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Research Papers: Gas Turbines: Structures and Dynamics

Remaining Technical Challenges and Future Plans for Oil-Free Turbomachinery

[+] Author and Article Information
Christopher DellaCorte

Glenn Research Center, National Aeronautics and Space Administration, Cleveland, OH 44135christopher.dellacorte@nasa.gov

Robert J. Bruckner

Glenn Research Center, National Aeronautics and Space Administration, Cleveland, OH 44135robert.j.bruckner@nasa.gov

J. Eng. Gas Turbines Power 133(4), 042502 (Nov 18, 2010) (7 pages) doi:10.1115/1.4002271 History: Received May 26, 2010; Revised June 22, 2010; Published November 18, 2010; Online November 18, 2010

The application of oil-free technologies (foil gas bearings, solid lubricants, and advanced analysis and predictive modeling tools) to advanced turbomachinery has been underway for several decades. During that time, full commercialization has occurred in aircraft air cycle machines, turbocompressors, cryocoolers, and ever-larger microturbines. Emerging products in the automotive sector (turbochargers and superchargers) indicate that a high volume serial production of foil bearings is imminent. The demonstration of foil bearings in auxiliary power units and select locations in propulsion gas turbines illustrates that such technology also has a place in these future systems. Foil bearing designs, predictive tools, and advanced solid lubricants that can satisfy anticipated requirements have been reported, but a major question remains regarding the scalability of foil bearings to ever-larger sizes to support heavier rotors. In this paper, the technological history, primary physics, engineering practicalities, and existing experimental and experiential database for scaling foil bearings are reviewed, and the major remaining technical challenges are identified.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Cross section view of simple radial foil bearing

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Figure 2

Journal and thrust foil bearings used to control radial and axial shaft motion, respectively

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Figure 3

Earliest foil bearings were inspired by magnetic tape/roller geometry and were used to replace rigid sleeve bearings in BRU demonstrator (5)

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Figure 4

Tape-type journal bearing under test

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Figure 5

15 kW BRU turbine using foil bearings in place of rigid gas bearings

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Figure 6

Early automotive gas turbine using foil bearings for the high-speed core shaft proved the technology for combustion driven turbomachines

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Figure 7

Cutaway photograph of the NASA oil-free turbocharger

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Figure 8

Early hybrid foil-magnetic bearing concept that nests the foil bearing inside electromagnetic coils to create a smart bearing (22)

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Figure 9

Fluid film thickness versus load at varying speeds (7). Smaller films can be sustained at lower speeds due to reduced thermal stresses on the bearing.

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