Application of oscillation flow to horizontal gas–particle two-phase flow

Abstract

The purpose of this study is to apply the oscillation flow induced by a combination of a circular cylinder and non-uniform soft fins to gas–solid two-phase flows to reduce the transport gas velocity and power consumption in a horizontal pipe. In order to evaluate the oscillation flow, several different sizes of square and circular cylinders are used to combine four pieces of soft fins with non-uniform lengths, which are mounted on the horizontal central plane in front of the particle supply. The test pipe comprises a horizontal acrylic pipe with a length of 5 m and an inside diameter of 80 mm. Spherical polyethylene particles with an average diameter of 2.3 mm and density of 978 kg/m3 were used as the test particles. The average gas velocity was 9–16 m/s, and the solid mass flow rate was 0.11–0.51 kg/s. It is found that the combination of a circular cylinder or square cylinder of L = 10 mm with non-uniform soft fins causes the lowest pressure drop and highest velocity fluctuation in the oscillation flow based on single-phase flow (gas only) measurement. Compared to conventional gas–solid two-phase flows, the reduction in the minimum transport velocity, pressure drop, power consumption, and additional pressure drop were obtained using a combination of a circular cylinder with non-uniform soft fins. This combination provides the highest reduction rates in the minimum conveying velocity and an additional pressure drop by approximately 10.0% and 34.1%, respectively. Based on particle image velocimetry measurements, the time-mean particle velocity and particle fluctuating velocity of a circular cylinder with non-uniform soft fins were higher than those of conventional flows near the bottom part of the pipe, thus easily accelerating and suspending particles near the pipe bottom, even at lower gas velocities.