Characteristics of tip leakage flow inside the tip clearance of an axial compressor

The study of flow field characteristics inside the tip clearance is essential for understanding tip leakage flow (TLF) generation mechanisms. This paper investigates the TLF flow field in a single-stage axial compressor using a particle image velocimetry visualization system, alongside proper orthogonal decomposition and omega vortex identification methods, to analyze the flow at the mid-axial cross section under varying rotational speeds. The results reveal that the time-averaged flow field inside the clearance can be divided into four distinct regions, largely unaffected by speed variations: the high-speed region at the blade leading edge, the diverting and steering region of TLF, the TLF and main stream convergence region, and the trailing edge low-velocity region. Notably, two distinct directions of TLF are observed. At the blade leading edge, TLF flows directly from the upstream field to the lower blade, with a maximum velocity of approximately 2.2 times that of the main flow. Between 30% and 40% of the blade length, radial vortices dominate the diverting and steering of the main flow, forming a precessing vortex structure. Subsequently, TLF from the pressure side accelerates upstream, intersecting with the main flow to form a low-velocity tip leakage vortex region, obstructing the upstream flow. As rotational speed increases, the diverging and steering region shifts downward, and the disturbances in the internal and upstream flow fields further intensify. Furthermore, TLF from the downstream field bypassing the tip is observed between blades. These findings offer valuable data to improve understanding and optimize control strategies of TLF.