Stiffness and damping characteristics of conical multirecess hybrid journal bearing for different load arrangements

This paper presents the results of an experimental investigation into the dynamic structural stiffness and damping characteristics of a 21.6‐cm(8.5in.)-diameter compliant surface foil journal bearing. The goal of this development was to achieve high levels of damping without the use of oil, as is used in squeeze film dampers, while maintaining a nearly constant dynamic stiffness over a range of frequencies and amplitudes of motion. In the experimental work described herein, a full compliant foil bearing was designed, fabricated, and tested. The test facility included a non-rotating journal located inside the bearing. The journal was connected to an electrodynamic shaker so that dynamic forces simulating expected operating conditions could be applied to the structurally compliant bump foil elements. Excitation test frequencies to a maximum of 400Hz at amplitudes of motion between 25.4 and 102μm were applied to the damper assembly. During testing, both compressive preload and unidirectional static loads of up to 1335 and 445N, respectively, were applied to the damper assembly. The experimental data from these tests were analyzed using both a single degree of freedom model and an energy method. These methods of data analysis are reviewed here and results are compared. Excellent agreement in results obtained from the two methods was achieved. Equivalent viscous damping coefficients as high as 1050N.s∕cm(600lbf.s∕in) were obtained at low frequencies. Dynamic stiffness was shown to be fairly constant with frequency.

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Advancements in the Structural Stiffness and Damping of a Large Compliant Foil Journal Bearing: An Experimental Study

Volume 6: Turbo Expo 2004 ◽

10.1115/gt2004-53860 ◽

2004 ◽

Cited By ~ 7

Author(s):

Mohsen Salehi ◽

Hooshang Heshmat ◽

James F. Walton

Keyword(s):

Journal Bearing ◽

Dynamic Stiffness ◽

Operating Conditions ◽

Test Facility ◽

Squeeze Film ◽

Structural Stiffness ◽

Low Frequencies ◽

Equivalent Viscous Damping ◽

Damping Characteristics ◽

Stiffness And Damping

This paper presents the results of an experimental investigation into the dynamic structural stiffness and damping characteristics of a 21.6 cm (8.5inch) diameter compliant surface foil journal bearing. The goal of this development was to achieve high levels of damping without the use of oil, as is used in squeeze film dampers, while maintaining a nearly constant dynamic stiffness over a range of frequencies and amplitudes of motion. In the experimental work described herein, a full compliant foil bearing was designed, fabricated and tested. The test facility included a non-rotating journal located inside the bearing. The journal was connected to an electrodynamic shaker so that dynamic forces simulating expected operating conditions could be applied to the structurally compliant bump foil elements. Excitation test frequencies to a maximum of 400 Hz at amplitudes of motion between 25.4μm to 102μm were applied to the damper assembly. During testing, both compressive preload and unidirectional static loads of up to 1335N and 445N, respectively, were applied to the damper assembly. The experimental data from these tests were analyzed using both a single degree of freedom model and an energy method. These methods of data analysis are reviewed here and results are compared. Excellent agreement in results obtained from the two methods was achieved. Equivalent viscous damping coefficients as high as 1050 N.s/cm (600 lbf.s/in) were obtained at low frequencies. Dynamic stiffness was shown to be fairly constant with frequency.

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Effect of Manufacturing Tolerances on Stiffness and Damping of Hydrodynamic Journal Bearings

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.139-141.2662 ◽

2010 ◽

Vol 139-141 ◽

pp. 2662-2667

Author(s):

Wu Bin Xu ◽

Peter J. Ogrodnik ◽

Mike J. Goodwin ◽

Gordon Bancroft

Keyword(s):

Journal Bearing ◽

Design Stage ◽

Design Parameters ◽

Damping Characteristics ◽

Theoretical Predictions ◽

Bearing Stiffness ◽

Manufacturing Tolerances ◽

Hydrodynamic Journal Bearing ◽

Stiffness And Damping ◽

Bearing System

From a manufacturing viewpoint, the manufacturing tolerances of a hydrodynamic journal bearing system are inevitable. To examine and understand the effect of manufacturing tolerances on dynamic characteristics of a hydrodynamic journal bearing system can help engineers to confidently choose reasonable tolerances at design stage or to enable the system with certain manufacturing tolerances to operate closer to the theoretical predictions. This study presented a theoretical analysis method to determine and demonstrate the effect of manufacturing tolerances on bearing stiffness and damping, in which the concepts of limits, tolerances and nominal dimensions are introduced in. The results show that the manufacturing tolerances of a hydrodynamic journal bearing system have profound influences on the bearing stiffness and damping, and the magnitude of effect depends on system design parameters in the form of Sommerfeld number. The presented method will better predict system stiffness and damping characteristics.

