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Research Papers: Multiphase Flows

An Experimental Study on the Gas Entrainment in Horizontally and Vertically Installed Centrifugal Pumps

[+] Author and Article Information
Martin Neumann

AREVA Endowed Chair of Imaging Techniques in
Energy and Process Engineering,
Technische Universität Dresden,
Dresden 01062, Germany
e-mail: martin.neumann@tu-dresden.de

Thomas Schäfer

Institute of Fluid Dynamics,
Helmholtz-Zentrum Dresden-Rossendorf,
Bautzner Landstrasse 400,
Dresden 01328, Germany
e-mail: thomas.schaefer@hzdr.de

André Bieberle

Institute of Fluid Dynamics,
Helmholtz-Zentrum Dresden-Rossendorf,
Bautzner Landstrasse 400,
Dresden 01328, Germany
e-mail: a.bieberle@hzdr.de

Uwe Hampel

AREVA Endowed Chair of Imaging Techniques in
Energy and Process Engineering,
Technische Universität Dresden,
Dresden 01062, Germany;
Institute of Fluid Dynamics,
Helmholtz-Zentrum Dresden-Rossendorf,
Bautzner Landstrasse 400,
Dresden 01328, Germany
e-mail: u.hampel@hzdr.de

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received October 2, 2015; final manuscript received February 23, 2016; published online May 25, 2016. Assoc. Editor: Mark R. Duignan.

J. Fluids Eng 138(9), 091301 (May 25, 2016) (9 pages) Paper No: FE-15-1711; doi: 10.1115/1.4033029 History: Received October 02, 2015; Revised February 23, 2016

In this work, we have studied how gas accumulates in an industrial centrifugal pump under various steady-state two-phase flow conditions. Thereby, we considered both horizontal and vertical pump installation positions. Phase fractions within the impeller region of the pump have been quantitatively disclosed using high-resolution gamma-ray computed tomography (HireCT) and applying time-averaged rotation-synchronized CT scanning technique. The study was made for inlet volumetric gas flow rates between 0% and 5%. To account for different inlet flow conditions, which are assumed to occur during unwanted gas entrainment by hollow vortices, we produced disperse and swirling gas–liquid inlet flows. In this way, the influence of inlet flow boundary conditions on the pump performance as well as gas fraction distributions and gas holdup within the impeller wheel region could be successfully analyzed and compared with respect to the impeller alignment. It was shown that the installation position offers only a minor effect on the pump performance in comparison to the inlet flow conditions. In addition, for the first time, thin gas films at the pressure side of the impeller wheel blades could be visualized in an industrial centrifugal pump.

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References

Figures

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Fig. 1

Sketch of the pump test facility with the inclinable modular test section

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Fig. 2

Sketch of main components of HireCT system for two-phase flow investigations in a centrifugal pump with a rapidly rotating impeller

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Fig. 3

Data-processing scheme for time-averaging rotation-synchronized computed tomography

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Fig. 4

Suction side relative pressure ps as a function of the impeller rotational speed nP for horizontal and vertical installation positions, with adjusted operation conditions for vertical throttled

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Fig. 5

Flow rate performance curves at nominal rotational speed of nP = 1480 rpm: liquid flow rate QL as function of inlet gas fraction εin with swirling and disperse gas flow regime at the centrifugal pump inlet, for horizontal as well as vertical orientation

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Fig. 6

Left: Housing of the investigated centrifugal pump with highlighted radiographic section and right: exemplary radiographic scan of the centrifugal pump showing the internal components

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Fig. 7

Comparison of rotation-averaged radiographic scans performed at the centrifugal pump (a) horizontally and (b) vertically installed, for inlet gas volume fractions of 2% and 4%, at nominal impeller rotational speed of nP = 1480 rpm. (For interpretation of the colorbar in this figure, the reader should refer to the online version).

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Fig. 8

Upper row: Comparison of liquid-phase fraction reconstructions for various rotational speeds of the flooded pump. Lower row: Comparison of scaled reconstructions to prove possible artificial deviations due to rotational speed fluctuations.

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Fig. 9

Gas fraction distribution and gas holdup εres within the horizontally installed pump for various inlet gas volume fractions εin and both inlet flow regimes (left: swirling inlet flow and right: disperse inlet flow) at nominal rotation speed of nP = 1480 rpm

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Fig. 10

Gas fraction distribution and gas holdup εres within the vertically installed pump for various inlet gas volume fractions εin and both inlet flow regimes (top: swirling inlet flow and bottom: disperse inlet flow) at nominal rotation speed of nP = 1480 rpm

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Fig. 11

Measured gas holdup εres within the impeller region at various inlet gas fractions εin for both installation positions and inlet flow regimes at nominal rotation speed of nP = 1480 rpm

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Fig. 12

Differential pressure at various inlet gas volume fractions for both installation positions and inlet flow regimes at nominal rotational speed of nP = 1480 rpm (error bars show standard deviation of measured values)

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Fig. 13

Gas films found at the pressure side of the impeller wheel blades for two various operating points (left: vertical installation position, εin = 3%, disperse inlet flow and right: horizontal installation position, εin = 1%, disperse flow)

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