Screech Suppression via Heat Release Modification
Navy SBIR FY2013.1

Sol No.: Navy SBIR FY2013.1
Topic No.: N131-002
Topic Title: Screech Suppression via Heat Release Modification
Proposal No.: N131-002-0658
Firm: Creare Inc.
P.O. Box 71
Hanover, New Hampshire 03755
Contact: Darin Knaus
Phone: (603) 643-3800
Web Site:
Abstract: 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.
Benefits: The proposed research program will provide fundamental insight into transverse instabilities in augmentors and their mitigation and control. 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. The data may subsequently be used to develop new heat release models and screech mitigation strategies for augmentors. In addition, this program will demonstrate a technology for screech suppression that is suitable for retrofit on systems such as the F-135 Joint Strike Fighter. This technology could allow the existing system to operate over a larger flight envelope, and could also be beneficial for future thrust growth of the engine.