The effect of decay on churn flow transition in a vertical gas–liquid swirling flow

Abstract

Gas–liquid two-phase swirl flow has been widely used in industry, especially the decayed swirl flow. However, axial development of the decayed swirl flow which is closely related to the effective length of swirl are lack of understanding. In this work, effects of decay on churn flow transition induced by a vane-typed swirler were investigated by a visualization experiment in a long vertical pipe (inner diameter of 62 mm and total length of 11 m). The results show that under the effect of swirl, churn flow can transform to a swirling annular flow, meanwhile the pressure drop increases and its fluctuation weakens compared with these in the non-swirl churn flow. However, the length of the transformed swirling annular flow is limited, due to the decay of swirl intensity. Then the effect of swirl decay on churn flow transition has been analyzed by the theoretical model proposed by our previous work (Liu et al., 2019). Finally, a new method was proposed here to predict the effective length of swirling annular flow transformed from churn flow in the vertical pipe, by combining the swirl decayed model and churn flow transition model in the swirl flow.