TURBOMACHINERY COMMITTEE BEST 1994 PAPER AWARD - DYNAMIC CONTROL OF ROTATING STALL IN AXIAL-FLOW COMPRESSORS USING AEROMECHANICAL FEEDBACK

Dynamic control of rotating stall in an axial flow compressor has been implemented using aeromechanical feedback. The control strategy devel oped used an array of wall jets, upstream of a single-stage compressor , which were regulated by locally reacting reed valves. These reed val ves responded to the small-amplitude pow-field pressure perturbations that precede rotating stall. The valve design was such that the combin ed system, compressor plus reed valve controller, was stable under ope rating conditions that had been unstable without feedback. A 10 percen t decrease in the stalling pow coefficient was obtained using the cont rol strategy, and the extension of stable flow range was achieved with no measurable change in the steady-state performance of the compressi on system. The experiments demonstrate the first use of aeromechanical feedback to extend the stable operating range of an axial flow compre ssor, and the first use of local feedback and dynamic compensation tec hniques to suppress rotating stall. The design of the experiment was b ased an a two-dimensional stall inception model, which incorporated th e effect of the aeromechanical feedback. The physical mechanism for ro tating stall in axial pow compressors was examined with focus on the r ole of dynamic feedback in stabilizing compression system instability. As predicted and experimentally demonstrated the effectiveness of the aeromechanical control strategy depends on a set of nondimensional co ntrol parameters that determine the interaction of the control strateg y and the rotating stall dynamics.