• The KSFM Journal of Fluid Machinery
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• v.6 no.2 s.19
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• pp.7-14
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• 2003

This paper describes reliability characteristics of an air foil journal bearing for high-speed turbomachinery at a room temperature. To verify the reliability of air foil journal bearing, lift-off characteristics, load carrying capacity, and 10,000 cycle start-stop test were performed with a motor-driven test rig. A lift-off test shows the relationship between the rotating speed of the shaft and the frictional torque with bearing surface. About a load-carrying capacity, the tested air foil journal bearing produced a load capacity of 500N at an operating speed of 15,000rpm, which is compared with results of numerical analysis and empirical coefficients. Finally, the trends in change of start torque, stop torque, and bearing temperature were shown during a 10,000-cycle start-stop test of an air foil journal bearing. We found that an air foil bearing performs well, as a supported bearing for the high-speed turbocompressor.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.199-206
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• 2002

This paper describes a reliability characteristics of an air foil journal bearing for high speed turbomachinery at room temperature. To verify the reliability of air foil journal bearing, lift-off characteristics, load carrying capacity, and 10,000 cycle start-stop test were performed with motor driven test rig. Lift-off test shows the relationship between the rotating speed of the shaft and the frictional torque with bearing surface. About load carrying capacity, the tested air foil journal bearing produced a load capacity of 500N at an operating speed of 15,000rpm, which is compared with results of numerical analysis and empirical coefficients. Finally, The trends in change of start torque, stop torque, and bearing temperature were shown during 10,000 cycle start-stop test of an air foil journal bearing. from the results of this work, an air foil bearing will be done well, as a supported bearing for high speed turbo-compressor.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.803-809
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• 2005

This paper presents the theoretical model to investigate the effect of Coulomb damping in the sub-structure of a foil bearing. Foil deflection is restricted by friction of bumps. Equivalent viscous damping of the bump foils is derived from the Coulomb friction. Dynamic equation of the bumps is constituted by stiffness and damping terms. This point give the difference from Heshmat's frictionless and simple compliance bump model. The fluid is modeled with the compressible Reynolds equation. A perturbation approach is used to determine the static and dynamic performance of the bearing from the coupled fluid-structural model. The analysis result shows that the static and dynamic performance is enhanced by bump friction. This analysis technique would be extended to development of a high performance bearing.

• The KSFM Journal of Fluid Machinery
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• v.9 no.1 s.34
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• pp.47-55
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• 2006

This paper presents the theoretical model to investigate the effect of Coulomb damping in the sub-structure of a foil bearing. Foil deflection is restricted by friction of bumps. Equivalent viscous damping of the bump foils is derived from the Coulomb friction. Dynamic equation of the bumps is constituted by stiffness and damping terms. This point give the difference from Heshmat's frictionless and simple compliance bump model. The fluid is modeled with the compressible Reynolds equation. A perturbation approach is used to determine the static and dynamic performance of the bearing from the coupled fluid-structural model. The analysis result shows that the static and dynamic performance is enhanced by bump friction. This analysis technique would be extended to development of a high performance bearing.

• Tribology and Lubricants
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• v.21 no.6
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• pp.256-262
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• 2005

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.

• Tribology and Lubricants
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• v.18 no.2
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• pp.153-159
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• 2002

This paper describes a durability characteristics of an air-lubricated bump foil journal bearing for high speed turbomachinerys at room temperature. At first, lift-off test and load capacity test were performed to understand the general characteristics of an air-lubricated bump foil Journal bearing. A 52 N weighted bump foil bearing sleeve was lilted off from a rotating Journal at about 3,000 rpm, and produced a load capacity of 500 N at an operating speed of 15,000 rpm. The next was 500 cycles lift-off test with an air-lubricated bump foil journal bearing that had a molybdenum disulfide(MoS$_2$) solid lubricant coated top foil. Data from measuring bearing torque and temperature and the observation of rubbing surfAce were included in results. Therefore the results of this work will aid in proving durability of air-lubricated bump foil journal bearings.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.212-219
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• 2001

This paper describes a durability characteristics of an air-lubricated bump foil journal bearing for high speed turbomachinerys at room temperature. At first, lift-off test and load capacity test were performed to understand the general characteristics of an air-lubricated bump foil journal bearing. A 52N weighted bump foil bearing sleeve was lifted off from a rotating journal at about 3,000rpm, and produced a load capacity of 500N at an operating speed of 15,000rpm. The next was 500 cycles lift-off test with an air-lubricated bump foil journal bearing that had a molybdenum disulfide(MoS$_2$) solid lubricant coated top foil. Data from measuring bearing torque and temperature and the observation of rubbing surface were included in results. Therefore the results of this work will aid in proving durability of air-lubricated bump foil journal bearings.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.177-185
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• 2000

The characteristics of multi-leaf feil bearing are investigated. The Foil bearing is preloaded and has several leaf foils modeled by curved beams. An analysis of the air foil bearing was performed, considering effects of foil deflection and compressible lubrication equation simultaneously. A parametric study shows that the number of foils significantly affect the static characteristics of air foil bearings and describes what the minimum film thickness means. The results include pressure profile, load capacity, dimensionless torque and minimum film thickness in the foil bearing.

• Tribology and Lubricants
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• v.17 no.4
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• pp.290-296
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• 2001

Lift-off means that the rotating journal surface separates from the leaf surface in an air-lubricated multi-leaf foil journal bearing. Lift-off builds up minimum film thickness which will provide load capacity between leaves and journal. In this paper an analysis of air-lubricated multi-leaf foil journal bearing was performed with effects of multi-leaf foil deflection and compressible lubrication equation simultaneously. Minimum film thickness built up versus journal speed predicts the lift off characteristics and these results will be useful in designing and selecting the proper speed of the air-lubricated multi-leaf foil journal bearing.