Performance and Secondary Flow Structures Characterization in a Highly Loaded Low-Pressure Compressor Under Distorted Inflow Conditions

Abstract A highly loaded 1.5-stage axial compressor representative of the first stage of a modern booster was tested in the von Karman Institute (VKI)-R4 facility with an inlet total pressure distortion replicating realistic engine installation effects. Given the significant impact of the distortion on the stage operability, the flow features responsible for the observed performance loss were identified and characterized. To this end, time-averaged and time-resolved measurements were employed to gain a comprehensive understanding of the involved physical phenomena. Additionally, full-annulus URANS (unsteady Reynolds-averaged Navier–Stokes) simulations were performed to characterize the distortion transfer mechanisms and the flow reorganization. Unlike typical cases where the intensification of secondary flows leads to a reduction of stability and performance, the present stage responded unexpectedly to the inlet distortion, exhibiting an increased stall margin compared to the clean machine. Beyond the clean stall boundary, a significant performance reduction was observed in distorted conditions, yet without the onset of rotating stall. This behavior was attributed to the propagation of critical flow structures within the distorted region and to a severe flow redistribution taking place after the distortion screen.