Active Control of an Axial Flow Compressor via Pulsed Air Injection

Abstract

This paper presents the use of pulsed air injection 
\nto control the onset of rotating stall in a low-speed, axial flow 
\ncompressor. By measuring the unsteady pressures near the rotor face, a control 
\nalgorithm determines the magnitude and phase of the first mode of rotating 
\nstall and controls the injection of air in the front of the rotor face. 
\nExperimental results show that this technique slightly extends the stall point 
\nof the compressor and eliminates the hysteresis loop normally 
\nassociated with rotating stall. A parametric study is used to determine the 
\noptimal control parameters for suppression of stall. Analytic 
\nresults---using a low-dimensional model developed by Moore and Greitzer combined 
\nwith an unsteady shift in the compressor characteristic to model the 
\ninjectors---give further insights into the operation of the controller. Based on 
\nthis model, we show that the behavior of the experiment can be explained 
\nas a change in the bifurcation behavior of the system under nonlinear 
\nfeedback. A higher fidelity simulation model is then used to further verify 
\nsome of the specific performance characteristics that are observed in 
\nexperiments.
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