Non-Uniform Flows in Axial Compressors Due to Tip Clearance Variation

An approximate analysis is presented for the asymmetric velocity non-uniformities that can exist in an axial compressor due to variations in tip clearance around the circumference. Calculations have been carried out for several different compressor configurations, as well as for both rotating (fixed to rotor) and stationary clearance variations. The numerical results show that, for a given compressor, the ratio of (per cent) variation in axial velocity to (per cent) variation in pressure rise coefficient due to asymmetric clearance increases as flow decreases, although this trend in not necessarily true for the magnitude of actual velocity non-uniformity. In addition, the velocity non-uniformity due to a rotating clearance can be substantially larger than that due to a stationary clearance.