Active stall control in axial flow compressor using artificial hub stall

Here we propose a new concept of stall suppression to expand the stable flow range of a compressor, i.e. the stall area is controlled when the flow rate is lower than the natural stall point. An artificial standing stall around the hub is formed using movable hub flaps equipped in front of the rotor for the purpose of gathering stall cells. The standing stall causes a displacement effect which is expected to increase the velocity near the tip of the rotor. In order to examine the feasibility of the new concept, a stability analysis was performed using a two dimensional actuator disk model. The compressor in hub stall condition was analyzed to be stable; the first instability at low flow rate appeared at the tip of the rotor, not the hub. Through the test using the research compressor equipped with experimental hub flaps instruments, some interesting results were obtained on the steady state performance of a hub stalled compressor. Dynamic control of the hub stalled compressor was demonstrated successfully to allow compressor operation beyond the natural stall point using proportional logic of the inlet air velocity near the tip of the rotor.