Distribution Of Water Droplets Research Articles

Comparative Study of Droplet Diameter Distribution: Insights from Experimental Imaging and Computational Fluid Dynamics Simulations

The interfacial area between two phases plays a crucial role in the mass transfer rate of gas–liquid processes such as absorption. In this context, the droplet size distribution within the flow field of a droplet-based absorber significantly affects the surface area, thereby influencing the absorption efficiency. This study focuses on developing a computational fluid dynamics (CFD) model to predict the size and distribution of water droplets free-falling in a transparent square tube. This model serves as a digital twin of our experimental setup, enabling a comparative analysis of experimental and computational results. For the accurate measurement of droplet size and distribution, specialized experimental equipment was developed, and a high-speed camera along with Fiji software was used for the capturing and processing of droplet images. At the point of injection and at two different heights, the sizes and distributions of falling droplets were measured using this setup. The interaction between the liquid water droplets and the gas phase within the square tube was modeled using the Eulerian–Lagrangian (E-L) framework in the STAR-CCM+ software. The E-L multiphase CFD model yielded approximations with errors ranging from 11 to 27% for various average mean diameters, including d10, d20, d30, and d32, of the liquid droplets at two distinct heights (200 mm and 400 mm) for both nozzle plates. This comprehensive approach provides valuable insights into the dynamics of droplet-based absorption processes.

Assessment of surface irregularities created by controlled liquid droplet on the surface of stainless steel AISI 304L

Surfaces created by the erosive action of water droplets have not been sufficiently explored because of their stochastic structure, which depends on hydraulic parameters. This article details the complex analysis of surfaces created by the controlled distribution of water droplets on the surface of AISI 304L using an ultrasonically stimulated water jet. The traverse speed of the jet controlled the distribution of the water droplets. The surface topology was modified in an interleaved mode when the trajectories were parallel for all samples. Additionally, the second layer treated the other half of the preprepared samples with a perpendicular trajectory with respect to the parallel trajectory. The 3D surface reconstruction was performed using a noncontact MicroProf FRT measuring instrument. Several profile roughness parameters (Ra, Rz, Rv, Rp, Rsk, and Rku), areal surface roughness parameters (Sa, Sz, Sp, Sv, Ssk, Sku, Sdr, Sk, Spk, and Svk) and surface isotropy values were measured for the surfaces generated using variations in the traverse speed of the jet. The measurement results show a decreasing trend of surface roughness upon an increase in the traverse speed, and a better surface finish was also measured for the cross-hatch trajectory compared to the linear trajectory. The results also show that the generated surfaces have deeper valleys with truncated peaks, which are suitable for use in a wide range of technical and medical applications. This study shows the potential utilization of controlled liquid droplet impingement for surface preparation in various application domains.

Online Multiphase Flow Measurement of Crude Oil Properties Using Nuclear (Proton) Magnetic Resonance Automated Measurement Complex for Energy Safety at Smart Oil Deposits

The necessity of a flow express control of oil dispersed system (ODS) properties, such as crude oil, oil products, water–oil emulsions, and polluted waters, is substantiated. This control is necessary for the production and preparation of oil for transportation through the pipeline and oil refining, oil products, and wastewater treatment systems. A developed automatic measuring complex (AMC) is used to implement the concept of digital oil deposits. The primary measuring device is a relaxometer developed by us based on nuclear (proton) magnetic resonance (PMR). The design and operation algorithm of the AMC and the relaxometer are described. Equations have been developed to determine the ODS characteristics using the measured PMR parameters. This makes it possible to determine the flow rates of crude oil, the concentration of water in the oil, the concentration of asphaltene, resins, and paraffins in the oil, as well as the density, viscosity, and molecular weight of the oil. Additionally, it is possible to determine the dispersed distribution of water droplets in emulsions in oil production and treatment units. Data on this distribution will improve the management of separation processes. It has been established that the implemented control of multiphase ODS using PMR parameters (relaxation times, populations of proton phases, and amplitudes of spin-echo signals) makes it possible, using AMC, to assess the consumption of electricity in technological processes at the digital oil deposits, as well as during the transportation of oil and oil products through pipelines. AMC makes it possible to reduce electrical energy consumption in technological installations and reduce pollution emissions into wastewater. The advantages of using the developed AMC are shown in examples of its application. Such as an assessment of the influence of the gas factor on electricity consumption during oil transportation through pipelines or compensation for the additional moment of resistance on the shaft of the submersible motor, which is caused by surface tension forces at the interface of water droplets in the emulsion.

