Liquid Zone Research Articles

Multi-scale flow atomization characteristics of Jatropha biodiesel swirl liquid film breakup

The characteristics of the spray and droplets produced by liquid film breakup are crucial for understanding the atomization process in industrial furnace atomizers. This study employed high-speed camera technology to capture images of Jatropha biodiesel (JB) spray at various pressures and Ohnesorge numbers (Oh). Image processing methods were employed to analyze the evolution morphology and proper orthogonal decomposition (POD) of fuel swirl spray, revealing the instability, breakup length, spray cone angle, fractal characteristics of the liquid film breakup zone, and droplet distribution characteristics. The results indicated that the JB jet evolution progressed through stages: cylindrical jet, torsion liquid film, open swirl, complete swirl, and fully developed mode. The evolution and disintegration of the liquid film exhibited a complex structure with ligaments, perforations, and droplet separation. Flow disturbances induced the Klystron effect, characterizing microscopic droplet motion. As spray pressure increased, the growth rate of the disturbance wave increased, the breakup length decreased, the atomization cone angle enlarged, and the fractal dimension (FD) of the liquid film breakup zone increased. The droplet size distribution followed a log-normal distribution, with a substantial increase in the number of small droplets as injection pressure increased. This study provides valuable insights into the multi-scale flow atomization of biodiesel in industrial furnace, and is of great significance for the design, operation, and optimization of spraying systems in various industrial applications.

Impact of adding high-concentration neutron poisons to reactor moderator system for guaranteed shutdown

To ensure a reliable shutdown of the proposed advanced heavy water reactor (AHWR) of Indian origin during emergency conditions, it is imperative to use an increased concentration of liquid neutron poison for injection into the moderator system due to its higher reactivity. The sudden injection of this liquid poison may cause a surge in radiolytic product (H2O2 and H2) yield, posing safety risks. If H2/D2 yield exceeds 4 % (v/v), a combustible mixture with oxygen can be formed and presence of oxidizing H2O2 can enhance corrosion. Hence, accurate estimation of H2O2 and H2 is imperative from the reactor safety point of view. We investigated gadolinium and boron (two liquid neutron poisons) at varying concentrations through high energy electron beam and gamma radiolysis. The radiolytic yields from both the liquid neutron poisons of equivalent concentrations at a constant dose and operating moderator conditions in electron beam and gamma radiolysis were compared. The molecular product yield was observed to be concentration and dose-rate-dependent for both the neutron poisons. Electron radiolysis exhibited a higher yield of H2O2, whereas gamma radiolysis resulted in a greater H2 yield. In electron radiolysis, the H2O2 yield decreased with increasing B concentration. These results give an overall estimation of radiolytic products for a particular dose rate, total dose and effect of head space volume over liquid irradiation zone from these two liquid poisons of a particular concentration. These insights will aid in selecting suitable poisons and managing their effects effectively to avoid hydrogen deflagrations after emergency shutdown.

Mathematical modeling of the thermal process of arc erosion with current carrying heating effect in a temperature gradient

This paper presents a mathematical model aimed at comprehensively understanding the thermal processes associated with arc erosion of closed electrical contacts triggered by the instantaneous explosion of micro-asperities including Thomson effect and Joule heat source. The phenomenon involves vaporization and liquid zones, and the temperature distribution is governed by a generalized heat equation, accounting for the heating effect due to current flow in temperature gradients and effect of heat source. The proposed model allows for a nuanced analysis of the thermal dynamics, shedding light on the complex phenomena involved in arc erosion. The proposed method in this paper employs similarity transformation techniques to effectively reduce the complexity of the problem, transforming it into a set of manageable ordinary differential equations. The study establishes the existence and uniqueness of the solution through rigorous analysis. The behavior of the solution of the problem is successfully considered for special cases of Thomson and thermal coefficients. By leveraging similarity transformations, the paper offers a powerful approach for unraveling the intricacies of the thermal processes in arc erosion of closed electrical contacts, providing valuable insights into the phenomena associated with current-carrying heating in the presence of temperature gradients.

