Numerical simulation of gas-liquid flows in a centrifugal rotor

Two-phase flows generally represent an adverse condition for centrifugal pumps. Research about this topic tends to be focused on performance evaluation through experimental approaches, while numerical works are quite scarce. In this paper, the numerical investigation of the gas-liquid flow in a centrifugal rotor is carried out. An Euler-Euler, polydispersed approach is adopted, together with several gas-liquid equations to model the relevant interphase interactions. The rotor geometry is a flat radial rotor, for which previously obtained experimental data to be used as input and for validation is available. Numerical results agree well with experimental ones for a range of operating conditions. They are further explored to investigate the effect of different interphase interactions on the results. Outcomes from this work can help with the understanding of the complex mechanisms associated with gas-liquid flows in centrifugal rotors, and contribute with the progress of numerical models for its solution

Study of the effect of viscosity on the head and flow rate degradation in different multistage electric submersible pumps using dimensional analysis

Multistage Electrical Submersible Pumps (ESPs) undergo performance degradation when operating with highly viscous fluids. Several studies on this subject seek to provide models to predict the pump performance under such conditions. However, some of those models require knowledge of geometric parameters or are only designated for radial-type pumps. In this article, dimensional analysis is used as an alternative to analyse head and flow rate degradation of different pumps without the need of any major geometric parameters. To accomplish this task, head curves for two multistage, mixed-flow type ESPs are obtained through a computational fluid dynamics (CFD) program for a wide range of viscosities and different rotational speeds. The numerical head curves were compared with experimental data under equivalent operating conditions and a good agreement was found. When adequate normalisations are used together with relevant dimensionless numbers, the head values obtained from the different ESPs proved to match quite well along curves of constant specific speeds. Experimental head values from literature for a radial-type centrifugal pump with volute operating with different fluid viscosities were used to extend the present analysis for a different pump geometry. Results from this procedure turned out to match the ESPs data well. A straightforward expression to correlate head and flow rate correction factors due to viscosity follows from the present approach, thus yielding a useful tool that might help in proposing a general method to estimate performance degradation

Numerical investigation of the effect of viscosity in a multistage electric submersible pump

Electric submersible pump (ESP) systems are commonly used as an artificial lift technique by the petroleum industry. Operations of ESPs in oil wells are subjected to performance degradation due to the effect of oil viscosity. To understand this effect a numerical study to simulate the flow in three stages of a multistage mixed-flow type ESP operating with a wide range of fluid viscosities, flow rates, and rotational speeds was conducted. The problem was solved by using a commercial computational fluid dynamics (CFD) software. The numerical model was validated with experimental head curves from the literature at different viscosities and rotational speeds available for the same ESP model used in this study, and good agreement was found. Performance degradation was evaluated by analyzing the effect of viscosity on head and flow rate. In addition, a flow field analysis to compare the flow behavior when the pump operates at different viscosities was carried out. The interaction between stages was also analyzed, and the influence of a previous stage on the upstream flow was evidenced. The flow field was analyzed at a curved surface that follows the complex mixed-flow geometry of the stages. CFD proved to be useful for exploring this kind of feature, a task whose accomplishment by means of experimental methods is not trivial. Such analysis helps to understand the flow pattern behind head and flow rate degradation when the Reynolds number is decreased. The results from this work are helpful as they provide a basis to estimate performance degradation for general scenarios

Multiple Wire-Mesh Sensors Applied to the Characterization of Two-Phase Flow inside a Cyclonic Flow Distribution System

Wire-mesh sensors are used to determine the phase fraction of gas–liquid two-phase flow in many industrial applications. In this paper, we report the use of the sensor to study the flow behavior inside an offshore oil and gas industry device for subsea phase separation. The study focused on the behavior of gas–liquid slug flow inside a flow distribution device with four outlets, which is part of the subsea phase separator system. The void fraction profile and the flow symmetry across the outlets were investigated using tomographic wire-mesh sensors and a camera. Results showed an ascendant liquid film in the cyclonic chamber with the gas phase at the center of the pipe generating a symmetrical flow. Dispersed bubbles coalesced into a gas vortex due to the centrifugal force inside the cyclonic chamber. The behavior favored the separation of smaller bubbles from the liquid bulk, which was an important parameter for gas-liquid separator sizing. The void fraction analysis of the outlets showed an even flow distribution with less than 10% difference, which was a satisfactorily result that may contribute to a reduction on the subsea gas–liquid separators size. From the outcomes of this study, detailed information regarding this type of flow distribution system was extracted. Thereby, wire-mesh sensors were successfully applied to investigate a new type of equipment for the offshore oil and gas industry