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As one of the core pieces of equipment in the multiphase mixing system, the helical axial-flow multiphase pump plays a vital role in the process of offshore oil extraction. In order to explore the influence of the impeller blade outlet setting angle on the internal flow of the helical axial-flow multiphase pump, this paper increases the outlet setting angle of the flow surface by -3°, -1.5°, and 1.5°, respectively, based on the original multiphase pump. It calculates the flow characteristics of the impeller with four different outlet setting angles (including the original impeller) under the design condition with different inlet gas volume fractions (GVFs = 0, 10%, 30%, 50%, and 70%) by adopting the Euler-Euler non-homogeneous flow model and SST k-w turbulence model. Furthermore, it compares its external characteristic curve and the internal pressure, velocity, gas distribution, and other rules of change of the impeller and guide vane under higher inlet GVF conditions (50%). The results show that in the pure water state, increasing the outlet setting angle appropriately can enhance both the pressure pressurization capability and efficiency of the helical axial-flow multiphase pump; the pressure pressurization capability and efficiency of each scheme decrease with an increase in inlet GVF, and at 50%- 70% inlet GVF, the option of increasing the outlet setting angle by -1.5° is better; as the blade outlet setting angle decreases, the axial cross-sectional pressure after gas-liquid mixing increases, the overall velocity distribution is more uniform, and the vortex formed due to the counter-pressure flow in the secondary guide vane is reduced; the accumulation of gas phase on the backside of the impeller and guide vanes improves, leading to a reduction in flow losses. [ABSTRACT FROM AUTHOR]

As one of the core pieces of equipment in the multiphase mixing system, the helical axial-flow multiphase pump plays a vital role in the process of offshore oil extraction. In order to explore the influence of the impeller blade outlet setting angle on the internal flow of the helical axial-flow multiphase pump, this paper increases the outlet setting angle of the flow surface by −3°, −1.5°, and 1.5°, respectively, based on the original multiphase pump. It calculates the flow characteristics of the impeller with four different outlet setting angles (including the original impeller) under the design condition with different inlet gas volume fractions (GVFs = 0, 10%, 30%, 50%, and 70%) by adopting the Euler–Euler non-homogeneous flow model and SST k-ω turbulence model. Furthermore, it compares its external characteristic curve and the internal pressure, velocity, gas distribution, and other rules of change of the impeller and guide vane under higher inlet GVF conditions (50%). The results show that in the pure water state, increasing the outlet setting angle appropriately can enhance both the pressure pressurization capability and efficiency of the helical axial-flow multiphase pump; the pressure pressurization capability and efficiency of each scheme decrease with an increase in inlet GVF, and at 50%–70% inlet GVF, the option of increasing the outlet setting angle by −1.5° is better; as the blade outlet setting angle decreases, the axial cross-sectional pressure after gas–liquid mixing increases, the overall velocity distribution is more uniform, and the vortex formed due to the counter-pressure flow in the secondary guide vane is reduced; the accumulation of gas phase on the backside of the impeller and guide vanes improves, leading to a reduction in flow losses.

Multiphase pump is a cost-effective option for subsea oil and gas field development. The ability to handle different inlet gas volume fractions (GVFs) especially high inlet GVF is critical to the development of pump performance. In this study, the two-phase flow characteristics in normal impeller and split vane impeller at different inlet GVFs were investigated by steady numerical simulations. The gas distribution on blade-to-blade plane and meridional flow channel at different inlet GVFs were analyzed and compared. Gas accumulation area and movement characteristics of the gas-liquid flow in impeller flow passage were also pointed out by unsteady simulations. Experimental results of the pump differential pressure were compared with the numerical simulation results, to validate the accuracy of numerical simulation method. The flow characteristics in pump with modified impeller and its performance at different inlet GVFs were both compared with that of the normal impeller. The steady simulation results of normal impeller in different inlet GVFs show that gas concentrating area in the flow passage increases as inlet GVF grows. The unsteady simulation results indicate that gas pocket firstly occurs on the pressure side of impeller, then moves to the suction side in the middle area of blade and finally transfers to outlet of impeller and disappears. The errors between numerical simulation results and experiment data are below 10 %, which validated the feasibility of the numerical simulation method. Simulation results on the split vane impeller demonstrate that the gas accumulation area in flow passage of the modified impeller is dramatically decreased compared to that of the normal impeller. The performance of the modified impeller is generally better than the normal impeller especially in high inlet GVF conditions. [ABSTRACT FROM AUTHOR]