Spherical and Conical Spiral Groove Bearings—Part II: Load Capacity and Stability

1975 ◽  
Vol 97 (2) ◽  
pp. 243-249 ◽  
Author(s):  
J. Bootsma
Keyword(s):  
Load Capacity ◽  
Journal Bearings ◽  
Negative Stiffness ◽  
Necessary Condition ◽  
Radial Load ◽  
Spiral Groove ◽  
Complete Filling ◽  
Lubricating Film ◽  
Unloaded State ◽  
The Stability

The theory developed in Part I is applied to the solving of problems encountered in practice. The manner in which the axial and radial load capacity and stiffness depend on bearing dimensions, particularly on groove dimensions, is shown. The important aspect that spherical and conical spiral groove bearings, just as spiral groove journal bearings, can be stable even if not subjected to a radial load is investigated. A necessary condition for the stability of these bearings in the radially unloaded state is shown to be the complete filling of the bearing gap with a lubricant. In the case of an incompletely filled bearing gap the interaction between the gas-to-liquid interface and the pressure distribution in the lubricating film is such that these bearings have a negative stiffness.

Study on the performance of gas foil journal bearings with bump-type shim foil

2020 ◽  
pp. 135065012096900
Author(s):  
Hongyang Hu ◽  
Ming Feng ◽  
Tianming Ren
Keyword(s):  
Dynamic Stability ◽  
Load Capacity ◽  
Practical Interest ◽  
Journal Bearings ◽  
Working Environment ◽  
Foil Thickness ◽  
The Novel ◽  
Improvement Potential ◽  
Stiffness Model ◽  
The Stability

The upscaling of turbomachinery using gas foil journal bearings (GFJBs) is limited because of their limited load capacity and dynamic stability. The improvement potential of shim foil inserted under the bump foil of such bearings is investigated in terms of better bearing performance. The arch height difference Δ hb between the shim foil and bump foil can be zero or not to attain the different effect. By considering the local hardening structural stiffness and an Initial installation clearance due to the shim foil, the static and dynamic characteristics of the novel bearing were calculated through the finite difference method (FDM) and perturbation method, respectively. In the analysis, a modified bump stiffness model considering the variable foil thickness was established, and a 2 D thick plate model was adopted for the top foil. The characteristics of novel GFJB with and without preload were compared with the traditional bearing. The results indicate that the load capacity and direct stiffness of the novel GFJB with shim foil can be increased largely, especially when there is a preload (Δ hb≠0). And the improvement is reinforced as the increment of Δ hb. Moreover, the stability threshold speed ( STS) of rotor supported by the novel GFJBs is enhanced by the preload, which means better stability. In addition, an air compressor test has also been conducted to verify the improved supporting performance of novel bearings. Based on this study it is convinced that the addition of shim foil under a GFJB's bump foil can be of practical interest in the quest of enhanced load capacity and dynamic stability. Moreover, the installation of shim foil is not affected by the working environment and could even be retrofited on the existing GFJBs.

Design and Performance of Compliant Thrust Bearings With Spiral-Groove Membranes on Resilient Supports

1981 ◽  
Vol 103 (3) ◽  
pp. 373-384 ◽  
Author(s):  
L. Licht ◽  
W. J. Anderson ◽  
S. W. Doroff
Keyword(s):  
Load Capacity ◽  
Journal Bearings ◽  
Spiral Groove ◽  
Thrust Bearings ◽  
Flexible Membranes ◽  
And Performance

Novel thrust bearings, with spiral-groove, flexible membranes mounted on resilient supports, were designed and their performance convincingly demonstrated. Advantages of surface compliance were thus combined with the superior load-capacity of the spiral-groove geometry. Loads of 127–150N (29–33 lb) were comfortably supported on an area 42 cm2 (6.5 in.2), at speeds 43,000–45,000 rpm and mean clearances 15–20 μm (600–800 μin.), by these self-acting and air-lubricated bearings. Support-worthiness was proved under exacting conditions, when tested in conjunction with foil journal-bearings and a 19N (4.3 lb)-rotor, excited in a pitching mode by a total unbalance of 43 μm.N (6100 μin.oz).

