Measurement of Axisymmetric Two-Phase Flows by an Improved X-ray-Computed Tomography Technique

Abstract

An improved X-ray-computed tomography technique was proposed to measure the phase concentration at a cross-section of axisymmetric two-phase flows. A theoretical algorithm, that is, the Tikhonov Regularization (TR) based Abel's inversion method, was developed to reconstruct the spatial distribution of the phase concentration based on the projection data. A digital pulsed X-ray imaging facility was recommended to capture the dynamic variation of the projection data at a pulse width of ∼100 ns to freeze the dynamics. The acquired projection data were first calibrated carefully to take into account the nonideal hardware factors, of which the bimodal energy model was introduced for a better description of the polyenergetic X-ray source so as to emendate the beam-hardening effect. X-ray imaging experiments were performed around a bubble column with an inside diameter of 100 mm to demonstrate the feasibility of the proposed new approach. The results showed good performance of the TR method in reconstructing the gas holdup profiles in the bubble column, which agreed well with the extensively referenced correlations in the literature. The TR method had a particularly stronger capability to reconstruct the spatial distribution of the gas holdup with less sensitivity to the experimental errors than the conventional filtered back-projection (FBP) method. The uncertainty analysis indicated that the proposed technique can be applied to measure the axisymmetric two-phase flow with accepted accuracy.