The influence of tip clearance size on axial compressor rotor aerodynamics

This paper aims at the numerical analysis of the influence of tip clearance size on aerodynamics in a subsonic high-speed small-scale compressor rotor. The numerical results are firstly compared with the available experimental data to demonstrate the validity of the computations. Then, numerically obtained flow fields are analyzed to identify the effects of the tip clearance size on the behavior of tip leakage vortex, which is closely related to the performance characteristic of the rotor. It is found that the behavior of the tip leakage vortex is considerably influenced by the tip clearance size. Under the same downstream condition, the low energy fluid accumulating around the leakage vortex expands, and the loss level in the vortex core decreases with the tip clearance increased. There is no abrupt change in the nature of leakage vortex in the cases of τ/c=1.0% and 1.7%, but the "breakdown" of leakage vortex occurs in the case of τ/c=2.7%. The vortex "breakdown" causes a sudden growth of the casing wall boundary layer, which has a large blockage effects. Therefore, a sudden drop in total pressure ratio occurs as the tip clearance size increases from 1.7%c to 2.7%c, and the rotor operate at near stall condition in the case of τ/c=2.7%.