Water Droplet Size Distribution Research Articles

A constrained machine learning surrogate model to predict the distribution of water-in-oil emulsions in electrostatic fields

Accurately describing the evolution of water droplet size distribution in crude oil is fundamental for evaluating the water separation efficiency in dehydration systems. Enhancing the separation of an aqueous phase dispersed in a dielectric oil phase, which has a significantly lower dielectric constant than the dispersed phase, can be achieved by increasing the water droplet size through the application of an electrostatic field in the pipeline. Mathematical models, while being accurate, are computationally expensive. Herein, we introduced a constrained machine learning (ML) surrogate model developed based on a population balance model. This model serves as a practical alternative, facilitating fast and accurate predictions. The constrained ML model, utilizing an extreme gradient boosting (XGBoost) algorithm tuned with a genetic algorithm (GA), incorporates the key parameters of the electrostatic dehydration process, including droplet diameter, voltage, crude oil properties, temperature, and residence time as input variables, with the output being the number of water droplets per unit volume. Furthermore, we modified the objective function of the XGBoost algorithm by incorporating two penalty terms to ensure the model’s predictions adhere to physical principles. The constrained model demonstrated accuracy on the test set, with a mean squared error of 0.005 and a coefficient of determination of 0.998. The efficiency of the model was validated through comparison with the experimental data and the results of the population balance mathematical model. The analysis shows that the initial droplet diameter and voltage have the highest influence on the model, which aligns with the observed behaviour in the real-world process.

Effect of Droplet-Laden Fibers on Aerodynamics of Fog Collection on Vertical Fiber Arrays.

Growing population, along with rapid urbanization, has led to severe water scarcity, necessitating development of novel techniques to mitigate this looming problem. Fog contains water in the form of liquid droplets suspended in air, which can be collected on a porous structure placed in the path of the fog flow. We first develop an artificial fog-generating system using the thermodynamic principle of mixing of air streams followed by condensation, which closely mimics the liquid water content and droplet size distribution of natural fog. We then investigate how collected fog droplets growing on fiber surfaces alter the aerodynamics of fog flow across vertical fiber arrays, called harps, thus affecting their fog collection efficiency. As deposited droplets grow on the fiber surface, they increase the area occluded by droplet-laden fibers, thus increasing the effective shade coefficient (SCact), which increases with time from its initial geometric value (SCgeo), eventually reaching a quasi-steady state, as droplet shedding due to gravity and droplet growth due to fog collection balance each other. We find that this difference in the SCgeo and SCact is governed by local fiber geometry and its physico-chemical morphology; the process dynamics is captured by a nondimensional number, SC*, which increases with the length scale corresponding to the critical volume of droplet shedding relative to the fiber diameter, V*. Thus, there is a significantly greater increase in the effective shade coefficient for thin fibers having larger values of V* as compared to fibers with larger diameters which have lower V* values. On hydrophobic fibers, the quasi-steady state is achieved faster, and the time-averaged SCact is lower as compared to hydrophilic fibers due to the lower critical volume of droplet shedding. The shape of droplets growing on harp fibers affects the aerodynamics of fog flow, its inertial capture mechanism, and efficiency, which can guide design considerations for fog harps toward achieving optimal fog collection performance.

Modelling droplet size distribution in inline electrostatic coalescers for improved crude oil processing

Water-in-oil emulsions pose significant challenges in the petroleum and chemical industrial processes, necessitating the coalescence enhancement of dispersed water droplets in emulsified oils. This study develops a mathematical model to predict the evolution of water droplet size distribution in inline electrostatic coalescers (IEC) as a promising means to improve the water separation efficiency of current oil processing systems. The proposed model utilizes the population balance modelling approach to effectively simulate the dynamic and complex processes of coalescence and breakage of droplets in crude oil which directly influence the separation efficiency of the process. The method of classes as an effective mathematical technique is selected to solve the population balance equation (PBE). The accuracy of the model and considered assumptions agree well with experimental data collected from the literature. The results demonstrate the model's ability to accurately simulate droplet coalescence and breakage in emulsified oil while predicting droplet size distribution and water removal efficiency. The electric field strength, residence time, and fluid flow rate significantly influence the coalescence of droplets. At 4 kV and 5 m3/h after 4 s the mean diameter of droplets (D50) and separation efficiency reach the maximum of 94.3% and 432 µm, respectively. The model enables the optimization of operational conditions, resulting in increased performance and reliability of oil-processing systems while reducing the energy consumption and use of chemical demulsifiers. Additionally, utilization of the device in optimized conditions significantly reduces the size and weight of downstream separation equipment, which is particularly advantageous for heavy oils and offshore fields.

