Measurement of thickness and analysis on flow characteristics of upper swirling liquid film in gas-liquid cylindrical cyclone

Abstract

The gas-liquid cylindrical cyclone (GLCC) is a device used to separate gas from liquid in offshore or subsea oil and gas production systems. The liquid film swirling along the upper cylinder wall in the GLCC is referred to as “upper swirling liquid film” (USLF). The flow patterns of USLF have a great influence on GLCC’s separation performance. However, the dynamics of the gas-liquid flow in a GLCC, especially the USLF characteristics, have not been well understood. In this study, experiments were conducted to investigate flow characteristics of USLF in a GLCC. The range of gas and liquid Reynolds numbers, Reg and Rel, was 27,869 ≤ Reg ≤ 68,120 and 2,881 ≤ Rel ≤ 14,335 respectively. The USLF’s thickness was measured using button electrodes. The results showed that the liquid film became thinner after leaving the inlet and the circumferential fluctuation of the thickness was not significant. The gas-liquid velocities had significant influences on film thickness, which increased almost linearly as liquid velocity increased, while presented a roughly S-shaped distribution as gas velocity increased. The friction factors of GLCC were determined based on the measured liquid film thickness and pressure drop. Additionally, the USLF’s flow patterns include swirling annular flow and swirling churn flow. Finally, a judgment criterion for flow pattern transition was established under the minimum gas-liquid interfacial stress theory. The model could accurately predict the transition condition. This work may provide a basis for comprehensive understanding of USLF characteristics.