Spherical and Conical Spiral Groove Bearings—Part I: Theory

1975 ◽  
Vol 97 (2) ◽  
pp. 236-242 ◽  
Author(s):  
J. Bootsma
Keyword(s):  
Perturbation Method ◽  
Pressure Distribution ◽  
Load Capacity ◽  
Liquid Interface ◽  
Operating Conditions ◽  
Spiral Groove ◽  
Lubricating Film ◽  
Incomplete Filling ◽  
Gas To Liquid ◽  
Comparison Of The Results

The performance of spherical and conical spiral groove bearings lubricated with a Newtonian, incompressible liquid is investigated. This work covers both complete and incomplete filling of the bearing gap with a liquid. In an incompletely filled bearing gap a gas-to-liquid interface occurs. Under radially eccentric operating conditions the location of the interface is related to the pressure distribution in the lubricating film. Part I treats a theory based on the smooth pressure concept. A perturbation method serves to determine the pressure distribution and, in the case of an incompletely filled bearing gap, also the location of the gas-to-liquid interface. From the pressure distributions, different for the two cases, formulas have been derived for the radial and axial load capacity. Comparison of the results obtained with this perturbation method with the results obtained with a numerical method lead to the conclusion that the former results can be used in practice as long as practically no cavitation occurs in the bearing. Previously reported experiments with spiral groove journal bearings confirm this. In spiral groove bearings the groove dimensions which lead to a satisfactory operation of the bearing are generally such that even with fairly marked eccentricities there is practically no occurrence of cavitation. Part II will treat the results obtained with the theory of Part I.

Thermoelastic influences in journal bearing lubrication

1986 ◽  
Vol 403 (1824) ◽  
pp. 111-134 ◽  
Keyword(s):  
Film Thickness ◽  
Theoretical Investigation ◽  
Journal Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Thermal Distortion ◽  
Two Dimensional ◽  
Thickness Increase ◽  
Minimum Film Thickness ◽  
The Stability

A theoretical investigation is made to study the way in which thermal distortion of bearing components modifies the characteristics of journal bearings. The thermoelastic treatment developed is two-dimensional and incorporates an existing thermohydrodynamic analysis. It is applied to circular and partial arc bearings for a range of parametric groups governing the bearing operation. The results show that for a fixed journal position, the effect of thermal distortion is to reduce the minimum film thickness, increase the load capacity, increase the peak temperatures and pressures, and also to enhance considerably the stability of the bearing. The effects are more marked for larger oil-lubricated bearings and higher speeds of operation and it is suggested that discrepancies observed between experimental results and existing theory could be largely explained by this phenomenon.

The Application of Double Conical Journal Bearings in High Speed Centrifugal Pumps — Parts 1 and 2

1975 ◽  
Vol 189 (1) ◽  
pp. 221-230 ◽  
Author(s):  
C. Ettles ◽  
O. Svoboda
Keyword(s):  
Axial Load ◽  
High Speed ◽  
Load Capacity ◽  
Correct Choice ◽  
Journal Bearings ◽  
Radial Load ◽  
Centrifugal Pumps ◽  
Half Angle ◽  
Bearing Materials ◽  
Flow Compensation

Conical bearings can in principle support a combination of radial and axial load. Their application to centrifugal pumps is considered, which allows the thrust bearing of the conventional arrangement to be dispensed with. It is shown that with low pressure oil lubrication, the axial load of this type of bearing is limited to the ratio (axial load/radial load)=Tan A, where A is the half angle of the cone. Methods of avoiding this limitation are considered. The feasibility of water lubricated inclined journal bearings for centrifugal pumps is analysed. A ‘Vee’ configuration double conical journal bearing is considered with a central high pressure feed from the pump outlet. Although the enhancement of viscosity due to turbulence is not as great as anticipated, the bearing is shown to have an adequate axial and radial load capacity. It is shown that flow compensation or restriction to each side of the bearing is necessary to maintain the escaped flow at an acceptable level. The limits of bearing operation are set by acceptable film thickness rather than excessive temperature rise. For this reason, the correct choice of bearing materials to run under thin film or no film conditions in the presence of dirt is probably more important than correct hydrodynamic design.

Misalignment Effect on the Static and Dynamic Characteristics of Hydrodynamic Journal Bearings

1995 ◽  
Vol 117 (4) ◽  
pp. 717-723 ◽  
Author(s):  
Z. L Qiu ◽  
A. K. Tieu
Keyword(s):  
Dynamic Characteristics ◽  
Reynolds Equation ◽  
Static Load ◽  
Load Capacity ◽  
Vertical Direction ◽  
Journal Bearings ◽  
Static And Dynamic Characteristics ◽  
Flow Friction ◽  
The Stability ◽  
Side Flow

This paper solves the Reynolds equation by the finite difference method in a fixed coordinate system with the static load acted in the vertical direction. All static and dynamic characteristics (including load capacity, attitude angle, side flow, friction force, misaligned moments, and eight linear force coefficients) of a horizontally grooved bearing under different eccentricity and misalignment conditions are presented and compared with available experimental data. The effects of misalignment on all these bearing characteristics and on the stability of the rotor-bearing system are analyzed.

