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Research Papers: Flows in Complex Systems

Unsteady Flow Patterns for a Double Suction Centrifugal Pump

[+] Author and Article Information
José González

Área de Mecánica de Fluidos, Universidad de Oviedo, Campus de Viesques, 33271 Gijón (Asturias), Spainaviados@uniovi.es

Jesús Manuel Fernández Oro, Katia M. Argüelles Díaz, Eduardo Blanco

Área de Mecánica de Fluidos, Universidad de Oviedo, Campus de Viesques, 33271 Gijón (Asturias), Spain

J. Fluids Eng 131(7), 071102 (Jun 22, 2009) (9 pages) doi:10.1115/1.3153367 History: Received January 25, 2008; Revised April 16, 2009; Published June 22, 2009

The flow in a double suction centrifugal pump is presented in this paper. The static performance of the machine has been obtained in a proper test rig, and the results have been compared with equivalent numerical results from an Unsteady Reynolds Averaged Navier–Stokes Equations (URANS) calculation. In a second step, the numerical results have been exploited to get detailed information about the flow inside the turbomachine. The main goal of the study is, on one hand, the validation of the numerical procedure proposed and, on the other hand, the detailed flow-field analysis for the machine, which points out the possibilities and drawbacks of the pump design. For a double suction machine, the inlet flow is characterized by the existence of a particular geometry that tries to force a uniform flow, at least for the nominal flow rate. On the contrary, at off-design conditions the lack of uniformity produces an unsteady incidence that gives rise to strong hydraulic loading variations. Instantaneous and average pressure fields have been analyzed in this paper to study the evolution of such inlet flow unsteadiness throughout the impeller and the volute. The analysis of both static and dynamic effects on the pump shaft has been carried out from the numerical calculation of the radial forces. The results have shown that the performance of the double suction centrifugal pump is suitable for typical design conditions. The best operation point or nominal flow rate is found to be at φ=0.274, which turns out to produce a specific speed ωS=1.25, well in the range for centrifugal impellers. This operating point is also found to be the one with better efficiency and with better flow characteristics, regarding the axisymmetry of the flow pattern and the fluid forces obtained. However, some particular features produce also interesting results for off-design operating points.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Experimental set-up for the pump measurements

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Figure 2

Sketch of the pump unstructured mesh. (Inlet and outlet pipe far enough to impose boundary conditions.)

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Figure 3

Unstructured mesh considered for the numerical study (a detail is enlarged)

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Figure 4

Schematic of the pump defining the reference planes

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Figure 5

Comparison of the performance curves (nondimensional variables)

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Figure 6

Numerical prediction for the exit flow angle (seven studied flow rates)

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Figure 13

Radial velocity at the impeller outlet averaged in the relative frame

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Figure 14

Swirling or tangential velocity at the impeller outlet averaged in the relative frame

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Figure 15

Integrated pressure force on the impeller due to the flow (only pressure effect)

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Figure 16

Fluctuating pressure as a function of flow rate at two different volute positions, Z=0

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Figure 17

Fluctuating pressure force at the blade passing frequency

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Figure 7

Static pressure distribution in the Z=0 plane for the nominal flow rate (φ=0.274)

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Figure 12

Velocity field around the volute tongue for three flow rates (φ=0.126, φ=0.274, and φ=0.364)

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Figure 11

Prerotation angle after the inlet tongue section, Z=0.062 for six of the analyzed flow rates

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Figure 10

Averaged tangential velocity field at the impeller inlet (Z=0.15) and three flow rates (φ=0.126, φ=0.274, and φ=0.364)

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Figure 9

Nondimensional static pressure distribution at the suction, in the inlet tongue (Z=0.25) and three flow rates (φ=0.126, φ=0.274, and φ=0.364)

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Figure 8

Pressure field at the plane X=0 for three different flow rates: φ=0.126, φ=0.274, and φ=0.364

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