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Research Papers: Multiphase Flows

# Thermodynamic Effect on Rotating Cavitation in an Inducer

[+] Author and Article Information
Yoshiki Yoshida1

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

Yoshifumi Sasao, Yuka Iga, Toshiaki Ikohagi

Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba, Sendai, Miyagi 980-8577, Japan

Mitsuo Watanabe, Tomoyuki Hashimoto

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

1

Contributing author.

J. Fluids Eng 131(9), 091302 (Aug 18, 2009) (7 pages) doi:10.1115/1.3192135 History: Received April 14, 2008; Revised June 21, 2009; Published August 18, 2009

## Abstract

Cavitation in cryogenic fluids has a thermodynamic effect because of the thermal imbalance around the cavity. It improves cavitation performances in turbomachines due to the delay of cavity growth. The relationship between the thermodynamic effect and cavitation instabilities, however, is still unknown. To investigate the influence of the thermodynamic effect on rotating cavitation appeared in the turbopump inducer, we conducted experiments in which liquid nitrogen was set at different temperatures (74 K, 78 K, and 83 K) with a focus on the cavity length. At higher cavitation numbers, supersynchronous rotating cavitation occurred at the critical cavity length of $Lc/h≅0.5$ with a weak thermodynamic effect in terms of the fluctuation of cavity length. In contrast, synchronous rotating cavitation occurred at the critical cavity length of $Lc/h≅0.9–1.0$ at lower cavitation numbers. The critical cavitation number shifted to a lower level due to the suppression of cavity growth by the thermodynamic effect, which appeared significantly with rising liquid temperature. The unevenness of cavity length under synchronous rotating cavitation was decreased by the thermodynamic effect. Furthermore, we confirmed that the fluid force acting on the inducer notably increased under conditions of rotating cavitation, but that the amplitude of the shaft vibration depended on the degree of the unevenness of the cavity length through the thermodynamic effect.

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## Figures

Figure 1

Cryogenic Inducer Test Facility of JAXA

Figure 2

Schematic diagram of the test inducer showing the installed pressure sensors and shaft displacement sensor

Figure 3

Development view of the inducer showing location of pressure sensors along the inducer blade

Figure 4

(a) Estimated cavity region under supersynchronous rotating cavitation and (b) estimated cavity region under synchronous rotating cavitation

Figure 5

(a) Photographs of supersynchronous rotating cavitation in water from Ref. 7. (b) Photographs of synchronous rotating cavitation in water from Ref. 7.

Figure 6

Variation in the thermodynamic function Σ(T) of nitrogen and water

Figure 7

Cavitation performances and cavity length of each channel (top), and variations in dominant frequency of shaft vibration (bottom) (uncertainty in ψ/ψ0=0.01, σ/σ0=0.02, Lc/h=0.03, and ω/Ω=0.005)

Figure 8

(a) Fluctuations of cavity lengths for each channel in the case of supersynchronous rotating cavitation (left: 74 K, right: 83 K) (uncertainty in Lc/h=0.03) and (b) fluctuations of cavity lengths for each channel in the case of synchronous rotating cavitation (left: 74 K, right: 83 K) (uncertainty in Lc/h=0.03)

Figure 9

Influence of temperature on cavity length and the region where the rotating cavitations occurs at 74 K, 78 K, and 83 K (uncertainty in σ/σ0=0.02 and Lc/h=0.03)

Figure 10

(a) Variations in cavity length (top), fluid force (top), and shaft vibration (bottom) for 74 K (uncertainty in σ/σ0=0.02, Lc/h=0.03, and F/Fref=0.03) and (b) variations in cavity length (top), fluid force (top), and shaft vibration (bottom) for 83 K (uncertainty in σ/σ0=0.02, Lc/h=0.03, and F/Fref=0.03)

Figure 11

(a) Instant vector orbits of fluid force under typical supersynchronous rotating cavitation at 74 K and 83 K (uncertainty in F/Fref=0.03) and (b) time-averaged vector orbits of fluid force during synchronous rotating cavitation at 74 K and 83 K (uncertainty in F/Fref=0.03)

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