Research Papers: Flows in Complex Systems

Decomposition of Deterministic Unsteadiness in a Centrifugal Turbomachine: Nonlinear Interactions Between the Impeller Flow and Volute for a Double Suction Pump

[+] Author and Article Information
Jesús Manuel Fernández Oro, Katia M. Argüelles Díaz, Francisco Israel Guerras Colón

Área de Mecánica de Fluidos, Universidad de Oviedo, Campus de Viesques, Gijón 33271, Asturias, Spain

José González

Área de Mecánica de Fluidos, Universidad de Oviedo, Campus de Viesques, Gijón 33271, Asturias, Spainaviados@uniovi.es

J. Fluids Eng 133(1), 011103 (Jan 28, 2011) (10 pages) doi:10.1115/1.4002885 History: Received November 26, 2009; Revised October 27, 2010; Published January 28, 2011; Online January 28, 2011

Modern designs for centrifugal pumps consider flow unsteadiness as a main concern. The averaged impact of blade to blade structures and impeller-tongue or impeller-diffuser interactions is considered relevant to accurately address the machine performance. In this framework, the search for a comprehensive way to explain unsteady patterns would be particularly desirable. In the present paper, an analysis of the deterministic interaction between the impeller flow and both the inlet and outlet volute tongues in a double suction centrifugal pump is carried out. The zero velocity condition imposed in both tongues gives rise to an interaction that, up to the authors’ knowledge, has not yet been studied for this type of pumps. A well-tested numerical model, developed by the authors for previous studies with the same pump, has been exploited to predict deterministic correlations in the interaction region. Therefore, the main goal of this paper becomes the evaluation of the nonuniformities induced by both the inlet and the outlet tongues over the blade to blade distributions within the impeller. As a consequence, fluctuation levels in the blade loadings, derived from deterministic nonuniformities of the inlet tongue, can be provided in the relative frame of reference. The collected data using the numerical model can be further employed to establish modeling issues for deterministic stresses. Since more and more often, it becomes a widespread practice for pump manufacturers to include the analysis of the unsteady flow patterns in the design process, the availability of methodological tools to characterize pure unsteady terms in the early stages may be extremely useful for designers. Comparison of deterministic fluctuations with unresolved turbulence intensities is also available in this study, showing the importance of unsteady mechanisms in the modeling of pumping turbomachines.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

Sketch of the double suction centrifugal pump (left) and two different cuts (right)

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Figure 2

Unstructured mesh for the numerical domain. Detail of the impeller mesh, including the definition of the reference planes for the study.

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Figure 3

Comparison of performance curves

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Figure 4

Deteministic velocity decomposition as a function of the reference frame

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Figure 5

Decomposition of the deterministic flow velocity at the impeller outlet

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Figure 6

Contours with spatial nonuniformities in the volute flow

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Figure 7

Blade to blade gradients in the relative frame of reference

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Figure 8

Comparison of RMS values of pure impeller-tongue interaction at different operating conditions

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Figure 9

Temporal evolution of the pure interaction component at the impeller outlet

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Figure 10

Temporal evolution for the impeller-tongue interaction

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Figure 11

Contours of deterministic kinetic energy for different operating conditions

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Figure 12

Time-averaged turbulent kinetic energy for different operating conditions

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Figure 13

Contours of averaged turbulent (left) and deterministic (right) kinetic energy at design conditions in the impeller inlet

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Figure 14

Convection of path lines released from the inlet at nominal conditions

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Figure 15

Deterministic (left) and turbulent (right) kinetic energy within the impeller for three different flow rates



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