Sonoprocessing of oil: Asphaltene declustering behind fine ultrasonic emulsions

Despite the transition toward carbon-free energy carriers, liquid fossil fuels are expected to occupy an important market share in the future. Therefore, it is crucial to develop innovative technology for better combustion reducing the emissions of pollutants associated with their utilization. Water in oil (w/o) emulsions contribute to greener combustion, increasing carbon efficiency and reducing emissions. Water content, emulsions stability, and droplet size distributions are key parameters in targeting the efficient use of emulsions as combustibles. In particular, for fixed water content, the finer the emulsion, the better its beneficial effect on combustion. In this work, two emulsions, mechanically and ultrasonically generated, were compared. Cryogenic scanning electron microscopy (cryo-SEM) allowed the visualization of water droplets inside the oily matrix. No surfactants were added to the oil, due to its high asphaltenic content. Asphaltene molecular aggregates, namely clusters, act as natural surfactants stabilizing the emulsions by arranging at w/o interface and forming a rigid film. The asphaltenic rigid film is clearly visualized in this work and compared for the two emulsions. The results showed finer water droplets in the ultrasonically generated emulsion, together with a reduction in the thickness of the asphaltenic film. Ultrasonically induced cavitation favored the de-clustering (breakage of intermolecular forces) of asphaltene molecules. Thus, smaller clusters allowed to stabilize smaller water droplets resulting in an ultra-fine emulsion, which improves the combustion performances of the fuel.

Atomization characteristics of different water/heavy fuel oil emulsions in a pressure-swirl injector

In the present study, different water in heavy fuel oil (HFO) emulsion fuels containing 5, 10, 15% water content have been prepared under ultrasound irradiation without surfactant. The stability of the prepared emulsion fuels has been investigated. The best stability was observed for the emulsion fuel containing 5% water (E5) due to its more uniform water droplet size distribution. Then, the atomization behavior and spray characteristics of the emulsion fuels have been investigated in a pressure-swirl injector using a high speed camera. The examined ranges for temperature and pressure were (60–110 °C), and (10–25 bar), respectively. The breakup length for each fuel sample in each operating condition was calculated through the image processing analysis. It was found that the micro explosion phenomena associated with the evaporation of the water droplets in the fuels has the most impact on the emulsion fuel spray characteristics. The best atomization performance was observed for E5 considering all examined fuel samples. A 68% decrease in the breakup length was observed for E5 compared to the neat HFO at 90 °C and 15 bar.

Tailoring Pickering Double Emulsions by in Situ Particle Surface Modification

Fundamental studies on the formation and stability of Pickering double emulsions are crucial for their industrial applications. Available methods of double emulsion preparation involve multiple tedious steps and can formulate a particular type of double emulsion, that is, water-in-oil-in-water (w/o/w) or oil-in-water-in-oil (o/w/o). In this work, we proposed a simple single-step in situ surface modification method to stabilize different types of double emulsions using hematite and silica particle systems which involves the addition of oleic acid. In the emulsification studies, we use (i) a combination of hematite and oleic acid, which is termed the binary system, and (ii) a mixture of hematite and silica particles together with oleic acid, which is designated as the ternary system. The wettability of hematite particles is tuned by direct or sequential addition of oleic acid to the water-decane medium. The direct surface modification (which involves the addition of a known quantity of oleic acid to the oil-water mixtures at once) of hematite particles in both binary and ternary systems shows transitional phase inversion from oil-in-water (o/w) to water-in-oil (w/o) emulsions. However, sequential surface modification results in the transition of a single emulsion to double emulsions. In the case of the binary system, the sequential surface modification of the hematite-particle-stabilized o/w emulsion can be converted into double emulsions of o/w/o type. However, in the case of the ternary system, i.e., in the presence of silica particles, sequential surface modification of hematite particles stabilizes both single (o/w) and double (w/o/w and o/w/o) emulsions. The critical concentration of oleic acid required to form a double emulsion is observed to be dependent on the ratio of the surface area of the silica particle to the total surface area of particles (S) and mixing protocols. A study of the size distribution of oil and water droplets of double emulsions shows that droplet size can be controlled by oleic acid concentration and magnitude of S. The arrangements of the particles at interfaces are visualized by SEM imaging. In this way, we developed an easy and novel single-step method of double emulsion preparation and provide a strategy to tailor the formation of different types of emulsions with a single/binary particle system by sequential in situ surface modification of the particles.

