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Research Papers: Flows in Complex Systems

Rotordynamic Forces Acting on Three-Bladed Inducer Under Supersynchronous/Synchronous Rotating Cavitation

[+] Author and Article Information
Yoshiki Yoshida

Japan Aerospace Exploration Agency, Kakuda Space Center, Koganezawa 1, Kimigaya, Kakuda, Miyagi 981-1525, Japanyoshida.yoshiki@jaxa.jp

Masato Eguchi

 Ebara Research Company, Ltd., 4-2-1 Honfujisawa, Fujisawa, Kanagawa 251-8502, Japaneguchi.masato@ebara.com

Taiichi Motomura, Hirotaka Kure

 IHI Corporation, 229 Tonogaya, Mizuho, Nishitama, Tokyo 190-1297, Japan

Masaharu Uchiumi

Japan Aerospace Exploration Agency, Kakuda Space Center, Koganezawa 1, Kimigaya, Kakuda, Miyagi 981-1525, Japan

Yoshiyulki Maruta

 Ebara Research Company, Ltd., 4-2-1 Honfujisawa, Fujisawa, Kanagawa 251-8502, Japan

J. Fluids Eng 132(6), 061105 (Jun 23, 2010) (9 pages) doi:10.1115/1.3425727 History: Received October 07, 2008; Revised March 17, 2010; Published June 23, 2010; Online June 23, 2010

Asymmetric cavitation, in which cavity lengths are unequal on each blade, is known as a source of cavitation induced shaft vibration in turbomachinery. To investigate the relationship of the uneven cavity length and rotordynamic force in a cavitating inducer with three blades, we conducted two experiments. In one, the growth of cavity unevenness at the inception of synchronous rotating cavitation in cryogenic flow was observed, and in the other, the rotordynamic fluid forces in water were examined by using a rotordynamic test stand with active magnetic bearings. Rotordynamic performances were obtained within a wide range of cavitation numbers, and whirl/shaft speed ratios included supersynchronous/synchronous rotating cavitation. These experimental results indicate that the shaft vibration due to the rotating cavitation is one type of self-excited vibrations arising from the coupling of cavitation instability and rotordynamics.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 10

Increase in the amplitude of shaft vibration as a function of the fluid force (uncertainty in F/Fo=0.05 and ε/εo=0.03)

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Figure 11

EBARTS with active magnetic bearing

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Figure 12

FFT analyses of pressure fluctuations at the interblade of the inducer at various rotor shaking frequencies in whirl motion (cavitation condition: just before supersynchronous rotating cavitation) (uncertainty in frequency=0.25 Hz)

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Figure 13

FFT analyses of pressure fluctuations at the interblade of the inducer at various rotor shaking frequencies in whirl motion (cavitation condition: deep synchronous rotating cavitation) (uncertainty in frequency=0.25 Hz)

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Figure 14

Definition of the fluid reaction forces Fr (normal) and Ft (tangential)

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Figure 15

Transfer functions under typical rotating cavitations: (a) noncavitating flow, (b) supersynchronous rotating cavitation, and (c) synchronous rotating cavitation (uncertainty in frequency=0.25 Hz, Fr/ε=0.02, and Ft/ε=0.02)

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Figure 16

Estimated hydrodynamics (cavitation)-rotordynamics coupling mechanism

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Figure 17

Schema of hydrodynamics (cavitation)-rotordynamics coupling mechanism

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Figure 4

Waterfall of pressure fluctuation under synchronous rotating cavitation at Pos. 4

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Figure 1

Cryogenic inducer test facility of JAXA

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Figure 2

Schematic of the test section showing the locations of pressure sensors and shaft displacement sensors

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Figure 3

Developmental view of the inducer showing locations of pressure sensors along the inducer blade

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Figure 5

Example of estimated cavity region obtained from the measured pressure distribution under typical synchronous rotating cavitation

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Figure 6

Cavitation performances, cavity length of each channel (top), shaft vibration (middle), and variations in frequency of shaft vibration (bottom) (uncertainty in Ψ/Ψo=0.01, σ/σo=0.02, Lc/h=0.03, and ω/Ω=0.005)

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Figure 7

(a) Fluctuations of cavity length under the conditions of supersynchronous rotating cavitation (uncertainty in Lc/h=0.03) and (b) fluctuations of cavity length under the conditions of synchronous rotating cavitation (uncertainty in Lc/h=0.03)

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Figure 8

Influence of the temperature on rotating cavitations (uncertainty in σ/σo=0.02)

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Figure 9

Cavity length of each channel, fluid force (top), the amplitude of shaft vibration (middle), and the Lissajous figures showing the orbit of shaft vibration (bottom) (uncertainty in Lc/h=0.03, F/Fo=0.05, and ε/εo=0.03)

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