Vibration Considerations in Foil-Bearing Design

1999 ◽  
Vol 66 (2) ◽  
pp. 432-438 ◽  
Author(s):  
A. A. Renshaw
Keyword(s):  
Slip Flow ◽  
Bending Stiffness ◽  
The Other ◽  
Bearing Surface ◽  
Web Handling ◽  
Foil Bearings ◽  
Viscous Forces ◽  
Foil Bearing ◽  
Bearing Design ◽  
Two Parameters

The semianalytic foil-bearing solution algorithm of Eshel and Elrod (1965) is extended to the solution of the linearized, free vibration problem for one-dimensional self-pressurized foil bearings. The results demonstrate that unwanted variations in the spacing between the moving foil and the stationary bearing surface can be eliminated through proper design. The penetration depth through which vibration of the free span penetrates into the foil bearing is determined by two exponential exponents, one describing inlet penetration, the other describing outlet penetration. When the inlet exponent is large and negative and the outlet exponent is large and positive, there is negligible coupling between the vibration of the free spans and the vibration of the spacing between the foil and the stationary bearing surface. This decoupling is desirable in magnetic recording and web handling applications and can be achieved by properly selecting two dimensionless parameters, one describing the ratio of the viscous forces to the tape tension, the other describing the ratio of the tape transport speed to the wave speed in the tape. The values of these two parameters in current designs of both magnetic tape recording and web-handling devices are consistent with the design goal of minimizing foil vibration over the bearing. The inlet and outlet exponents are the roots of a fourth-order polynomial, and, in most cases, good estimates for these roots can be found without explicitly solving the foil-bearing problem. The effects of the air compressibility, tape bending stiffness, and slip flow are also investigated. Tape bending stiffness is found to play a significant role in vibration coupling. These results provide new insight into the influence of vibration on foil-bearing design.

Successful Oil-Free Version of a Gas Compressor Through Integrated Design of Foil Bearings

2008 ◽  
Author(s):  
Jonathan L. Wade ◽  
Daniel R. Lubell ◽  
Dennis Weissert
Keyword(s):  
Integrated Design ◽  
Pass Rate ◽  
Working Fluid ◽  
Acceptance Test ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Higher Power ◽  
Bearing Design ◽  
Maintenance Requirements ◽  
Conventional Oil

In the pursuit of higher power density turbomachinery the rotor speeds and temperatures have been increased to the limits of conventional oil lubricated bearings. Additionally, with conventional oil lubricated bearings there is a risk of oil contaminating the working fluid; this is unacceptable for some applications. When properly designed and integrated the foil gas bearing is one option that can easily operate at higher temperatures and DN’s than conventional oil lubricated bearings systems. This is a case study of a small variable speed gas compressor that progressed through a variety of bearing configurations. The compressor was initially designed with ball bearings; the ball bearing design did not meet the compressor life targets for some operating regimes, requiring extra maintenance. The second iteration was to move to a foil bearing design; unfortunately because of design constraints an under-sized bearing was selected. The under-sized foil bearing provided only marginally better unit life, and was much more sensitive in the build process and the acceptance test pass rate fell dramatically. Unique field operation experience showed a variety of failures and successes from a marginal design. Finally, a properly sized foil bearing was integrated into the pump, capitalizing on the foil bearing strengths. With the properly sized foil bearings the pumps have seen a 100% acceptance test pass rate, no field failures, and the pumps are exceeding the desired life without any maintenance requirements.

The Wing Foil: A Novel Compliant Radial Foil Bearing Design

2017 ◽  
Author(s):  
Erik E. Swanson ◽  
P. Shawn O’Meara
Keyword(s):  
Test Data ◽  
High Performance ◽  
State Of The Art ◽  
Design Features ◽  
Critical Speeds ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Support Element ◽  
Bearing Design ◽  
Multidimensional Array

To meet the challenging demands for high performance, affordable compliant foil bearings, a novel compliant support element has been developed. This recently patented, novel support element uses a multidimensional array of multiple, formed, cantilever “wing foil” tabs. The wing foil bearing has all the features required to achieve state of the art performance (Gen III for radial bearings). This paper describes two radial foil beings using the wing foil and the unique design features. Test data for a 31.75 mm diameter bearing operating in air and in steam up to 42 krpm are presented to demonstrate the performance of this bearing. It is shown to have low subsynchronous vibration and reasonable damping through rigid shaft critical speeds.

