Thermal Features of Compliant Foil Bearings—Theory and Experiments

Salehi, Mohsen; Swanson, Erik; Heshmat, Hooshang

doi:10.1115/1.1308038

Cited by 88 publications

(40 citation statements)

References 7 publications

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“…The technique was developed by Pinkus and Bupara [15] and is based on the assumption that the effect of pressure gradients on the shear rate of the fluid is much smaller compared with the runner drag effect. The Couette Approximation was applied successfully for predicting the temperature distribution in the air film of compliant foil journal bearing and compliant foil seals [16,17]. Accordingly, the temperature distribution in the air film is expressed as, [17]:…”

Section: Thermal Analysismentioning

confidence: 99%

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Fluid Flow and Thermal Features of Gas Foil Thrust Bearings at Moderate Operating Temperatures

Gad

Kaneko

2015

Mechanisms and Machine Science

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This study aims to analyze the flow characteristics and the thermal features of foil thrust bearing. The flow in the gas film is modeled with 2D compressible Reynolds equation including effects of centrifugal forces in the gas film. The Couette Approximation is adopted for the analysis of temperature distribution in the gas film, and the small perturbations method is used to calculate its dynamic force coefficients. The results show that the Couette Approximation can be used to calculate the temperature distribution in foil thrust bearing with reasonable accuracy and the analysis of the fluid flow reveals that most of the side-leakage occurs in the low-temperature converging region removing less than 5 % of the heat generated in the gas film. Furthermore, with the proper control of cooling flow rate through the bump foils, more than 70 % of the heat generated in the gas film can be removed.

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Section: Thermal Analysismentioning

confidence: 99%

“…The Couette Approximation was applied successfully for predicting the temperature distribution in the air film of compliant foil journal bearing and compliant foil seals [16,17]. Accordingly, the temperature distribution in the air film is expressed as, [17]:…”

Section: Thermal Analysismentioning

confidence: 99%

Fluid Flow and Thermal Features of Gas Foil Thrust Bearings at Moderate Operating Temperatures

Gad

Kaneko

2015

Mechanisms and Machine Science

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“…Such was the conclusion made by Salehi who used a Couette Approximation to the energy equation to analytically predict resulting temperatures in a foil air bearing. Based on his work he estimates that 80 percent of the heat is absorbed via conduction into the journal and bearing and the rest is carried away with the air exiting as side leakage (ref 7). Therefore, considering its placement in an engine it is probable that the bearing and Journal will be running hotter than the surrounding environment.…”

Section: N As A/tm-2004-2131 Gomentioning

confidence: 99%

An Experimental Investigation into the Temperature Profile of a Compliant Foil Air Bearing

Radil

Zeszotek

2004

Tribology Transactions

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Public reporting burden for this collection of Information is estimated to average 1 liour per response, including tlie time for reviewing instructions, searcfiing existing data sources, gatfiering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503. AGENCY USE ONLY (/.eai'e WanA)REPORT DATE May 2004 REPORT TYPE AND DATES COVERED Technical Memorandum TITLE AND SUBTITLE 12b. DISTRIBUTION CODE ABSTRACT (Maximum 200 words)A series of tests was performed to determine the internal temperature profile in a compliant bump-type foil journal air bearing operating at room temperature under various speeds and load conditions. The temperature profile was collected by instrumenting a foil bearing with nine, type K thermocouples arranged in the center and along the bearing's edges in order to measure local temperatures and estimate thermal gradients in the axial and circumferential directions. To facilitate the measurement of maximum temperatures from viscous shearing in the air film, the thermocouples were tack welded to the backside of the bumps that were in direct contact with the top foil. The mating journal was coated with a high temperature solid lubricant that, together with the bearing, underwent high temperature start-stop cycles to produce a smooth, steady-state run-in surface. Tests were conducted at speeds from 20 to 50 krpm and loads ranging from 9 to 222 N. The results indicate that, over the conditions tested, both journal rotational speed and radial load are responsible for heat generation with speed playing a more significant role in the magnitude of the temperatures. The temperatiire distribution was nearly symmetric about the bearing center at 20 and 30 krpm but became slightiy skewed toward one side at 40 and 50 krpm. Surprisingly, the maximum temperatores did not occur at the bearing edge where the minimum film thickness is expected but rather in the middle of the bearing where analytical investigations have predicted the air film to be much thicker. Thermal gradients were common during testing and were strongest in the axial direction from the middle of the bearing to its edges, reaching 3.78 °C/mm. The temperature profile indicated the circumferential thermal gradients were negligible. SUBJECT TERMSFoil air bearings; Gas bearings; Turbomachinery • TECHNICAL PUBLICATION. Reports of completed research or a major significant phase of research that present the results of NASA programs and include extensive data or theoretical analysis. Includes compilations of significant scientific and technical data and information deemed to be of continuing reference value. NA...

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“…They also found that load capacity dropped slightly with temperature. An experimental investigation was presented by Salehi, et al, (2001) about the thermal characteristics of bump foil air bearings. A 100 mm diameter foil bearing operated at speeds up to 30 krpm employing cooling air across the bearing between top foil and bump foil.…”

Section: Experimental Studies Of Thermal Characteristicsmentioning

confidence: 99%

“…This predicted result of temperature could be useful in the design of compliant foil seals and foil bearings. An analytical investigation was done by Salehi, et al, (2001) about the thermal characteristics of bump foil air bearings with cooling fluid. In parallel, an experimental program was performed.…”

Section: Experimental Studies Of Thermal Characteristicsmentioning

confidence: 99%

Studies on thermal effects in aerodynamic foil journal bearings

Zhou

2016

JAMDSM

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With extensive application of foil gas journal bearings in high temperature conditions, the effect of increasing temperature on performance in the bearings have attracted more attention. High temperature can result in significant effects on static and dynamic characteristics and stability in foil gas journal bearings. In-depth understanding about thermal performance of foil bearings is in favor of structural optimization and developing more advanced foil bearings. This paper presents a short introduction about operational mechanisms and advantages of foil gas journal bearings firstly. Then, many works concerning thermal effects in foil gas journal bearings are detailedly reviewed. The problems that need to be improved or developed in the study of thermal effects of foil bearings are also presented, that is, accuracy and reliability of thermal predicting model, cooling methods and details of bearings and solid lubricant coatings which can be applied to a more wide temperature range.

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Thermal Features of Compliant Foil Bearings—Theory and Experiments

Cited by 88 publications

References 7 publications

Fluid Flow and Thermal Features of Gas Foil Thrust Bearings at Moderate Operating Temperatures

Fluid Flow and Thermal Features of Gas Foil Thrust Bearings at Moderate Operating Temperatures

An Experimental Investigation into the Temperature Profile of a Compliant Foil Air Bearing

Studies on thermal effects in aerodynamic foil journal bearings

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