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Research Papers: Multiphase Flows

Thermodynamic Effect on a Cavitating Inducer—Part I: Geometrical Similarity of Leading Edge Cavities and Cavitation Instabilities

[+] Author and Article Information
Jean-Pierre Franc

LEGI, Grenoble Institute of Technology, Université Joseph Fourier, Centre National de la Recherche Scientifique, BP 53, 38041 Grenoble Cedex 9, Francejean-pierre.franc@inpg.fr

Guillaume Boitel, Michel Riondet

LEGI, Grenoble Institute of Technology, Université Joseph Fourier, Centre National de la Recherche Scientifique, BP 53, 38041 Grenoble Cedex 9, France

Éric Janson, Pierre Ramina, Claude Rebattet

 CREMHYG, Grenoble Institute of Technology, BP 95, 38402 Saint-Martin d'Hères Cedex, France

Centre de Recherches et d'Essais de Machines Hydrauliques de Grenoble, France.

J. Fluids Eng 132(2), 021303 (Feb 17, 2010) (8 pages) doi:10.1115/1.4001006 History: Received September 29, 2008; Revised December 14, 2009; Published February 17, 2010; Online February 17, 2010

The thermodynamic effect on a cavitating inducer is investigated from joint experiments in cold water and Refrigerant 114. The analysis is focused on leading edge cavitation and cavitation instabilities, especially on alternate blade cavitation and supersynchronous rotating cavitation. The cavity length along cylindrical cuts at different radii between the hub and casing is analyzed with respect to the local cavitation number and angle of attack. The similarity in shape of the cavity closure line between water and R114 is examined and deviation caused by thermodynamic effect is clarified. The influence of rotation speed on cavity length is investigated in both fluids and analyzed on the basis of a comparison of characteristic times, namely, the transit time and a thermal time. Thermodynamic delay in the development of leading edge cavities is determined and temperature depressions within the cavities are estimated. Thresholds for the onset of cavitation instabilities are determined for both fluids. The occurrence of cavitation instabilities is discussed with respect to the extent of leading edge cavitation. The thermodynamic delay affecting the occurrence of cavitation instabilities is estimated and compared with the delay on cavity development.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Characteristic time τ∗ of water, R114, liquid oxygen, and liquid hydrogen as a function of temperature

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Figure 2

Cavity length versus inducer cavitation number σv at three different radii, r1, r2, and r3, from hub to casing visible on Fig. 6 (water, nominal flowrate)

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Figure 3

Cavity length versus ratio σ(r)/α of local cavitation number to angle of attack at three different radii from hub to casing (same data as Fig. 2)

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Figure 4

Cavity length versus [σ(r)/α]−2 at three different radii from hub to casing (same data as Fig. 2)

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Figure 5

Influence of rotation speed on cavity length for water and R114 at 20°C. Data are relative to nominal flowrate and cavity length is measured along medium radius r2.

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Figure 6

Comparison of typical leading edge cavities in water (without thermodynamic effect) and Refrigerant 114 at 40°C. The value of the cavitation number for R114 is significantly smaller than that in water and was adjusted to correspond to a similar extent of cavitation

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Figure 7

Comparison, between water and R114, of the mean shape of cavity closure line for different degrees of development of cavitation. No data are available in R114 corresponding to the longer cavity shown in water because of thermodynamic effect, which shortens cavities.

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Figure 8

Cavity length versus cavitation number for water and R114 at two different radii between hub and casing

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Figure 9

B-factor of Stepanoff versus cavity length. Influence of radius between hub and casing. Cavity length is made nondimensional using blade spacing (R114 20°C, nominal flowrate).

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Figure 10

B-factor of Stepanoff versus inducer cavitation number. Influence of radius between hub and casing. Cavity length is made nondimensional using blade spacing.

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Figure 11

Threshold values of cavitation number for onset and desinence of cavitation instabilities (ABC and SSR) for water and R114 at two different temperatures. Influence of rotation speed at nominal flowrate.

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Figure 12

Correlation between onset or desinence of cavitation instabilities (ABC and SSR) with the length of corresponding leading edge cavities for water and R114 at nominal flowrate

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Figure 13

Comparison of thermodynamic delay on cavity length and cavitation instabilities

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Figure 14

Thermodynamic delay on cavitation instabilities versus rotation speed (R114 20°C, nominal flowrate)

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Figure 15

Thermodynamic delay on cavitation instabilities versus liquid temperature

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