Oil Bubble Research Articles

Bubbles in Transformer Oil: Dynamic Behavior, Internal Discharge, and Triggered Liquid Breakdown

It is generally accepted that the presence of bubbles severely degrades the electric strength of liquid dielectrics, but the influencing factors and mechanisms have yet to be elucidated. Dynamic behavior, partial discharges (PDs) inside bubbles, and their effects on the breakdown of transformer oil are investigated experimentally and theoretically in this study. The results show that, under a nonuniform electric field, the presence of bubbles does not significantly affect the PD inception voltage (PDIV) and breakdown voltage (BV) of the liquid, as bubbles migrate to the region with lower field strength under dielectrophoretic force. In a uniform electric field, conversely, bubbles greatly reduce PDIV and BV; an increase in the number of bubbles or a slower voltage rise rate appears to exacerbate this effect. The PDIV observed in the experiment is much higher than the theoretical value calculated by the Townsend theory or streamer criterion, which may be due to the lack of free electrons inside the bubble, thus resulting in scarce internal discharge. The addition of X-rays enhances the radiation ionization and then eliminates the inconsistency between the theoretical and measured values of PDIV, which supports our hypothesis. The bubble-triggered breakdown of liquid dielectrics, namely, once a discharge occurs inside the bubble, likely triggering the breakdown of the liquid gap, is observed. The electric field enhancement caused by surface charges and the instability of the gas–liquid interface may account for this.

Bio-emulsifier supplementation from Pseudomonas putida that cultivated on medium containing waste palm oil as feed additive on poultry

The purpose of this study to determine effect of bio-emulsifier from Pseudomonas putida as feed supplement on the performance of broiler chickens. The experiment was divided in two phases. In phase 1: test of oil bubbles formation in water using bio-emulsifier, and phase 2 : in vivo test bio-emulsifier in animal. 200 one-day-old male and female broiler strain Cobb were used. On d 14, chicks were separated by sex and placed in 40 pens, sex separate (100 males or 100 females) and randomly assigned 4 treatments and 5 replicates of 5 birds each for 14 d (21d-35 d). The diets were based of corn, concentrate and rice bran meal and supplemented with: 0, 0.5,1 and 1.5 g/kg bio-emulsifier. The observed parameters were feed intake (FI), average daily gain (ADG), and feed conversion ratio (FCR). Result of experiment 1: as expected, supplementation of bio-emulsifier was increased small oil bubbles formation in medium oil in water, whereas in experiment 2 showed FI, ADG and FCR unaffected by dietary supplementation with bio-emulsifier on broiler at finisher phase (week 4 and 5) (P>0.05) and did not decrease on broiler performance. The results give new information that bio-emulsifier from Pseudomonas putida could potentially as a new alternative feed additive in the future on broiler performance.

Buckling versus Crystal Expulsion Controlled by Deformation Rate of Particle-Coated Air Bubbles in Oil.

Oil foams stabilized by crystallizing agents exhibit outstanding stability and show promise for applications in consumer products. The stability and mechanics imparted by the interfacial layer of crystals underpin product shelf life, as well as optimal processing conditions and performance in applications. Shelf life is affected by the stability against bubble dissolution over a long time scale, which leads to slow compression of the interfacial layer. In processing flow conditions, the imposed deformation is characterized by much shorter time scales. In practical situations, the crystal layer is therefore subjected to deformation on extremely different time scales. Despite its importance, our understanding of the behavior of such interfacial layers at different time scales remains limited. To address this gap, here we investigate the dynamics of single, crystal-coated bubbles isolated from an oleofoam, at two extreme time scales: the diffusion-limited time scale characteristic of bubble dissolution, ∼104 s, and a fast time scale characteristic of processing flow conditions, ∼10–3 s. In our experiments, slow deformation is obtained by bubble dissolution, and fast deformation in controlled conditions with real-time imaging is obtained using ultrasound-induced bubble oscillations. The experiments reveal that the fate of the interfacial layer is dramatically affected by the dynamics of deformation: after complete bubble dissolution, a continuous solid layer remains; after fast, oscillatory deformation of the layer, small crystals are expelled from the layer. This observation shows promise toward developing stimuli-responsive systems, with sensitivity to deformation rate, in addition to the already known thermoresponsiveness and photoresponsiveness of oleofoams.

