Development and Validation of an X‐ray Tomograph for Two‐Phase Flow

Abstract

This paper describes the development and validation of a high spatial resolution X-ray tomograph designed for the investigation of air-water two-phase flow. The device hardware mainly comprises a 60 keV X-ray source, a detector, and an accurate mechanical bench. Our study concentrated on accurate quantification with emphasis on the reconstruction procedure. As is well known, absorption gradients induce reconstruction artifacts when using standard algorithms based on uniform regularization. In the particular case of two-phase flow in a pipe, this leads to poor measurement accuracy in the vicinity of the walls. To overcome such effects, improved algorithms were developed during this study that involve spatially adaptive regularization methods. Preliminary calibration performed on static phantoms clearly exhibited the benefits of the advanced reconstruction algorithms. A validation procedure was carried out on an air-water bubble column, equipped with an optical probe, which could be translated in order to explore the 80 mm x 80 mm square cross section. Comparisons of local void fraction measurements were performed pixel by pixel. They demonstrate the accuracy improvement induced by the advanced reconstruction algorithms.

Ultrasonic detection of moving interfaces in gas–liquid two-phase flow

“…This is a good expression of the relationship between the vertical oscillation of the interface and the internal velocity fluctuation for an elliptic motion, which should be correspond with the potential flow approximation by Eq. (7). For instance, the sign of the velocity switches when the water surface attains its deepest level.…”

“…One of the merits of ultrasonic sensing is its non-invasive nature, whereas optical [4] and electrical probing [5,6] requires the invasive submersion of the sensor into the flow. Another merit is the facility of handling ultrasound relative to X-rays [7] or electric capacitance tomography [8,9]. In addition, ultrasound directly detects the local interface position from the reflected wave whereas computer tomography uses information from along the entire signal path.…”

Quantitative measurement of gas hold-up distribution in a stirred chemical reactor using X-ray cone-beam computed tomography

“…With their devices radial or two-dimensional time-averaged gas hold-up profiles have been recorded. The use of X-ray CT for gas holdup measurements has been described by Pike et al [23] and recently by Hervieu et al [24] with application to two-phase flow in a pipe, by Kantzas and Kalogerakis [25], who monitored the fluidisation characteristics of a fluidised bed reactor, by Reinicke et al [26] and Toye et al [27], who used it in packed catalyst beds, and by Vinegar and Wellington [28], who measured fluid transport in porous media. All the above-mentioned techniques yield time-averaged rather than instantaneous phase distribution images.…”

Ultrasound Flow-Monitoring and Flow-Metering of Air–Oil–Water Three-Layer Pipe Flows

“…To handle the strong unsteady three dimensionality of multiphase pipe flows in the measurement section, several strategies are now being developed such as by electric capacitance [21], [22], by optical rays [23], [24], and acoustic approaches. Among various non-invasive monitoring principles, ultrasound has multiple advantages in comparison with others.…”