Abstract: The steady circumferential non-uniform tip clearance structure was given by changing the ellipticity of rotor casing in a transonic single axial compressor. The effect of circumferential non-uniform rotor tip clearance on perfor-mance characteristic and stability working boundary of the compressor was experimented detailly on a high rotating speed compressor test facility. The mechanism of the internal flow instability of the compressor induced by the circumferential non-uniform tip clearance was also presented by measuring the dynamic pressure flowfield parameters of rotor tip clearance. The experimental results show that the circumferential non-uniform tip clearance has almost no effect on the mass flow, pressure ratio and adiabatic efficiency of the compressor, but it has significant effect on the aerodynamic stability of the compressor. As the ellipticity of rotor casing raised, the stability operation range of the compressor decreased. The stability margin loss is higher at high speed working area than that at middle and low speed working area. The circumferential non-uniform tip clearance can lead to the radial redistribution of aerodynamic load of the compressor rotor blade and weaken work capacity at rotor blade tip area. At design speed, compared to the small tip clearance, as a result of the interaction between tip leakage vortex and passage shock with the large tip clearance, the high static pressure area at the pressure surface of adjacent blade enlarges, and the blocking effect on rotor passage becomes more serious.

Key words: transonic axial compressor, circumferential non-uniform tip clearance, flow instability, tip clearance leakage vortex, experimental investigation