Comparative Analysis of Simulation and Analysis of Bubble Motion Characteristics in Transformer Oil Based on Horizontal Set Method and Phase Field Method

Large power transformer is the key equipment for realizing power energy transmission and voltage conversion in the power system, but in actual operation, its internal transformer oil is prone to cause partial discharge of suspended bubbles due to various factors, which endangers the safe operation of the transformer. Therefore, this paper conducts simulation research on the generation mechanism and motion law of suspended bubbles in transformer oil, first of all, based on Comsol simulation software, the motion model of suspended bubbles is constructed, considering the degree of distortion of bubbles and the regular characteristics of motion trajectories under different bubble number, initial position, size, and other influencing factors, and then comparing and analyzing the difference between the simulation results under the horizontal set method and the phase field method two interface tracking methods, and finally obtaining the multi-faceted motion mechanism of suspended bubbles in multiple physics.

Tailoring structure and properties of long-lived emulsion foams stabilized by a natural saponin glycyrrhizic acid: Role of oil phase

Novel supramolecular nanofibrils assembled from food-grade saponin glycyrrhizic acid (GA) are effective building blocks to make complex multiphase systems, e.g., emulsion foams. In this work, the effects of different oil phases (castor oil, sunflower oil, dodecane, and limonene) on the formation, stability and structural properties of long-lived emulsion foams prepared by GA nanofibrils (GNs) were investigated. The obtained results showed that soft-solid emulsion foams (4 wt% GNs) can be fabricated, independently of oil phase, and their structural properties, viscoelasticity, and tribological properties can be well tuned by oil phase polarity. Compared to the GNs aqueous foams, the presence of jammed emulsion droplets in the liquid channels and at the surfaces of bubbles can provide a higher bubble stability for emulsion foams. For more polar oil phase (castor oil), GNs showed a higher affinity to the oil–water interface with a lower interfacial tension, thus forming smaller oil droplets and bubbles, which leads to the higher mechanical strength, denser network microstructures, and lower friction coefficients of emulsion foams. However, the limonene foam exhibited weak storage stability and rheological properties, as well as the relatively low lubrication, which may be related to the formation of oil droplet aggregates and clusters induced by the volatility of limonene. GN-based emulsion foams are thermoresponsive, independently of oils, and the temperature-switchable process for the destabilization and regeneration of foams can be controlled and repeated. These emulsion foams based on natural saponin nanofibrils with tunable properties have potential sustainable applications in foods, pharmaceuticals, and personal care products.

Navigating the Oil Bubble: A Non-linear Heterogeneous-agent Dynamic Model of Futures Oil Pricing

We investigate short-term futures oil pricing over the 2003-2019 time-period in order to analyze the bubble-like dynamics, which characterizes the 2007-2009 years according to a large body of recent literature. Our research, based on the LPPL methodology and a flexible three-agent model (hedgers, fundamentalist speculators and chartists), confirms the presence of a bubble price pattern, which we attribute to the strong destabilizing behavior of speculators. In our view, this can be related to incorrect interpretation of market signals (or to the inability of trading against the market), especially by fundamentalists, combined with imitation across different categories of agents. This sets off positive feedback reactions along with self-reinforced herding of the kind best detected by the LPPL methodology.

Removal of sticky silicone oil adhered to the retinal surface: comparison of methodological safety and effectiveness.

