3-D Measurements of Optically Opaque Multiphase Flows Using Limited Angle X-ray Tomography

Many gas-liquid multiphase flows of engineering and scientific interest become optically opaque due to refraction and reflection at phase interphases. Typical optical methods, such as particle image velocimetry, fail for such flows. Radiation-based methods, such as X-ray densitometry (2-D) and tomography (3-D), offer an alternative, however these methods are challenging for high-speed, multiphase flows. A high speed, limited angle, Scanning Electron Beam X-ray Tomography (SEB-XT) suitable for these flows has been developed at the University of Michigan. Recent upgrades have increased the imaging rate from 20 Hz to O(kHz), as well as improved the image quality. Testing of the improved system is done using phantoms of known geometry and material composition, which allows for the imaging resolution (spatial and temporal) to be characterized. These tests are paired with digital simulations to identify and address critical factors contributing to image degradation. System performance is demonstrated using a complex, fully 3-D bubbly flow. Finally, the design and construction of a new 3-inch flow loop is presented.