The Dynamics of Instabilities in Aircraft Engine Compressors

Dr. James D. Paduano, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology

In aeroengine compression systems, fluid mechanical instabilities canlead to violent oscillatory events -- rotating stall, surge, and blade flutter. These events must be avoided during operation; thus they place constraints on engine design that limit overall performance. Active stabilization of compressor instabilities promises to dramatically change these constraints and thereby improvefuture engine performance. Understanding the dynamics of these instabilities is the first step to effective control. This talk will describe the hierarchy of physical mechanisms that govern rotating stall and surge dynamics in compression systems. To date the concept of working at the highest level of this hierarchy -- that is, using the most simplified and aggregate models -- has been successfully applied to designing control laws which work in the laboratory. Thus the focus will be a description of these dynamics, and how they have been altered by control. Current efforts in fluid dynamic and control theoretic modeling and identification will also be discussed.