Foil bearings. Guidelines for testing of the performance of foil journal bearings. Testing of load capacity, friction coefficient and lifetime

2013 ◽  
Keyword(s):  
Friction Coefficient ◽  
Load Capacity ◽  
Journal Bearings ◽  
Foil Bearings

Experimental Investigation of Prototype Water-Lubricated Compliant Foil Bearings

2011 ◽  
Vol 490 ◽  
pp. 97-105 ◽  
Author(s):  
Artur Olszewski ◽  
Michał Wodtke ◽  
Piotr Hryniewicz
Keyword(s):  
Experimental Investigation ◽  
Friction Coefficient ◽  
Gas Turbines ◽  
High Speed ◽  
Journal Bearings ◽  
Radial Load ◽  
Sliding Speed ◽  
Good Tolerance ◽  
Foil Bearings ◽  
Water Pumps

First gas-lubricated compliant foil bearings (CFBs) were built in the 1950s. Due to their significant advantages, such as oil-free operation, good tolerance to bearing misalignment and very low maintenance, they have been penetrating the bearing applications for high speed compressors, air-cycle machines and gas turbines. The work presented here investigates a novel idea of water-lubricated compliant foil bearings, which could be used in applications where environmentally friendly lubrication is desired, for example in hydroelectric turbines or water pumps. Experimental results collected for three prototype water-lubricated foil journal bearings are presented. The tests were conducted under steady radial load and with the sliding speed varied incrementally. A sequence of design improvements is presented, with the best bearing demonstrating friction coefficient of about 0.01 at the sliding speed of about 4 m/s and the radial load of about 300 kPa. Encountered difficulties, research methodology and the testing equipment are also described.

Performance Analysis of Double-Bumped Air Foil Bearings

2007 ◽  
Author(s):  
Y. C. Kim ◽  
D. H. Lee ◽  
K. W. Kim
Keyword(s):  
Theoretical Model ◽  
Friction Coefficient ◽  
Performance Analysis ◽  
Active Region ◽  
Load Capacity ◽  
Equivalent Stiffness ◽  
Vertical Deflection ◽  
Foil Bearings ◽  
Damping Coefficients ◽  
Stiffness And Damping

This paper presents a theoretical model for the analysis of double-bumped Air Foil Bearings (AFBs). The stiffness and damping coefficients of the double bump vary depending on the external load and its friction coefficient. The double bump can be either in the single or double active region depending on vertical deflection. The equivalent stiffness and damping coefficients of the bump system are derived from the vertical and horizontal deflection of the bump, including the friction effect. The results of the performance analysis for a double bumped AFB are compared with those obtained for a single bumped AFB. This paper successfully proves that a double bumped AFB has higher load capacity, stiffness, and damping than a single bump AFB in a heavily loaded condition.

Performance Characteristics of Compliant Journal Bearings

1991 ◽  
Vol 113 (3) ◽  
pp. 639-644 ◽  
Author(s):  
C. R. Lin ◽  
H. G. Rylander
Keyword(s):  
Friction Coefficient ◽  
Load Capacity ◽  
Journal Bearings ◽  
Performance Characteristics ◽  
Coefficient Increase ◽  
Minimum Film Thickness ◽  
Final Design ◽  
Deformation Coefficient ◽  
Behavior Characteristics ◽  
Two Sides

This investigation of compliant journal bearings is directed toward the fundamental behavior characteristics which are necessary when compliance is factored into the final design. Analytical determintation of performance characteristics are shown as a function of the bearing flexibility. As the deformation coefficient increases, load capacity decreases, the cavitation angle and friction coefficient increase, attitude angle may increase or decrease, stability is improved for attitude angles less than 0.8, and minimum film thickness will occur near the two sides of the bearing.

The Static Performance Analysis of Air Foil Journal Bearings Considering Three-Dimensional Structure of Bump Foil

2005 ◽  
Author(s):  
Dong-Hyun Lee ◽  
Young-Cheol Kim ◽  
Kyung-Woong Kim
Keyword(s):  
Finite Element ◽  
Load Capacity ◽  
Three Dimensional ◽  
Element Model ◽  
Journal Bearings ◽  
Dimensional Structure ◽  
Suggested Model ◽  
3 Dimensional ◽  
Foil Bearings ◽  
Static Performance

The calculation of bump foil deflection is very important to predict the performance of foil bearings more accurately, because the foil bearings consist of top foil and its elastic foundation usually called bump foil. For the purpose of this, a finite element model considering 3-dimensional structure of the bump foil is developed to calculate the deflection of inter-connected bump. The results obtained from the suggested model are compared and analyzed with those from the previous proposed deflection models. In addition, load capacity of the foil bearings is analyzed by using this model.

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.

Rotordynamic Performance of a Rotor Supported on Bump Type Foil Gas Bearings: Experiments and Predictions

2006 ◽  
Vol 129 (3) ◽  
pp. 850-857 ◽  
Author(s):  
Luis San Andrés ◽  
Dario Rubio ◽  
Tae Ho Kim
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Load Capacity ◽  
Test System ◽  
Foil Bearings ◽  
Rotor Imbalance ◽  
Synchronous Motion ◽  
Damping Characteristics ◽  
Rotor Surface ◽  
Stiffness And Damping

Gas foil bearings (GFBs) satisfy the requirements for oil-free turbomachinery, i.e., simple construction and ensuring low drag friction and reliable high speed operation. However, GFBs have a limited load capacity and minimal damping, as well as frequency and amplitude dependent stiffness and damping characteristics. This paper provides experimental results of the rotordynamic performance of a small rotor supported on two bump-type GFBs of length and diameter equal to 38.10mm. Coast down rotor responses from 25krpm to rest are recorded for various imbalance conditions and increasing air feed pressures. The peak amplitudes of rotor synchronous motion at the system critical speed are not proportional to the imbalance introduced. Furthermore, for the largest imbalance, the test system shows subsynchronous motions from 20.5krpm to 15krpm with a whirl frequency at ∼50% of shaft speed. Rotor imbalance exacerbates the severity of subsynchronous motions, thus denoting a forced nonlinearity in the GFBs. The rotor dynamic analysis with calculated GFB force coefficients predicts a critical speed at 8.5krpm, as in the experiments; and importantly enough, unstable operation in the same speed range as the test results for the largest imbalance. Predicted imbalance responses do not agree with the rotor measurements while crossing the critical speed, except for the lowest imbalance case. Gas pressurization through the bearings’ side ameliorates rotor subsynchronous motions and reduces the peak amplitudes at the critical speed. Posttest inspection reveal wear spots on the top foils and rotor surface.

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