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Research Papers

Rotordynamic Force Prediction of a Shrouded Centrifugal Pump Impeller—Part I: Numerical Analysis

[+] Author and Article Information
Eunseok Kim

Mem. ASME
Department of Mechanical Engineering,
Texas A&M University,
College Station, TX 77840
e-mail: euns670@tamu.edu

Alan Palazzolo

Fellow ASME
Department of Mechanical Engineering,
Texas A&M University,
College Station, TX 77840
e-mail: a-palazzolo@tamu.edu

Contributed by the Technical Committee on Vibration and Sound of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received June 18, 2015; final manuscript received January 18, 2016; published online April 15, 2016. Assoc. Editor: John Yu.

J. Vib. Acoust 138(3), 031014 (Apr 15, 2016) (10 pages) Paper No: VIB-15-1221; doi: 10.1115/1.4032722 History: Received June 18, 2015; Revised January 18, 2016

Computational fluid dynamics (CFD) is employed to calculate the fluid-induced forces in the leakage path of an incompressible shrouded centrifugal impeller. Numerical solutions of the whirling shrouded impeller at the centered position provide the radial and tangential impedances that can be modeled as a quadratic function of whirl frequency. Calculated impedance results on a face-seal impeller can be modeled with a second-order function of whirl frequency and the predicted rotordynamic coefficients show reasonable agreement with the test results by Bolleter et al. (1989, “Hydraulic Interaction and Excitation Forces of High Head Pump Impellers,””Pumping Machinery: Third Joint ASCE/ASME Mechanics Conference, La Jolla, CA, pp. 187–194). However, the present analysis shows that the calculated impedance curves for a conventional wear-ring seal impeller using three-dimensional (3D) numerical approach have “bumps” and “dips” which can be observed in the bulk flow analysis of impeller models by Childs (1989, “Fluid-Structure Interaction Forces at Pump Impeller-Shroud Surfaces for Rotordynamic Calculations,” J. Vib., Acoust., Stress, Reliab. Des., 111(3), pp. 216–225). After reviewing previous predictions and experiments that showed the bump and dip in the computed and measured forces, the current study focuses on the estimation of the possible sources causing the peaks. The selected possible sources are inlet tangential velocity at the shroud entrance, flow rate of primary passage, shape of the shroud leakage path, and seal clearance. The fluid-induced forces of the conventional wear-ring seal impeller are calculated and analyses on the effects of these variables are provided.

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References

Figures

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Fig. 4

Influence of grid density on impedance curves of face-seal impeller (a) radial and (b) tangential

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Fig. 3

Circular whirl orbit motion of the impeller

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Fig. 2

Cut plane view of 3D eccentric grid (a) face-seal impeller and (b) wear-ring seal impeller

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Fig. 1

Nominal configuration of impeller (a) face-seal impeller and (b) wear-ring seal impeller [7]

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Fig. 5

Impedances for the face-seal impeller according to ISR (a) radial and (b) tangential

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Fig. 6

Leakage flow rate at seal outlet of the wear-ring seal impeller according to the total node number

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Fig. 7

Influence of grid density on impedance curves of the wear-ring seal impeller (a) radial and (b) tangential

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Fig. 8

Radial impedances for the wear-ring seal impeller according to the ISR (a) combined (shroud + seal), (b) shroud, and (c) seal

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Fig. 9

Tangential impedances for the wear-ring seal impeller according to the ISR (a) combined (shroud + seal), (b) shroud, and (c) seal

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Fig. 10

Averaged forces measured by Franz and Arndt [13] (a) radial and (b) tangential

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Fig. 11

Measured tangential forces according to the flow rate by Franz and Arndt [13]

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Fig. 12

Impedances on the shroud for three flow rates of the primary passage (a) radial and (b) tangential

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Fig. 13

Velocity vector plots of the wear-ring seal impeller at (a) shroud entrance and (b) seal inlet

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Fig. 14

Modified shroud geometry on stator-side

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Fig. 16

Averaged circumferential velocity according to the shape of shroud

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Fig. 17

Impedances on the shroud according to the secondary flow path geometry (a) radial and (b) tangential

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Fig. 18

Radial impedances for the wear-ring seal impeller according to the seal clearance (a) combined (shroud + seal), (b) shroud, and (c) seal

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Fig. 19

Tangential impedances for the wear-ring seal impeller according to the seal clearance (a) combined (shroud + seal), (b) shroud, and (c) seal

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Fig. 15

Vector plots in the added recirculation zone (A2)

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