Application of Materials on Foil Thrust Bearings for Micro Turbines

2011 ◽  
Vol 201-203 ◽  
pp. 2759-2762
Author(s):  
Quan Zhou ◽  
Yu Hou ◽  
Ru Gang Chen
Keyword(s):  
Thrust Bearing ◽  
Load Capacity ◽  
Bearing Surface ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Soft Surface ◽  
Static Part ◽  
Micro Turbine ◽  
Foil Thrust Bearing

Foil bearing that has a soft surface is a kind of air bearing. The performances of foil bearings are greatly affected by the materials of bearing surface, which is called foil element. In order to estimate the performance of foil bearings, two kinds of foil thrust bearings that are made of different materials respectively were tested in a micro turbine system, which contains rotation part and static part. Load capacity and stability of these foil thrust bearings were investigated in experiments. The results show that bearing which contains rubber has higher load capacity and bearing which contains copper foil has higher stability. According to the work in this paper, applications with different requirements can adopt suitable foil thrust bearing.

scholarly journals Design, Fabrication and Performance of Open Source Generation I and II Compliant Hydrodynamic Gas Foil Bearings

2007 ◽  
Author(s):  
Christopher DellaCorte ◽  
Kevin C. Radil ◽  
Robert J. Bruckner ◽  
S. Adam Howard
Keyword(s):  
Performance Testing ◽  
Foil Bearings ◽  
Metal Foils ◽  
Foil Bearing ◽  
Starting Point ◽  
Design And Manufacturing ◽  
Bearing Design ◽  
And Performance ◽  
First And Second Generation ◽  
Widespread Dissemination

Foil gas bearings are self-acting hydrodynamic bearings made from sheet metal foils and are used in selected lightly loaded, highspeed turbo-machines such as compressors and small microturbines. The general lack of familiarity of the foil bearing design and manufacturing process has hindered their widespread dissemination. Using information from publicly available literature, this paper demonstrates design, fabrication and performance testing of first and second generation bump style foil bearings and serves as an effective starting point for new Oil-Free turbomachinery development activities.

scholarly journals The Dynamic Characteristics of a Turborotor Simulator Supported on Gas-Lubricated Foil Bearings—Part 1: Response to Rotating Imbalance and Unidirectional Excitation

1970 ◽  
Vol 92 (4) ◽  
pp. 630-647 ◽  
Author(s):  
L. Licht
Keyword(s):  
Dynamic Characteristics ◽  
Rotational Speed ◽  
Load Capacity ◽  
Shake Table ◽  
Brayton Cycle ◽  
Physical Size ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Experimental Apparatus ◽  
Bearing Design

A 16-in-long rotor, weighing approximately 21 lb, was supported by air-lubricated foil bearings. In physical size and in mass distribution, the rotor was closely matched with that of an experimental Brayton cycle turboalternator unit. The rotor was stable in both the vertical and horizontal attitudes at speeds up to 50,000 rpm. A detailed description of the experimental apparatus and of the foil bearing design are given. The paper contains data of response of the rotor to rotating imbalance, symmetric and asymmetric, and to excitation by means of a vibrator (shake table). It is concluded that the gas-lubricated foil-bearing suspension is free from fractional-frequency whirl and suffers no loss of load capacity when excited at frequency equal half the rotational speed. On contrast with rigid gas bearings, the foil bearing imposes no stringent requirements with respect to dimensional tolerances, cleanliness, or limitations of journal motion within the narrow confines of bearing clearance.