Characteristic parameters measurement and flow prediction of slug flow based on ultrasound technology

Slug flow exists over a wide range of gas and liquid flow rates. For the case of smaller liquid volume fraction, this paper proposes a method for accurately identifying the flow structure of horizontal pipe slug flow based on the ultrasonic inner wall echo signal at the top of the pipe. The arrival and departure time of the slug is determined by analyzing the amplitude of the inner wall echo signal from both the test signal and reference signal and the rate of change of the test signal, respectively. Based on the accurate flow structure identification results, characteristic parameters can be calculated including the length ratio between the liquid film zone and the slug unit (lf/lu) and the average liquid film thickness in the liquid film zone (hf). The system of equations describing the relationship between the two parameters and the two-phase flow rates is constructed. By solving it, the flow rates of gas and liquid can be predicted. Experiments are carried out with the superficial velocity of gas and liquid ranging from 0.8 to 2.5 m/s and 0.1 to 0.4 m/s, respectively, where the pipeline’s inner diameter is 50 mm. The experimental results indicate that the mean absolute percentage errors for the predicted gas and liquid flow rates are 12.9605 % and 6.3517 %, respectively.

Design and development of vehicle cryo-compressed hydrogen storage vessel

Compared with other hydrogen storage methods, cryo-compressed hydrogen storage has significant advantages in terms of mass hydrogen storage density, volume hydrogen storage density, hydrogen storage cost, safety and evaporation loss. The key component of cryo-compressed hydrogen storage is cryo-compressed hydrogen storage vessel. In order to reasonably design and optimize the performance of cryo-compressed hydrogen storage tank, the author uses carbon fiber and low temperature resin to prepare composite one-way plate from the material, and then makes the one-way plate into relevant splines for testing. The relevant parameters of the spline are tested in the liquid nitrogen temperature zone, such as elastic modulus, Poisson’s ratio, thermal conductivity, etc. Using the relevant mechanical properties of the carbon fiber composite one-way plate obtained from the experiment, the target storage tank is designed to provide the actual storage tank for the subsequent low temperature and high pressure storage tank experiment.

Towards Understanding Formation Mechanism of Cellular Structures in Laser Powder Bed Fused AlSi10Mg.

A new approach is proposed that identifies three different zones of the Si-rich network structure (the cellular structure) in laser powder bed fused (LPBF) AlSi10Mg alloy, based on the variation in morphology, grain growth transition, and melt pool solidification conditions. The three identified zones are denoted in the present work as the liquid solidification zone (LSZ), the mushy solidification zone (MSZ), and the heat affected zone (HAZ). The LSZ is the result of liquid-solid transformation, showing small planar growth at the boundary and large cellular growth in the center, while the MSZ is related to a semisolid reaction, and the HAZ arises from a short-time aging process. The boundary between the LSZ and MSZ is identified by the change of grain growth direction and the Si-rich network advancing direction. The boundary between MSZ and HAZ is identified by the start of the breakdown of the Si-rich network. In addition, it is found that the fracture is generated in and propagates along the HAZ during tensile tests.

Reduction in Apparent Permeability Owing to Surface Precipitation of Solutes by Drying Process and Its Effect on Geological Disposal

Disposal tunnels in geological repositories are ventilated continuously for over 50 years until their closure. Under these conditions, an unsaturated zone of mixed liquid and gas phases forms around the tunnels. Moreover, drying is assumed to progress from the host rock to the tunnels. To understand these drying processes, this study investigated the migration and precipitation of solutes via capillary forces during drying in packed columns using silica sand or glass beads as packed layers and X-ray CT analysis. In addition, the apparent permeability of a column packed with silica sand containing precipitation was examined using a flow experiment. The results indicate that the precipitation and accumulation of solutes were significant near the drying surfaces of the columns. The apparent mass transfer coefficient at a relatively early stage of the drying process indicates that the migration rate of solutes depends strongly on the capillary forces during the drying process. Furthermore, the apparent permeability of the columns with precipitation decreased significantly. These indicate that the precipitation and accumulation of solutes with drying in the groundwater reduce the porosity and permeability, and the advection of groundwater around the repository may be suppressed.

