y. Hua ◽  
M. M. Khonsari
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Pressure Profile ◽  
Load Carrying Capacity ◽  
Carrier Fluid ◽  
Shear Thinning Fluids ◽  
Contact Configuration ◽  
Load Carrying ◽  
Traction Coefficient ◽  
Higher Temperature ◽  
Performance Results

Thermoelastohydrodynamic analysis of a powder slurry containing a mixture of MoS2 particles and a carrier fluid is presented for a line-contact configuration. The constitutive equation of the slurry is a non-Newtonian formulation based on experimental data. The model includes provisions for elastic/plastic deformation of particles in the slurry. Through this deformation, particles are shown to contribute to the load-carrying capacity. The viscosity of the carrier fluid is shown to increase considerably as a result of adding a large amount of particles, thus appreciably affecting the EHL behavior of powder slurries. Performance results are presented for the pressure profile, film thickness, temperature distribution, and traction coefficient for a number of sliding/rolling ratios. The existence of particles in slurry is shown to give rise to a higher temperature field and tends to increase the traction coefficient compared to typical shear thinning fluids.

Optimization of Groove Geometry for Thrust Air Bearing to Maximize Bearing Stiffness

2007 ◽  
Author(s):  
Hiromu Hashimoto ◽  
Masayuki Ochiai ◽  
Tadashi Nanba
Keyword(s):  
High Speed ◽  
Design Methodology ◽  
Logarithmic Spiral ◽  
Load Carrying Capacity ◽  
Air Bearing ◽  
Thrust Bearings ◽  
Load Carrying ◽  
Bearing Stiffness ◽  
The Stability ◽  
Very High

Hydrodynamic gas film bearings are widely used for very high speed, lightly loaded rotating machinery. In the design of hydrodynamic gas film bearings, it is of cardinal importance to enhance the stiffness of gas films for minimizing the vibration due to external excitations. Among various types of hydrodynamic gas film thrust bearings, grooved bearings have an advantage of high stiffness and load carrying capacity, but the stiffness of the bearings strongly depends on groove geometry. Therefore, when the groove geometry is designed suitably, it is expected to improve considerably the stability characteristics of the bearings. However, the conventional bearing geometries are based on the fixed logarithmic spiral curve, and there is no literature treating how to change effectively the groove geometry to improve drastically the bearing characteristics. In this paper, the entirely new optimum design methodology, in which the groove geometry can be changed flexibly by using the spline function, is presented to maximize the stiffness of gas films for grooved thrust bearings, and the effectiveness of the methodology is verified experimentally.

Optimization of Groove Geometry for Thrust Air Bearing to Maximize Bearing Stiffness

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Hiromu Hashimoto ◽  
Masayuki Ochiai
Keyword(s):  
High Speed ◽  
Design Methodology ◽  
Logarithmic Spiral ◽  
Load Carrying Capacity ◽  
Air Bearing ◽  
Thrust Bearings ◽  
Load Carrying ◽  
Bearing Stiffness ◽  
The Stability ◽  
Very High

Hydrodynamic gas film bearings are widely used for very-high-speed, lightly loaded rotating machinery. In the design of hydrodynamic gas film bearings, it is of cardinal importance to enhance the stiffness of gas films to minimize vibration due to external excitations. Among various types of hydrodynamic gas film thrust bearings, grooved bearings have an advantage of high stiffness and load-carrying capacity, but the stiffness of the bearings strongly depends on groove geometry. Therefore, when the groove geometry is suitably designed, it is expected to considerably improve the stability characteristics of the bearings. However, conventional bearing geometries are based on a fixed logarithmic spiral curve, and there is no literature on how to effectively change the groove geometry to drastically improve the bearing characteristics. In this paper, the entirely new optimum design methodology, in which the groove geometry can be flexibly changed by using the spline function, is presented to maximize the stiffness of gas films for grooved thrust bearings. The effectiveness of the methodology is experimentally verified.

Externally Pressurized Compliant Air Bearing Operating on a Rough Moving Surface

1975 ◽  
Vol 97 (1) ◽  
pp. 63-68 ◽  
Author(s):  
H. Lau ◽  
C. M. Harman
Keyword(s):  
Surface Roughness ◽  
Carrying Capacity ◽  
Center Of Pressure ◽  
Load Carrying Capacity ◽  
Air Bearing ◽  
Moving Surface ◽  
Analytical Results ◽  
Load Carrying ◽  
Flow Requirement

An externally pressurized compliant air bearing with potential for operation on surfaces of moderate unevenness or roughness such as might be encountered in vehicle guideways is considered. Analytical results are presented which show the effect on load carrying capacity, flow requirement, and center of pressure location of variation of bearing compliance, surface roughness, bearing speed, and bearing slope.

Optimal design of an annular thrust air bearing using parametric computational fluid dynamics model and genetic algorithms

2017 ◽  
Vol 232 (10) ◽  
pp. 1203-1214 ◽  
Author(s):  
Qiang Gao ◽  
Lihua Lu ◽  
Wanqun Chen ◽  
Guanglin Wang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Geometrical Parameters ◽  
Load Carrying Capacity ◽  
Air Bearing ◽  
Dynamics Model ◽  
Computational Fluid Dynamics Model ◽  
Load Carrying

The performance of air bearing is highly influenced by the geometrical parameters of its restrictor. This study aims to maximize the load-carrying capacity and stiffness of air bearing, and minimize its volume flow rate by optimizing the geometrical parameters of restrictor. To facilitate the calculation of air bearing performance, a parametric computational fluid dynamics model is developed. Then, it is combined with multiobjective optimization genetic algorithm to search the Pareto optimal solutions. Furthermore, as a case study, the optimal design of an annular thrust air bearing is implemented. The stiffness of air bearing is improved 38.5%, the load-carrying capacity is improved 33.9%, and the volume flow rate is declined 19.6%, which are finally validated by experiments. It proves the reliability of proposed parametric computational fluid dynamics model and genetic optimization algorithm.

scholarly journals The Effect of a Surface Roughness on Load Carrying Capacity in Slide Journal Bearing Lubricated with Oil of Non-Newtonian Properties

2019 ◽  
Vol 49 (3) ◽  
pp. 497-526
Author(s):  
Andrzej Miszczak
Keyword(s):  
Surface Roughness ◽  
Journal Bearing ◽  
Height Function ◽  
Journal Bearings ◽  
Expected Value ◽  
Numerical Calculations ◽  
Operating Parameters ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Gap Height

Abstract The Author presents the method that taking account an influence of surface roughness on both flow and operating parameters of a slide journal bearing in the paper. For this purpose, the expected value for the gap height function should be determined. The expected value is then the most probable value of the height of the lubrication gap. There are presented the results of analytical and numerical calculations of flow and operating parameters in slide journal bearings. Numerical calculations were performed using the finite difference method as well as own calculation procedures and the Mathcad 15 software.

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

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

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

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