DOES INTERNAL CONVECTION PROMOTE MICRO-EXPLOSION OF W/O EMULSION DROPLETS?

W/O emulsions are considered as a beneficial alternative to the use of fossil hydrocarbon fuels and not treated vegetable oils. The presence of a dispersed phase composed of water allows to reduce pollutant emissions and also increases combustion efficiency because of the so-called micro-explosion phenomenon. This micro-explosion has a strong stochastic behavior, and its realization depends on several parameters such as water droplet size distribution and motion during heating. This paper aims to provide a better understanding of the impact of the water droplet behavior on the atomization rate. PLIF technique is used to visualize and track the motion of the water droplets dispersed inside heated emulsion drops. Natural convection of the water droplets is observed, and its impact on coalescence and atomization rate is investigated. Emulsion with small size distributions and high droplet velocity tends to show a low or nonexistent micro-explosion rate, while coarse emulsions show an important coalescence rate, resulting in a high micro-explosion occurrence. Finally, a dimensionless indicator measuring dispersed-phase motion intensity is proposed.

Effect of centrifugal force (G) on stability of natural emulsions (water/oil) present in fresh virgin olive oils

Fresh virgin olive oils (VOOs) just obtained has a cloudy appearance, due to the presence of emulsified water and solid dispersed particles. The stability of these emulsions mainly depends on the water droplet size distribution and the presence of natural emulsifying agents in the oils. In this work, the effect of centrifugation force and time on fresh unfiltered VOOs from the horizontal decanter centrifuge (HDC) and vertical centrifuge separator (VCS) has been studied. The turbidity, moisture, insoluble impurities and phenol content of the oils were analyzed. The increasing of centrifugation force and time decrease the parameters studied of the unfiltered VOOs studied. The VCS oils showed a higher stability of the emulsion, since presented slightly higher values of the parameters studied after application the different centrifugation treatments. Fresh VOOs obtained in the mills can be considered metastable natural emulsions difficult to break with the current centrifugation systems of the olive extraction process.

Investigation of Water Droplet Size Distribution in Conventional and Sustainable Aviation Turbine Fuels

Investigation of Water Droplet Size Distribution in Conventional and Sustainable Aviation Turbine Fuels

Emulsifying properties of sugar-based surfactants prepared by chemoenzymatic synthesis

Sugar Fatty Acid Esters (SFAEs) are a class of non-ionic surfactants that can be synthesized from inexpensive natural resources. Depending on carbon chain length and nature of the sugar head group, SFAEs cover a wide range of hydrophilic–lipophilic balance (HLB) values, which result in tunable tenside properties and in turn relevant for a wide variety of industrial applications. Three sugar-based surfactants (6-O-lauroyl-, 6-O-palmitoyl- and 6-O-stearoyl-1-O-butyl glucopyranosides) have been prepared by a lipase-catalyzed esterification of isomeric mixture of n-butyl glucosides. Specifically, their interfacial features together with W/O emulsifying properties and stability over time have been finely evaluated (interfacial tension (IFT) values, W/O emulsion turbidity and water droplet size distribution), resulting 6-O-palmitoyl- and 6-O-stearoyl-1-O-butyl glucopyranosides as the most efficient ones.

