Influence of Blade Lean on Performance and Shock Wave/Tip Leakage Flow Interaction in a Transonic Compressor Rotor

Abstract

Blade lean has been extensively used in axial compressor stators to control flow separations, but its influence mechanism on transonic compressor rotors remains to be revealed. The aim of this study is to numerically explore the influence of blade lean on the performance and shock wave/tip leakage flow interaction in a transonic compressor rotor. The effects of leaned pattern (positively lean and negatively lean), leaned angle and leaned height were studied. Results showed that, compared with baseline configuration, the efficiency and total pressure ratio of the entire constant rotating speed line of positively leaned rotor were both decreased. The absolute value of peak efficiency was reduced by as much as 4.34% at 20° lean angle, whereas the maximum reduction of peak total pressure ratio was 0.1 at 20° lean angle. The tip leakage flow streamlines of baseline transonic rotor can be divided into two parts, i.e., the primary vortex and secondary vortex which arises after the shock. Due to shock/tip leakage vortex interaction, the primary vortex enlarged and low-momentum region showed up after the shock; under near stall (NS) condition, tip leakage vortex breakdown occurred after interacting with shock. As positively leaned angle increased, the shock and the shock/tip leakage vortex interaction point moved upstream. In addition, the phenomenon of tip leakage vortex breakdown was enhanced. For negatively leaned rotors, as negatively leaned angle increased, the peak efficiency and total pressure ratio showed a tendency of first increasing and then decreasing. At 5° leaned angle, the peak efficiency was increased by 0.8% at most, and the maximum increment of total pressure ratio was 0.05 at 5° leaned angle. Besides, the loading of blade tip reduced and the loading moved toward trailing edge, resulting in the downstream movements of primary vortex, shock front and shock/tip leakage vortex interaction location. The results may help to improve the near tip flow field of transonic compressor rotor with leaned blade technology.