Linear computed tomography of two-phase distribution in a rectangular channel

Abstract

Two-phase flow is closely linked with the efficiency and safety of industrial processes in many fields, and there are various instruments for measuring the two-phase distribution. Among them, γ-ray and ultrafast X-ray tomography systems are most promising to break the technical barrier of gas-liquid measurement in the flow channel of high-temperature and high-pressure (up to 15 MPa/342 °C) nuclear reactors. Hence, A CT measurement method has been developed for imaging a two-phase distribution of a central plane oriented in axial direction in a rectangular duct, which was tested theoretically using a numerical phantom and experimentally on a preliminary tomographic hardware with a mechanically traversed gamma source and a detector unit, as well as a static phantom simulating gas bubbles in the pipe. After completing experimental and numerical imaging of a multi-bubbles phantom, the two-phase contrast and locations of bubbles in the experimental and simulated reconstruction images showed a good agreement and supported the feasibility of applying the linear scanning technique to realize two-phase detection in rectangular channels. The sensitivity analyses of scanning range, photon-registering time and scanning step length conveyed the optimal experimental strategy for this system. Morphological operation has also been imposed on image processing achieving elimination of severe ringing artefacts.