Breakup and collision of water droplet for mass injection pre-compression cooling

The breaking and bouncing coefficients of water droplets in water injection pre-compression cooling are tested in this paper. The test results show that there appears bimodal structure on the droplet size distribution of water droplets due to the combination and secondary crushing of water droplets under the action of high-speed airflow; water droplets are mainly broken by shear under most measuring conditions; when the spray pressure is higher than a certain pressure value (7 MPa), the interference between the nozzles is significantly reduced; the impingement of water droplets against blades would increase the average diameter of particles. By test verification, the optimal rebound coefficient and elastic recovery coefficient are obtained. The experimental results can improve the computational accuracy of the two-phase flow of CFD calculation and make it much closer to the real test or situation.

Determining Characteristics and Engine Emission of Steam Generated Water-in-Diesel Emulsion Fuel


 
 
 Water-in-diesel emulsion fuel (W/D) is an effective method for reducing emission of nitrogen oxides (NOx) from a diesel engine. However, the current approach of producing W/D has its disadvantages in terms of cost and complexity. Therefore, a new approach to produce W/D is developed where water is introduced in vapour state, instead of as liquid, into the fuel. This new method may simplify the emulsion production process as it requires less mechanical parts than any previous non- surfactant emulsion forming methods. The objective of this study is to determine the physical characteristics of steam generated W/D and its engine emission. The characteristics to be determined include the size distribution of water droplets as well as water content. Engine emission will be measured from a 5 kW single cylinder, direct injected, air cooled diesel engine.
 
 

Numerical analysis of the equalization capability of submerged perforated sheets for wwer-1500 horizontal steam generator

The results of a study on the equalization of a non-uniform steam load using different submerged perforated sheets (SPSs) are presented for a full-scale horizontal WWER-1500 steam generator (SG). The calculations performed with the STEG code are used. A short description of the 3D thermal-hydraulic code STEG is presented. A new model of gravitational separation based on empirical correlations for the size distribution of water droplets and for the modal droplet diameter is implemented in the STEG code. Three variants of the distribution of an SPS perforation degree are analyzed. Various characteristics are compared: the distributions of the superficial velocity on the SPS and evaporation surface, the fractions of the steam flow rate with high velocity in the steam region and the steam moisture at the outlet from the SG. The SPS perforation degrees, which significantly improve the equalization of the non-uniform steam load, are found using the STEG code.

Cenosphere formation of heavy fuel oil/water emulsion combustion in a swirling flame

Heavy fuel oil (HFO) is a good alternative and economical fuel for power generation and marine transport industry because of its low price and high energy density. However, HFO's incomplete and complex combustion results in high levels of emissions. One way to improve HFO combustion and reduce its high-level pollutant emissions is by emulsifying HFO with water to form water-in-oil emulsion fuel by virtue of its characteristic of the micro-explosion phenomenon of emulsion fuel. In this work, we tested HFO samples with water contents of 0% (normal HFO), 5%, 10%, 20%, and 30% in mass. A lab-scale burner with an air-blast nozzle and swirling airflow was applied to simulate the industrial boiler's typical features. The properties of various water contents emulsion fuel, including composition, water droplet size distribution, heating value, density, viscosity, and TGA were analyzed. The influence of water-HFO emulsion on the swirling flame combustion performance and the primary pollutant emissions, listed as CO, CO2, NOx, SOx, particulate matter (PM), and its composition, was studied. The results show that, in general, multiple various beneficial processes come into effect when water-in-HFO emulsion augments the combustion. HFO emulsion technology offers tremendous potential to enhance combustion processes' efficiency with reduced SOx, NOx, and particulate matter emissions. The emulsion fuel has a considerable effect on the formation process of cenospheres. This effect varies with different water levels in HFO due to the different intensities of secondary atomization of emulsion fuel combustion.

Characterization of electrical current and liquid droplets deposition area in a capillary electrospray

A comprehensive study was conducted to investigate the effects of applied voltage, distance between needle tip and counter electrode, liquid flow rate, pH and conductivity of water on the electrical current in a capillary electro-spray. Atomic Force Microscopy (AFM) was employed to measure the size distribution of water droplets, which presented a mean diameter of 299 ​± ​76 ​nm. Statistical analysis using three-way ANOVA and nonlinear multivariate regression model were employed to study the interactions of applied voltage, distance between needle tip and counter electrode, and liquid feed rate with electrical current, and to develop regression equations to predict the current. It was found that electrical current was significantly (p ​< ​0.05) influenced by applied voltage (0 to ±10 ​KV) and the distance (2, 3 and 4 ​cm), but not by the liquid feed rate (1–10 ​μl/min) within the range investigated in this work. A water contact indicator was employed for the first time in the electrospray system to investigate the effect of parameters mentioned above on the liquid droplets deposition area. The experimental data demonstrated that increasing the distance of the capillary needle, liquid feed rate, pH, and conductivity, resulted in increased electrosprayed area.