Options on temporary water allocation rights and their pricing

AbstractThis paper presents a methodology for defining the spot price of temporary water allocation rights for trading zones within the water market in the southern Murray–Darling Basin situated in Australia. The historical spot price is then used to calibrate a stochastic process depicting the dynamics of the water price, allowing the computation of prices of options on the underlying water price with the aim of producing reference prices to catalyse an options trading market. The most suitable stochastic model representing the water price dynamics is selected through comparing the option prices generated from four different models. Using the selected stochastic model, the most liquid trading zone in the Murray–Darling Basin water market (Zone 7) is used to demonstrate how the methodologies developed in the paper are used to calibrate the log‐mean stochastic model representing the stochastic spot price dynamics and compute prices for call and put options on the underlying water spot prices. Sensitivities of the water options prices to market input data can be calculated from the formulae provided in the paper. The results presented in this work can serve as a reference tool by industry practitioners and the farming community in using options for effective risk management of water resources.

Research on whole-process covert attack method of liquid zone control system in a nuclear reactor

隐蔽攻击对核反应堆液体区域控制系统的安全运行构成了严重威胁. 然而, 隐蔽攻击的成功实施不仅需要掌握被攻击对象的精确模型, 而且很难在攻击完成后无痕退出. 为此, 本文针对核反应堆液体区域控制系统提出了一种四阶段全程隐蔽攻击方法. 首先, 在攻击筹备阶段, 通过最大似然估计离线设计最大似然形式下的双模<i>H</i>₂最优无偏FIR; 之后, 在状态估计阶段, 利用该FIR对攻击开始时刻的系统状态进行估算; 然后, 在攻击实施阶段, 结合预期攻击目的和系统当前状态设计攻击实施序列, 并将其注入至系统信号传输通道中, 实现隐蔽攻击; 最后, 在攻击退出阶段, 根据系统状态偏移量构建约束优化问题以给出最优攻击退出序列从而实现攻击退出过程的静默化. 此外, 本文基于系统噪声强度和攻击模型精度, 分情况对全程隐蔽攻击方法的可行性进行了仿真验证. 实验结果表明, 在上述影响因素单独或综合作用下, 所提攻击方法都能够隐蔽地完成攻击目标并无痕退出.

Novel electrolyte assisted ultralow-temperature zinc battery

Secondary battery is an indispensable component in energy storage as it can uninterruptedly store the energy and release it when being required. Among them, zinc (Zn) rechargeable battery gains much attention due to its cost advantage. However, poor climate adaptation much weaken the competitiveness, and temperature-induced deterioration can be mainly blamed on the slow reaction-kinetics of Zn anode under low temperature. Under this scenario, an anti-freezing electrolyte with Zinc (II)Bis(trifluoromethanesulfonyl)imide (Zn(TFSI)2) salt and ternary solvents of acetonitrile (AN), methyl acetate (MA) and dichloromethane (DCM) is proposed. It successfully broadens the working temperature of Zn secondary battery to − 90 °C. The elaborately regulated solvation can ensure smooth ion-transfer in liquid zone, more importantly, it expedites the desolvation without much affecting the interface transportation. With the optimized electrolyte configuration, reversible Zn plating/stripping at ultra-low temperature has been realized. The Zn|polytriphenylamine (PTPAn) battery thus can reserve 70 % capacity at − 80 °C, and present extremely stable cycling and impressive rate capability at − 80 °C and − 60 °C. The results well address the kinetics issues encountered in the low-temperature Zn secondary battery, and reveals that only with appropriate solvation, the high ion-permeability of the interface as well as easy de-solvation can be guaranteed. The work provides a guideline for designing advanced electrolyte, and supplies a reliable and effective strategy for the all-weather electrochemical energy storage.

