TABLE OF CONTENTS Ben T. Zinn [*] and Timothy C. Lieuwen [ ]
Georgia Institute of Technology, Atlanta, Georgia
Copyright 2005 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.
Combustion instabilities are characterized by large-amplitude oscillations of one or more natural acoustic modes of the combustor. Such instabilities have been encountered during the development and operation of propulsion (e.g., rockets, ramjets, and afterburners), power generation (e.g., land-based gas turbines), boiler and heating systems, and industrial furnaces. These instabilities are spontaneously excited by a feedback loop between an oscillatory combustion process and, in general, one of the natural acoustic modes of the combustor. In general, the occurrence of instabilities is problematic because they produce large-amplitude pressure and velocity oscillations that result in thrust oscillations, severe vibrations that interfere with control-system operation, enhanced heat transfer and thermal stresses to combustor walls, oscillatory mechanical loads that result in low- or high-cycle fatigue of system components, and flame blowoff or flashback. These phenomena may result in premature component wear that could lead to costly shutdown or catastrophic component and/or mission failure. Consequently, considerable research and development efforts have been invested during the past half-century to elucidate the processes responsible for the excitation of these instabilities and the development of approaches for their prevention. The objective of this chapter is to provide an overview of the causes, characteristics, and control of these instabilities.
Figure 1.1 summarizes the conditions under which combustion...