Analysis of Water Droplet Distribution in Wind for the Fluidic Sprinkler

The fluidic sprinkler, a relatively new type of rotating sprinkler, has been the subject of quite a lot of research about its structural parameters, hydraulic characteristics, and water distribution profile, albeit under indoor conditions. The fluidic sprinkler’s performance in terms of water distribution profile and droplet size distribution pattern in wind has seen little investigation. To obtain information about its droplet size distribution in wind, the Thiess Clima Laser Precipitation Monitor was employed. Drop diameter, drop velocity, and the number of drops at varying distances from the fluidic sprinkler were measured in both wind and no wind at three operating pressures of 250, 300, and 350 kPa. The logistic model was adopted to fit a relationship between the drop diameter and the cumulative numeric frequency (CNF) and the cumulative volumetric frequency (CVF) values resulting in very high correlation coefficient (R2) values of above 0.99 for all conditions. At 250, 300, and 350 kPa, drops traveled 0.6, 1.0, and 1.3 m, respectively, farther in wind than in no wind along the direction of throw. Drops exhibited a spectrum of velocities and diameters at a given radial distance from the sprinkler. Up to two-thirds of the radius of throw, the proportion of drops with diameters ranging from 0.125 mm to 1.00 mm were above 80% at 300 and 350 kPa.

The Digitalization of Bottle Tests Nuclear Magnetic Resonance Evaluation of Emulsion Stability

Bottle tests are the preferred meth-od to test petroleum emulsion stability in the industry today. A new technique using nuclear magnetic resonance (NMR) is available to evaluate both stability and demulsification behavior of emulsions. The NMR scans the water fraction throughout the entire length of the emulsion sample. These rapid measurements are designed to dynamically probe the emulsion, capturing its separation as a digital image. This case study presents the ways NMR has helped predict the effects of future well line-up changes. Introduction Emulsion stability negatively impacts oil processing operations and plant design. The assessment of emulsion stability is performed at wellheads and gas/oil separation plants (GOSPs). Bottle tests are largely used for emulsion assessment, due to their simplicity and low cost. These tests depend on the visual identification of the separated water layer as the only quantifiable parameter. NMR is one of the alternative methods for emulsion assessment that can pro-vide information for all emulsion components. These components include the water layer; the oil/water interface - including the rag layer (the dense-pack zone [DPZ] of droplets above the interface); the remaining water-in-oil emulsion; and the dry-oil continuous phase. The DPZ - or rag layer - is of particular importance for oil processing, as its occurrence in separation vessels can lead to process upsets, resulting in excessive concentration of oil at the vessel’s water outlets. This interfacial phenomenon is particularly critical in the production of heavy oils, oils with high solid content, and oils forming highly stable emulsions. NMR is not only capable of measuring the water fraction throughout the entire emulsion sample, but can also provide a digital image of the water separating in the sample. More advanced NMR analyses are able to determine the water droplet size distribution (DSD) in the emulsion, and how the distribution changes during separation. It is also possible to obtain information on the droplet sizes at each position in the sample, as they change in time. Bottle tests are limited to the visualization of the free-water layer. Measurement errors are common if the oil/water interface is not clear. Unlike the NMR, any water still emulsified in the oil cannot be measured as it is not visible. The formation of the rag layer cannot be identified either. In addition, the efficiency of separation calculated from bottle test results, or emulsion separation index (ESI), requires knowledge of the water cut of the sample. The production water cut can be provided by the oil-processing operations, but the value is hardly the same found at sampling points. If the water cut is not known, it needs to be accurately measured in the sample after the bottle test. Usually the total amount of water is measured after centrifugation. It is difficult to guarantee that the emulsion is fully separated, as some droplets could still be unresolved at the interface. Another test limitation is the determination of separation efficiency when the water quality is poor. The presence of an oil-in-water emulsion could be the cause of cloudiness, contributing to an inefficient separation. But most of all, no readings can be made if the emulsion does not separate spontaneously. With NMR it is possible to determine the sedimentation rate of water droplets, even if no coalescence takes place (and no free-water layer is formed).

