Numerical investigation of the influence of impeller-diffuser gap (A-and B-GaPs) on unsteady flow in a centrifugal pump at part flows

Taiki Takamine, Satoshi Watanabe

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Because of the high energy density of multi-stage centrifugal pump, it is really important to ensure the reliability of the pumps thus the stability of rotor system in the wide flow rate range. Rotating stall is a well-known unsteady flow phenomenon in which one or several stall cell structures propagate circumferentially in impeller and/or diffuser. Rotating stall alters the peripheral pressure distribution of rotors, and therefore it is often regarded as one of the primary trigger of unstable fluid force acting on the rotor system. One possible factor which could affect the rotating stall is a geometrical relationship between the rotor and the stator. In the present study, unsteady RANS simulations of internal flow in a centrifugal pump are carried out. The pump is the partial model of the final stage of the three-stage centrifugal pump used in our previous study. In order to investigate the effect of the gap between impeller trailing edge and diffuser leading edge on the unsteady flow of the pump, three cases of impeller-diffuser gap is simulated; one is the smaller gap case with original impeller. The other cases are two larger gap cases with only cutting the impeller blades and with cutting the both impeller blades and impeller shroud walls. For all gap cases, the computations are conducted for the nominal flow rate and the low flor rate with 10% of the nominal flow rate. As a result, the rotating stall is observed only in the larger gap case with the cut shroud walls, indicating that the key phenomenon for the stable formation of the stall cell is not only the weakened rotor-stator interaction, but also the other phenomenon attributed to the enlarged gap between the impeller shroud walls and the diffuser walls. In the shroud cut case, a part of the main flow blocked by the stalled region and the secondary flow on the diffuser walls tend to flow into the side gaps more easily than other cases. They might be the important phenomenon associated with the diffuser rotating stall in the enlarged wall gap condition.

Original languageEnglish
Title of host publicationFluid Applications and Systems
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791859056
DOIs
Publication statusPublished - Jan 1 2019
EventASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019 - San Francisco, United States
Duration: Jul 28 2019Aug 1 2019

Publication series

NameASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019
Volume3B-2019

Conference

ConferenceASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019
CountryUnited States
CitySan Francisco
Period7/28/198/1/19

All Science Journal Classification (ASJC) codes

  • Fluid Flow and Transfer Processes

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  • Cite this

    Takamine, T., & Watanabe, S. (2019). Numerical investigation of the influence of impeller-diffuser gap (A-and B-GaPs) on unsteady flow in a centrifugal pump at part flows. In Fluid Applications and Systems [5372] (ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019; Vol. 3B-2019). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/AJKFluids2019-5372