Behavior Of Particles Research Articles

A feasible strategy for triboelectric separation of coal-series kaolin using a cascade electrostatic field

The coal-series kaolin in China possesses abundant resources, and its efficient utilization can be promoted by separation. In this paper, a cascade electrostatic field was designed for the triboelectric separation of coal-series kaolin. The motion behavior of charged particles with different size fraction in cascade electrostatic field was investigated by high-speed dynamic camera system, and the distribution characteristic of charge-to-mass ratio of products was analyzed by the coulometer. The influence of key operating parameters (e.g., feed speed, rotation speed and plate voltage) on product distribution were studied by electric separation test. The results indicated that the charge-to-mass ratio of the product after separation has the characteristics of cascade distribution. In addition, compared with 0.05–0.25 mm and 0.25–0.125 mm, the dispersion performance of 0.125–0.074 mm coal-series kaolin in the cascade electrostatic field was poor. For 0.5–0.25 mm, 0.125–0.25 mm and 0.074–0.125 mm coal-series kaolin, the decarburization efficiency after separation in cascade electric field was 47.09 %, 53.48 % and 44.63 %, respectively. Our study indicates that the setting of cascade electrostatic field achieved efficient purification and enrichment of coal-series kaolin.

The hazardous protective glass material for gamma, neutrons, and behaviors of charged particles: Results of adding barium oxide concentrations

The objective of this research is to examine the effectiveness of gamma and neutron shielding, as well as to investigate the behavior of charged particles in glass compositions with the formula xBaO:5SnO2:10Na2O:10CaO:10Li2O: (65-x)SiO2. These glass compositions will be created using the melt quenching technique (MQT). The findings indicated that the physical characteristics, such as density and molar volume, exhibited a comparable pattern. The gamma-ray shielding capacity of the glass system was assessed by comparing it with theoretical, simulation, and experimental values obtained using WinXCom, PHITS (Particle and Heavy Ion Transport Code System) Monte Carlo simulation, and Compton scattering technique (CST), respectively. The results revealed that the total attenuation (μm), effective atomic number (Zeff), and electron density (Nel) exhibited a consistent increase with higher BaO contents. Additionally, this increase led to a decrease in scattering energy within the Compton energy range. The half-value layer (HVL) exhibited superior shielding characteristics compared to alternative substances. Furthermore, the addition of more BaO atoms in the glass structure results in an increased ability of the material to stop the motion of charged particles with larger mass. Conversely, lower concentrations of BaO demonstrate an efficient barrier against fast neutrons. The simulation revealed that BaO can be utilized as an additive in glass materials to enhance their radiation shielding properties in environments with high levels of radiation.

Study of the behavior of dust particles in helium turbines considering the effects of particle deposition and resuspension

The deposition of graphite dust poses significant challenges to the helium turbines in high-temperature gas-cooled reactors. In this study, FLUENT, a Computational Fluid Dynamics (CFD) program was used with a discrete-phase model and a random-walk model to calculate the trajectories of particles (assumed spherical). Considering the interactions between particles and the wall as well as the resuspension effect of the fluid, a particle-deposition model was established and coupled to the flow-field calculations of blades with film cooling using user-defined functions. The influence of different deposition models, particle diameters, and blowing ratios on deposition were investigated. The results show rebounding and resuspending particles significantly affect the particle-deposition rate and its distribution. With increasing particle diameter, the deposition rate initially increases and then decreases. The influence of blowing ratio on deposition is complex; as the blowing ratio is increased, the deposition rate of small particles increases, while that of large particles decreases.

Assessing particle crushing mechanism and optimizing design for recycled aggregates in road bases via a novel particle crushing DEM method

This study introduced an innovative and effective algorithm that aims to provide a comprehensive simulation of particle crushing behavior in complex granular materials. Based on the Griffith's strength theory, the algorithm was formulated and implemented using the discrete element method (DEM). This algorithm accurately simulates the crushing behavior of real particles under arbitrary three-dimensional stress states. The robustness of the proposed method and the distribution pattern of the resulting child particles were verified through a series of single- and multi-particle crush tests. The findings demonstrate that the proposed approach exhibits exceptional generalizability, effectively describes the particle crushing behavior of granular materials, and features high efficiency and cost-effectiveness. The particle crushing simulations were conducted accordingly via DEM on a combination of natural gravel (NG), recycled mortar (RM), and recycled brick (RB) aggregates for use in road bases. The results revealed the particle crushing mechanisms in single-, binary-, and ternary-type recycled aggregate mixtures. Additionally, this study revealed the influence of recycled aggregate types on particle crushing within these different mixtures. The ternary design charts and tables were developed to determine the maximum contents of recycled aggregates in accordance with the particle crushing value requirements for different highway classes and aggregate base types. This study not only holds significant theoretical importance in developing efficient particle-crushing algorithms, but also offers valuable insights and scientific references for improving the resourceful utilization of recycled aggregates derived from construction and demolition wastes in road bases.

