In many industrial applications, gas-liquid two-phase flows are observed. Annular flows are one of the most common flow patterns encountered in natural gas pipelines and pipe fittings. Predicting erosion damages in this type of flows due to the presence of sand particles is also a challenging issue.  Many factors such as liquid film thickness, and sand loading, and flow rate, have significant effects on the maximum erosion rate. The ability to predict erosion rate in the multiphase production of oil and gas is of great importance for sizing lines, analyzing failures and limiting production rates. Computational fluid dynamics (CFD) can be utilized as a valuable tool to investigate this kind of flows and erosion pattern predictions. This study includes three parts. First, the gas-liquid annular flows in the pipe are analyzed using the volume of fluid (VOF) method to solve the governing equations and for tracking the gas-liquid interface for incompressible multiphase flow conditions. The results from 3D transient simulations are compared with the experimental data available in the literature and good agreement was found. Second, sand particles with different sizes and mass flow rates are injected into the pipe and a Lagrangian approach is used for predicting the particle trajectories. Third, the DNV erosion model is used for evaluating the rate of erosion in these simulations. The erosion results for bend angles of 30^o^, 60^o^ and 90^o^ at different orientations are compared with those of the two-phase gas-particle flows. In gas-particle flow, the particle impact frequency at the erosion hotspot for 30^o^ elbow is less than those in the 60^o^ and 90^o^ elbows. Thus, the 30^o^ elbow experiences less erosion damage.  It was found that the pipe orientation does not affect the erosion rate significantly. In gas-liquid-particle flows, the film thickness in the bend, however, plays a major role on the value of particle impact velocity and the corresponding erosion rates. At the bend entrance in upward and downward vertical pipes, the film thickness is uniform; however, when the flow enters the bend, due to the combined action of gravity, centrifugal effect and formation of secondary flows the liquid film becomes non-uniform.  In the upward orientation, film thickness along the outer radius of the bend becomes thicker that enhances the liquid film cushioning effect, and as a result, the direct impingements of particles at high speeds on the inner surface of the outer radius decrease and consequently, cause less erosion rate in this area. For gas and liquid superficial velocities of 40 and 0.4 m/s in 90^o^ elbow, the impact velocities for gas-particle and gas-liquid-particle flow at the location of maximum erosion are, respectively, 38 and 14 m/s. In addition, among the studied bend geometries, the 30^o^ elbow is the most erosion-resistant configuration for both two-phase and three-phase flows.


Cfd Evaluation of Bend Angle Effects on Sand Particle Erosion in Multiphase Flows

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

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