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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

NUMERICAL STUDY OF THE EFFECTS OF TIP CLEARANCE AND INLET DIFFUSION ON INDUCER BACKFLOW

D. Tate Fanning
Brigham Young University, Provo, UT 84062, USA

Ryan K. Lundgreen
The Ohio State University, Columbus, OH 43210, USA

R. Daniel Maynes
Brigham Young University, Provo, Utah, 84602

Steven E. Gorrell
Brigham Young University, Provo, UT 84062, USA

Kerry Oliphant
Concepts NREC, 217 Billings Farm Road, White River Junction, VT 05001, USA

Abstract

Inducers are used as a first stage in pumps to hinder cavitation and promote stable flow. Inducers bring the fluid on board the blades, and pressurize the working fluid sufficiently such that cavitation does not develop in the rest of the pump, and allow the pump to operate at lower inlet head conditions. Despite the distinct advantages of inducer use, an undesirable region of backflow and resulting cavitation can form near the tips of the inducer blades. Inlet tip backflow is often attributed to tip leakage flow, or the flow induced by the pressure differential across an inducer blade at the tip. We examine backflow of a single inducer geometry at varying flow coefficients with a tip clearance of τ = 0.32%, and no tip clearance. Removing the tip clearance prevents tip leakage flow. At all flow coefficients below design, we observe backflow penetrating up to 14% further upstream in the inducer with no tip clearance. The backflow region in the inducer with no tip clearance experiences higher velocities and extends further into the core flow. However, the inducer with tip clearance develops a larger vortex at the leading edge of the blades. A comprehensive analysis of these simulations suggests that blade inlet diffusion, not tip leakage flow, is the driving force for the formation of backflow.

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