Active Feedback Control of Rotating Stall and Surge in Axial Flow Compression with Inlet Distortions

We propose here new methods for system identification and active feedback control of axial flow compressors under conditions of incipient rotating stall and surge in the presence of inlet distortions. The nonlinear Moore-Greitzer model of rotating stall, which has proven useful for both simulation of rotating stall/surge dynamics of axial compression systems and for control design studies, will be utilized to develop new nonlinear control architectures. The program will be specifically targetted for quick transition to commercial applications in two ways. First, concepts which utilize a limited number of actuators, and/or utilize actuators which are "ganged" together to provide mechanical simplicity, will be developed, so that implementation risks and costs will be reduced. Second, cooperation with engine manufacturers (GE, Pratt and Whitney) and NASA Lewis during phase II will allow experimental implementation of the proposed concepts. Three concepts which have yet to be exploited in the arena of rotating stall/surge control will be explored. First, non-axisymmetric placement of a limited number (1 or 2) of high-capacity actuators promises to reduce complexity while maintaining controllability of rotating stall modes. Second, such placement can be specifically designed to improve the distortion tolerance of the compression system. Finally, treating the distortion problem as a nonlinear disturbance-rejection problem allows the full power of nonlinear control design techniques to be brought to bear. Previous work by Scientific System, MIT (Greitzer, Paduano, Epstein) and Dr. Abed in the fields of Bifurcation Analysis, System Identification and Stochastic Robust Control will be used to solve these problems. General Electric (GE) has expressed interest in supporting this joint effort with MIT and Univ. of Maryland. Anticipated Military Benefits/Potential Commercial Applications of the Research or Development: Active control of rotating stall and surge in axial multistage compressors is one of the most promising technologies for the development of fuel-efficient "Smart Engines" for both military and commercial aircraft. There are applications in the process control industry also since they ut