This study numerically investigated the effects of the geometry modifications in the vicinity of the shroud cavity area of a high flow coefficient, multi-stage, inline centrifugal compressor on its efficiency. The modifications in the shroud cavity area cover the lean of the seal teeth geometries and their streamwise positioning. The baseline four teeth seal geometry has been modified which resulted in 15 % reduction in the leakage mass flow and increased the compressor’s efficiency by 0.17 % by even reducing the number of the teeth to three.

Modifications in the radial inlet duct geometry aimed to reduce the pressure difference across the shroud cavity by providing further static pressure recovery at the shroud cavity outlet. The modified inlet duct design resulted in a further 0.13 % rise in efficiency in spite of the minor 4 % additional drop in the leakage mass flow. The modified inlet duct performed better only in presence of the shroud cavity leakage flow. Excluding the leakage the modified inlet duct resulted in a lower efficiency value compared to the efficiency value obtained with the existing inlet duct. These findings point out a possible reduction in the mixing loss between the main flow and the shroud cavity leakage flow with the modified inlet duct design which reduced the Mach number level close to the shroud side wall due to the increased static pressure. As the final conclusion on the design of the radial compressors this work shows the importance of considering the leakages at the early stages of the compressor design even deciding on the meridional flow path.

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