Comparison of circumferential slot with stepped clearance structure in a single-stage axial-flow compressor

After the reliability of a calculation model has been verified, a numerical simulation for a single-stage subsonic axial-flow compressor was conducted of the working characteristics of a real wall casing, circumferential slot one and stepped clearance structure under the condition of 71% design speed. The simulation results show that both the circumferential slot casing and stepped clearance structure can enlarge the compressor stable operating range to a certain extent. However, the circumferential slot plays a more explicit role in controlling the blade tip leakage vortexes in the blade leading edge, thus making it more suitable to be designed at the front half portion of a blade flow passage. The stepped clearance structure can fulfil its due function of diffusion stabilization when located in both the front and rear half portion of the blade flow passage. When the above structure is allocated in the leading edge of a blade, the compressor will suffer a relatively large drop in efficiency. In case the clearance structure is located in the blade trailing edge, it can contribute to a reduction of the area of the separation zone in the blade wake, thus playing a beneficial role in enhancing compressor efficiency.