Passive Optical Sensor for Real Engine Diagnostics

ABSTRACT: Combustion instabilities, such as screech, are an ongoing challenge for augmented military propulsion systems. Diagnostics that elucidate the mechanism(s) of combustion instability are needed to increase the robustness of current engines and to develop improved design rules for future systems. Diagnostic measurements in augmentors are challenging due to the hostile environment and limited optical access. In this program, we are developing fiber-optically coupled, passive optical sensors for measuring heat release and fuel distribution in real engines. The measurement is based on passive optical spectroscopy of flame emissions. Two sensor embodiments are being developed: an imaging sensor, and a line-of-sight (LOS) probe with increased sensitivity and time response. The sensors are intended to be flush-mounted on the internal surfaces of an engine for ground-based research. In Phase I, we developed and demonstrated proof-of-concept prototypes for both sensor embodiments. Sensor performance was demonstrated using a single flameholder augmentor rig with good optical access. In Phase II, we will extend the TRL of both sensor embodiments. We will develop an imaging sensor capable of capturing four images of different spectral bands on a single camera, and we will also investigate a high-speed imaging embodiment. Phase II will conclude with a J-85 engine test. BENEFIT: The outcome of this project will be a new TRL 6 diagnostic for measuring heat release and fuel distribution in augmentors and other combustors. This technology could potentially provide novel insight into augmentor combustion processes such as augmentor screech, ignition, propagation, and lean blowout. Beyond Phase II, the technology could be extended into a flight sensor for active combustion control in augmentors and other combustors. We expect to commercialize the sensor via licensing to an existing supplier of combustion diagnostic tools. The sensor will then be available for use in a wide range of military and commercial combustion systems.