Лазерне зміцнення інструментів та деталей обладнання ремонтних майстерень автомобільного транспорту в АПК

The purpose of this work is to study the effect of laser processing on the surface layers of alloys and to study their microstructure and features in order to improve their mechanical properties and increase the production resource of relevant tools and parts of equipment for repair shops of automobile transport in the agricultural sector. The effect of laser processing on the near-surface microstructure of alloys was studied. It is shown which steel will have the maximum hardness as a result of laser hardening among steels 40H13, 30H13 and 20H13. As a result of the change in the chemical composition, the levels of martensitic transformation points in the liquid state zones decrease, and a significant amount of residual austenite (40-60%), characterized by a dispersed structure, remains in them. This has a positive effect on the operational characteristics of irradiated products, especially when exposed to external shock loads. The optimal level of dissolution in R6M5, 9HS and HVG steels of initial carbides to obtain the maximum possible hardness during their laser processing was determined. The value of microhardness and heat resistance of bronze as a result of its laser hardening was investigated. Therefore, the influence of laser processing on the near-surface microstructure of alloys was investigated in order to improve their mechanical properties and increase the resource of production of appropriate tools and parts of automobile transport repair workshops equipment in the agricultural sector. It was determined that the maximum hardness is achieved in the case of hardening steel 40H13, since the carbon content in it is the highest compared to steels 30H13 and 20H13. Also, to obtain the maximum possible hardness during laser processing of R6M5 steel, it is enough to dissolve 30% of the original carbides and 60-70% for 9HS and HVG steels. Treatment of bronze by laser hardening made it possible to achieve values of microhardness up to 700 Hμ50, and heat resistance of the layer up to 350°С. The service life of products made of these laser-hardened alloys is increased by an average of 4-5 times compared to standard heat treatment.

Uncertainty propagation in the simulation of a nuclear power plant operational transient

With the continuous deployment of various intermittent energy sources on the grid there is an increasing opportunity for nuclear reactors to perform power maneuvers which can help alleviate issues related to supply oscillations during some periods of high renewable output. While utility specific codes can model such transients for safety assessments, there is a need to increase confidence in the application of these codes and to quantify the capabilities and accuracies of models in predicting these transients. In this work a power maneuver from 100 % full power to 59 % full power for a large CANDU reactor was studied using the TRACE-PARCS toolset. The work was computationally expensive as it examined both the effects of i) nuclear data library uncertainty which requires re-generation of the few-group cross sections and regeneration of an equilibrium core using 4 years of synthetic fuelling, and ii) initial core burn-up distribution involving the simulation of online fuelling operations over a period of 1400 days.The figures of merit considered in this work include changes in the average liquid zone controller fill level, individual channel powers, and the timing of adjuster bank withdrawals and reinsertions. Amongst the 100 s of simulated transients, the average time between adjuster bank withdrawals to override the Xenon transient and absolute standard deviations in these timings were found to be consistent between different nuclear datasets. The observed standard deviations were small, suggesting that the sensitivity to both nuclear data and initial core configuration is relatively small for both the adjuster withdrawal phase and the reinsertion phase. The contributions to total uncertainty due to both the core initial conditions and the nuclear data uncertainty were determined. During the early phase of the transient (i.e., adjuster withdrawals) nuclear data uncertainty and initial condition uncertainties were found to contribute nearly equally to total uncertainty, with slightly larger contributions due to nuclear data uncertainty. For adjuster bank reinsertions later in the transient it was observed that the contribution to total uncertainty by initial condition uncertainty was on average twice that of nuclear data uncertainties.The transients were compared to an actual power maneuver in a ∼900 MW CANDU reactor. In all cases, the model’s behaviour, while qualitatively correct, systematically over-predicted the time durations between adjuster movements and this difference exceeded the envelope of simulations that account for nuclear data and initial core configuration. Sensitivity studies performed to investigate the discrepancies suggest that additional refinements to the RRS emulator used in this work are required to match the station RRS more closely and that the transient evolution is highly sensitive to the initial excess reactivity in the core, which was observed to be lower in the station than in the TRACE simulations. Based on the simulation results the combined impact of the emulator responses, initial average zone levels, and incrementals modelling have a larger uncertainty than those related to nuclear data and initial core burnup distribution.

