A novel numerical approach for assessing the gas-liquid flow characteristics in pipelines utilizing a two-fluid model

Abstract

The accumulation of liquid condensate in the wet gas pipelines gives negative effects on the piping efficiency and flow managements. Accurate prediction of the condensate behavior is of crucial importance in the pipeline engineering. In this study, the one-dimensional two-fluid model with the stratified modeling in its source term is used to describe the gas-liquid kinetic motion along the pipe and the flow fields obtained from the newly proposed numerical approach are utilized to analyze the flow characteristics. Firstly, four cases with varying inlet liquid fractions, outlet pressures, and different meshes are utilized to investigate the gas-liquid steady-state variations along the pipe. The numerical results indicate that the outlet pressure influences the working pressure of the inlet gas-liquid, subsequently altering the equilibrium state and momentum exchange direction near the inlet, resulting in different condensate distributions in the pipeline. In the transient analysis with initial empty pipe, the inlet gas-liquid mainly impacts the pressure wave propagations in pressure spread stage, the gas kinetic motion in gas filling stage and the motion of the dividing interface between different regions in liquid filling stage, which is validated by the proposed numerical approach through comparison with the simulation tool OLGA designed by Schlumberger. Furthermore, when the liquid condensates appear in the initial state, the transition zones have two physical forms between different flow regions, which include the sudden dividing interface due to the high liquid amount carried by the inlet gas and the transition region resulted from the liquid accumulations.