Abstract: Gas-liquid decayed swirl flow is widely used in industrial fields, however, the key problem, the effect of decay on the development of flow characteristics in the swirl flow, is unclear. Axial development of flow pattern and pressure drop in an air-water two-phase flow in a horizontal tube with an inner diameter of 25 mm and a length of 4 m is studied by experiment. The swirl flow patterns at different regions downstream of the vane type swirler are studied by visualization experiment, and the pressure drop fluctuation signals in different regions along the streamwise direction are measured. The results show that under the effect of centrifugal force, gas-liquid phase interface in the swirl flow is reconstructed, leading to the formation of special swirling flow patterns. However, due to the swirl decay, swirl flow patterns change continuously, and it gradually transform to non-swirl flow pattern. The pressure drop in the swirl flow gradually decreases along the streamwise, and finally approximates to the pressure drop in a non-swirl flow. Different swirl flow patterns have different maintenance distances, and the distance is affected by the flow rate upstream of the swirler. Finally, according to the analysis of flow pattern and pressure drop signals, the flow pattern maps at different regions in the horizontal swirl flow are proposed.

Key words: gas-liquid two-phase, swirl flow, flow pattern, pressure drop, decay