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

The objective of this research effort is to develop a 3-D tomographic reconstruction strategy along with user-friendly software for providing spatially and temporally resolved temperature and H2O concentration data cubes in augmentor flow fields at rate of 50 kHz. This strategy model will be validated in a laboratory turbulent flame and demonstrated in the augmentor test-rig at Air Force Research Laboratory (AFRL) using an existing 30-beam “Time-Division Multiplexing (TDM)” laser system. High-speed, three dimensional data will be enabled by efficient use of hyperspectral radiation, and will capture the dominant spatial and temporal instability modes in the augmentor along with their interaction and spatio-temporal evolution. The 3D tomographic model we are developing is very unique due to its ability to deal with large number of grid points or unknowns without a priori 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. Measurements in the laboratory flames will pave the way for designing the optimum beam configuration for the implementation of this 3D tomographic system in an augmentor test stand located at WPAFB. BENEFIT: Development of a 3D tomographic reconstruction model along with compact, hyperspectral imaging sensor system that provides high temporal and moderate spatial resolution will enable engine manufacturers to monitor the combustion processes and relevant dynamic 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 and propulsion. The tomographic gas thermometry strategies developed are expected to find numerous applications in fundamental and applied fluid dunamics, heat transfer, and multiphase flow problems. The hyperspectral source that will be used in this research effort will also have broad impacts in remote sensing, microscopy, biological imaging, and other applications that require high-speed such as pulsed magnetic fields research. With minor modifications, the sensor system might become important for high-speed swept-source optical coherence tomography imaging, thus opening the door to new imaging capabilities.