From linear to rotating compressor cascade: Assessment of data transferability

Improving the efficiency of gas turbines requires a detailed understanding of secondary flow phenomena, including tip leakage vortices (TLVs) and corner separation. While linear compressor cascades are commonly used for simplifying flow studies, their ability to replicate flow features in annular rotating cascades remains insufficiently explored. This study evaluates the transferability of flow characteristics between these configurations using wall-resolving large eddy simulations for identical blade geometries. Specifically, the effects of cascade geometry, relative end wall motion, and rotation on secondary flows are assessed. In our study, linear cascade results overpredict total pressure losses associated with the TLV by up to 10% compared to annular rotating cascades while reproducing the TLV structure with reasonable accuracy. Within the blade passage, rotation shifts the distribution of mass flow crossing the gap toward the blade's front half, increasing the TLV intensity by 50% and altering its roll-up location from 20% chord (non-rotating) to 10% chord (rotating). Oppositely, the TLV size remains similar. Furthermore, rotation reduces corner separation losses to a third of the non-rotating annular cascade, transforming its topology from double-sided to single-sided. Relative end wall motion, while exerting limited direct effects, induces flow redistribution, aligning TLV positions between the linear cascade with end wall motion and the annular rotating cascade. The present findings underscore the importance of incorporating relative end wall motion into linear cascade studies for improved TLV predictions. However, the pronounced effects of rotation on flow structure and loss mechanisms reveal fundamental limitations of linear cascades for precisely approximating secondary flows in rotating systems.