Compression system stability and active control

The compression system instabilities known as surge ana rotating stall are natural limits to the performance of all compressors and are especially tro ubling in gas turbine engines, In the last 15 years, rapid progress has bee n made in understanding this complex problem through the application of con trol technology; in particular, system identification techniques have prove n to be useful. New findings include the roles of compressibility and nonli nearity in the stall-inception process. These findings have been used to im plement feedback control schemes that have achieved increased stability in a variety of compressors and engines. Approaches fall into one of two categ ories: (a) operating range extension through active damping of linear distu rbances, or (b) manipulation of the nonlinear system dynamics to maintain t he operating point close to the instability boundary in the presence of dis turbances seen in operation.