Advanced Fuel System for Low-Bandwidth Screech Suppression

ABSTRACT: Combustion stability is critical to the performance of augmented military jet engines. Instabilities such as screech can result in reduced augmentor performance, blowout, or even catastrophic failure. Screech remains a difficult problem to predict and mitigate, and its occurrence can limit the operational flight envelope of military systems. Many of the passive techniques used to suppress combustion instabilities in stationary gas turbines are unsuitable for military propulsion systems. Advanced active control techniques involving high-bandwidth active cancellation of instabilities have not been applied to real systems due to their inherent complexity. In this research program, Creare and Georgia Institute of Technology propose to further develop an advanced fueling system for low-bandwidth active screech suppression. The fueling system provides control of the spatial distribution of heat release, allowing for manipulation of symmetry and convective time delays in the augmentor without structural modifications. In Phase I, we demonstrated the feasibility of this approach for transverse instability suppression in a single flame holder augmentor rig. In Phase II, we will design, fabricate, and demonstrate our approach with more realistic geometry and operating conditions. Design activity will be supported by an existing computational fluid dynamics (CFD) tool for predicting fuel distribution in augmentors. BENEFIT: Technology derived from this project will be in two forms. First, we will develop a novel fueling system for low-bandwidth active control of augmentor screech. The system will be suitable for retrofit into modern military systems such as the F-35 Joint Strike Fighter. In addition, this research program is expected to improve the overall understanding of the mechanism(s) that couple heat release and acoustics in augmentor systems. This new insight will help expand the flight envelope for augmented military jet engines, increase the robustness of augmentor systems, and lead to more capable, cost-effective aircraft.