Integrating properties and conditions to predict spray performance of alternative aviation fuel by ANN model

Alternative aviation fuel has been confirmed benefits for GHGs reduction and energy saving. Alternative fuel use should meet drop-in fuel requirement, and one of the important factors to ensure combustion completeness is to achieve spray requirement in the whole envelop of flight. Alternative fuels are characterized different fuel properties at low temperature comparison with traditional jet fuel. For understanding fuel properties and spray-related processes under different conditions, alternative aviation fuel, including Fischer Tropsch (FT), cellulose hydrotreating jet fuel (CHJ) and traditional jet fuel (RP-3), were investigated spray performance. According to empirical equation deduced from experiment data (283 K-343 K), deviations to RP-3 enhanced significantly on surface tension and viscosity at low temperature aera (243 K-273 K). As the complex and discontinuous interaction between nozzle structure and fuel properties with temperature, and thus it is difficult to obtain appropriate empirical equation or simulation results at low temperature. Moreover, non-drop-in fuel like pure FT fuel cannot comply with the same spray mechanism as drop-in fuel. The artificial neural network (ANN) approaches have been involved to solve the complex relationship of properties with spray performance. ANN-spray model coupling with ANN-mass flow can predict not only cone angle and liquid length but also SMD and velocity in liquid zone and droplet zone with above 0.99 total correlation coefficient. Coupling simulation results of mass flow and spray performance, FT and CHJ as well as blend fuels present more obvious difference to RP-3 in droplet size distribution and velocity distribution at low temperature.

Model of a post-caldera volcano-hosted and vapor-dominated system through a numerical simulation study of the Bedugul geothermal field, Bali Island, Indonesia

To significantly increase the use of geothermal resources, describing geothermal systems in post-calderas is essential because this type of system is infrequent and has not yet been thoroughly researched. The Bedugul geothermal field (BGF), Bali Island, Indonesia, is a representative system with a complex structure composed of a vapor-dominated zone formed above a deep liquid reservoir. This study examines the BGF system and updates a conceptual model, particularly the fluid flow and heat transfer in the reservoir. A dual-porosity model and TOUGH2 EOS1 equation of state for water and steam module are used to simulate natural state conditions, including calderas with a domain area of 148.8 km2 and a thickness of 3.3 km. The BGF model was calibrated using the available geosciences data, temperature core holes and deep explorations wells and then evaluated statistically. A reliable natural state model with decent accuracy was obtained by optimizing the parameter calibration of the physical and structural properties of the reservoir model; the anisotropic and heterogeneous fracture permeability distribution and specific boundary conditions are crucial to the calculation accuracy. The BGF model reveals hot hydrostatic liquid, vapor-dominated, and transition zones and an overpressured liquid domain that is specific to a vapor-dominated geothermal system overlying a liquid reservoir. Occurrence of counterflow is also a noted feature in the vapor-dominated zone. Because of the high pressure in the steam zone, around 47 bar at a near-saturation temperature of 260 °C, the BGF is characterized as a premature field of a vapor-dominated system.

1G and microgravity tank self-pressurization: Research on cryogenic fluid thermal stratification

