A4 Conference proceedings

Effect of Free-Stream Velocity Definition on Boundary Layer Thickness and Losses in Centrifugal Compressors


Publication Details
Authors: Tiainen Jonna, Jaatinen-Värri Ahti, Grönman Aki, Turunen-Saaresti Teemu, Backman Jari
Publication year: 2017
Language: English
Title of parent publication: ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition
Volume number: 2C
Start page: 1
End page: 14
Number of pages: 14
ISBN: 978-0-7918-5080-0
JUFO-Level of this publication: 1
Open Access: Not an Open Access publication

Abstract

The estimation of boundary layer losses requires the accurate specification of the free-stream velocity, which is not straightforward in centrifugal compressor blade passages. This challenge stems from the jet-wake flow structure, where the free-stream velocity between the blades cannot be clearly specified.
In addition, the relative velocity decreases due to adverse pressure gradient. Therefore, the common assumption of a single free-stream velocity over the blade surface might not be valid in centrifugal compressors.

Generally in turbomachinery, the losses in the blade cascade boundary layers are estimated e.g. with different loss coefficients, but they often rely on the assumption of a uniform flow field between the blades. To give guidelines for the estimation of the mentioned losses in highly distorted centrifugal compressor flow fields, this paper discusses the difficulties in the calculation of the boundary layer thickness in the compressor blade passages, compares different free-stream velocity definitions, and demonstrates their effect on estimated boundary layer losses. Additionally, a hybrid method is proposed to overcome
the challenges of defining a boundary layer in centrifugal compressors.


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Last updated on 2018-19-10 at 07:55