Theoretical study of the influence of the changing environment on the process of rainfall irrigation

The technology of sprinkler irrigation has a higher coefficient of land use compared to that of regular irrigation, due to the absence of irrigation erosion, the prevention of unnecessary absorption of water into the soil, the high degree of mechanization and automation of the irrigation process, the saving of equipment and fuel costs, the availability of irrigation in areas with uneven relief, the uniform moistening of the root layer. It has the advantage of achieving the same growth and development of the plant in all parts of the field. At the same time, there are opportunities to achieve savings as a result of giving mineral fertilizers in the form of suspension during irrigation. This article examines the distribution of water droplets on the field surface during sprinkler irrigation and the influence of wind speed on the intensity of irrigation. Water drop motion and wind motion were analyzed in one coordinate system. As a result, a mathematical model of the resistance coefficient of the environment and the movement of a water droplet in a variable environment was developed.

Flow characteristics of heavy oil-water flow during high water-content cold transportation

As the water content in heavy oil gathering systems increases to 70–90% and large-scale popularization of cold transportation. Understanding the characteristics of heavy oil-water flow during high water-content cold transportation has greatly gained in importance. Here, a comprehensive flow loop experiment and microscopic observation was employed to investigate the flow characteristics of oil-water flow at low temperatures. The flow patterns of cold transportation were studied experimentally. The flow pattern maps were also created in detail, taking into account the temperatures (60–20 °C), mixture velocities (0.1–1.0 m/s), and water contents (70–90%). The relevant influencing factors of the pressure gradient were then investigated. The lubrication coefficient and viscosity models were used to modify the pressure gradient models, and average relative deviations were within ±25%. Moreover, the distinction between the oil-sticking layer and wax deposition formation mechanisms was highlighted. According to microscopic observation, the major elements impacting the strength of the oil-sticking layer were asphaltene aggregation and water droplet distribution. Finally, an evaluation method for predicting the minimum heavy oil-gathering temperature during high water-content cold transportation was presented. The findings of this study greatly contribute to understanding the mechanisms of cold transportation.

Study on the relationship between the characteristics of water droplets on the shed of composite insulators and the pollution flashover voltage

The anti-pollution flashover characteristic of composite insulators is the main indicators to evaluate their electrical performance, and the pollution flashover voltage can directly characterize the anti-pollution flashover characteristics of the insulators. This paper proposed an on-line detection method for the pollution flashover voltage of composite insulators. Samples of composite insulator shed with different hydrophobicity were prepared by using NaOH solution with pH value of 13 and temperature of 80 °C. According to the distribution of water droplets on the surface of the sample, the characteristic parameter of the number of water droplets was proposed. The samples with different characteristic parameters were smear-stained and used for the pollution flashover voltage test. The relationships between the number of water droplets on the sample surface and the pollution flashover voltage and leakage current were obtained, which can provide guidance for the evaluation of the operation state of composite insulators.

Recognition of Hydrophobicity Class of Polymeric Insulators Employing Residual Morphological Neural Network and Granulometry-Based Image Analysis

Hydrophobicity is an important property of polymeric insulators that allow formation of discrete water droplets on the insulator surface. However, with aging or under extreme humidification, the insulator surface loses its hydrophobic property, resulting in continuous water channel formation, which may lead to dry band arcing and subsequently flashover, thereby affecting the long-term performance of the insulator. Therefore, accurate recognition of hydrophobic class (HC) is important as it provides information regarding the surface condition of the insulator. Considering the above-said facts, this article investigates the feasibility of employing residual morphological neural network (Res-Morph-NN) to accurately recognize different HCs of polymeric insulators. In addition, for better understanding of the distribution of water droplets on the insulator surface, a novel approach based on multiscale mathematical morphology, i.e., granulometry, is used in this article. Our investigations revealed significant alterations in the granulometric patterns with the change in HC of polymeric insulators. The efficacy of the proposed framework employing Res-Morph-NN has been validated on HC images obtained from the experiment as well as on large set of images obtained from an online database, which returned satisfactory results. The proposed method can be efficiently used to discriminate different hydrophobicity classes, which can be implemented for monitoring insulator surface condition in real time.

