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Research Papers: Flows in Complex Systems

Performance and Radial Loading of a Mixed-Flow Pump Under Non-Uniform Suction Flow

[+] Author and Article Information
B. P. M. van Esch

 Technische Universiteit Eindhoven, P.O. Box 513, 5600MB Eindhoven, The Netherlandsb.p.m.v.esch@tue.nl

J. Fluids Eng 131(5), 051101 (Apr 01, 2009) (7 pages) doi:10.1115/1.3089539 History: Received June 26, 2008; Revised January 19, 2009; Published April 01, 2009

Many centrifugal pumps have a suction velocity profile, which is nonuniform, either by design like in double-suction pumps, sump pumps, and in-line pumps, or as a result of an installation close to an upstream disturbance like a pipe bend. This paper presents an experimental study on the effect of a nonuniform suction velocity profile on performance of a mixed-flow pump and hydrodynamic forces on the impeller. In the experiments, a newly designed dynamometer is used, equipped with six full Wheatstone bridges of strain gauges to measure the six generalized force components. It is placed in between the shaft of the pump and the impeller and corotates with the rotor system. A high accuracy is obtained due to the orthogonality of bridge positioning and the signal conditioning electronics embedded within the dynamometer. The suction flow distribution to the pump is adapted using a pipe bundle situated in the suction pipe. Results of measurements show the influence of the suction flow profile and blade interaction on pump performance and forces. Among the most important observations are a backward whirling motion of the rotor system and a considerable steady radial force.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Waterjet propulsion system employing a mixed-flow pump with stator bowl and nozzle

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Figure 2

Examples of measured axial velocity distribution in a plane just upstream of the impeller. Velocities are normalized with the average axial velocity.

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Figure 3

Experimental facility

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Figure 4

Cross section of the mixed-flow pump indicating the position of the dynamometer

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Figure 5

Drawing of dynamometer showing four posts (left) and cross section of dynamometer with spline part and sealing jackets

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Figure 6

Dynamometer with electronics for bridge power supply and signal conditioning (left) and dynamometer mounted on the shaft

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Figure 7

Axial velocity profiles along a vertical traverse, with and without a pipe bundle installed

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Figure 8

Comparison of velocity profile B with measured profiles in a waterjet intake duct (Fig. 3)

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Figure 9

Manometric head for uniform suction flow, at different shaft speeds

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Figure 10

Impeller torque for uniform suction flow, at different shaft speeds

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Figure 11

Axial force on the impeller for uniform suction flow, at different shaft speeds

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Figure 12

Static head for uniform and nonuniform suction flows, at small and large tip clearances

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Figure 13

Impeller torque for uniform and nonuniform suction flows, at small and large tip clearances

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Figure 14

Pump efficiency based on static head for uniform and nonuniform suction flows, at small and large tip clearances

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Figure 15

Axial force for uniform and nonuniform suction flows, at small and large tip clearances

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Figure 16

Force vector plot in the inertial frame of reference, normalized with impeller weight Fg in water, for uniform suction flow profile

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Figure 17

Force vector plot for frequencies up to and including shaft frequency, for uniform suction flow profile

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Figure 18

Force vector plot for frequencies above shaft frequency showing rotor-stator blade interaction and backward whirl of the impeller

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Figure 19

Normalized steady fluid-induced force, for different flow rates and suction flow profiles

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Figure 20

Vector plot of normalized steady fluid-induced force for different flow rates and shaft speeds, and suction velocity profile B

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Figure 21

Magnitude of normalized steady fluid-induced force for different shaft speeds and suction velocity profile B

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Figure 22

Direction of steady fluid-induced force vector for different shaft speeds and suction velocity profile B

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Figure 23

Comparison of radial forces as given in literature with measured values of Fig. 2

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