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Dynamic Characteristic of Multirecess Externally Pressurized Oil Journal Bearing

Journal of Lubrication Technology ◽

10.1115/1.3453254 ◽

1978 ◽

Vol 100 (4) ◽

pp. 467-471 ◽

Cited By ~ 10

Author(s):

M. K. Ghosh

Keyword(s):

Perturbation Theory ◽

Theoretical Analysis ◽

Dynamic Characteristic ◽

Reynolds Equation ◽

Journal Bearing ◽

Journal Bearings ◽

Harmonic Vibrations ◽

Damping Characteristics ◽

Stiffness And Damping ◽

Generalized Reynolds Equation

This paper describes a theoretical analysis of the dynamic behavior of multirecess externally pressurized oil journal bearings for a nonrotating journal subjected to plane harmonic vibrations. The generalized Reynolds’ equation for a finite bearing has been solved using perturbation theory. Stiffness and damping characteristics of a capillary compensated bearing are given.

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Analysis of the Stiffness and Damping Characteristics of an Externally Pressurized Porous Gas Journal Bearing

Journal of Lubrication Technology ◽

10.1115/1.3453085 ◽

1977 ◽

Vol 99 (2) ◽

pp. 295-301 ◽

Cited By ~ 9

Author(s):

N. S. Rao

Keyword(s):

Reynolds Equation ◽

Journal Bearing ◽

Dynamic Pressure ◽

Porous Wall ◽

Small Perturbations ◽

One Dimensional ◽

Damping Characteristics ◽

Flow Through ◽

Stiffness And Damping ◽

Gas Journal Bearing

The dynamic behavior of an externally pressurized porous gas journal bearing is analyzed by assuming one dimensional flow through porous wall. A periodic (displacement) disturbance is imposed on the bearing, and the dynamic pressure distribution is determined by small perturbations of the Reynolds equation. Stiffness and damping for various design conditions are calculated numerically using a digital computer and presented in the form of design charts and tables.

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96. Computer Keyboard Keys: Stiffness and Damping Characteristics

10.3320/1.2766009 ◽

2001 ◽

Author(s):

R. Marklin ◽

M. Nagurka

Keyword(s):

Damping Characteristics ◽

Computer Keyboard ◽

Stiffness And Damping

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Stiffness and damping coefficients of an inclined journal bearing

Mechanism and Machine Theory ◽

10.1016/0094-114x(77)90010-6 ◽

1977 ◽

Vol 12 (4) ◽

pp. 339-355 ◽

Cited By ~ 4

Author(s):

A Mukherjee ◽

J.S Rao

Keyword(s):

Journal Bearing ◽

Damping Coefficients ◽

Stiffness And Damping

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

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2718233 ◽

2006 ◽

Vol 129 (3) ◽

pp. 850-857 ◽

Cited By ~ 36

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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Experimental and Theoretical Rotordynamic Characteristics of a Hybrid Journal Bearing

Journal of Tribology ◽

10.1115/1.2832446 ◽

1997 ◽

Vol 119 (1) ◽

pp. 132-141 ◽

Cited By ~ 17

Author(s):

J. T. Sawicki ◽

R. J. Capaldi ◽

M. L. Adams

Keyword(s):

Journal Bearing ◽

Operating Conditions ◽

Dynamic Force ◽

Test Results ◽

Force Measurements ◽

Lubrication Equation ◽

Load Cells ◽

Theoretical Predictions ◽

Stiffness And Damping

This paper describes an experimental and theoretical investigation of a four-pocket, oil-fed, orifice-compensated hydrostatic bearing including the hybrid effects of journal rotation. The test apparatus incorporates a double-spool-shaft spindle which permits independent control over the journal spin speed and the frequency of an adjustable-magnitude circular orbit, for both forward and backward whirling. This configuration yields data that enables determination of the full linear anisotropic rotordynamic model. The dynamic force measurements were made simultaneously with two independent systems, one with piezoelectric load cells and the other with strain gage load cells. Theoretical predictions are made for the same configuration and operating conditions as the test matrix using a finite-difference solver of Reynolds lubrication equation. The computational results agree well with test results, theoretical predictions of stiffness and damping coefficients are typically within thirty percent of the experimental results.

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