INTERROGATION OF GAS/OIL FLOW IN A VERTICAL USING TWO TOMOGRAPHIC TECHNIQUES

摘要

Two tomographic techniques have been applied to the flow in a 67 mm internal diameter vertical pipe. One is Electrical Capacitance Tomography (ECT) mounted on the outside of the non-conducting pipe wall. Another technique, known as the Wire Mesh Sensor (WMS) was used. The measuring systems provide time and cross-sectionally resolved information about the spatial distribution of the phases. The information can be used to obtain space and time averaged void fractions, radial profiles of time averaged void fraction and cross-sectional averaged time series of void fraction. Simultaneous measurements were made with the two techniques for gas superficial velocities of 0.05 - 5.5 m/s and liquid superficial velocities of 0 - 0.7 m/s with air and silicone oil as the fluids. Bubble, slug and churn flows were identified from the characteristic signatures of the Probability Density Functions of the cross-sectionally averaged void fraction. In addition, the detailed shape of individual large bubbles has been extracted. The output of both instruments shows clearly that the shapes of the large bubbles in slug flow are distinctly different from the smooth bullet-shaped. In this larger diameter pipe, the interface is much more disturbed. In addition, flow can be classified according to the sizes of bubbles present. Distributions of bubble sizes are presented and the fractions of gas flowing in different bubble sizes classes quantified.