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Research Papers: Gas Turbines: Structures and Dynamics

Start-Stop Characteristics and Thermal Behavior of a Large Hybrid Airfoil Bearing For Aero-Propulsion Applications

[+] Author and Article Information
Daejong Kim1

Mechanical and Aerospace Engineering,  University of Texas at Arlington, Arlington, TX 76019 daejongkim@uta.edu

George Zimbru

Mechanical and Aerospace Engineering,  University of Texas at Arlington, Arlington, TX 76019

1

Corresponding author.

J. Eng. Gas Turbines Power 134(3), 032502 (Dec 28, 2011) (9 pages) doi:10.1115/1.4004487 History: Received February 06, 2011; Revised June 23, 2011; Published December 28, 2011; Online December 28, 2011

Air/gas foil bearings (AFB) have shown a promise in high-speed micro to mid-sized turbomachinery. Compared to rolling element bearings, AFBs do not require oil lubrication circuits and seals, allowing the system to be less complicated and more environment-friendly. Due to the smaller number of parts required to support the rotor and no lubrication/seal system, AFBs provide compact solution to oil-free turbomachinery development.While foil bearing technology is mature in small industrial machines and power generation turbines, its application to aero-propulsion systems has been prohibited due to the reliability issues relevant to unique aero-propulsion environments such as severe rubbing due to the very slow acceleration of typically heavy rotors. This paper presents a hybrid air foil bearing (a combination of hydrostatic and hydrodynamic) with 102 mm in diameter designed for aero-propulsion applications, and preliminary test results on start-stop friction characteristics and thermal behavior at low speeds below 10,000 rpm are presented. The bearing could withstand 1000 start/stop cycles with 6 rev/s2 acceleration under a static load of 356 N (43.4 kPa).

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Photo of manufactured HAFB from [17]

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Figure 2

Photo of load capacity test rig

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Figure 3

Photo of top foil (back side) with thermo couples; arrow shows the direction of rotor rotation for torque measurements

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Figure 4

Benchmark friction curve from [20]

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Figure 5

Friction torque during controlled acceleration to 2000 rpm (13 rpm/s)

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Figure 6

Friction torque during controlled acceleration to 4000 rpm (13 rpm/s)

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Figure 7

Photo of loaded top foil after the test at 4000 rpm in the incorrect direction of rotor rotation (CCW rotation)

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Figure 8

Photo of rotor surface after the test at 4000 rpm in the incorrect direction of rotor rotation (CCW rotation)

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Figure 9

Thermal response at 4000 rpm, 445 N

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Figure 10

Thermal response at 6000 rpm, 445 N

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Figure 11

Air mass flow rate at 6000 rpm, 445 N

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Figure 12

Thermal response at 6000 rpm, 445 N, repeated with constant air flow of 67 SLPM

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Figure 13

Thermal response at 8000 rpm, 445 N

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Figure 14

Thermal response at 10,000 rpm, 445 N

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Figure 15

Photo of the loaded top foil after tests presented in Fig. 11

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Figure 16

Supply pressures and resultant total flow rate during tests at 8000 rpm under 445 N

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Figure 17

Thermal responses at 8000 rpm under 445 N with various pressures at the regulator

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Figure 18

Thermal responses at 10,000 rpm under 445 N with various pressures at the regulator

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Figure 19

Photo of top foil after tests shown in Fig. 1 and Fig. 1

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Figure 20

Description of two shim bumps to eliminate sagging of top foil

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Figure 21

Photo of top foil before endurance test after break-in run at 5000 rpm for 30 mins under 400 N; white mark at the center is the grinding mark of thermal bulge before test

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Figure 22

Photo of top foil after total 200 start/stop cycles under 356 N between stand and 2000 rpm

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Figure 23

Photo of top foil after total 400 accumulated start/stop cycles under 356 N between stand and 2000 rpm

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Figure 24

Photo of top foil after total 1000 accumulated start/stop cycles under 356 N between stand and 2000 rpm

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