Research Papers

Pumping Unit Power-Density Improvement by Application of Counter-Rotating Impellers Design

[+] Author and Article Information
Stefano Tosin

Institute of Jet Propulsion and Turbomachinery,
Technische Universitaet Braunschweig,
Braunschweig 38108, Germany
e-mail: ing.tosin@gmail.com

Jens Friedrichs

Chair at Institute of Jet Propulsion
and Turbomachinery,
Technische Universitaet Braunschweig,
Braunschweig 38108, Germany

Andreas Dreiss

Pumps and Drives Flowserve Corp.,
Hamburg 22047, Germany

1Corresponding author.

Manuscript received May 12, 2015; final manuscript received March 8, 2016; published online May 17, 2016. Assoc. Editor: Stephen W. T. Spence.

J. Turbomach 138(11), 111004 (May 17, 2016) (12 pages) Paper No: TURBO-15-1093; doi: 10.1115/1.4033162 History: Received May 12, 2015; Revised March 08, 2016

In many industrial areas, downsizing the pumping system is a decisive aim of the designers. The reasons could be multiple means; in a single-stage pump, increasing the power density of the pump means actually reducing the production costs. The main goal of this study was the comparison in terms of power density of a conventionally designed single-stage pump with a novel design concept based on the counter-rotating (CR) principle. In order to simplify the experimental investigations for the present study, the volute geometry was fixed instead of reducing the pump outflow diameters for a fixed design point. The energy concentration was then increased by raising the developed hydraulic power within the same envelope. The design of the impellers was carried out with an in-house design tool, based on inverse design method. Numerical results highlight the advantageousness of the new layout, in terms of power concentration, compared to the conventional impeller. Numerical predictions are also in significant agreement with the experimental investigation results, obtained in a specifically developed CR motors test rig. The experimental optimization of the rotational speed ratio of the CR impellers has shown the possibility to further increase the head in off-design condition and thereby the pump power density.

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Fig. 1

CFD analysis of CR axial-flow pump design

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Fig. 2

Typical velocity profiles in a CR axial-flow pump

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Fig. 3

CR (a) axial- and (b) mixed-flow pump velocity triangles

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Fig. 4

Meridional section

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Fig. 5

FR design parameters

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Fig. 6

SR design parameters

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Fig. 7

Picture of the CR mixed-flow impellers in the test rig

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Fig. 8

Flowchart of the design tool

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Fig. 9

(a) Circulation distribution and (b) slope of the curve

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Fig. 10

Meridional sections of the SR conventional design

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Fig. 11

Design variable's distributions along the meridional distance: (a) Γ, (b) W relative velocity, (c) βb blade angle, (d) Cm; Cm meridional velocity with and without blockage, (e) Wu tangential relative velocity component, (f) χb blockage factor, (g) Cu tangential absolute velocity component, and (h) U tangential velocity

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Fig. 12

Zero-thickness blade streamline sections in conformal plane (a) and profile meridional length (b)

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Fig. 13

Simulation 3D domain

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Fig. 14

Details of the blade mesh at a midspan section

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Fig. 15

Mesh study total to static efficiency values at design capacity and speed for the CR configuration, for different mesh sizes and wall refinement [13]

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Fig. 17

Test rig instrumentation

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Fig. 18

Comparison between the CR (left): design capacity Q = 37 l/s and rated head H = 15 m, RR speed ωRR = 19.5 Hz and conventional SR (right) mixed-flow pump: design capacity Q = 37 l/s and rated head H = 11 m, RR speed ωSR = 19.5 Hz

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Fig. 19

Efficiency and head coefficient comparison between the CR and conventional designs

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Fig. 20

Power-density comparison between the CR and conventional designs

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Fig. 21

Ideal schematization of a possible driver system to run the CR impellers




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