Experimental and numerical study on the interaction of a water mist spray with a turbulent buoyant flame

This paper presents a detailed experimental and numerical study on the interaction, at a reduced scale, between a turbulent buoyant propane flame of about 15.5 kW and a water mist spray with a flow rate of 0.43 L/min from a nozzle positioned at 1 m above the burner. The water spray has been characterized experimentally without a fire, by measuring the water mass flux and droplet size distributions at the level of the burner surface. The whole assembly was installed under a hood and the following three parameters were measured: (1) the chemical heat release rate (HRR) (using the oxygen consumption method), (2) the rise in gas temperature at the top, and (3) the radiative heat flux at 0.72 m from the axis of the burner and at a height of 0.05 m. Reductions of about 40% and 30% were recorded for, respectively, the gas temperature (in the hood) and the radiative heat flux, while the chemical HRR did not change. Computational Fluid Dynamics (CFD) simulations with the Fire Dynamics Simulator (FDS, version 6.7.0) predicted relatively well the gas temperature, without a reduction in the HRR, but, in contrast to the experiments, the radiative heat flux did not change.

Modeling of oil–water separation efficiency in three-phase separators: Effect of emulsion rheology and droplet size distribution

The multi-fluid Eulerian multiphase model coupled with the inhomogeneous population balance model is applied to predict the gas, oil, and water separation behavior and emulsion destabilization in a high-pressure horizontal three-phase separator. The population balance model is applied to predict the evolving droplet size distribution due to droplet coalescence in the crude oil emulsion. The effect of water fraction on the emulsion viscosity was incorporated to predict the existence of the dense packed layer or zone (DPZ) – a high water-fraction emulsion layer formed at the interface between the oil and water phases. The novel emulsion viscosity model incorporates a dependence on the local droplet size. Parameter estimation for the droplet coalescence kernel in the population balance equation is determined from experimental measurements of emulsion separation kinetics. A proportional integral derivative (PID) controller logic is used to maintain the gas/oil and oil/water interface levels by automatically adjusting the oil and water outlet pressure, respectively. The pilot separator experimental measurements include inlet and outlet flowrates and density, and electrical capacitance measurement of the vertical water concentration profile. The CFD model determines the flow patterns, phase distributions and the dispersed water droplet size distribution in the emulsion in the separator. The model results are in good agreement with the data for the separation efficiency from the water flow rate in and out of the separator, the phase distributions and the DPZ at different flow rates and water fractions. This study demonstrates the importance in multiphase separator design and troubleshooting of including the influence of water fraction on emulsion viscosity and the droplet size distribution with droplet coalescence phenomena. The methodology presented has significant advantages over previously published methods and improves on the value and potential impact toward research and industry practice.

Rainfall interception and redistribution by maize farmland in central Iran

Study regionMaize farmland in Varamin, located southwest of Tehran (Iran). Study focusThe aims of this study were to: (1) monitor throughfall and stemflow during rainstorms beneath maize canopies over two growing seasons (2015, 2016); (2) evaluate the effect of maize canopy structure (leaf area index, plant height) on throughfall, stemflow, and interception; and (3) develop an analytical model of rainfall partitioning by maize from controlled rainfall simulations. New hydrological insights for the regionRainfall or irrigation interception by crops and residues has often been overlooked in hydrologic modelling in Iran. However, our results confirm that interception by maize canopy can significantly reduce total water input to the surface (19.9 % and 11.2 % of natural and simulated rainfalls, respectively). Although rainfall amounts and rates were similar between simulations and natural rainfall, differences in interception value may still exist between simulated and natural conditions due to the formation, size distribution, and movement of water droplets emitted from simulation systems vs. natural rainfall water droplets. Throughfall and interception significantly correlated with LAI and height of the maize canopy above thresholds of 2.5 (LAI) and 180 cm (height). The analytical model performed well under natural rain conditions. These results may help farmers’ irrigation scheduling achieve higher irrigation water use efficiency for maize fields, particularly in arid agricultural lands.