The electrical submersible pump (ESP) plays a crucial role in artificial lift operations in the oil and gas industry.
The viscosity of the pumped fluid significantly influences the flow dynamics within the ESP, thereby impacting
the performance of the machine. In this context, flow visualization techniques can unveil intricate details of the
flow in ESP impellers, thus providing a deeper understanding of the relationship between flow behavior and
pump performance. This is the main idea of the present document, which utilizes the particle image velocimetry
(PIV) technique to experimentally investigate a mineral oil flow, 𝜇 = 14 𝑐𝑃, in a transparent prototype of a real
impeller, P23 model. The paper reports insights into the flow in the pump’s rotating component at different flow
rates that correspond to percentages of the best efficiency point (BEP). Average velocity fields and turbulent
kinetic energy plots indicate that flow dynamics are highly dependent on the operating conditions of the ESP.
A comparison between results for oil and water completes the analysis, as it highlights the effects of viscosity
on the flow characteristics. This type of study is useful to validate numerical simulations, support mathematical
models, and develop improved impeller designs.
Tag: flow visualization
Development of a transparent pump prototype for flow visualization purposes
The presence of emulsions in centrifugal pumps has always been a top issue for oil and gas exploration companies. These oil-water mixtures cause financial losses along the production chain, as they often induce pumps to operate in an unstable and inefficient manner. As there is a clear dependence between the pump performance and the flow arrangement in the impellers, this current paper aims to broaden the understanding on the behavior of emulsions inside the stage of a centrifugal pump. Thus, the paper describes the design and fabrication of a new transparent pump prototype for visualization purposes focused on academic studies. The new prototype is completely transparent, so it enables visual access and light entrance from the front and sides. Besides, the new pump is able to operate with twophase flows, since the dispersed phase can be injected directly into the impeller channels, through the shaft. Some tests were then conducted with this new prototype. They provided successful results which are presented and discussed here. Therefore, the new transparent prototype is an innovative alternative to help engineers and researchers investigate twophase flows in rotating and stationary pump parts.
Flow visualization in centrifugal pumps: A review of methods and experimental studies
Methods for flow visualization have been decisive for the historical development of fluid mechanics. In recent years, technological advances in cameras, lasers, and other devices improved the accuracy and reliability of methods such as High-Speed Imaging (HSI) and Particle Image Velocimetry (PIV), which have become more efficient in visualizing complex transient flows. Thus, the study of centrifugal pumps now relies on experimental techniques that enable a quantitative characterization of single- and two-phase flows within impellers and diffusers. This is particularly important for oil production, which massively employs the so-called Electrical Submersible Pump (ESP), whose performance depends on the behavior of bubbles and drops inside its impellers. Visualization methods are frequently used to study gas-liquid flows in pumps; however, the visualization of liquid-liquid dispersions is complex and less common, with few publications available. Methods to characterize the motion of gas bubbles are often unsuitable for liquid drops, especially when these drops are arranged as emulsions. In this context, there is room to expand the use of visualization techniques to study liquid-liquid mixtures in pumps, in order to improve the comprehension of phenomena such as effective viscosity and phase inversion with focus on the proposition of mathematical models, for example. This is a main motivation for this paper, which presents a review of researches available in the literature on flow visualization in centrifugal pumps. A broad set of studies are reported to provide the reader with a complete summary of the main practices adopted and results achieved by scientists worldwide. The paper compares the methods, investigates their advantages and limitations, and suggests future studies that may complement the knowledge and fill the current gaps on the visualization of single-phase flows, gas-liquid, and liquid-liquid mixtures.
Experimental analysis on the behavior of water drops dispersed in oil within a centrifugal pump impeller
This paper aims to investigate the behavior of water drops in an oil continuous medium inside a centrifugal pump impeller working at eight operational conditions (up to 1200 rpm and 2.8 m³/h) with two-phase liquid-liquid flows. Water-in-oil dispersions were produced with low water fractions around 1% in volume, thus the dispersed phase became arranged as water drops. Experiments for pump performance and flow visualization were conducted using a high-speed camera and a pump prototype with a transparent shell. Flow images revealed that the large water drops usually deform, elongate, and break up into smaller ones, especially at high pump rotations and oil flow rates, while small water drops tend to keep their spherical geometry without deformations and fragmentations. A sample of drops were tracked and their equivalent diameters, residence times, and velocities were calculated. The tracking indicated that the water drops travel random trajectories in the channels, generally undergoing a deceleration along their pathway. Furthermore, the residence times and the average velocities of water drops strongly depend on the flow conditions. For the conditions tested, the water drops presented equivalent diameters between 0.1 and 6.0 mm, average velocities from 0.4 to 1.7 m/s, and residence times between 30 and 152 ms. For a more complete analysis, the results achieved in this study are constantly compared with results available in literature regarding oil drops in oil-in-water dispersions.
Experimental Investigation of Oil Drops Behavior in Dispersed Oil-Water Two-Phase Flow within a Centrifugal Pump Impeller
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.
Experimental and Numerical Study of Oil Drop Motion within an ESP Impeller
The Electrical Submersible Pump (ESP) is a multistage centrifugal pump used in the petroleum industry as an artificial lift method. The ESP usually works with the presence of two-phase liquid-liquid flows that constitute dispersions and emulsions, causing performance losses and operational problems. This research aims to investigate the behavior and evaluate the dynamics of individual oil drops in an oil-in-water dispersion within an ESP impeller. The study adopts experimental and numerical approaches. Initially, experiments were performed using an experimental facility with a high-speed camera and an ESP prototype working at 600 rpm and 900 rpm, for water flows around the Best Efficiency Point (BEP) and with the injection of oil drops at a low flow rate. The acquired images were processed, and a drop sample was tracked, enabling the analysis of the size, shape, path, velocity, and acceleration of the oil drops. Numerical simulations were executed in ANSYS® software to define relevant parameters related to water and oil drops, such as velocities, accelerations, forces, turbulent dissipation, and residence time. The images reveal a unique flow pattern of dispersed drops in a continuous water phase. The oil drops’ diameters vary from tenths of a millimeter to around 3 mm. The drops’ trajectories can be classified into three different regions within the impeller channels. The drops’ velocities stay in the order of 1 m/s, while accelerations can reach hundreds of m/s2. The velocity profiles show that the oil drops tend to decelerate during their trajectory, while the acceleration profiles suggest peaks at the channel inlet and outlet. High intense turbulence is present in the impeller entrance zone. The evaluation of the residence time and the particle Reynolds number suggest that smaller oil drops follow the water streamlines, while larger oil drops tend to be affected by external forces. The main forces that govern the oil drop motion are the drag, the pressure gradient, and the virtual mass forces. The force from the pressure gradient is tenfold greater than the force from the drag. The virtual mass effect is significant only in the impeller inlet. In general, in this research, numerical results show a satisfactory agreement with the experimental data.