Manufacturing Effects in Microfabricated Gas Bearings: Axially Varying Clearance

2002 ◽  
Vol 124 (4) ◽  
pp. 815-821 ◽  
Author(s):  
E. S. Piekos ◽  
K. S. Breuer
Keyword(s):  
Detrimental Effect ◽  
Load Capacity ◽  
Journal Bearings ◽  
Narrow Channels ◽  
Low Speed ◽  
Gas Bearings ◽  
Complete Closure ◽  
The Stability

The effect of axially-varying clearance on microfabricated gas journal bearings is explored. This variation commonly arises from difficulties inherent to etching deep, narrow channels. Two types of clearance variation commonly observed in etched bearings are investigated: taper and bow. Both shapes are shown to have a detrimental effect on load capacity and bearing stability compared to a cylindrical bearing with the minimum clearance. For the same variation magnitude, taper is shown to have a more serious effect, including complete closure of the stability corridor at low speed for some cases. Methods are suggested for estimating variable-clearance bearing performance using cylindrical bearing data.

An Approximate THD Theory for Journal Bearings

1990 ◽  
Vol 112 (2) ◽  
pp. 224-229 ◽  
Author(s):  
G. Gupta ◽  
C. R. Hammond ◽  
A. Z. Szeri
Keyword(s):  
Journal Bearing ◽  
Load Capacity ◽  
Pressure Coefficient ◽  
Journal Bearings ◽  
Maximum Pressure ◽  
Substantial Agreement ◽  
Interactive Mode ◽  
Lubricant Flow ◽  
Bearing Load ◽  
Sophisticated Model

The aim of this paper is to make available to the industrial designer results of the thermohydrodynamic theory of journal bearings, by providing a simplified, yet accurate model of journal bearing lubrication that can be implemented on a personal computer and be used in an interactive mode. The simplified THD theory we propose consists of two coupled ordinary differential equations for pressure and energy and an algebraic equation for viscosity, which are to be solved iteratively. Bearing load capacity, maximum bearing temperature, maximum pressure, coefficient of friction and lubricant flow rate calculated from this simplified theory compare well with results from a more sophisticated model. We also make comparisons with experimental data on full journal bearings, demonstrating substantial agreement between experiment and simplified theory.

Comparative Evaluation of MoS2 and WS2 as Powder Lubricants in High Speed, Multi-Pad Journal Bearings

1999 ◽  
Vol 121 (3) ◽  
pp. 625-630 ◽  
Author(s):  
C. Fred Higgs ◽  
Crystal A. Heshmat ◽  
Hooshang Heshmat
Keyword(s):  
Comparative Evaluation ◽  
High Speed ◽  
Solid Lubricants ◽  
Extreme Environment ◽  
Journal Bearings ◽  
Lubricating Film ◽  
Constant Friction ◽  
Traction Coefficient ◽  
Limiting Value ◽  
Selection Of

As part of a program to develop solid/powder-lubricated journal bearings, a comparative evaluation has been performed to aid in determining whether MoS2 and WS2 powder are suitable lubricants for high-speed, extreme-environment multi-pad journal bearings. Plots of traction coefficients, friction, frictional power loss, and bearing pad temperature are presented as a means for comparing various powder lubricants. This paper primarily focuses on experiments carried out on a three-pad journal bearing and a disk-on-disk tribometer. Results showed that MoS2 traction curves resemble that of SAE 10 synthetic oil. Unlike liquid lubricants, powder films have a limiting shear strength property. Once the powder reaches this limiting value, the maximum traction coefficient is limited and the powder essentially shears along sliding walls. Experimental traction data shows evidence of this property in various powders. The thermal performance of the bearing was evaluated at speeds up to 30,000 rpm and loads up to 236 N. Although WS2 displayed constant friction coefficient and low temperature with increasing dimensionless load, MoS2 exhibited frictional behavior resembling that of a hydrodynamic lubricating film. In this paper, an attempt has been made to provide a criterion for the selection of solid lubricants for use in those tribosystems that may be operated in a high speed/load regime (i.e., high strain rates) as an alternative yard stick to conventional comparative approaches.

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