Three-dimensional flows near rotor tip in an axial compressor I-experimental and theoretical studies

The flow fields near the rotor tip region of an axial compressor are measured by stereoscopic particle image velocimetry (SPIV) on a large-scale low-speed axial compressor test facility under both the design and near-stall conditions, and the flow mechanisms of some typical secondary flow structures are studied. According to the measured results, many secondary flow structures can be identified, such as the tip leakage vortex, corner vortex, passage vortex and inlet guide vane wake. Among these complicated flows, the tip leakage vortex and corner vortex are the two key flow structures contributing to large flow blockages and losses. In the design condition, the evolution of tip leakage vortex determines the flow blockage and causes a blockage of about 0.35% of the total massflow at the outlet of the rotor passage. In the near-stall condition, the corner vortex causes the most significant flow blockage and makes a maximum blockage of about 8.5% of the total massflow inside the rotor passage. Finally, theoretical analysis is made to clarify the evolution mechanism of the corner vortex. The results show that the evolution of the corner vortex is mainly determined by the spanwise distribution of the streamwise velocity in the rotor passage.