Visualization of two-phase gas-liquid flow in a radial centrifugal pump with a vaned diffuser

Abstract

The operation of centrifugal pumps with gas-liquid mixtures is a common problem in the oil and gas industry. The main problem is related to the accumulation of gas inside the Electric Submersible Pump (ESP) impellers, which causes degradation of the pump pressure-rise. Literature about global performance parameters of centrifugal pumps operating with gas-liquid flows is limited, and studies focused on understanding the complex flow patterns occurring inside impellers are even scarcer. In this scenario, this work presents an experimental work developed to carry out, simultaneously, head evaluation and high-speed flow visualization in a two-stage centrifugal pump with radial-type impellers and a vaned diffuser. The pump casing and the first stage impeller were replaced by equivalent pieces reproduced with great fidelity using a transparent material in order to allow flow visualization while minimizing the effect of non-original pump parts on performance. Results show flow pattern transitions in the impeller channels when the rotating speed, the inlet gas flow rate and the liquid flow rate are changed, whereas only a single flow pattern was observed in the diffuser for the whole range of tested operating conditions. In addition, increasing the rotating speed causes, in general, a decrease of the bubble diameters inside the impeller, improving the pump's ability to handle higher gas flow rates and ultimately extending the operational window of the pump. This analysis can provide a source of data that can be useful to support theoretical models or to validate numerical simulations.