Governing equations of motion are derived for a bulk-flow model of the leakage path between an impeller shroud and a pump housing. The governing equations consist of a path-momentum, a circumferential-momentum, and a continuity equation. The fluid annulus between the impeller shroud and pump housing is assumed to be circumferentially symmetric when the impeller is centered; i.e., the clearance can vary along the pump axis but does not vary in the circumferential direction. A perturbation expansion of the governing equations in the eccentricity ratio yields a set of zeroth and first-order governing equations. The zeroth-order equations define the leakage rate and the circumferential and path velocity distributions and pressure distributions for a centered impeller position. The first-order equations define the perturbations in the velocity and pressure distributions due to either a radial-displacement perturbation or a tilt perturbation of the impeller. Integration of the perturbed pressure and shear-stress distribution acting on the rotor yields the reaction forces and moments acting on the impeller face. Calculated results yield predictions of possible resonance peaks of the fluid within the annulus formed by the impeller shroud and housing. Centrifugal acceleration terms in the path-momentum equation are the physical origin of these unexpected predictions. For normalized tangential velocities at the inlet to the annulus, uθ0(0) = Uθ0(0)/Riω of 0.5, the phenomenon is relatively minor. As uθ0(0) is increased to 0.7, sharp peaks are predicted. Comparisons for rotordynamic coefficient predictions with test results of Bolleter et al. show reasonable agreement for cross-coupled stiffness and direct damping terms. Calculated results are provided which make comparisons between seal forces and shroud forces for a typical impeller/wear-ring-seal combination.
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July 1989
This article was originally published in
Journal of Vibration, Acoustics, Stress, and Reliability in Design
Research Papers
Fluid-Structure Interaction Forces at Pump-Impeller-Shroud Surfaces for Rotordynamic Calculations
D. W. Childs
D. W. Childs
Mechanical Engineering Department, Texas A&M University, College Station, TX 77843
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D. W. Childs
Mechanical Engineering Department, Texas A&M University, College Station, TX 77843
J. Vib., Acoust., Stress, and Reliab. Jul 1989, 111(3): 216-225 (10 pages)
Published Online: July 1, 1989
Article history
Received:
December 1, 1986
Online:
November 23, 2009
Citation
Childs, D. W. (July 1, 1989). "Fluid-Structure Interaction Forces at Pump-Impeller-Shroud Surfaces for Rotordynamic Calculations." ASME. J. Vib., Acoust., Stress, and Reliab. July 1989; 111(3): 216–225. https://doi.org/10.1115/1.3269845
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