To compare safety and effectiveness among methods to remove sticky silicone oil bubbles adhered to the retinal surface. This retrospective nonrandomised case series included 14 eyes of 14 patients who had sticky silicone oil residue during silicone oil removal surgery. For small sticky silicone oil bubbles (< 2-disc diameter), aspiration was performed with a 23-gauge vitreous cutter. Residual tiny oil bubbles were then removed with a silicone-tipped flute needle or internal limiting membrane (ILM) peeling. For large sticky silicone oil bubbles (≥ 2-disc diameter) that could not be removed with a 23-gauge vitreous cutter, we devised a more efficient active removal method involving a modified 22-gauge venous indwelling cannula device. The mean preoperative best-corrected visual acuity (BCVA; logarithm of the minimum angle of resolution [logMAR]) significantly improved from 1.28 ± 0.63 logMAR to 0.77 ± 0.58 logMAR (p = 0.014). The postoperative BCVA and improvement in BCVA were significantly better in the ILM peeling group than in the non-ILM peeling group (p = 0.004 and p = 0.045, respectively). Postoperative complications included residual sticky silicone oil bubbles in seven eyes without ILM peeling (50.0%), retinal neuroepithelial layer damage in two eyes (14.3%), and temporary hypotony in five eyes (35.7%). Various methods can safely and efficiently remove sticky silicone oil bubbles adhered to the retinal surface. A 22-gauge venous indwelling cannula enabled simple and safe removal of large sticky silicone oil bubbles, while small residual sticky silicone oil bubbles could be completely removed by ILM peeling.

An Artificial Intelligent Approach for Black Oil PVT Properties

In absence of experimental oil fluid samples, it is usually difficult to select the suitable correlation to estimate oil properties. However, the accuracy of these empirical correlations has become insufficient for the best calculation. The main objective of this work is to test the capability of Particle Swarm Optimization with Neural Network (PSONN) and Neuro-Fuzzy (NFuzzy) approaches to predict oil properties with simply and accurately. The proposed approaches are developed based on clustering the oil data into the three groups (light, medium and heavy light oil). Over five hundred of black oil samples were collected from Middle East Field to train the hybrid models whereas additional oil data samples were selected to validate. The developed models used to estimate bubble points pressure (Pb), solution gas oil ratio at and below Pb, undersaturated oil compressibility, saturated formation volume factor, saturated and undersaturated density. The recommended guidelines and optimal configuration of the PSONN and NFuzzy models are developed to estimate any oil property in future. Statistical error analyses show that the proposed models exhibit a robust predictive capability for estimating oil properties. The validation results show the PSONN model achieve the lowest average absolute percent relative error (0.04, 2.89 and 1.0) for estimating formation volume factor, gas oil ratio and oil compressibility respectively whereas the NFuzzy model obtains the best approximation in oil density and bubble point pressure with average absolute percent relative error (0.18 and 0.97) respectively.

Heterogeneous hydrocarbon seepage at Mictlan asphalt knoll of the southern Gulf of Mexico

Hydrocarbon seepage plays an essential role in defining seafloor morphology and increasing habitat heterogeneity in the deep sea whereby asphalt volcanism ranks among the most complex and proliferous hydrocarbon discharge systems that have been described to date. In this study, seepage of hydrocarbon gas and oil as well as asphalt deposits were investigated at Mictlan Knoll in the southern Gulf of Mexico. A multi-disciplinary approach was used including hydroacoustic surveys and visual seafloor observations to study the seafloor manifestations of hydrocarbon seepage. Mictlan Knoll is an asphalt volcano characterized by a crater-like depression surrounded by an elevated rim. Asphalt deposits are widespread in the depression where a large area of extensive asphalt deposits correlates with a high backscatter area (~75,000 m2). Numerous asphalt deposits appear relatively fresh and probably extruded recently, as oil bubbles were seen to emanate locally within areas covered by extensive asphalt deposits. An area of more irregular seafloor morphology occurring in the northern part of the depression is interpreted to be related to the active extrusion of asphalt below or within older surficial deposits. Additionally, 25 hydroacoustic anomalies indicative for gas bubble emissions were detected. Gas volume quantifications conducted during seafloor inspections with a remotely-operated vehicle (ROV) at a single gas escape site situated above a gas hydrate outcrop revealed up to 0.1 × 106 mol CH4/yr. Gas emission at this site, monitored by an autonomous scanning sonar device, indicated a highly variable bubble release activity. Based on our findings, it is proposed that Mictlan Knoll hosts the most extensive asphalt deposits known to date in the Gulf of Mexico.