Ultrasonic Pulsating Water Jet Peening: Influence of Pressure and Pattern Strategy.

Peening techniques are nowadays attracting more research attention due to their association with the extending of the service life and improving surface texture of engineering components. Ultrasonic pulsating water jet peening represents a new way of mechanical surface treatment. Accelerated water droplets via hammer effect cause small elastic-plastic deformations on the surface. This work deals with peening of aluminum alloy using an ultrasonic pulsating water jet, where periodically acting water droplets were used as the peening medium. The aim of the work was the feasibility study of the peening process and to observe the effects of pressure (p = 10, 20 and 30 MPa) and pattern trajectory (linear hatch and cross hatch). The peened surfaces were analyzed by the surface roughness profile parameters Ra and Rz and the microhardness along the peening axis into the material. Graphically processed results show a clear increase of measured values with increasing pressure (p = 10, 20 and 30 MPa), where the roughness values ranged from 1.89 µm to 4.11 µm, and the microhardness values ranged from 43.3 HV0.005 to 47 HV0.005, as compared to 40.3 HV0.005 obtained for the untreated sample. The achieved results indicate potential using of an ultrasonic pulsating water jet as a new method of surface treatment of metals. By controlled distribution of water droplets, it is possible to achieve a local distribution of surface roughness, and at the same time, strengthening of the subsurface layers in the material without thermal influence on the material.

Microbial Degradation Rates of Natural Bitumen.

Microorganisms are present in nearly every oil or bitumen sample originating from temperate reservoirs. Nevertheless, it is very difficult to obtain reliable estimates about microbial processes taking place in deep reservoirs, since metabolic rates are rather low and differ strongly during artificially cultivation. Here, we demonstrate the importance and impact of microorganisms entrapped in microscale water droplets for the overall biodegradation process in bitumen. To this end, we measured degradation rates of heavily biodegraded bitumen from the Pitch Lake (Trinidad and Tobago) using the novel technique of reverse stable isotope labeling, allowing precise measurements of comparatively low mineralization rates in the ng range in microcosms under close to natural conditions. Freshly taken bitumen samples were overlain with artificial brackish water and incubated for 945 days. Additionally, three-dimensional distribution of water droplets in bitumen was studied with computed tomography, revealing a water bitumen interface of 1134 cm2 per liter bitumen, resulting in an average mineralization rate of 9.4–38.6 mmol CO2 per liter bitumen and year. Furthermore, a stable and biofilm-forming microbial community established on the bitumen itself, mainly composed of fermenting and sulfate-reducing bacteria. Our results suggest that small water inclusions inside the bitumen substantially increase the bitumen–water interface and might have a major impact on the overall oil degradation process.

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.

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.

Effect of in-cylinder air-water interaction on water evaporation and performance characteristics of a direct water injected GDI engine

Water injection is one of the promising strategies for modern downsized GDI engines to meet performance and emission requirements under wide operating conditions. However, the benefits of water injection strongly depend upon water evaporation and distribution of water vapours inside the combustion chamber. In this regard, water injector location and orientation are two significant geometrical parameters which decide the in-cylinder positioning of the water spray, evaporation, and vapour distribution. Therefore, this CFD study presents the effects of water injector location, and orientation on the in-cylinder air-water interaction, water evaporation, vapour distribution, performance and emission characteristics of a wall-guided GDI engine. It also presents the effects of water injector location and orientations on water evaporation rate, water droplet distribution, heat release rate, IMEP, and exhaust emissions. In this study, the spark-plug is considered as located in the middle of the cylinder head, and the water injector is mounted in between the exhaust valves. Four locations of the water injector (21 mm, 25 mm, 29 mm, and 33 mm from the spark-plug) are considered for the investigation. Also, the injector orientation is varied from 12° to 28°, in the step of 4°. The engine is operated under naturally aspirated and full-load conditions at an engine speed of 2000 rev/min. Analysis of results shows that the water evaporation rate increases when more amount of water is sprayed in the region where the velocities of water droplets are in the opposite direction of that of the in-cylinder air. It is found that the water injector located at 29 mm with the orientation of 24° is found to be optimum configuration, where the IMEP improved by about 9.2%, while NOx and soot emissions reduced by about 48.2% and 22.6% respectively compared to those of the case of no_water.

