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TECHNICAL PAPERS

Performance and Internal Flow Characteristics of a Very Low Specific Speed Centrifugal Pump

[+] Author and Article Information
Young-Do Choi1

Department of Systems Design, Division of Systems Research, Faculty of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501 Japanydchoi@mach.me.ynu.ac.jp

Junichi Kurokawa, Jun Matsui

Department of Systems Design, Division of Systems Research, Faculty of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501 Japan

1

Corresponding author.

J. Fluids Eng 128(2), 341-349 (Sep 05, 2005) (9 pages) doi:10.1115/1.2169815 History: Received May 16, 2004; Revised September 05, 2005

In very low specific speed range (ns<0.25), the efficiency of the centrifugal pump designed by the conventional method becomes remarkably low. Therefore, positive-displacement pumps have been widely used for long. However, the positive-displacement pumps remain associated with problems such as noise and vibration and they require high manufacturing precision. Since the recently used centrifugal pumps are becoming higher in rotational speed and smaller in size, there appear to be many expectations to develop a new centrifugal pump with high performance in the very low specific speed range. The purpose of this study is to investigate the internal flow characteristics and its influence on the performance of a very low specific speed centrifugal pump. The results show that large reverse flow at the semi-open impeller outlet decreases absolute tangential velocity considerably which in turn decreases the pumping head.

Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic view of test pump 1 and tip clearance c

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Figure 2

Test pump 2 and PIV measurement system

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Figure 3

Test impellers for test pump 1

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Figure 4

Test impellers for test pump 2

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Figure 5

Performance curves of test pump 1 with change of tip clearance ratio (uncertainty of ϕ=±1.39%, of ψ=±1.0%, of ν=±1.49%, of η=±2.29%, of nsl=±1.15%)

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Figure 14

Change of absolute tangential velocity ratio by tip clearance ratio (impellers B′ and C′, Q∕Q0=1.0) (uncertainty of vθ∕rω=±0.75% and ±2.35% static pressure and LDV, respectively)

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Figure 15

Change of absolute tangential velocity ratio by specific speed variation (Q∕Q0=1.0)

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Figure 6

Effect of tip clearance ratio on efficiency (uncertainty of ηmax=±2.29%, of ηD.P.=±2.29%)

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Figure 7

Performance curves of test pump 2 (impellers D(β2=90deg) and E(β2=30deg)) (uncertainty of ϕ=±1.41%, of ψ=±2.16%, of ν=±1.5%, of η=±3.18%, of nsl=±2.21%)

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Figure 8

Absolute tangential velocity at impeller outlet (uncertainty of υθ∕rω=±2.35%)

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Figure 9

Change of slip factor by tip clearance ratio (Q∕Qd=1.0) (uncertainty of k=±2.35%)

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Figure 10

Phase averaged velocity vectors of test pump 2 (uncertainty of vθ∕u2=±3.75%, of vr∕u2=±3.75%). (a) Impeller D (Q∕Q0=1.0, PTV). (b) Impeller E (Q∕Q0=1.0, PTV). (c) Impeller D (Q∕Q0=0.25, PTV).

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Figure 11

Phase-averaged relative velocity vectors (impeller D, Q∕Q0=1.0, area 3, PIV) (uncertainty of vθ∕u2=±3.5%, of vr∕u2=±3.5%). (a) Plane 1 (z∕b=0.05). (b) Plane 2 (z∕b=0.5). (c) Plane 3 (z∕b=0.95).

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Figure 12

Absolute tangential velocity ratio (impeller D, Q∕Q0=1.0, c∕b2=0.125, PIV) (uncertainty of vθ∕rω=±3.5%)

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Figure 13

Change of absolute tangential velocity ratio by blade outlet angle (Impellers D and E, Q∕Q0=1.0, PIV) (uncertainty of vθ∕rω=±3.5%)

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