Inter-stage energy characteristics of electrical submersible pump under gassy conditions

Abstract

Owing to the complex operational conditions of deep-sea or underground, the energy and flow characteristics in the electrical submersible pump (ESP) conditions are even more chaotic under gas-liquid flow, which degrades the energy conversion efficiency. At present, few studies have been carried out to demonstrate the difference between stages of ESP under gassy conditions. In this study, based on the Eulerian–Eulerian inhomogeneous model, an ESP with three stages was simulated to investigate the inter-stage differences in energy characteristics and flow patterns under both pure water and gas-liquid two-phase flow in detail. The simulation results are in good agreement with the experimental data. Gas phase distribution, external and internal characteristics in the ESP with three stages were analyzed at different flow rate with inlet gas volume fraction (IGVF) of 5%, 10%, and 15%. With the rise of IGVF, the degree of gas aggregation in the impellers and diffusers increases significantly, and the influence of the vortex formed by the gas concentration expands, and the differences vanish in gas distribution and flow trajectory between different flow channels. The proportion of gas in the flow channel is negatively correlated with the flow rate. Meanwhile, the variation law of head and efficiency under different inlet gas content conditions is fitted to the equation. The gas distribution pattern became further chaotic as the number of stages increases. The turbulence kinetic energy in the impeller is highly consistent with the gas aggregation pattern in terms of position distribution and change trend. At designed and best efficiency flowrate, the volume average of turbulence kinetic energy inside the second and third impeller is significantly higher than the first impeller. Overall, this study comprehensively reveals the gas phase distribution pattern, energy and internal flow characteristics in the ESP, which is helpful for the optimization design of such a pump and the improvement of the energy conversion efficiency under gassy condition.