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Research Papers: Applications

High-Speed Rotor With Air Bearings Mounted on Flexible Supports: Test Bench and Experimental Results

[+] Author and Article Information
G. Belforte, F. Colombo, T. Raparelli, V. Viktorov

Dipartimento di Meccanica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy

J. Tribol 130(2), 021103 (Apr 25, 2008) (7 pages) doi:10.1115/1.2908905 History: Received November 28, 2006; Revised February 18, 2008; Published April 25, 2008

A test bench for rotors supported by air bearings floating on O-rings is designed in order to study the whirl phenomenon and characterize the stability threshold with damping elements mounted on bearings. The work includes a description of the test bench and some preliminary experimental results. A rotor of 1kg mass and 37mm diameter is rotated up to 75,000rpm by an air turbine machined on the rotor. Capacitance probes, placed in two radial planes, allow orbit scanning of both the rotor and the bushing at different rotating speeds and suitable load devices permit measurement of the static and dynamic stiffness of the rotor-bearing system. Curves of rotational response using rubber O-rings of three different materials are shown and compared. Also presented are the Fourier spectra of the signals for rotor displacement. The phenomenon of whirl instability is shown in terms of whirl frequency and orbit amplitudes of the rotor and bearings. The effects of both supply pressure and angular velocity on the stability threshold are shown.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 2

Bushing and thrust bearing

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Figure 3

Test bench components

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Figure 4

Gauging with the Linear Height

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Figure 5

Supply hole magnification (200×): (a) turbine side; (b) nose side

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Figure 6

Orbit amplitudes of rotor; ps=0.6MPa gauge pressure: (a) turbine side; (b) nose side

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Figure 7

Orbit amplitudes of bushing; ps=0.6MPa gauge pressure

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Figure 8

Displacement vectors on measuring planes

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Figure 9

Phase shift φrt; ps=0.6MPa gauge pressure

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Figure 10

Phase shift φbt; ps=0.6MPa gauge pressure

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Figure 12

Phase shift φbt−φbn

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Figure 13

Dynamic stiffness of the single O-ring

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Figure 14

Dynamic equivalent damping of the single O-ring

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Figure 15

Rotor orbits in stable condition (a) and at stability threshold (b)

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Figure 16

Frequency spectra of rotor displacement; W=50krpm

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Figure 17

Supply gauge pressure at stability threshold

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Figure 18

Whirl ratio at stability threshold

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Figure 19

Orbit amplitude versus supply pressure; ω=30,000rpm

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Figure 20

Orbit amplitude versus rotational speed; ps=0.22MPa

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Figure 11

Phase shift φbn; ps=0.6MPa gauge pressure

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