A New Model for Estimation of Bubble Point Pressure Using a Bayesian Optimized Least Square Gradient Boosting Ensemble

Accurate estimation of crude oil Bubble Point Pressure (Pb) plays a vital rule in the development cycle of an oil field. Bubble point pressure is required in many petroleum engineering calculations such as reserves estimation, material balance, reservoir simulation, production equipment design, and optimization of well performance. Additionally, bubble point pressure is a key input parameter in most oil property correlations. Thus, an error in a bubble point pressure estimate will definitely propagate additional error in the prediction of other oil properties. Accordingly, many bubble point pressure correlations have been developed in the literature. However, they often lack accuracy, especially when applied for global crude oil data, due to the fact that they are either developed using a limited range of independent variables or developed for a specific geographic location (i.e., specific crude oil composition). This research presents a utilization of the state-of-the-art Bayesian optimized Least Square Gradient Boosting Ensemble (LS-Boost) to predict bubble pointpressure as a function of readily available field data. The proposed model was trained on a global crude oil database which contains (4800) experimentally measured, Pressure–Volume–Temperature (PVT) data sets of a diverse collection of crude oil mixtures from different oil fields in the NorthSea, Africa, Asia, Middle East, and South and North America. Furthermore, an independent (775) PVT data set, which was collected from open literature, was used to investigate the effectiveness of the proposed model to predict the bubble point pressure from data that were not used during the model development process. The accuracy of the proposed model was compared to several published correlations (13 in total for both parametric and non-parametric models) as well as two other machine learning techniques, Multi-Layer Perceptron Neural Networks (MPL-ANN) and Support Vector Machines (SVM). The proposed LS-Boost model showed superior performance andremarkably outperformed all bubble point pressure models considered in this study.

New insights into the mechanisms of ultrasonic emulsification in the oil–water system and the role of gas bubbles

Ultrasonic emulsification (USE) assisted by cavitation is an effective method to produce emulsion droplets. However, the role of gas bubbles in the USE process still remains unclear. Hence, in the present paper, high-speed camera observations of bubble evolution and emulsion droplets formation in oil and water were used to capture in real-time the emulsification process, while experiments with different gas concentrations were carried out to investigate the effect of gas bubbles on droplet size. The results show that at the interface of oil and water, gas bubbles with a radius larger than the resonance radius collapse and sink into the water phase, inducing (oil–water) blended liquid jets across bubbles to generate oil-in-water-in-oil (O/W/O) and water-in-oil (W/O) droplets in the oil phase and oil-in-water (O/W) droplets in the water phase, respectively. Gas bubbles with a radius smaller than the resonance radius at the interface always move towards the oil phase, accompanied with the generation of water droplets in the oil phase. In the oil phase, gas bubbles, which can attract bubbles nearby the interface, migrate to the interface of oil and water due to acoustic streaming, and generate numerous droplets. As for the gas bubbles in the water phase, those can break neighboring droplets into numerous finer ones during bubble oscillation. With the increase in gas content, more bubbles undergo chaotic oscillation, leading to smaller and more stable emulsion droplets, which explains the beneficial role of gas bubbles in USE. Violently oscillating microbubbles are, therefore, found to be the governing cavitation regime for emulsification process. These results provide new insights to the mechanisms of gas bubbles in oil–water emulsions, which may be useful towards the optimization of USE process in industry.

Hierarchically cell-window structured porous cordierite prepared by particle-stabilized emulsions using potato starch as a modifier

Porous cordierite ceramics (PCCs) with hierarchical microstructures were prepared by particle-stabilized emulsions method using potato starch (PS) as a modifier. The formation of hierarchical structure was ascribed to the removal of oil bubbles and consumption of PS during the sintering process. The volume shrinkage of samples tended to be stable with a solid content of 40 vol. %. When the PS content was 25 wt. %, PCCs with a controlled hierarchical pore structure up to 91.4% porosity, compressive strength of 5.76 MPa, and pore size of 6.19 μm was obtained. The thermal conductivity of PCCs was optimized to 0.4325 W/m K, along with the pore size distribution showing a single peak trend at the same time. The chemical corrosion of PCCs in both strong acid and alkaline medium was inhibited by the stable cordierite phase. The method of preparing PCCs with controlled hierarchical structured was potentially applicable in catalyst carrier and filtration.

