Numerical Simulation of Two-Phase Slug Flow Liquid-Carryover in a Converging T-junction

摘要

In the offshore platform, T-junction has been extensively used as preliminary gas-liquid separator due to its compact design. Frequently, a sudden slug generation causes liquid carryover issues leading to excessive liquid in the gas feed for downstream equipment. Geometry features of T-junction and slug flow are believed to be the root cause of this problem. Based on the literature review, previous works mostly focused on improving two-phase separation in the standard T-junctions without taking into account the impact of inlet flow regime. Moreover, there is no published research on the separation performance of converging T-junction, which is a promising design. The objective of this research is to numerically evaluate the hypothesis that converging T-junction yields better phase separation under slug flow compared with regular and reduced T-junctions. Three-dimensional Computational Fluid Dynamics (CFD) software FLUENT 17.2 and specialized User Defined Functions was utilized to study the evolutionary process of air-water slug flow and its phase separation behavior in converging T-junctions over eight different geometry designs. The incompressible Volume of Fluid (VOF) method was used to capture the transient distribution of segregated gas-liquid interface. The validity of the present model was compared with the experimental data taken from the air-water two-phase flow in 3-inch diameter main pipe of T-junction. The validated model gave a strong foundation to proceed with converging T-junction simulation. The research found that the converging T-junction can increase by upto 20% of separation efficiency compared with regular and reduced T-junction at the same operating conditions. Moreover, the converging T-junction with the main and converging diameter ratio of 0.67 and 0.4, respectively, to be optimal in improving the phase separation over a wide spectrum of air and water superficial velocities.