Visualization of Oil Droplets Within ESP Impellers

The objective of this research is to investigate the path of oil drops within an Electrical Submersible Pump (ESP) impeller, to evaluate its size and velocity as function of water flow rate and the ESP rotation speed. An experimental study was conducted at University of Campinas - Brazil with an ESP prototype designed to allow flow visualization within the impeller through a transparent shell. A high-speed camera with lighting set captures images of the oil droplets at a rate of 1000 frames per second. The set of data was performed at three rotational speeds — 600 rpm, 900 rpm and 1200 rpm — for three water flow rates — 80%, 100% and 120% of the best efficiency point (BEP). The results reveal that the oil drops become smaller when the rotational speed increases. The same behavior is noticed when the water flow rate increases. Generally, the oil droplets have spherical and elliptical shapes that change as function of their position inside the impeller channel. Furthermore, the drops have random trajectories, but a pattern can be detected in three cases: droplets near the pressure blade, droplets near the suction blade and droplets that move from the suction blade to the pressure blade. The average velocity of the oil droplets that move near the suction blade is significantly higher than the average velocity of the droplets that move near the pressure blade. Velocity changes as function of the impeller radius suggest different accelerations that may be caused by drag forces and pressure forces. The size of the oil drops has no significant influence on their velocities.