Flow regime identification of air-water two-phase counter-current flow in vertical annulus and eccentricity effect analysis：a machine learning approach

Abstract

Gas-liquid two-phase counter-current flow has been involved in many industrial fields, due to the existence of the inner pipe and the variation of the eccentricity of the inner and outer pipes, the flow regimes are difficult to be visual identification. To solve this problem, a vertical annulus with adjustable eccentricity was designed. Experiments were carried out under different combination of gas-liquid flowrate and eccentricity. The feature vector was formed by PDF and principal components of PSD of two differential pressure signals. The clustering algorithm CFDP based on local density was used to cluster the experimental data, results show that this method can realize the identification of flow regimes without prior information, and the flow regime transition boundary agrees with the experimental results. The influence of pipe eccentricity on the flow regime transition is analyzed. The results show that, in most cases, pipe eccentricity has no obvious influence on the flow regimes. However, in the flow regime transition region, such as the bubbly flow to slug flow transition region, when the eccentricity is at a medium value, that is, e = 0.25,0.5,0.75, the flow is more likely to transit to slug flow, however, when e = 0,1. The flow tends to remain bubbly flow.

Measurement of air-water counter-current flow rates in vertical annulus using multiple differential pressure signals and machine learning

“…The 0.27-2.80 Hz frequency band reaches a maximum at V sg = 0.994 m s −1 , which may be related to flow regime changes. In another paper by the author focusing on flow regime identification [36], the issue of flow regime transformation under the same column configuration was studied. The results showed that under the counter-current flow conditions of gas-liquid twophase, the flow regime transformation is mainly influenced by gas superficial velocity, with the gas superficial velocity for the transformation from slug flow to churn flow being approximately V sg = 1.0 m s −1 .…”

“…According to the research in another paper by the author [36], which focuses on flow pattern identification under the same column configuration, the flow patterns involved in this experiment include bubble flow, slug flow, and churn flow. Due to equipment limitations, annular flow cannot be generated.…”