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Research Papers: Multiphase Flows

# Thermodynamic Effect on Cavitation Performances and Cavitation Instabilities in an Inducer

[+] Author and Article Information
Kengo Kikuta

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

Yoshiki Yoshida

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

Mitsuo Watanabe, Tomoyuki Hashimoto

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

Katsuji Nagaura

Foundation for Promotion of Japanese Aerospace Technology, Koganezawa 1, Kimigaya, Kakuda, Miyagi 981-1525, Japan

Katsuhide Ohira

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

J. Fluids Eng 130(11), 111302 (Sep 22, 2008) (8 pages) doi:10.1115/1.2969426 History: Received May 25, 2007; Revised July 02, 2008; Published September 22, 2008

## Abstract

Based on the length of the tip cavitation as an indication of cavitation, we focused on the effect of thermodynamics on cavitation performances and cavitation instabilities in an inducer. Comparison of the tip cavity length in liquid nitrogen ($76K$ and $80K$) as working fluid with that in cold water $(296K)$ allowed us to estimate the strength of the thermodynamic effect on the cavitations. The degree of thermodynamic effect was found to increase with an increase of the cavity length, particularly when the cavity length extended over the throat of the blade passage. In addition, cavitation instabilities occurred both in liquid nitrogen and in cold water when the cavity length increased. Subsynchronous rotating cavitation appeared both in liquid nitrogen and in cold water. In the experiment using liquid nitrogen, the temperature difference between $76K$ and $80K$ affected the range in which the subsynchronous rotating cavitation occurred. In contrast, deep cavitation surge appeared only in cold water at lower cavitation numbers. From these experimental results, it was concluded that when the cavity length extends over the throat, the thermodynamic effect also affects the cavitation instabilities as a “thermal damping” through the unsteady cavitation characteristics.

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## Figures

Figure 5

Typical optical visualization of cavitating inducer in cold water

Figure 6

Location of pressure taps along the blade

Figure 7

Waterfalls of unsteady pressure wave form at Pos. 2, 4, and 6(uncertainty in σ=0.001)

Figure 8

Typical unsteady pressure distribution showing the estimated cavity region in liquid nitrogen

Figure 9

Cavitation performance, cavity length, and pressure amplitude of cavitation instabilities in cold water (296K) (uncertainty in σ=0.001, ψ∕ψ0=0.01, Ccl=0.05)

Figure 14

Photograph under the condition of deep cavitation surge at lower cavitation numbers in cold water (296K)

Figure 15

Comparison of cavity lengths in liquid nitrogen (80K, Q∕Qd=1.00, 1.05) with those in water (296K, Q∕Qd=1.00 and 1.06) (uncertainty in σ=0.001, Ccl=0.03(nitrogen), Ccl=0.03(water))

Figure 1

Cryogenic inducer test facility of JAXA

Figure 2

Schematic diagram of the drive unit

Figure 3

Section of the test inducer in liquid nitrogen, showing the location of pressure sensors

Figure 4

Variation of the thermodynamic function Σ(T) of hydrogen, nitrogen, oxygen, and water

Figure 10

Cavitation performance, cavity length, torque, and pressure amplitude of cavitation instabilities in liquid nitrogen (76K and 80K) (uncertainty in σ=0.001, ψ∕ψ0=0.01, Ccl=0.03)

Figure 11

FFT analyses of unsteady pressure fluctuation at Pos. 4 (upper: in water (296K); lower: in liquid nitrogen (80K)) (uncertainty in f*=2πf∕Ω=0.005)

Figure 12

Estimated temperature depression ΔT as a function of the cavity length Ccl (uncertainty in Ccl=0.03)

Figure 13

Range of occurrence of cavitation instability in water (296K) and liquid nitrogen (76K and 80K) (uncertainty in σ=0.001)

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