The Wing Foil: A Novel Compliant Radial Foil Bearing Design

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Erik E. Swanson ◽  
P. Shawn O'Meara
Keyword(s):  
Test Data ◽  
High Performance ◽  
State Of The Art ◽  
Design Features ◽  
Critical Speeds ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Support Element ◽  
Bearing Design ◽  
Multidimensional Array

To meet the challenging demands for high performance, affordable compliant foil bearings (CFBs), a novel compliant support element has been developed. This recently patented, novel support element uses a multidimensional array of multiple, formed, cantilever “wing foil” tabs. The wing foil bearing has all the features required to achieve state-of-the-art performance (Gen III for radial bearings). This paper describes two radial foil bearings using the wing foil and the unique design features. Test data for a 31.75 mm diameter bearing operating in air and in steam up to 42 krpm are presented to demonstrate the performance of this bearing. It is shown to have low subsynchronous vibration and reasonable damping through rigid shaft critical speeds.

EXPERIMENTAL INVESTIGATION OF A FOIL BEARING STRUCTURE WITH A POLYMER COATING UNDER STATIC LOADS

Tribologia ◽  
2018 ◽  
Vol 278 (2) ◽  
pp. 153-158 ◽  
Author(s):  
Grzegorz ŻYWICA ◽  
Paweł BAGIŃSKI
Keyword(s):  
Numerical Models ◽  
Static Characteristics ◽  
Static Loads ◽  
Foil Bearings ◽  
Metal Foils ◽  
Foil Bearing ◽  
Supporting Layer ◽  
Bearing Design ◽  
Bearing Structure ◽  
Very High

Gas foil bearings can operate at very high temperatures and rotational speeds. The operation under such conditions requires developing an appropriate bearing design, including the use of advanced material solutions. This article presents one of the basic stages of work on a new foil bearing, namely, experimental research on the structural supporting layer of such a bearing regarding its static loads. Tests of the bearing were carried out on a test rig specially prepared for this purpose. Changing the magnitude and direction of the load was possible. The elasto-damping elements of the bearing were made of thin metal foils. In addition, a layer of carefully selected polymer was applied onto one side of the top foil in order to protect the surface and reduce friction. Characteristics of the structure of the foil bearing were determined at various load variants after taking a series of measurements upon it. The conducted research has yielded much information about static characteristics of the structural supporting layer of a new foil bearing in which the top foil’s surface is covered with a layer of polymer. These results can be used, among other things, to optimise the bearing design and to verify numerical models.

Derivation of Governing Equations For Self-Acting Foil Bearings

1967 ◽  
Vol 89 (3) ◽  
pp. 334-339 ◽  
Author(s):  
E. J. Barlow
Keyword(s):  
Boundary Conditions ◽  
Numerical Solutions ◽  
Bending Stiffness ◽  
The Self ◽  
Governing Equations ◽  
Foil Bearings ◽  
Foil Bearing

Contained is the derivation of the equations for the self-acting foil bearing. These equations include the effects of bending stiffness of the tape and of compressibility of the lubricant. They are nonlinear, and the boundary conditions are divided equally between the two ends of the tape. These complications even make obtaining numerical solutions difficult. Linearized solutions are derived for large wrap angles neglecting the bending stiffness of the tape.

Foil Gas Bearing With Compression Springs: Analyses and Experiments

2007 ◽  
Vol 129 (3) ◽  
pp. 628-639 ◽  
Author(s):  
Ju-ho Song ◽  
Daejong Kim
Keyword(s):  
Loss Factor ◽  
Load Capacity ◽  
Underlying Structure ◽  
Equivalent Viscous Damping ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Different Types ◽  
Structural Loss ◽  
Compression Springs ◽  
Gas Bearing

A new foil gas bearing with spring bumps was constructed, analyzed, and tested. The new foil gas bearing uses a series of compression springs as compliant underlying structures instead of corrugated bump foils. Experiments on the stiffness of the spring bumps show an excellent agreement with an analytical model developed for the spring bumps. Load capacity, structural stiffness, and equivalent viscous damping (and structural loss factor) were measured to demonstrate the feasibility of the new foil bearing. Orbit and coast-down simulations using the calculated stiffness and measured structural loss factor indicate that the damping of underlying structure can suppress the maximum peak at the critical speed very effectively but not the onset of hydrodynamic rotor-bearing instability. However, the damping plays an important role in suppressing the subsynchronous vibrations under limit cycles. The observation is believed to be true with any air foil bearings with different types of elastic foundations.

