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 nonaxisymmetric 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 could be obtained:(1) With tip clearance asymmetry increasing,the stall points on compressor performance curves shifted 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 tip clearance asymmetry increasing,the average stall performance was also decreased.(3) On the other hand,however,the size of the stall-unstall hysteresis loops on the performance map decreased with the increasing of the tip clearance asymmetry,which showed that it was easier for the compressor to recover from stall.As a whole, the experimental results showed that,such treated casings were detrimental to the compressor performances.