Windage and Leakage Losses in Impeller Back Gap and Labyrinth Seal Cavities of Supercritical CO<sub>2</sub> Centrifugal Compressors

Windage and Leakage Losses in Impeller Back Gap and Labyrinth Seal Cavities of Supercritical CO<sub>2</sub> Centrifugal Compressors

The windage loss in impeller back gap and labyrinth seal cavities significantly impacts the aerodynamic performances of supercritical carbon dioxide (sCO<sub>2</sub>) compressors. To accurately calculate windage loss, essential factors affecting the skin friction coefficients <i>C&...

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Bibliographic Details
Main Authors: Bing Tang, Jianxin Liao, Zhuobin Zhao, Qinghua Deng, Jun Li, Zhenping Feng
Format: Article
Language:English
Published: MDPI AG 2025-03-01
Series:Applied Sciences
Subjects:
skin friction coefficient
impeller back gap
labyrinth seal
supercritical CO<sub>2</sub> compressor
Online Access:https://www.mdpi.com/2076-3417/15/7/3678
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Summary:The windage loss in impeller back gap and labyrinth seal cavities significantly impacts the aerodynamic performances of supercritical carbon dioxide (sCO<sub>2</sub>) compressors. To accurately calculate windage loss, essential factors affecting the skin friction coefficients <i>C</i><sub>f,d</sub> (disk-type gap) and <i>C</i><sub>f,s</sub> (shaft-type gap), including Reynolds number <i>Re</i>, pressure ratio <i>π</i>, and radius ratio <i>η</i>, are investigated in this paper. The flow characteristics of the gap are analyzed and prediction models are proposed. The results indicate that both <i>C</i><sub>f,d</sub> and <i>C</i><sub>f,s</sub> decrease with increasing <i>Re</i> and grow with <i>π</i> and <i>η</i>, attributable to expanded high-vorticity regions caused by enhanced flow instability and larger vortices. The leakage flow rate <i>m</i> is unchanged for <i>Re</i> < 10<sup>6</sup> since the fluid can flow into the impeller back gap, and slightly decreases for <i>Re</i> ≥ 10<sup>6</sup> due to the centrifugal force and the inhibition effect of the vortices filling inlet regions. Moreover, the <i>m</i> grows with <i>π</i> and <i>η</i> due to a larger pressure difference and through-flow area. Maximal relative deviations of 6.23% and 6.83% can satisfy the requirements for calculating accurate windage loss in the impeller back gap and labyrinth seal cavities, which help the primary design of sCO<sub>2</sub> compressors.
ISSN:2076-3417

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