A review of emulsion flows, their characterization and their modeling in pumps

In the engineering field, emulsions and liquid-liquid two-phase flows within centrifugal pumps are generally unwanted as emulsions will have negative effects on pump operation. Besides, emulsions are usually formed when the oil and water phases are brought together in a process called emulsification, which is enhanced by high shear rates. This topic has been extensively researched over the past decades, with sophisticated theories regarding the phenomena involved in emulsions formation and characterization in pumps. Besides, given the complexity of the physics governing emulsions, studies on their modeling within pumps, based on empirical correlations or computational fluid dynamics models, are insufficient and remain limited. This review aims to provide a complete overview of investigations on liquid-liquid flow in centrifugal pumps. Characteristics of these mixtures, such as stability, phase inversion, droplet size distribution and rheological behavior, are discussed. Current approaches and techniques for analyzing pump performance handling emulsion and twophase liquid-liquid flow are reviewed thoroughly. The limitations of the existing models are studied, and potential future developments are proposed.