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.

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.

On the Integration of Hot Foil Bearings Into Gas Turbine Engines: Theoretical Treatment

2019 ◽  
Author(s):  
Hooshang Heshmat ◽  
James F. Walton
Keyword(s):  
High Temperature ◽  
System Dynamics ◽  
High Performance ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Structural Stiffness ◽  
Foil Bearings ◽  
Foil Bearing ◽  
High Temperature Operation ◽  
Bearing System

Abstract To achieve high power density Gas Turbine Engines (GTEs), R&D efforts have strived to develop machines that spin faster and run hotter. One method to achieve that goal is to use high temperature capable foil bearings. In order to successfully integrate these advanced foil bearings into GTE systems, a theoretical understanding of both bearing and rotor system integration is essential. Without a fundamental understanding and sound theoretical modeling of the foil bearing coupled with the rotating system such an approach would prove application efforts fruitless. It is hoped that the information provided in this paper will open up opportunistic doors to designs presently thought to be impossible. In this paper an attempt is made to describe how an advanced foil bearing is modeled for extreme high temperature operation in high performance turbomachinery including GTEs, Supercritical CO2 turbine generators and others. The authors present the advances in foil bearing capabilities that were crucial to achieving high temperature operation. Achieving high performance in a compliant foil bearing under the wide extremes of operating temperatures, pressures and speeds, requires a bearing system design approach that accounts for the highly interrelated compliant surface foil bearing elements such as: the structural stiffness and frictional characteristics of the underlying compliant support structure across the operating temperature and pressure spectrum; and the coupled interaction of the structural elements with the hydrodynamic pressure generation. This coupled elasto-hydrodynamic-Finite Element highly non-linear iterative methodology will be used by the authors to present a series of foil bearing design evaluations analyzing and modeling the foil bearing under extreme conditions. The complexity of the problem of achieving foil bearing system operation beyond 870°C (1600°F) requires as a prerequisite the attention to the tribological details of the foil bearing. For example, it is necessary to establish how both the frictional and viscous damping coefficient elements as well as the structural and hydrodynamic stiffness are to be combined. By combining these characteristics the influence of frictional coefficients of the elastic and an-elastic materials on bearing structural stiffness and hence the bearing effective coupled elasto-hydrodynamic stiffness coefficients will be shown. Given that the bearing dynamic parameters — stiffness and damping coefficients — play a major role in the control of system dynamics, the design approach to successfully integrate compliant foil bearings into complex rotating machinery systems operating in extreme environments is explored by investigating the effects of these types of conditions on rotor-bearing system dynamics. The proposed rotor/bearing model is presented to describe how system dynamics and bearing structural properties and operating characteristics are inextricably linked together in a manner that results in a series separate but intertwined iterative solutions. Finally, the advanced foil bearing modeling and formulation in connection with resulting rotor dynamics of the system will be carried out for an experimental GTE simulator test rig. The analytical results will be compared with the experiments as presented previously to demonstrate the effectiveness of the developed method in a real world application [1].

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.

Critical Speeds Resulting From Unbalance Excitation of Backward Whirl Modes

1995 ◽  
Author(s):  
Lyn M. Greenhill ◽  
Guillermo A. Cornejo
Keyword(s):  
Test Data ◽  
Driving Force ◽  
Critical Speed ◽  
Critical Speeds ◽  
Rotordynamic Coefficients ◽  
Jeffcott Rotor ◽  
Rotor Bearing ◽  
Backward Whirl ◽  
Bearing Design

Abstract Most rotordynamic analyses typically ignore the potential for critical speeds to be created by traversing a backward precessional whirl mode. While not commonly recognized, a backward mode can be excited using unbalance as the driving force. Based on the analysis of a Jeffcott rotor-bearing model, it was found that the condition for this response to occur is strongly dependent on stiffness asymmetry in the rotordynamic coefficients at the supports. To illustrate the application of this result, a rotordynamic analysis on actual hardware is presented, in which the unbalance excited backward mode resonance is calculated to occur. Test data is also given indicating the presence of the predicted critical speed. It is important to note that although the resonance is due to the backward mode, the precessional direction is forward. Several recommendations are offered with respect to rotor-bearing design so that this unique critical speed situation may be avoided.

