Characteristics of slug flow in a vertical riser

Abstract

This paper presents the results of a series of experiments conducted on a vertical 67 mm internal diameter riser to study the characteristics of slug flow generated within a multiphase air-silicone oil mixture, for a range of injected superficial gas and liquid flow rates. Air/ silicone oil flows in a riser have been investigated using advanced instrumentation called Electrical Capacitance Tomography (ECT), described in Hammer (1983), Huang (1995) and Zhu et al. (2003). The ECT was used to determine: the velocities of the Taylor bubbles and liquid slugs, the slug frequencies, lengths of Taylor bubbles and liquid slugs, the void fractions within the Taylor bubbles and the liquid slugs over a range of superficial liquid (0.047 ≤ USL ≤ 0.38 m/s) and gas (0.344 ≤ USG ≤ 0.745 m/ s) velocities. An examination of the experimental data concluded that the rise velocity of the observed Taylor bubbles (structure velocity) were strongly dependent on the mixture superficial velocity. The void fraction within the liquid slug and the Taylor bubbles were observed to increase with gas superficial velocity. The lengths of liquid slug and Taylor bubbles were also observed to increase with an increase in the gas superficial velocity. The liquid slug frequency was observed to increase as the liquid superficial velocity increases, but was observed to be weakly dependant on the superficial gas velocity.