12th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
This paper presents the detailed analysis of the local topology evolution from compressor mode to loaded windmill. A first objective is to identify generic patterns of rotor separation topology at windmill and bring light on the mechanisms responsible for it. This study also aims at numerically providing new elements of understanding on tip leakage flows and curvature effects while shifting from compressor to turbine operation. Two machines were investigated : a conventional fan and an innovative design meant to reach both high compressor and turbine efficiencies. In compressor or turbine operation, the tip leakage flow is located on the blade suction side. However, the location of the latter is inverted from one mode to the other. The inversion of the pressure gradient leads, near the hub boundary layer of a blade passage, to an inversion of the cross-flow direction.