Research Papers: Flows in Complex Systems

An Experimental Study of the Flow Field Inside the Diffuser Passage of a Laboratory Centrifugal Pump

[+] Author and Article Information
Qiaorui Si

National Research Center of Pumps,
Jiangsu University,
Zhenjiang City 212013, China
e-mail: siqiaorui@gmail.com

Patrick Dupont

Ecole Centrale de Lille,
Lille 59046, France
e-mail: Patrick.Dupont@ec-lille.fr

Annie-Claude Bayeul-Lainé

Arts et Métiers Paristech,
Lille 59046, France
e-mail: annie-claude.bayeul@lille.ensam.fr

Antoine Dazin

Arts et Métiers Paristech,
Lille 59046, France
e-mail: antoine.dazin@lille.ensam.fr

Olivier Roussette

Arts et Métiers Paristech,
Lille 59046, France
e-mail: Olivier.Roussette@ensam.EU

Shouqi Yuan

National Research Center of Pumps,
Jiangsu University,
Zhenjiang City 212013, China
e-mail: shouqiy@ujs.edu.cn

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received June 20, 2014; final manuscript received January 22, 2015; published online March 13, 2015. Assoc. Editor: Bart van Esch.

J. Fluids Eng 137(6), 061105 (Jun 01, 2015) (12 pages) Paper No: FE-14-1322; doi: 10.1115/1.4029671 History: Received June 20, 2014; Revised January 22, 2015; Online March 13, 2015

Measurements are processed on a centrifugal pump model, which works with air and performs with the vane-island type diffuser of a real hydraulic pump, under five flow rates to investigate the internal flow characteristics and their influence on overall pump performance. The mean flow characteristics inside the diffuser are determined by using a miniature three-hole probe connected to an online data acquisition system. The flow structure at the inlet section of the diffuser is analyzed in detail, with a focus on the local pressure loss inside the vaneless gap and incidence angle distributions along the hub-to-shroud direction of the diffuser. Some existing calculations, including leakage effects, are used to evaluate the pressure recovery downstream of the impeller. Furthermore, particle image velocimetry (PIV) measurement results are obtained to help analyze the flow characteristics inside the vane-island diffuser. Each PIV measuring plane is related to one particular diffuser blade-to-blade channel and is analyzed by using the time-averaged method according to seven different relative positions of the impeller. Measurement results show that main loss is produced inside the vaneless part of the diffuser at low flow rates, which might have been caused by the strong rotor–stator interaction. When the impeller flow rate is greater than the diffuser design flow rate, a large fluctuating separated region occurs after the throat of the diffuser on the pressure side. Mean loss originates from the unsteady pressure downstream of the diffuser throat. For better characterization of the separations observed in previous experimental studies, complementary unsteady static pressure measurement campaigns have been conducted on the diffuser blade wall. The unsteadiness revealed by these measurements, as well as theirs effects on the diffuser performance, was then studied.

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Fig. 1

Test rig apparatus: (a) test loop, (b) probe installation diagram, and (c) three-hole probe locations traverses

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Fig. 2

Probe calibration characteristics: (a) three-hole probe size and (b) probe angle coefficient Cα

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Fig. 3

Pressure coefficients of the pump components: (a) overall pressure coefficients of the pump and diffuser and (b) pressure coefficients of the impeller

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Fig. 4

Fluid leakage models

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Fig. 5

Pump components flow rate

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Fig. 6

Flow angle α at diffuser inlet radius R3: (a) Q/Qn = 0.386, (b) Q/Qn = 0.581, (c) Q/Qn = 0.762, (d) Q/Qn = 0.968, and (e) Q/Qn = 1.12

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Fig. 7

Absolute velocity coefficient v* at diffuser inlet radius R3: (a) Q/Qn = 0.386, (b) Q/Qn = 0.581, (c) Q/Qn = 0.762, (d) Q/Qn = 0.968, and (e) Q/Qn = 1.12

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Fig. 8

Static pressure coefficient ΔPsta* at diffuser inlet radius R3: (a) Q/Qn = 0.386, (b) Q/Qn = 0.581, (c) Q/Qn = 0.762, (d) Q/Qn = 0.968, and (e) Q/Qn = 1.12

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Fig. 9

Total pressure coefficient ΔPtot* at diffuser inlet radius R3: (a) Q/Qn = 0.386, (b) Q/Qn = 0.581, (c) Q/Qn = 0.762, (d) Q/Qn = 0.968, and (e) Q/Qn = 1.12

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Fig. 10

Average values at the inlet of the diffuser: (a) mean incidence flow angle and (b) radial velocity coefficient

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Fig. 11

Static pressure coefficient at the mean line: (a) Q/Qn = 0.386, (b) Q/Qn = 0.581, (c) Q/Qn = 0.762, (d) Q/Qn = 0.968, and (e) Q/Qn = 1.12

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Fig. 12

Evolution of static pressure coefficient downstream of the impeller

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Fig. 13

PIV acquisition system, impeller positions, and measuring plans: (a) PIV acquisition system, (b) data reduction area and lighting method for results given in Tables 3 and 4, and (c) scheme of the impeller positions

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Fig. 14

Comparison of the results between probe and PIV measurement at midspan: (a) comparison of absolute flow angle α and (b) comparison of absolute velocity coefficient v*

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Fig. 15

Locations of pressure traverses in the vane diffuser

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Fig. 16

Statistical results of unsteady wall static pressure: (a) RMS at the pressure side, (b) RMS at the suction side, (c) averaged ΔPsta* at the pressure side, and (d) averaged ΔPsta* at the suction side

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Fig. 17

Auto PSD of the wall static pressure characteristic: (a) point 2, (b) point 4, (c) point 6, and (d) point 9




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