A correlation numerical model was constructed, and relevant experiments were simulated to investigate the influence of gravity level on the self-pressurization process of the cryogenic fluid of liquid nitrogen. The calculated results agreed well with the experimental data. On this basis, the influences of a normal gravity environment and a microgravity environment on the self-pressurization process of liquid nitrogen in the normal-temperature fluid Perfluoro-n-Pentane (PnP, or C5F12) tank of National Aeronautics and Space Administration (NASA) were analyzed. According to the calculation results, an explicit horizontal interface is formed between the gas and liquid phases in the tank during the 1G (G = 9.81 m/s2) self-pressurization process. The ullage pressure increases as time progresses, and obvious thermal stratification phenomena are observed in the ullage along the axial and radial directions. However, the thermal stratification of the liquid zone is not obvious. The ullage near the gas‒liquid interface shifts from counterclockwise movement to clockwise movement, while the liquid changes from clockwise movement to counterclockwise movement. In the process of microgravity self-pressurization, the gas‒liquid interface in the tank presents an irregular shape, and the ullage pressure increases continuously before 400 s and then tends to be stable. The axial thermal stratification of fluid in the tank tends to disappear as time progresses, but obvious radial thermal stratification is observed. The ullage in the tank moves up and down as a response to the Marangoni migration effect. The temperature of the liquid zone in the tank during 1G self-pressurization tends to be consistent more quickly than that during microgravity self-pressurization, and the average temperature is higher. However, the temperature reduction rate of the ullage in the tank during microgravity self-pressurization is higher than that during 1G self-pressurization. Numerical simulation results can provide references to further study the on-orbit pressure control technique of cryogenic liquid tanks.

Thermodynamic evaluation of viscosity behavior for CaO–SiO2–Al2O3–MgO slag systems examined at the temperatures range from 1500 to 1700 °C

This work showed an application of computational tools to understand systematically the behavior of viscosity on CSAM systems relevant to industrial uses. Consequently in this study, the viscosity experimental data obtained from the literature were compared with the thermodynamic calculated results via the software FactSage v.7.3 for melts in CaO–SiO2–Al2O3–MgO slag system with the range of compositions slags cover 0–100 wt% CaO, 0–100 wt% SiO2, 0–100 wt% Al2O3 and 0–15 wt% MgO at temperature ranges of 1500–1700 °C. Using open-source software in Python, the results of viscosity, liquid, and solid fraction of the slag, as a function of composition and temperature, are represented by multiple color maps and by iso-viscosity contours. The results of the viscosity values indicated that the effect of all the oxides in the CSAM slag system follows the well-known behavior trend observed in the literature. Viscosities of the slag were found to increase with increasing SiO2 contents and decrease with increasing basicities (high CaO). The increase in Al2O3 content increases the viscosity values. An increase of 0–15% MgO depolymerized the slag melt and decreases the viscosity. However, above 5% MgO content occur a decrease in the liquid zone (single phase) and a liquid fraction (two-phase region) of the slag. For a constant MgO concentration, the increase in temperature generates an expansion of low-viscosity zones associated with an increase in the liquid phase of the slag. From the comparison between the calculated and experimental viscosities data keeps up within 30% average relative deviation (Δ), the predictions are considered acceptable for viscosity in the CSAM slag system at high temperatures.

Influence of recoil pressure, mushy zone flow resistance and reflectivity on melt pool shape in laser powder bed fusion simulation

Melt pool dimensions (depth: D and width: W) are strongly correlated with defects generated in laser powder bed fusion. The melt pool dimensions have been evaluated by CFD simulation including solid–liquid–gas phase change and laser multiple reflection. Such a multi-physics simulation requires a large number of parameters. Preliminary simulations for parameter identification require a lot of time and effort. The parameter sensitivity to the melt pool dimensions is important; however, the systematic evaluations have hardly been found in the literature. In this study, we performed systematic parametric evaluation for three parameters related to recoil pressure, flow resistance in solid–liquid mushy zone and Fresnel laser reflection. As a result, the D values increased with increasing recoil pressure, but the W values did not. The flow resistance force influenced the velocities in the mushy zone but not the melt pool dimensions. The D increased with increasing reflectivity, but the W did not. The melt pool dimensions varying recoil pressure, flow resistance force and reflectivity were all inconsistent with the experimental melt pool dimensions. In order to agree with the experimental melt pool dimensions, the problems to be solved were discussed by comparing the previous studies.

