Gas bearings in oil-free microturbomachinery for gas process applications and power generation (< 400 kW) must be reliable and inexpensive, ensuring low drag power and thermal stability. Bump-type foil bearings (B-FBs) and overleaf-type foil bearings are in use in specialized applications, though their development-time (design and prototyping), exotic materials, and excessive manufacturing cost still prevent their widespread usage. Metal mesh foil bearings (MMFBs), on the other hand, are an inexpensive alternative that uses common materials and no restrictions on intellectual property. Laboratory testing shows that prototype MMFBs perform similarly as typical BFBs but offering significantly larger damping to dissipate mechanical energy due to rotor vibrations. This paper details a one-to-one comparison of the static and dynamic forced performance characteristics of a MMFB against a BFB of similar size and showcases the advantages and disadvantages of MMFBs. The bearings for comparison are a Generation I BFB and a MMFB, both with a slenderness ratio L/D = 1.04. Measurements of rotor lift-off speed and drag friction at start-up and airborne conditions were conducted for rotor speeds to 70 krpm and under identical specific loads (W/LD = 0.06 to 0.26 bar). Static load versus bearing elastic deflection tests evidence a typical hardening nonlinearity with mechanical hysteresis; the MMFB showing two to three times more material damping than the BFB. The MMFB exhibits larger drag torques during rotor start-up and shut-down tests though bearing lift-off happens at lower rotor speeds (∼15 krpm). As the rotor becomes airborne, both bearings offer very low drag friction coefficients, ∼0.03 for the MMFB and ∼0.04 for the BFB in the speed range 20–40 krpm. With the bearings floating on a journal spinning at 50 krpm, the MMFB dynamic direct force coefficients show little frequency dependency, while the BFB stiffness and damping increases with frequency (200–400 Hz). The BFB has a much larger stiffness and viscous damping coefficients than the MMFB. However, the MMFB material loss factor is at least twice as large as that in the BFB. The experiments show the MMFB, when compared to the BFB, has a lower drag power and earlier lift-off speed, and with dynamic force coefficients having a lesser dependency on whirl frequency excitation.
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ASME Turbo Expo 2012: Turbine Technical Conference and Exposition
June 11–15, 2012
Copenhagen, Denmark
Conference Sponsors:
- International Gas Turbine Institute
ISBN:
978-0-7918-4473-1
PROCEEDINGS PAPER
A Metal Mesh Foil Bearing and a Bump-Type Foil Bearing: Comparison of Performance for Two Similar Size Gas Bearings Available to Purchase
Luis San Andrés,
Luis San Andrés
Texas A&M University, College Station, TX
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Thomas Abraham Chirathadam
Thomas Abraham Chirathadam
Southwest Research Institute®, San Antonio, TX
Search for other works by this author on:
Luis San Andrés
Texas A&M University, College Station, TX
Thomas Abraham Chirathadam
Southwest Research Institute®, San Antonio, TX
Paper No:
GT2012-68437, pp. 859-869; 11 pages
Published Online:
July 9, 2013
Citation
San Andrés, L, & Chirathadam, TA. "A Metal Mesh Foil Bearing and a Bump-Type Foil Bearing: Comparison of Performance for Two Similar Size Gas Bearings." Proceedings of the ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. Volume 7: Structures and Dynamics, Parts A and B. Copenhagen, Denmark. June 11–15, 2012. pp. 859-869. ASME. https://doi.org/10.1115/GT2012-68437
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