Physics-Based Control Technology for Augmentor Screech Suppression

ABSTRACT: 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. Building on progress in Phase I, in this Phase II effort an improved flame dynamics model will be developed to describe flame-vortex dynamics in the vicinity of a bluff body flameholder. The model will be coupled to combustor multi-dimensional mean flow and acoustics via a commercial finite element solver, COMSOL Multiphysics, and validated against detailed experimental data obtained from two, two-dimensional combustors operating at afterburner-like dilatation ratios containing dissimilar flameholders: a backward facing step and a v-gutter bluff body. The model will be extended to a notional three-dimensional combustor geometry containing multiple bluff bodies to illustrate its capabilities in an afterburner-like environment. 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 flame dynamic model and combustor stability analysis tool 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 government agencies such as the Air Force and Navy as well as 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.