Liquid crystal micro-Fresnel zone plate with fine variable focusing properties

This study presents a liquid crystal micro-Fresnel zone plate (LC-MFZP) with fine variable focusing properties. The LC-MFZPs are fabricated via photochemical processes without any mechanical process. The focusing properties are investigated through numerical simulations and experiments. LC-MFZPs can generate a focusing spot with a specific incident wavelength such that the transmitted phase difference between their adjacent ring zones is π rad. When this difference is changed by the electrical reorientation of the LCs, the focusing spot disappears because the diffraction condition is no longer satisfied. Subsequently, another focusing spot at a specific incident wavelength is generated to satisfy the diffraction condition. The positions of these focusing spots differ because the focal lengths depend on the incident wavelength. Consequently, LC-MFZPs can be used to electrically control the focal length. This study may find applications in optical manipulation and optical trapping.

Experimental study on sub-regimes of air-water slug flow in a rectangular micro-channel

In mini/micro-channel two-phase flow, slug flow occurs easily because of the significant influence of surface tension and the low gravitational effect on the flow. Although an irregularity of slug flow has been reported, previous studies on mini/micro-channel slug flow have mainly concerned the slug flow with the alternate of film and liquid slug zones regularly. Therefore, the present study investigates sub-regimes of micro-channel slug flow with regular or irregular alternating film and liquid slug zones to understand their principal characteristics. Experiments are performed to visualize and simultaneously measure the transient local pressure of the air-water mixture flow in a horizontal rectangular channel with a 2 mm height and 1 mm width. Superficial Reynolds numbers for liquid and gas phases range from 56 to 1116 and 5.75 to 245, respectively. With the aid of visualization data, slug flow is categorized into two types of stable slug flow and four types of unstable slug flow. Present slug flow data is compared with previous correlations for predicting the regime of bubble formation mechanism, flow regime boundaries, and frictional pressure gradient. Measured temporal pressure records are analyzed using a fast Fourier transform and digital Butterworth filter, while a dominant frequency is identified from the normalized average power spectrum. Then, the local pressure fluctuation at the dominant frequency is examined for different types of slug flow using the visualization results. A morphological repetition is confirmed to be associated with the pressure fluctuation: the repeated film and liquid slug zones in both types of stable slug flow, the alternative between liquid-only flow and a group of gas bubbles and liquid slugs in type 3 unstable slug flow, and the periodic variation of bubble length in type 4 unstable slug flow. However, no correlation between morphological characteristics and pressure fluctuation is found in type 1 and 2 unstable slug flows.

NUMERICAL SIMULATION OF THE PROCESS OF AERODYNAMIC SEPARATION OF FINE-GRAINED BULK MATERIAL

Various methods can be used to numerically simulate the aerodynamic separation of fine-grained bulk material, including discrete element methods, finite element methods, and bounded domain methods. In all these methods, these equations are solved numerically, and the results are used to determine the trajectories and velocities of air and particles. The Discrete Element Method (DEM), on the basis of which the study will be conducted, is designed for modeling the granular flow of materials. The purpose of the research is to simulate the movement of fine-grained loose material under the influence of air flow and calculate the parameters of its aerodynamic separation in the Simcenter STAR-CCM+ software package. The following were selected as physical models: gas, two-dimensional, separated flow, gradients, ideal gas, isothermal fluid energy equation, unsteady implicit, turbulent, Reynolds averaging of the Navier-Stokes equation, K-Epsilon turbulence model, admissible two-layer K-Epsilon, wall distance, double layer for any y+, gravity, Lagrangian multiphase, DEM discrete element model, multiphase interaction. As a result of the numerical simulation of the movement of fine-grained loose material under the influence of the air flow in the Simcenter STAR-CCM+ software package, the distribution of their components in the area of the separator was constructed. The following parameters were adopted as research factors: the diameter of the particles of the liquid fraction and impurities d, the particle supply speed f, the air flow speed v. Based on the results of the processing of the obtained data set in the Wolfram Cloud software package, the patterns of changes in the position of the intersection line of the distribution of two fractions (distance x) and the content of impurities δ in the liquid zone of separation from research factors were established. The presented detailed method of numerical modeling can be used to study other methods of separation of fine-grained loose materials.