Nutritional factors associated with seasonal population increase of cacao thrips, Selenothrips rubrocinctus (Giard) (Thysanoptera), on cashew, Anacardium occidentale

1963 ◽  
Vol 53 (4) ◽  
pp. 681-713 ◽  
Author(s):  
R. G. Fennah
Keyword(s):  
Amino Acids ◽  
Water Stress ◽  
Amino Acid ◽  
Acid Concentration ◽  
Leaf Tissue ◽  
The Other ◽  
Amino Acid Concentration ◽  
Population Increase ◽  
Bearing Surface ◽  
Wet Season

The feeding of the cacao thrips, Selenothrips rubrocinctus (Giard), on cashew, Anacardium occidentale, one of its host plants in Trinidad, West Indies, is considered in relation to the annual period of maximum population increase on this host and to the choice of feeding sites on individual leaves. On trees observed for three years, populations regularly increased during the dry season, from a low level in December and January to a peak in April or May, and then rapidly declined during the wet season. Even when thrips were most abundant, some trees were free from attack, and this could not be attributed to protective morphological features, to specific repellent substances in the leaf, or to chance. S. rubrocinctus was found to feed on leaves that were subjected to water-stress and to breed only on debilitated trees: the evidence suggested that the adequacy of its supply of nutrients depends on the induction of suitable metabolic conditions within the leaf by water-stress.Both nymphs and adults normally feed on the lower, stomata-bearing surface of the leaf, but in a very humid atmosphere only a weak preference is shown for this surface and if, under natural conditions, it is exposed to insolation by inversion of the leaf, the insects migrate to the other surface. Since the thrips were shown to be indifferent to bodily posture, the observation suggests that their behaviour is governed primarily by avoidance of exposure to undue heat or dryness and only secondarily by the attractiveness of the stomata-bearing surface.Leaves of cashew tend not to become infested while still immature, and become most heavily infested, if at all, soon after they have hardened. Breeding does not occur on senescent leaves. The positions of feeding thrips are almost random on leaves under abnormal water-stress, but otherwise conform to certain patterns that mainly develop in fixed sequence. On reversal of an undetached leaf and consequent transfer of thrips from one surface to the other, there is no appreciable change in their distribution pattern or the apparent acceptability of the substrate. Changes of pattern were readily induced by injury to the plant during a period of water-stress and less easily, or not at all, when water-stress was low. Injury of areas of the leaf by heat was followed by their colonisation by thrips, and partial severance of branches by increased attack on their leaves.Leaves detached from uninfested trees invariably became acceptable for feeding within four hours. During this period, leaf water-content declined and the ratios of soluble-carbohydrate content and α-amino acids to fresh-leaf weight fell slightly and rose considerably, respectively. In the field, the latter ratio was invariably higher for infested than for uninfested leaf tissue, even on portions of the same leaf. If the nutrient value of leaf tissue is determined by the rate at which α-amino acids are extractable through a stylet puncture, the observed change in acceptability for feeding following plucking may be accounted for by the increase in α-amino-acid concentration. Feeding that is restricted on any one tree to the margins of local leaf injuries during prolonged high water-stress and totally absent when stress is low can be correlated with an α-amino-acid content in the living marginal tissue that is high or low, respectively. The ability of thrips to establish themselves and breed on leaves of a particular tree in the dry season and their failure to do so on leaves of the same tree in the wet season conforms with the greater or less amino-acid concentration occurring in the leaf at these respective times.

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