Research Papers: Fundamental Issues and Canonical Flows

X-Ray Measurements in a Cavitating Centrifugal Pump During Fast Start-Ups

[+] Author and Article Information
S. Duplaa

Institut Supérieur de l'Aéronautique et de l'Espace (ISAE),
Université de Toulouse,
10 Avenue Edouard Belin,
BP 54032,
31055 Toulouse, Cedex 4, France
e-mail: sebastien.duplaa@isae.fr

G. Bois

Arts et Métiers ParisTech/Laboratoire de Mécanique de Lille (LML, UMR CNRS 8107),
8 Boulevard Louis XIV,
59046 Lille Cedex, France

Manuscript received July 10, 2012; final manuscript received January 7, 2013; published online March 26, 2013. Assoc. Editor: Frank C. Visser.

J. Fluids Eng 135(4), 041204 (Mar 26, 2013) (9 pages) Paper No: FE-12-1321; doi: 10.1115/1.4023677 History: Received July 10, 2012; Revised January 07, 2013

The start-up of rocket engine turbopumps is generally performed in a few seconds or even less. It implies that these pumps reach their nominal operating conditions after a few rotations only. During the start-up, the flow evolution within the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed increase. Significant pressure fluctuations, which may result in the development of cavitation, are observed. A centrifugal impeller whose transient behavior during start-ups has been detailed in a previous publication is considered. Three different cases of fast start-ups have been identified according the final operating point (Duplaa et al., 2010, “Experimental Study of a Cavitating Centrifugal Pump During Fast Start-Ups,” ASME J. Fluids Eng., 132(2), p. 021301). The aim of this paper is to analyze the evolution during the start-ups of the local amount of vapor in the blade to blade channels of the pump by fast X-ray imaging. This technique has enabled to calculate the time-evolution of the fluid density within the pump, which appears to be correlated with pressure time-evolutions. For each investigated start-up, X-ray measurements have been performed at three different sections of the impeller height. For each investigated start-up and section tested, measurements have been performed for several initial positions of the impeller, to estimate the measurement uncertainty, and to obtain records from different beam angles, like in tomography.

Copyright © 2013 by ASME
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Fig. 1

Photography and scheme of the test rig: (a) configuration 2, (b) configuration 1

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Fig. 2

Photography of the Plexiglas impeller

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Fig. 3

Scheme of the hub conception

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Fig. 4

Pressure evolutions: (a) case 1, (b) case 2, (c) case 3

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Fig. 5

Classification of the start-ups

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Fig. 7

Location of test sections and definition of the frame x − y axis

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Fig. 8

Relative vapor length in the pump

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Fig. 9

Relative vapor length and density profile in the pump during fast start-ups (section 1): (a) case 1, (b) case 2, (c) case 3

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Fig. 10

Density profiles for the three sections: (a) case 1, (b) case 2, (c) case 3

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Fig. 11

Axial density distribution and iso-density curves during fast start-up: (a) case 1, (b) case 2, (c) case 3

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Fig. 12

Relative uncertainty profiles due to the repeatability for the three sections: (a) case 1, (b) case 2, (c) case 3




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