Experimental investigation of the characteristics of the transition from spherical cap bubble to slug flow in a vertical pipe

Reliable and accurate prediction of the transition from spherical cap bubble to slug flow is crucial not only to the operation of industrial facilities such as the crude oil pipelines, bubble column, and nuclear reactors but also for model development for computational fluid dynamics (CFD) studies. The present paper presents a review of the transition mechanics from spherical cap bubble flow to slug flow in vertical pipes. The bubble flow was split into sub-regions, bubbles and spherical cap bubbles and the mechanisms to classify them (i.e., bubble terminal velocity and cap bubble velocity) was analysed. For now, the literature review does not present some important previous works. This paper presents an original data set of gas–silicone oil in vertical pipes to support the new findings. The experimental two-phase data classifies the flow patterns using the probability density function (PDF) and shows the important flow variables such as average void fraction, pressure gradient, slug body void fraction, liquid slug, Taylor bubble and slug unit lengths, structural velocity and frequency obtained by electrical capacitance tomography (ECT) and a wire mesh sensor (WMS).

In Situ Tuning Underwater Bubble Movement on Slippery Lubricant-Infused Anisotropic Microgrooved Surface by Unidirectional Mechanical Strain.

Numerous studies have focused on designing and fabricating functional interfaces that control movement behavior of underwater gas bubbles, which are ubiquitous in a variety of natural and industrial settings. Nevertheless, developing surfaces with in situ tunable bubble movement remain elusive because of current complicated tuning strategies on the specific materials. Inspired by natural pitcher plant and rice leaves, here we report a kind of slippery lubricant-infused anisotropic microgrooved surface (SLI-AMGS) fabricated by femtosecond laser direct writing technology and realize the in situ reversible switching between underwater bubble sliding and pinning by unidirectional mechanical tensile strain. Different experimental parameters including lubricant oil film thickness, bubble volumes and laser power have been researched to manifest the relationship with bubble sliding behaviors. The underlying mechanism of in situ reversible switching mainly lies on the decrease of the lubricant oil film thickness during the process of mechanical stretching in which the uniform and stable oil film layer becomes uneven. This uneven lubricant oil film results in an extraordinary increase of contact angle hysteresis and resistance. At last, we demonstrate a real-time dynamic modulation of the underwater bubble on the SLI-AMGS with a changing mechanical tensile strain for several repeatable times in different acid-based environments. Our work manifests great potential applications in widespread fields including underwater bubble microfluidics and microbubble robots.

Movement Law of Single Bubble in Static Oil

Movement Law of Single Bubble in Static Oil

LIPSS-covered annular ablation region induced on ZnO surface by focusing femtosecond laser beam spatially shaped by bubbles in cedar oil

In this paper, without circular scanning of laser focus, annular ablation region was reported to be induced by femtosecond laser static irradiation of ZnO surface immersed in oil, and these annular ablation regions were all covered by laser-induced periodic surface structures (LIPSS) upon irradiation of either linearly-polarized light or circularly-polarized light. This novel phenomenon was found to be related to the bubbles in-situ generated and attached at laser focus inside oil during irradiation process. With increasing irradiation pulse number, the shallow annular ablation region transited to a deep annular groove, and the unablated region surrounded by the annular ablation region was finally ablated to a LIPSS-covered spherical-crown-shaped bump. Finite-difference-time-domain (FDTD) simulation shows that the bubble at the laser focus may act as a beam shaping device to partly transform a Gaussian-intensity-profile beam to an annular-intensity-profile beam and the increased bubble size induces a decrease of the radius of the annular beam, which can roughly explain the experimentally observed morphology transformation phenomenon. Further analysis of light field transformation based on matrix optics further demonstrates that the annular intensity profile is originated from hollow beams generated after incident light passing through the bubble-type radial polarizer.

Bubbles in Crude Oil and Commodity Energy Index: New Evidence

This paper considers a long dataset of both Brent and West Texas Intermediate (WTI) crude oil prices and the Commodity (fuel) energy index (CEI) to identify possible bubbles. Using the Supremum Augmented Dickey–Fuller (SADF) test, we compare results from WTI and Brent with CEI. We prove that the CEI follows Brent crude oil (they provide similar bubble periods) and that Brent is recognized as a crude oil benchmark. Financial managers should incorporate it into their analysis and forecasts. The findings are strongly recommended to energy policymakers and investors.

