HYPERSPECTRAL SENSOR AND TOMOGRAPHIC RECONSTRUCTION FOR 2-D TEMPERATURE IMAGING IN AUGMENTORS

The primary objective of this Phase-II research effort is to build and deliver a sensor system that provides planar images of temperature and H2O concentration at 30 kHz in augmentor test rigs located at WPAFB. The system is based on hyperspectral H2O absorption tomography. Senor light from a rugged, high-power time-division multiplexed (TDM) source is distributed to 18 beams. The beams are judiciously arranged to obtain high spatial resolution and signal-to-noise ratio. The gas properties are reconstructed using a newly developed tomographic reconstruction algorithm. The high-frame-rate images will capture the dominant spatial and temporal instability modes in the augmentor along with their interaction and spatio-temporal evolution. The TDM source will repeatedly cycle through 19 different wavelengths, spending 440 ns on each one, to sample many key features in the H2O absorption spectrum. The proposed solution uses advanced hyperspectral sources (rather than traditional diode lasers) to monitor H2O absorption features, offering higher performance and straightforward inclusion of additional wavelengths needed to detect other important combustion species. Despite using absorption spectroscopy for determining the temperature and H2O concentration, this technology is fundamentally different from typical diode laser-based absorption sensors and has many advantages, specifically, allowing the acquisition of many spectral features covering a wide spectral range at very high speeds (typically 30 kHz) and thereby providing better temperature accuracy and spatial resolution.