Numerical study on gas –liquid two phase flow characteristic of multistage electrical submersible pump by using a novel multiple-size group (MUSIG) model

Abstract

Electrical submersible pumps (ESPs) face enormous challenges in the petroleum industry while handling gas–liquid two-phase flow. The major difficulty is caused by the accumulation of gas bubbles inside ESP-impellers, which results in mild to severe degradation in pump performance. Therefore, to analyze the influence of gas entrainment and bubble size, a combination of experimental and numerical analysis is performed on a five-stage mixed-flow ESP in the present study. The experiments are first conducted to analyze the performance of ESP under pure water conditions at different rotating speeds, followed by the gas–liquid two-phase flow experiments that are performed at constant rotating speed (1475 r/min) and for a wide range of inlet gas void fractions (IGVFs). For numerical calculations, a novel multiple-size group (MUSIG) model is applied in ANSYS CFX to analyze the performance and different flow patterns in ESP in different IGVFs and understand the coalescence and breakup phenomena of gas bubbles in the impeller flow passage. The simulation results from the MUSIG model are compared with the Euler–Euler two-fluid model and test results. The MUSIG model can more accurately predict the changes in the performance and internal flow-field of ESP under two-phase flow conditions. Moreover, when the MUSIG model is used to calculate the two-phase flow of the ESP, the first-stage impeller has a higher head than other stages because the flow inside the second and other stages is affected by the disoriented flow coming from the first-stage diffuser and other return channels. Furthermore, this study gives an insight into the comprehensive application of the novel MUSIG model for complex turbo-machine designs such as ESP.