Research Papers: Multiphase Flows

Numerical Analysis of Cavitation Instabilities in Inducer Blade Cascade

[+] Author and Article Information
Benoît Pouffary

 Centre National d’Etudes Spatiales, Evry 91023, France

Regiane Fortes Patella

 INPG-LEGI, Grenoble 38041, Cedex 9, France

Jean-Luc Reboud

CNRS-LEMD,  University of Grenoble, Grenoble 38042, France

Pierre-Alain Lambert

 Snecma, Vernon 27208, France

J. Fluids Eng 130(4), 041302 (Apr 07, 2008) (8 pages) doi:10.1115/1.2903823 History: Received September 08, 2005; Revised October 03, 2007; Published April 07, 2008

The cavitation behavior of a four-blade rocket engine turbopump inducer was simulated by the computational fluid dynamics (CFD) code FINE∕TURBO ™. The code was modified to take into account a cavitation model based on a homogeneous approach of cavitation, coupled with a barotropic state law for the liquid∕vapor mixture. In the present study, the numerical model of unsteady cavitation was applied to a four-blade cascade drawn from the inducer geometry. Unsteady behavior of cavitation sheets attached to the inducer blade suction side depends on the flow rate and cavitation number σ. Numerical simulations of the transient evolution of cavitation on the blade cascade were performed for the nominal flow rate and different cavitation numbers, taking into account simultaneously the four blade-to-blade channels. Depending on the flow parameters, steady or unsteady behaviors spontaneously take place. In unsteady cases, subsynchronous or supersynchronous regimes were observed. Some mechanisms responsible for the development of these instabilities are proposed and discussed.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Scheme of the barotropic state law ρ=ρ(P). Illustration of the speed of sound influence.

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Figure 2

Illustration of the ρv influence on the barotropic law ρ=ρ(P) and on the speed of sound distribution

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Figure 3

Inducer 3D geometry—frontal and meridian planes

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Figure 4

Blade cascade corresponding to the cut at constant radius of the 3D inducer geometry. The mesh topology is I-type; calculations were carried out with 26,660 internal nodes corresponding to y+ values close to 10–20.

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Figure 5

Performance chart at a nominal flow rate. Static pressure coefficient ψ vs σdownstream.

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Figure 6

Mean static load of the blade at midspan for three different cavitation numbers σdowstream

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Figure 7

Alternate blade cavitation (σ∼0.75). Density fields (kg∕m3) calculated in the blade cascade.

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Figure 8

Visualization, in the case of supersynchronous configuration, of the vapor structures (density fields) at five different times during a complete inducer rotation period

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Figure 9

Unstable alternate configuration: Figures illustrate density fields at six different times during approximately two inducer rotation periods

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Figure 10

Visualization, in the case of subsynchronous configuration, of the vapor structures (density fields) at five different times during a complete inducer rotation period

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Figure 11

Illustration of the propagation of the largest sheet in the case of subsynchronous configuration

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Figure 12

Time evolution of the nondimensional mass flow rate in the four channels (σ=0.75; supersynchronous configuration). The lines represent the outlet and inlet flow rates in Channels 1–4.

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Figure 13

Time evolution of the total pressure variation ΔPtot for each channel. ΔPtot=Pdownstream−Pupstream. Channels 1–4.

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Figure 14

Scheme of the flow velocity, instability propagation, and inducer rotation directions

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Figure 15

Time evolution of the blade loads in the supersynchronous configuration

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Figure 16

Description of the physical mechanism supposed to be responsible for supersynchronous cavitation instability: The rise of the cavity on the upper blade increases the angle of attack and the pressure near the leading edge, at the pressure side. Then, the cavity facing this leading edge tends to vanish because of the pressure rise.




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