Selection of operational parameters for a smart spraying system to control airborne PM10 and PM2.5 dusts in underground coal mines

Airborne dust in underground hard coal mines is an ongoing explosion and respiratory health hazard. The latest design solution for controlling dusts, the smart spraying system, is described. From the results of stand tests, the main factors determining the efficiency of the new device are: 1) the integrated real-time acquisition of dust particle size and concentration data, determined using a new optical dust meter; 2) the fractional distribution of water droplets; and 3) the selection of droplet size to capture PM10 and PM2.5. The latter two factors are automatically controlled, based on dust measurements, by varying the pressure of water and compressed air supplied to the sprayer nozzles. The effects of varying these parameters and the results of stand tests are presented. The spraying device was tested for the effectiveness of PM2.5 dust and PM10 dust reduction in underground conditions in the KWK Pniówek mine. The tests were based on the following Polish Standards: PN-91/Z-04030/05 and PN91/Z-04030/06, which define the methodology for measurements of inhalable and respirable dust at workplaces using the filtration-weighing method to determine the concentration of inhalable and respirable dust with the spraying system on and off. The results showed that the assumed objective, i.e. development of a dust control device that would reduce PM2.5 dust (by min. 25 %) and PM10 dust (by min. 20 %) more effectively than the currently used solutions, was achieved in the project. At the same time, the device, due to application of dust sensor, continuously adjusts the parameters of spraying streams to the dust concentration level, optimizing the consumption of water and compressed air. Similar results in reduction of PM10 and PM2.5 dust, with an average effectiveness of over 60 % is the undoubted advantage of the device.

Investigation of the trajectory uniformity in water dissolution ultraprecision continuous polishing of large-sized KDP crystal

Large-sized potassium dihydrogen phosphate (KDP) crystals are an irreplaceable nonlinear optical component in an inertial confinement fusion project. Restricted by the size, previous studies have been aimed mainly at the removal principle and surface roughness of small-sized KDP crystals, with less research on flatness. Due to its low surface damage and high machining efficiency, water dissolution ultraprecision continuous polishing (WDUCP) has become a good technique for processing large-sized KDP crystals. In this technique, the trajectory uniformity of water droplets can directly affect the surface quality, such as flatness and roughness. Specifically, uneven trajectory distribution of water droplets on the surface of KDP crystals derived from the mode of motion obviously affects the surface quality. In this study, the material removal mechanism of WDUCP was introduced. A simulation of the trajectory of water droplets on KDP crystals under different eccentricity modes of motion was then performed. Meanwhile, the coefficient of variation (CV) was utilized to evaluate the trajectory uniformity. Furthermore, to verify the reliability of the simulation, some experimental tests were also conducted by employing a large continuous polisher. The results showed that the CV varied from 0.67 to 2.02 under the certain eccentricity mode of motion and varied from 0.48 to 0.65 under the uncertain eccentricity mode of motion. The CV of uncertain eccentricity is always smaller than that of certain eccentricity. Hence, the uniformity of trajectory was better under uncertain eccentricity. Under the mode of motion of uncertain eccentricity, the initial surface texture of the 100 mm × 100 mm × 10 mm KDP crystal did achieve uniform planarization. The surface root mean square roughness was reduced to 2.182 nm, and the flatness was reduced to 22.013 μm. Therefore, the feasibility and validity of WDUCP for large-sized KDP crystal were verified.

Low-pressure drop size distribution characterization of impact sprinkler jet nozzles with and without aeration

