Three-dimensional flows near rotor tip in an axial compressor II-numerical simulation study

Based on experimental and theoretical studies of the three-dimensional rotor tip flows in a low-speed axial compressor, numerical simulation studies are conducted to clarify the effects of the changing tip clearance sizes and total inlet pressure distributions on the rotor tip flows. First, numerical simulation is conducted with the same geometry and boundary conditions as those in the experimental investigation, and the simulated results are validated by the experimental results. Further studies of the near tip flows are conducted by analyzing the simulated velocity, vorticity and static pressure fields. Then, by changing the tip clearance sizes and total inlet pressure distributions, numerical simulation is performed again and the near tip flows are analyzed in detail. The results show that when the tip clearance is smaller than 1% of the blade chord, the evolution of the corner vortex determines the stability of the rotor; however, as the tip clearance increases to 2% of the blade chord, the tip leakage vortex becomes the key flow structure. Moreover, it is found that the evolution procedure of the near suction surface two-dimensional vortex lines has a close relationship with the rotor tip flows.