3D Tomographic Reconstruction of Flow Fields for Spatio-Temporal Resolved Measurements in Augmentors

We propose an innovative sensor technology that combines a high-bandwidth Time-Division Multiplexing laser system along with a 3D tomographic reconstruction model to provide spatially and temporally resolved 3D temperature and H2O concentration image of the flow field at data rate of 50 kHz.  The primary objective of this Phase-I research effort is to perform the feasibility study of 3D tomographic reconstruction of temperature and H2O concentration in chemically reacting flows using a state-of-the art high bandwidth time-domain multiplexed (TDM) sensor.  A unique 3D tomographic reconstruction model will be developed and used in conjunction with multiple beams to obtain coarse temperature images.  The 3D tomographic model we propose to develop is very unique due to its ability to deal with large number of grid points or unknowns without apriori knowledge of the flow field.  A key attribute of the proposed solution is the use of advanced hyperspectral sources (rather than diode lasers) to monitor H2O absorption features.  Despite using absorption spectroscopy for determining the temperature and H2O concentration from hyperspectral TDM sensors, this technology is fundamentally different from typical diode laser-based absorption sensors and has many advantages, specifically, allowing the acquisition of many spectral windows (instead of specific spectral lines) covering wide spectral range at very high speeds (>10 kHz, typically 50 kHz) and thereby providing better temperature accuracy and power spectral density (PSD) functions.  This feasibility study will pave the way for designing the optimum source for the implementation in an augmentor test stand dictated by AFRL scientists during the Phase-II research effort along with user-friendly software for tomographic reconstruction of the flow field. BENEFIT: Development of a compact, hyperspectral imaging sensor system along with a 3D tomographic reconstruction model that provides high temporal and moderate spatial resolution will enable engine manufacturers to monitor the combustion processes and relevant dynamical phenomena at realistic operating conditions for the first time.  This capability is particularly critical for the design and modeling of advanced, ultra-compact, low-emission, gas turbine engines and for development of real-time combustion-control strategies. This technology will yield significant payoffs in military and commercial aviation as well as land- and sea-based power generation.  The hyperspectral source that will be used in this research effort will also have broad impacts in biological imaging, remote sensing, microscopy, and other applications that require high-speed such as pulsed magnetic fields research.  In particular, the sensor is likely to become important for next-generation swept-source optical coherence tomography imaging of biological  samples, opening the door to new medical applications.