Fast Passive Optical Sensor for Jet Engine Applications

ABSTRACT: We propose the development of a high-speed, passive, in-situ, hyperspectral sensor system and its integration into engine-scale augmentor test program at AEDC. In this effort, custom probe optics will be integrated into an existing mechanical engine probe to provide multiple views of the flame radiance coming from various locations in a turbine engine thrust augmentor. The light from the probe is routed to an innovative adaptive spectral imager, which uses computer-controlled spectral filters to monitor concentrations of multiple combustion product species at data rates of 50 kHZ. The spectral filters can be changed on the fly at rates of up to 20 kHZ, allowing the system to make a variety of different types of measurements in rapid succession. Temporally- and spatially-resolved measurements are to be processed to yield combustor properties such as species column density, local fuel/air ratio and heat release on a time-scale fast enough to resolve the evolution of the flame sheet as it passes between the fields of view of the probe. The time resolved data can be processed into a number of data products for direct comparison to fluid dynamic models. BENEFIT: The immediate result of the proposed program is a prototype sensor system for ongoing augmentor testing at AEDC and a general purpose high-speed hyperspectral readout for general application in combustion research. The sensor system is aligned with the AFRL roadmap for advanced augmentor development, which includes advanced sensors for experimental validation of augmentor models and augmentor performance. The sensor readout will serve as a diagnostic tool that can be combined with a variety of experimental techniques, including tomographic reconstruction to provide further insight to augmentor physics. The experimental verifications provided by the sensor will facilitate further model enhancement and establish confidence for advanced CFD techniques in design applications. The prototype adaptive spectral readout will be portable, simple to use, and could be readily applied in a variety of research and land-based combustion measurement applications. Given the unobtrusive, passive nature of the system, it is applicable not just for augmentor measurement, but also to any application requiring monitoring or control of combustion dynamics. The prototype could be used directly by commercial engine manufacturers and aerospace companies in component tests, engine tests, and in land-based installations.