Screech Suppression via Heat Release Modification

Combustion stability is critical to the performance of augmented military jet engines. Instabilities such as screech can result in reduced augmentor performance, increased sustainment requirements, 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, we propose to apply an advanced fueling system for low-bandwidth, active screech suppression. The fueling system, called CFIS (Carbureted Fuel Injection Scheme), 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 the proposed research program, we will apply CFIS fueling to a high-fidelity augmentor rig designed to generate screech instabilities that are relevant to modern engine designs (transverse instabilities). We will then apply and investigate strategies for mitigating screech by manipulating the heat release distribution using CFIS injectors.