Linear of annular cascade? Towards understanding the impact of simplied research cofiguration in turbo machinery

Abstract

A rotating annular axial compressor and its unrolled surrogate, a linear cascade with the same blade profile, are investigated using wall-resolved large-eddy simulations to determine whether results obtained from linear cascade studies can be transferred to a real compressor. Three intermediate configurations bridge the gap between the immobile linear cascade and the rotating annular cascade and provide detailed understanding of the effects at play. The main passage flow is well predicted by the linear cascade. Secondary flows, however, are noticeably affected by rotation and the geometry itself. The flow is redistributed radially with increased blockage in the casing region and suppressed corner separation through rotation. The differences in the geometry cause a higher cross-gap pressure gradient in the annular cascade, driving higher tip leakage flow and a stronger tip leakage vortex. Hence, although providing massive simplification in practical terms, secondary flow phenomena dominating the end wall losses, such as the tip leakage vortex and the corner separation, can be analyzed with a linear cascade to limited extend only.

Postprint (published version)