Study of gas­liquid two­phase flow in pipes with ultrafast electron beam X­ray CT

F. Fischer, U. Hampel

Institute of Safety Research, Forschungszentrum Dresden­Rossendorf, Bautzner Landstraße 400, 01328 Dresden, Germany, f.fischer@fzd.de

ABSTRACT

Electron beam X­ray CT is capable of fast measurement of multi­phase flows with frame rates of 1000 images per second and higher. The principle is based on the creation of a moving X­ray spot by electromagnetic deflection of a high­intensity electron beam across a circular target within an evacuated scanner enclosure. Together with a fixed fast X­ray detector this setup allows scanning of objects at frame rates well beyond that of classical CT machines. Our group has developed a scanner that is capable of scanning at up to 7 kHz frame rate and approximately 1 mm spatial resolution. The technique allows visualizing and measuring multiphase flows in vessels of moderate size. We have applied this fast electron X­ray tomography to the study of gas­liquid flow in a vertical pipe of 50 mm inner diameter. Different two­phase flow regimes from bubbly flow to churn­turbulent flow were produced and scanned. The data were processed using self­made image reconstruction software which implements the filtered backprojection technique and further post­processing algorithms for determination of gas­phase parameters, such as temporal and radial gas fraction profiles.

Keywords Electron beam tomography, X­ray tomography, flow measurement, two­phase flow