Interface Measurement of Moving Objects by Using a Fast X-ray CT Scanner

Measurement accuracy of a fast-scanning X-ray CT, designed to measure the unsteady void fraction and the interface area in multi-phase flow, was evaluated with spherical and cylindrical acrylic phantoms of known dimensions. Limitations of the spatial resolution and the object velocity were examined from the velocity and dimensions of the phantoms, X-ray fan beam thickness, and the scanning speed. Measurement errors less than 5% can be achieved by appropriate selection of the threshold level in binary images for stationary objects. However, the errors exceed over 20% for spherical objects moving at 1.0m/s. Another phantom simulating a unit of slug bubble frequently seen in multi-phase flow was scanned with the fast X-ray CT and its profile was compared with the phantom's actual dimensions. The results showed the system's successfull capability to reproduce the cylindrical part, while a further improvement is required to resolve detailed interface structure at the rear end of the phantom moving at large velocities.