The inlet-air distortion which was caused by high angle-of-attack flight was simulated by plugboard.Experiments were conducted on a transonic axial-flow compressor's rotor at 98% rotating speed.The flow-field characteristics and mechanism of performance degradation were analyzed in detail.The compressor inlet was divided into four sectors at circumference under inlet-air distortion.They were undistorted sector

transition sector A where the rotor was rotating into the distortion sector

distorted sector and transition sector B where the rotor was rotating out of the distortion sector.The experimental results show that compared with undistorted sector

there is a subsonic flow in transition sector A

so the pressure ratio is decreased by a large margin in this sector.However

the shock wave is enhanced in distortion sector and transition sector B

and thus the pressure ratio increases in these sectors.Because of the different works at circumference

the phase angle of total pressure changes 90° when the inlet total pressure distortion passes through compressor rotor.In addition

the frequency and amplitude of disturbances in front of the rotor strengthenes under inlet distortion

so the unstable flow would take place in advance.In addition

the position of stall inception is in one of the transition sectors.