Research on influence of Tip clearance effects on transonic compressor performance

In order to investigate the influence mechanism of the rotor tip clearance effect on the transonic rotor performance, a commercial software NUMECA is adopted for a transonic axial compressor stage to solve three dimensional steady simulations. The results show that both the peak efficiency and the mass flow at the choke condition decrease with the increase of tip gap, and the sensitivity curve in rotor peak efficiency is found to be approximately linear with an increase in tip clearance when the tip gap size is higher than the value of 0.5τ(τ represents the design tip clearance). Considering both the stall margin and efficiency change with the variation of tip clearance size, there exists an optimum tip gap of 0.5τ for this compressor, and the peak efficiency and stall margin are improved by about 0.22% and 3.1% respectively compared with the designed tip clearance. The tip leakage flows along the whole blade chord can be divided into three parts according to the flow structures, i. e., primary leakage zone, secondary leakage zone and common leakage zone. Each leakage zone plays a different role in the tip leakage flow structures and mechanisms. The dominant factors in the process of stall are different for the different tip clearances.