Passive and Active Methods to Enhance Axial-Flow Compressor Aerodynamics

A review is presented of some previous papers on two control techniques with application to axial-flow compressors. The first technique is a passive technique using stator blades with a forward swept leading edge as a means to prevent an early breakdown of the stator hub flow in a highly loaded single-stage axial-flow low-speed compressor. The second technique is a predetermined technique utilizing rotor tip injection to suppress spike-type stall inception in three single-stage axial-flow low-speed compressors of different design. The first technique is shown to work highly successful, especially at off-design conditions. The second technique is shown to be highly effective in raising the stall limit line. On the other hand, the associated efficiency drop can be significant, so that the injection technique may not be recommended for steady state operation. Injection should only be employed to enhance compressor stability during transient operation that means for a short time period only.