Impact sprinkler (20PY2 IS) outlet is a single-phase water flow, and the aeration impact sprinkler (20PY2 AIS) outlet is gas-liquid two-phase flow. The jet dispersing principle of AIS is somewhat different from conventional sprinklers and has advantages and the ability to working well at the low-pressure condition. The experimental study on the droplet size distribution of IS and AIS was carried out by the volume-weighted method to analyze the mean diameter (Dv), median diameter(D50), water droplets frequency distribution, and the cumulative frequency at different distances from sprinklers. Similarly, the velocity of the drop was measured by Laser Precipitation Monitor (LPM) and statically analyzed by using a number-weighted method. The results showed that both the drop diameters Dv and D50 increased with the distance from the sprinkler nozzle but decreased with an increase in the working pressure. Similarly, droplet frequency distribution at a diameter < 3.5 mm of both sprinklers increased with the working pressure. The quantity of larger droplets decreased with an increase in working pressure, and this trend amplified with an increase in the distance from the sprinkler nozzle. Under low-pressure (0.15 MPa, 0.2 MPa, and 0.25 MPa) and the absence of wind conditions, the droplet distribution of the AIS was more uniform and constant than the IS. The droplet's frequency distribution of AIS and IS nozzles was conformed to a logarithmic normal distribution. With the distance from the sprinkler increasing, the slope of the droplet cumulative frequency curve decreased gradually. Under the same pressure and at similar distances from the nozzle, the (D50) of the 20PY2IS was less than the 20PY2AIS, and the functional relationship between median diameter, working pressure, and distance from the sprinkler was established. When the pressure was set at 0.15 MPa and 10 m away from the sprinkler, the droplet's median diameter was 6% higher under AIS than under IS. At the working pressure of 0.25 MPa, the frequency distribution of water droplets under both nozzles was higher, and water droplets are more frequent for a different distance from a sprinkler. Droplet velocity was improved with the decreasing droplet diameter, but due to low pressure, there was not significantly influenced in velocity. The results may deliver a basis for additional efficient exploration of the AIS.

Effects of mixture parameters variation on the performance of corrugated plate dryer

Both experimental and theoretical works had been done to study the effects of mixture parameters on the performance of corrugated plate (CP) dryer. A water-air experimental branch had been established to simulate water-steam separation in a CP dryer. The effect of ambient relative humidity on the dryer experiment is analyzed. The diameter distribution of water droplets in air-water mixture at (CP) dryer entrance was measured by laser particle size analyzer. The effects of droplet diameter, moisture content and mixture flow velocity on the separation efficiency, pressure drop and the re-entrainment were studied. At the same time, a theoretical model for trajectory tracking of water particle in CP channel was established to illustrate experimental results. The conclusion shows that: 1) this effect of ambient relative humidity cannot be ignored or error could be introduced to experimental results. 2) The separation efficiency increases with the increase of inlet particle size, increases with the increase of inlet moisture content and increases first and then decreases with the increase of inlet velocity. 3) Critical airflow speed of re-entrainment decreases as the inlet moisture content increases. 4) The pressure drop is exponentially increasing with inlet airflow speed.

Effect of the nozzle arrangement of atomization equipment in icing cloud simulation system on the velocity field of water droplets and liquid water content distribution

The study of reproducing high altitude icing environment based on the icing cloud simulation system has gradually become a concern for researchers. They found that the parameters of water droplets were one of the most critical factors affecting the state of icing. However, the influence of nozzle arrangement on droplet parameters in the icing cloud simulation system is usually neglected. By reprogramming the software FLUENT, this study carried out a simulation analysis on the influence of nozzle arrangement in the icing cloud simulation system. Four user-defined functions were added to FLUENT to modify the vaporization law, so as to get more accurate results. A model of the atomization equipment in an ice cloud simulation system was developed and successfully validated with the parameter of ice shape and maximum ice thickness on the test rod. The error of maximum ice thickness is only 2.6%, and the maximum deviation and mean deviation are 1.13 mm and 0.68 mm, respectively. The homogeneity of water droplet distribution is proposed and defined, and the calculation method of the degree of homogeneity for water droplet distribution is given. The most reasonable nozzle arrangement in this study with the maximum degree of homogeneity of 78.32% and a spreading area of 14.67% of the total cross-section area is determined. This study shows certain reference significance for realizing a more uniform velocity field of water droplets and liquid water content distribution in the future.

Distribution of Water Droplets in Oil Emulsions before and after Hydrate Formation

The changes in the dispersion of inverse emulsions of oil and their stability during the formation/decomposition of natural gas hydrates are studied in the work. It is established that in the cycle of the formation/decomposition of natural gas hydrates, the aqueous phase coalesces in oil emulsions, containing more than 60 wt % of water, with the subsequent average diameter of droplets enlarging by 12–28%. It is shown that water-in-oil emulsions lose their stability with the subsequent separation into continuous phases in both the processes of hydrate formation and freezing. The separation efficiency of emulsions with water cuts of less than 40 wt % during the hydrate formation process is higher than in freezing/thawing.