Investigation of Flow Structure in a Narrow Clearance of a Low Specific Speed Centrifugal Impeller

Yumeno Inaba, Kento Sakai, Kazuyoshi Miyagawa, Masamichi Iino, Takeshi Sano

Research output: Contribution to journalArticlepeer-review


The disk friction loss is remarkably large in low specific speed centrifugal pumps, and an effective reduction method has not been established. Therefore, to develop the method, the loss mechanism was investigated. To grasp the internal flow structure in the narrow clearance, both experimental and computational approaches were used. An experimental apparatus that imitates clearance between a rotating impeller disk and a stationary casing disk was used and the static pressure distribution in the radial direction was measured. The internal flow where the disk friction loss occurs was investigated. In the case of outward flow, the static pressure decreased because the influence of the centrifugal force lessened toward the outer diameter of the disk, as the flow rate surged. For this reason, the pressure gradient became steep. According to the computational fluid dynamics (CFD) analysis, there was a vortex in the cross section of the clearance. This vortex encouraged flow recirculation and promoted the increase in the circumferential velocity in the potential core. When the flow rate grew, the vortex diminished. The circumferential velocity gradient and the shear stress intensified. As a result, the disk friction escalated. In the case of inward flow, the pressure gradient became steep as the flow rate increased. There was a vortex in the clearance, the size of which lessened when the flow rate surged. The disk friction had a minimum value at the flow rate was 6 X 10-4 m3/s. This research clarified that the vortex in the clearance has a remarkable effect on reducing the disk friction.

Original languageEnglish
Article number121109
JournalJournal of Fluids Engineering, Transactions of the ASME
Issue number12
Publication statusPublished - 2021 Dec

ASJC Scopus subject areas

  • Mechanical Engineering


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