Physics-Based Control Technology for Augmentor Screech Suppression

High frequency combustion instabilities in gas turbine thrust augmentors (called screech) are detrimental to performance and limit operational flexibility, but are unavoidable due to the nature of augmentor operation and design.  Present approaches to screech suppression via passive control provide acoustic damping over limited bandwidth, while active control methods are impractical for flight applications due to system weight.  Innovative control technologies which are lightweight and possess broad frequency capability are needed to suppress instabilities in flight systems.  In the proposed work proactive screech suppression technology will be developed to disrupt the underlying physical mechanisms for these instabilities before they arise.  This system is unlike present active control approaches which engage following onset of instability.  This new technology will be enabled through the identification of physical processes and dynamic mechanisms which control screech instabilities, and the formulation of appropriate analytical models describing their dynamic behavior.  Parametric analyses identifying the sensitivities of these physics to acoustic frequency, operating conditions, and geometric variations will be used to generate preliminary understanding of screech dynamics and to develop early control concepts.  This technology will not only be an enabler for thrust augmentors, but will also find application in other combustion systems susceptible to dynamic instability. BENEFIT: The screech suppression technology developed through this effort will have direct application to existing and planned thrust augmentor systems used in both military and commercial gas turbine propulsion systems.  As such it would be of interest to large aircraft engine manufacturers such as Pratt & Whitney, General Electric, and Rolls Royce.  Since the technology will be physics based, key dynamic models may be revisited and/or new models developed to adapt the control technology to other combustion systems which are susceptible to combustion instability such as aircraft and stationary gas turbine combustors, liquid rockets, boilers, and furnaces.  This opens the technology to application over a wide range of military and commercial markets.)