The working capability of multi-stage pumps, such as electrical submersible pumps (ESPs) handling multiphase flow, has always been a big challenge for petroleum industries. The major problem is associated with the agglomeration of gas bubbles inside ESP-impellers, causing pump performance degradation ranging from mild to severe deterioration (surging/gas pockets). Previous literature showed that the two-phase performance of ESPs is greatly affected by gas involvement, rotational speed, bubble size, and fluid viscosity. Thus, it is necessary to understand which parameter is actually accountable for performance degradation and different flow patterns in ESP, and how it can be controlled. The present study is mainly focused on (1) the main parameters that impede two-phase performance of different ESPs; (2) comparison of existing empirical models (established for two-phase performance prediction and surging initiation) with our single-stage centrifugal pump results to determine their validity and working-range; (3) gas-handling techniques applied to enhance the multiphase performance of ESPs. Firstly, it aims at understanding the internal flow mechanism in different ESP designs, followed by test studies based on empirical models, visualization techniques, bubble-size measurements, and viscosity analysis. The CFD-based (computational fluid dynamics) numerical analysis concerning multiphase flow is described as well. Furthermore, gas-handling design methods are discussed that are helpful in developing the petroleum industry by enhancing the multiphase performance of ESPs.

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 this study. The experiments are conducted to analyze the performance of ESP in pure water conditions under different rotating speeds, followed by the gas-liquid two-phase flow experiments that are performed at constant rotating speed (1475r/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 under different IGVFs and understand the coalescence and break-up phenomena of gas bubbles in the impeller flow passage. The simulation results from the MUSIG model are compared with 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, this study gives an insight regarding the comprehensive application of the novel MUSIG model for complex turbo-machines designs such as ESP.

To examine the cavitation noise characteristics of centrifugal pumps, the combination of test and simulation was applied in this study. The numerical method is based on spherical cavity radiation theory and the acoustic finite element method. A multi-field synchronized test-rig was built to study and validate the numerical results under cavitating flow and cavitation noise conditions. The three-dimensional unsteady flow-field simulation was carried out inside the centrifugal pump based on DES and the improved-RZGB cavitation model. The constructed numerical method for cavitation noise was used to solve the acoustic-field based on the flow-field solutions. The test–simulation comparison reveal that the numerical simulation results are consistent and reliable. The development of cavitation has a stronger influence on the strong vorticity regions in the impeller flow channel, and the vortex has a promotional-effect on the formation of cavitation. With the same cavitation number, the acoustic-power on the blade suction-side is greater than the pressure-side of the blade. As the cavitation number decreases, the pulsating radiated noise of cavitation volume is the primary noise-source for the increased acoustic-power value. At this stage, the SPL and total SPL at the model pump inlet show a decreasing trend during the severe cavitation-stage.