Effects of asymmetric tip clearance on axial flow compressor performance

Asymmetry of rotor tip clearance in compressors always exists to some extent. To investigate the effects of rotor tip clearance asymmetry on compressor performances, a series of axially-asymmetric tip clearance casing configurations were designed and experimented on a low speed, axial flow compressor with a single rotor. For each geometry, experiments were taken under both 5059 r/min and 8130 r/min conversion velocities. According to the experiments, several phenomena have been observed: (1) With the increase of asymmetric tip clearance, the stall points on compressor performance curves shift to the lower right, compared with the solid casing and symmetric tip clearance. To evaluate such shifting effects quantitatively, two parameters were defined. (2) With the increase of asymmetric tip clearance, the average stall performance is also decreased. (3) On the other hand, however, the size of the stall-unstall hysteresis loops on the performance map decrease with the increase of the asymmetric tip clearance, which shows that it is easier for the compressor to recover from stall. As a whole, the experimental results show that, such treated casings are detrimental to the compressor performances.