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Research Papers: Flows in Complex Systems

Influence of Nonflow Zone (Back Cavity) Geometry on the Performance of Pumps as Turbines

[+] Author and Article Information
Ashish Doshi

SVNIT,
Surat 395007, India;
Department of Mechanical Engineering,
Sardar Vallabhbhai National
Institute of Technology,
Surat 395007, India
e-mail: avd@med.svnit.ac.in

Salim Channiwala

Professor
SVNIT,
Surat 395007, India;
Department of Mechanical Engineering,
Sardar Vallabhbhai National
Institute of Technology,
Surat 395007, India
e-mail: sac@med.svnit.ac.in

Punit Singh

IISc,
Bangalore 560012, India;
Centre for Sustainable Technologies,
Indian Institute of Science,
Bangalore 560012, India
e-mail: punitsingh@iisc.ac.in

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received October 8, 2017; final manuscript received May 10, 2018; published online June 26, 2018. Assoc. Editor: Wayne Strasser.

J. Fluids Eng 140(12), 121107 (Jun 26, 2018) (13 pages) Paper No: FE-17-1647; doi: 10.1115/1.4040300 History: Received October 08, 2017; Revised May 10, 2018

The larger objective of this research comes from the fact that optimization studies in “pumps operated as turbines” have concentrated only within flow zones without any physical perception regarding the influence of nonflow zones such as back-cavities in standard end-suction pumps. Four pumps of different designs are selected and their back cavities are reduced by inserting solid material, leaving a very small axial clearance. The effects are investigated on an experimental platform, which reveal unique phenomena taking place. The first is associated with the reduction of expected disk friction (hence improvement in shaft torque), while the second is more intricate considering the effect on fluid momentum through reorganization of tangential velocities, based on the mixing zone theory proposed in the paper. The net effect of reducing the volume of nonflow zones (i.e., filling of cavity) is the enhancement of efficiency in the range of 1.3% to 3.6% (±0.4%) in turbine mode. The experimental disk friction coefficient as a function of blade Reynolds number is corroborated with the established theory proposed by different researchers. A significant phenomenon observed was the elimination of vibration and noise at overload operating conditions with the minimal axial clearance.

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References

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Figures

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Fig. 1

Control volume of PAT with flow zones and nonflow zones

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Fig. 2

Overview of the PAT test rig

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Fig. 7

View of BCF and impeller inlet for the 1.01-ns PAT (all dimensions in mm)

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Fig. 6

View of BCF and impeller inlet for the 0.63-ns PAT (all dimensions in mm)

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Fig. 5

View of BCF and impeller inlet for the 0.47-ns PAT (all dimensions in mm)

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Fig. 4

View of BCF and impeller inlet for the 0.38-ns PAT (all dimensions in mm)

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Fig. 3

PAT (a) without BCF and (b) with BCF in nonflow zone

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Fig. 8

0.38-ns PAT: overall characteristics at 1000 rpm

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Fig. 9

0.38-ns PAT: δ-parameter plot at 1000 rpm

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Fig. 10

0.47-ns PAT: overall characteristics at 1000 rpm

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Fig. 11

0.47-ns PAT: δ-parameter plot at 1000 rpm

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Fig. 12

δ-parameters chart for BCF at the BEP

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Fig. 13

0.63-ns PAT: overall characteristics at 1000 rpm

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Fig. 14

0.63-ns PAT: δ-parameter plot at 1000 rpm

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Fig. 15

1.01-ns PAT: overall characteristics at 1000 rpm

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Fig. 16

1.01-ns PAT: δ-parameter plot at 1000 rpm

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Fig. 20

Effect of BCF on mixing zone with internal flow physics for the 0.63-ns PAT

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Fig. 17

Change in theoretical disk friction losses [17,18] and comparison with Euler momentum and control volume losses

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Fig. 18

Comparison of experimental disk friction coefficients with the prediction in the literature [3134]

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Fig. 19

Effect of BCF on mixing zone with internal flow physics for the 0.38-ns PAT

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Fig. 21

ψ-ϕ curves of the 0.63-ns PAT

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Fig. 22

p-ϕ curves of the 0.63-ns PAT

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Fig. 23

η-ϕ curves of the 0.63-ns PAT

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Fig. 24

Illustration for the symbols related to BCF geometry used in Table 1

Tables

Errata

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