Visualisation of Two-Phase Gas-Liquid Pipe Flows Using Electrical Capacitance Tomography

Electrical Capacitance Tomography (ECT) has been used over a number of years to measure concentration distribution, and more recently velocity distribution, in two-phase flows. ECT is non-intrusive, and the reconstruction of the concentration and velocity distribution can be undertaken in real time and over an arbitrary number of zones in the flow cross-section. In this paper the concept of a ‘virtual instrument’ is introduced where zones of the image can be structured for comparison with other measurements. Numerical agreement with gamma-ray density measurements is shown to be excellent in slug and stratified flows. We present a series of measurements undertaken in complex oil/gas slug flows in a large flow loop. We present a variety of 2-D cross-sectional images, time series velocity and concentration graphs and 3-D contour plots. The good temporal and spatial resolution of ECT throws an extensive new light on these otherwise difficult to measure dynamic flow structures. In particular with bubbly-slug structures known as ‘ghosts’ ECT shows clearly that they are in fact bubbly waves which have extended ‘wings’ up and around the pipe.