Simulation on the process of single bubble floating and colliding oil droplet based on improved three-component pseudo-potential Boltzmann method

Air floatation is a widely used wastewater treatment technology, often used to remove oily contaminants and suspended matter with a specific gravity close to 1 in wastewater. The key to air float deoiling lies in the process of collision and contact between oil droplets and bubbles. Therefore, it is of great scientific significance and practical value to study the collision process and influencing factors. In this paper, improvement measures such as surface tension adjustment method, multi-relaxation scheme, and thermodynamic inconsistency correction were added to the original multiphase flow pseudo-potential model. On this basis, a multi-component multi-phase lattice Boltzmann program was compiled. The process of bubbles colliding with oil droplets was simulated and compared with experiments to verify the simulation method. Furthermore, the effects of different oil-gas diameter ratios, collision angles, interphase forces between oil and gas phases, and viscosity on the collision results were explored. The simulation results found that under positive collision conditions, when the diameter ratio of oil and gas is greater than 1.22, the bubble lifts the oil droplet at the bottom and the adhesion is relatively stable. As the diameter ratio of oil to gas decreases, the form of adhesion gradually changes, and when the diameter ratio is less than 0.821, it begins to take the form of a package. The collision angle mainly affects the momentum transfer efficiency from the oil droplet to the bubble. The smaller the collision angle, the more obvious the acceleration of the oil droplet. The large angle collision is not conducive to the stable adhesion between the bubble and the oil droplet. The interphase force between the oil and gas mainly affects the contact angle and adhesion stability of the bubbles and oil droplets. The greater the force, the greater the contact angle and the lower the stability. When the viscosity changes from 0.5 to 3 times the kinematic viscosity (2.158 × 10−6 m2/s) of the experimental oil, it has little effect on the simulation results.

Development of new models for predicting crude oil bubble point pressure, oil formation volume factor, and solution gas-oil ratio using genetic algorithm

Bubble point pressure (Pb), oil formation volume factor (BO), and solution gas-oil ratio (Rs) are considered the key parameters required to describe and characterize the crude oil. Accurate determination for crude oil properties are necessary for multi-operation in reservoir evaluation, such as reserve estimation, enhanced oil recovery, oil reservoir performance prediction, designing pipelines and production equipment, and reservoir simulation. Traditional techniques used to calculate PVT data are usually expensive or unavailable, so there are a huge number of empirical correlations developed to estimate PVT properties as a function of production data. But when we used these correlations to predict crude oil properties, big errors are attained. The main target of this study is to find a better and accurate approach for predicting the properties of crude oil. This paper developed new empirical correlations for predicting the properties of reservoir oil as a function of PVT properties such as (P, T, Bo, Rs) using genetic algorithm technique. The simulation model is built using MATLAB software which contains the optimization tool that includes a genetic algorithm tool in it. To validate these correlations, 130 data sets of different crude oils were used. The results obtained showed that the developed empirical correlations from the genetic algorithm model appeared excellent accuracy of predicting crude oil properties compared to their relevant published correlations. The average absolute error for all correlations that the genetic algorithm applied to them is decreased. This technique can be applied to predict crude oil properties with a high level of accuracy.

Experiment of Engine Lubricating Oil Bubble Fraction in the Driving Cycles

Cavitation phenomenon always occurs in gerotor pumps. Bubble fraction of oil has remarkable influence in bearing lubricating characteristic. Oil mass flow rate and density is measured in a gerotor oil pump performance test, bubble fraction is analyzed based on measured oil density. Experimental results show that bubble volume fraction linearly decrease with the increasing of outlet pressure at constant pump speed. With the increasing of pump speed, influence of outlet pressure on bubble mass fraction decreases gradually. In the driving cycles, bubble mass fraction also increases with the increase of pump outlet pressure, and has a closely positive correlation with oil flow and pump speed. When the temperature of lubricating oil rises from 25°C to 100°C, the average volume fraction decreases about 72.6%, and the average mass fraction decreases about 84.3%. The changing rate of oil bubble fraction apparently lags behind the pump speed, it means that oil bubble fraction in acceleration stage is much higher than deceleration stage.