Thermohydrodynamic Analysis of Bump Type Gas Foil Bearings: A Model Anchored to Test Data

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Luis San Andrés ◽  
Tae Ho Kim
Keyword(s):  
Test Data ◽  
Thermal Energy ◽  
Gas Flow ◽  
Energy Transport ◽  
Static Load ◽  
Isothermal Condition ◽  
Gas Temperature ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Forced Cooling

The paper introduces a thermohydrodynamic (THD) model for prediction of gas foil bearing (GFB) performance. The model includes thermal energy transport in the gas film region and with cooling gas streams, inner or outer, as in typical rotor-GFBs systems. The analysis also accounts for material property changes and the bearing components’ expansion due to temperature increases and shaft centrifugal growth due to rotational speed. Gas inlet feed characteristics are thoroughly discussed in bearings whose top foil must detach, i.e., not allowing for subambient pressure. Thermal growths determine the actual bearing clearance needed for accurate prediction of GFB forced performance, static and dynamic. Model predictions are benchmarked against published measurements of (metal) temperatures in a GFB operating without a forced cooling gas flow. The tested foil bearing is proprietary; hence, its geometry and material properties are largely unknown. Predictions are obtained for an assumed bearing configuration, with bump-foil geometry and materials taken from prior art and best known practices. The predicted film peak temperature occurs just downstream of the maximum gas pressure. The film temperature is higher at the bearing middle plane than at the foil edges, as the test results also show. The journal speed, rather than the applied static load, influences more the increase in film temperature and with a larger thermal gradient toward the bearing sides. In addition, as in the tests conducted at a constant rotor speed and even for the lowest static load, the gas film temperature increases rapidly due to the absence of a forced cooling air that could carry away the recirculation gas flow and thermal energy drawn by the spinning rotor; predictions are in good agreement with the test data. A comparison of predicted static load parameters to those obtained from an isothermal condition shows the THD model producing a smaller journal eccentricity (larger minimum film thickness) and larger drag torque. An increase in gas temperature is tantamount to an increase in gas viscosity, hence, the noted effect in the foil bearing forced performance.

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.

Flexure Pivot Tilting Pad Hybrid Gas Bearings: Operation With Worn Clearances and Two Load-Pad Configurations

2007 ◽  
Author(s):  
Luis San Andre´s ◽  
Keun Ryu
Keyword(s):  
High Speed ◽  
High Performance ◽  
Test System ◽  
Viscous Drag ◽  
Widespread Application ◽  
Critical Speeds ◽  
Gas Bearings ◽  
Foil Bearings ◽  
Modal Damping ◽  
Tilting Pad

Gas film bearings enable the successful deployment of high-speed micro-turbomachinery. Foil bearings are in use; however, cost and lack of calibrated predictive tools prevent their widespread application. Other types of bearing configurations, simpler to manufacture and fully engineered, are favored by commercial turbomachinery manufacturers. Externally pressurized tilting pad bearings offer a sound solution for stable rotor support. This paper reports measurements of the rotordynamic response of a rigid rotor, 0.825 kg and 28.6 mm in diameter, supported on flexure pivot tilting pad hybrid gas bearings. The tests are performed for various imbalances, increasing supply pressures, and under load-on-pad (LOP) and load-between-pad (LBP) configurations. Presently, the initial condition of the test bearings shows sustained wear and dissimilar pad clearances after extensive testing reported earlier, see Ref. [1]. In the current measurements, there are no noticeable differences in rotor responses for both LOP and LBP configurations due to the light-weight rotor, i.e. small static load acting on each bearing. External pressurization into the bearings increases their direct stiffnesses and reduces their damping, while raising the system critical speeds with a notable reduction in modal damping ratios. The rotor supported on the worn bearings shows a ∼10% drop in first critical speeds and roughly similar modal damping than when tested with pristine bearings. Pressurization into the bearings leads to large times for rotor deceleration, thus demonstrating the little viscous drag typical of gas bearings. Rotor deceleration tests with manually controlled supply pressures eliminate the passage through critical speeds, thus paving a path for rotordynamic performance without large amplitude motions over extended regions of shaft speed. The rotordynamic analysis shows critical speeds and peak amplitudes of motion agreeing very well with the measurements. The synchronous rotor responses for increasing imbalances demonstrate the test system linearity. Superior stability and predictable performance of pressurized flexure pivot gas bearings can further their implementation in high performance oil-free microturbomachinery. More importantly, the measurements show the reliable performance of the worn bearings even when operating with enlarged and uneven clearances.

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.

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.

Oil-Free Foil Bearings as a Reliable, High Performance Backup Bearing for Active Magnetic Bearings

2002 ◽  
Author(s):  
E. E. Swanson ◽  
H. Heshmat
Keyword(s):  
High Speed ◽  
High Performance ◽  
Dynamic Performance ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Stable Operation ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Limited Life ◽  
Rolling Element

Gas turbine engines and other high speed rotating machinery supported by magnetic bearings require some form of backup bearing to ensure reliable and safe operation. To date, this backup capability has been provided by either rolling element bearings or solid lubricated bushings. Both of these solutions have drawbacks — must notably limited life and uncertain dynamic performance. In many cases, the backup bearing system requires substantial maintenance following an activation event. An alternative approach investigated in this work is the use of a compliant foil bearing as a backup bearing. This work discusses tests of this concept on a test rig with a 63 kg rotor. In this application, the foil bearing demonstrated smooth, stable operation during a variety of simulated magnetic bearing failure events, and allowed for continued operation of the rotor following the simulated failures.

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