Experimental investigation of oil drops behavior in dispersed oil-water two-phase flow within a centrifugal pump impeller

• Published in: Experimental thermal and fluid science 2019-07, Vol.105, p.11-26
• Main Authors: Perissinotto, Rodolfo Marcilli, Monte Verde, William, Castro, Marcelo Souza de, Biazussi, Jorge Luiz, Estevam, Valdir, Bannwart, Antonio Carlos
• Format: Article
• Language: English
• Subjects: Centrifugal pump; Centrifugal pumps; Computational fluid dynamics; Deformation mechanisms; Dependence; Dispersions; Flow pattern; Flow rates; Flow velocity; Flow visualization; Fluid flow; High speed cameras; Impellers; Kinetic energy; Multiphase flow; Oil and gas production; Oil drop; Petroleum industry; Pressure; Pressure gradients; Product design; Researchers; Rotation; Shear stress; Suction; Turbulence; Two phase flow; Two-phase liquid-liquid flow; Velocity distribution; Viscous fluids; Water flow; Water velocity
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2019.03.009

[Display omitted] •Oil-in-water dispersions in a rotating environment were experimentally studied.•Oil drop behavior was investigated using flow visualization and image processing.•Equivalent diameters depend on rotational speed and, mainly, on water flow rate.•Turbulence, kinetic energy, and shear stress influence the oil drop breakage.•Velocities and accelerations depend on flow condition and oil drop trajectory.•Water velocity profiles and pressure gradients influence the oil drop motion. In oil production, one important artificial lift method involves the commonly used centrifugal pump. The use of this pump in the petroleum industry, however, is hindered by some unfavorable operational conditions. Operating centrifugal pumps with gas and viscous fluids, such as dispersions, may lead to a degradation of their performance. The objective of this paper is to analyze oil-water dispersions in a pump impeller, in order to investigate the behavior of oil drops, which may influence the pump working. Thus, experiments were carried out at different pump rotation speeds and water flow rates. Researchers used a facility with a pump prototype that enabled them to visualize the flow in all the impeller channels. Images, captured through a high-speed camera, revealed a unique flow pattern of oil drops dispersed in water. Processed with computer codes, the images indicated that the oil drops were, in general, spherical or elliptical, and only a few broke up in the impeller. The interaction with water caused the oil drops to rotate, deform, and deviate, thus moving in random paths. Size distributions suggested that the drops became smaller as the impeller rotation speed and water flow rate increased. This behavior was due to the turbulence-induced shear stress and kinetic energy. The oil drops’ equivalent diameters ranged from 0.1 to 6.0 mm; velocities took values measurable by units of m/s; accelerations reached hundreds of m/s2; and forces had magnitudes of thousandths of N. Researchers observed a clear dependence between flow conditions and drop dynamics. Carried by the water flow, the oil drops on the suction blade moved faster than those on the pressure blade of a channel. The drop dynamics were significantly influenced by the presence of adverse pressure gradients and water velocity fields.