Experimental application of extremum seeking on an axial-flow compressor

We show an application of the method of extremum seeking to the problem of maximizing the pressure rise in an axial flow compressor. First we apply extremum seeking to the Moore–Greitzer model and design a feedback scheme actuated through a bleed valve which simultaneously stabilizes rotating stall and surge and steers the system towards the equilibrium with maximal pressure. Then we implement the scheme on a compressor rig in Murray's laboratory at the California Institute of Technology. We perform stabilization of rotating stall via air injection and implement extremum seeking through a slow bleed valve. The experiment demonstrates that extremum seeking ensures the maximization of the pressure rise starting on either side of the stall inception point. The experiment also resolves a concern that extremum seeking requires the use of periodic probing—the amplitude of probing needed to achieve convergence is far below the noise level of the compressor system (even outside rotating stall).