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Multiphase pump is a cost-effective option for subsea gas and oil fields development. The ability of handling different gas volume fractions with high rotational speed is necessary to optimize the operating performance of a multiphase pump. Thus meeting the demand for increasing gas and oil production of undersea wells especially for those brownfields. This study aims to validate the performance of a three-stage helico-axial multiphase pump with new designed impellers and high rotational speed in both single and two-phase experiments. Then establish a numerical analysis method to predict the pump performance and evaluate the characteristics of multiphase flow with high reliability by using commercial CFD packages. The design volume flowrate of the pump is 100 m 3 /h and rotational speed is 4500 rpm. The experiment results show that the highest efficiency is 45% in water condition at the design parameters. There is not much difference on the pump performance at low inlet gas volume fractions (GVF) such as 5% and 10%, which indicates that multi-stage pump can prevent large performance degradation at low inlet GVFs. Numerical simulations are implemented by solving the three-dimensional steady Reynolds-Averaged Navier-Stokes (RANS) equations. The effects of various turbulence models, wall roughness, gas bubble sizes and interphase drag models on the hydraulic performance of multiphase are investigated. The results show that the predicted performance with Shear Stress Transport ( SST ) turbulence model at the optimal conditions agree well with the experiment data. Wall roughness should be considered since it has a significant effect on pump efficiency. Gas bubble size varies according to different inlet GVFs and rotational speed. The in-situ α g is high in diffuser and it varies with different interphase drag force models. The reliability of the numerical analysis method is proven by comparing the numerical results and experiments data. [ABSTRACT FROM AUTHOR]

Multiphase pumps are now in high demand as a result of undersea wells. The resulting sharp increase in the demand for multiphase pumps has made it necessary to optimize the operating performance of these pumps. The primary shortcoming of multiphase flow transport technology is that the characteristics of the internal flow change according to the gas volume fraction (GVF). This research aimed to establish a numerical analysis method that is used commercial CFD packages to evaluate the multiphase flow with high reliability and proposes a numerical method to investigate the effect of different GVFs on the flow characteristics. An appropriate combination of bubble size, closure interphase force model, and coefficient of force acting on the interface between the water and air phases is important for predicting the performance of the multiphase flow. The reliability of the new numerical analysis method was proven by comparing the numerical and experimental results. A model pump was produced and the structural stability of the prototype was secured through an analysis according to the API610 11th standard (Modal, Pressure Load). The model pump was made by AL7075 and the experiment device is connected with a 150A SUS pipe flange. The error range of the reliability verification of the multi-phase flow was about 0.5–1.5% at the flow rate used in the design. The numerical results obtained for pressure performance generally corresponded to high reliability within the operating range. Advanced computational fluid dynamics based on the three-dimensional steady and unsteady Reynolds-averaged Navier–Stokes equations were solved to analyze the detailed dynamic flow phenomenon with various GVFs. The effects of various interphase forces acting between the liquid and gas phase such as drag, lift, virtual mass, wall lubrication and turbulent dispersion forces, and the diameter of bubbles in the gas phase on the hydraulic performance were investigated. [ABSTRACT FROM AUTHOR]

Most multi-phase pumps used in crude oil production have been developed to satisfy certain pressure specifications. In the design of these pumps, the flow characteristics of the posterior stage are different from those of the prior stage. For this reason, the design of the second stage needs to be supplemented. To optimize performance in this stage, multi-objective optimization to simultaneously increase pressure and efficiency is reported in this article. Flow analyses of the single and multiple phases of the multi-phase pump were conducted by solving three-dimensional steady Reynolds-averaged Navier-Stokes equations. For the numerical optimization, two design variables related to the blade inlet angle were selected. The impeller and the diffuser blades were optimized using a systematic optimization technique combined with a central composite method and a hybrid multi-objective evolutionary algorithm coupled with a surrogate model. The selected optimal model yielded better hydrodynamic performance than the base model, and reasons for this are investigated through internal flow field analysis. [ABSTRACT FROM AUTHOR]