A computational fluid dynamics study for simulation of the unsteady state two-phase flow in vertical separators and plunger pumps simultaneously

Abstract

Abstract This study aims to find a robust and reliable method to simulate unsteady state two-phase flow in the sophisticated vertical separators connected to plunger pumps using computational fluid dynamics. The unsteady nature of reciprocating pumps and vertical two-phase gas-liquid flow forces the unsteady state boundary condition to the separators. Consequently, to simulate them, the plunger pump was considered a part of geometry, and an unsteady state turbulent two-phase flow was selected for the simulation method. Due to the geometry vastness and complexity of such a problem, the mesh generation method became vital for the convergence and reliability of simulations. Among several mesh generation methods and software, a new MATLAB meshing method developed to generate structural hexahedral mesh proved to be robust and very time-efficient. First, a set of experimental data of a simple separator was used to select, tune and validate the simulation method. Then, a real sample sophisticated separator and a plunger pump were analyzed using the method. Results demonstrated the ability of the model to predict phase separation and motions and its capability for modeling two-phase flow inside the helical, gravitational, and hybrid separators together with a plunger pump. Performing simulation for three up and two down strokes of the plunger showed that after disappearing the initial condition effects, the model represents the same results and separation efficiency for all cycles of plunger movements.