Experimental study on the leakage behavior of aerosol particles in capillary tubes

The leakage rate of aerosol particles is one of the most important parameters for source term evaluation of containment in severe accidents. In this study, gas leakage characteristics experiments were conducted on capillaries with different inner diameters and tube lengths under different pressure differential conditions. The effects of upstream and downstream pressure differential, capillary tube diameter, tube length, aerosol particle size, whether condensation or not, and release time on aerosol leakage rate were studied. The results show that when the pressure difference between the two ends of the capillary is greater than 0.2 MPa, the leakage rate of the capillary shows a pattern of first increasing and then decreasing with the increase of the pipe diameter; The influence of aerosol particle size on leakage rate mainly affects the inertial deposition effect, which increases with the increase of particle size, leading to a decrease in leakage rate; The condensation effect of steam in capillaries can lead to enhanced effects such as condensate capture, thermophoresis, and diffusion electrophoresis, which have a positive strengthening effect on the retention of aerosol particles.

Investigation of the Dominant Effects of Non-Spherical Particles on Particle–Wall Collisions

A deep understanding of the particle–wall collision (PWC) behaviors of non-spherical particles is important for managing gas–solid flows in industrial applications. It is important to identify the dominant parameters and to develop the common PWC prediction models for typical non-spherical particles. In this paper, different types of non-spherical particles were used to conduct the fundamental experiments. The effects of key parameters such as particle size, non-sphericity, wall roughness, and impact angle were analyzed. The results show that the trends of the collision coefficients with the impact angle for all non-spherical particles are similar. The dominant factors of particle–wall collisions are particle sphericity and wall roughness. A model with four parameters was fitted from the experimental data. The model can predict the collisions of non-spherical particles on rough steel walls with sizes ranging from 50 to 550 microns.

Full-scale study on the coupling settling behavior of droplets and PM10 particles based on the CLSVOF method and wetting experiments

Coal mines produce large quantities of dust during production and transportation of coal, especially respirable particulate matter of diameter < 10 µm (PM10). This not only jeopardizes the health of workers but also pollutes the environment. Currently, spraying is the most commonly used dust reduction technology. Traditional spraying techniques use pure water; however, the wetting and condensing of dust by pure water droplets is poor, resulting in low dust reduction efficiency. To address this issue, we used orthogonal tests to determine the optimal ratio of composite dust-reducing agents. Using the coupled level set and volume of fluid (CLSVOF) method, we investigated the dynamic wetting process of PM10 when using solutions of dust-reducing agents. We found that a particle size ratio of ≥ 2 and an initial velocity of droplets of 20–40 m/s resulted in optimal wetting and encapsulation of dust particles by droplets. We then conducted macroscopic experiments and found that the settling efficiency of PM10 reached 88.98 % when using a 1.5-mm caliber fine atomizing nozzle and a spray pressure of 6 MPa. Our findings reveal the dynamic wetting law of droplets and dust during the process of spray dust reduction, which could lead to improved efficiency of dust-reducing agents and better management of respirable dust. These findings will help to improve clean production in coal mines and the occupational health of coal miners.

Aggregation-Growth and Densification Behavior of Titanium Particles in Molten Mg-MgCl2 System.

In this work, the preparation of titanium sponge by magnesium thermal method is regarded as the liquid-phase sintering process of titanium, and powder-metallurgy sintering technology is utilized to simulate the aggregation-growth and densification behavior of titanium particles in a high-temperature liquid medium (the molten Mg-MgCl2 system). It was found that compared with MgCl2, Mg has better high-temperature wettability and reduction effect, which promotes titanium particles to form a sponge titanium skeleton at lower temperature. The aggregation degree of titanium particles and the densification degree of a sponge titanium skeleton can be improved by increasing the temperature and the relative content of Mg in the melting medium. The kinetics study shows that with the increase in temperature, the porosity of the titanium particle aggregates and the sponge titanium skeleton decreases, and their density growth rate increases. With the extension of time, the aggregation degree of titanium particles and the densification degree of sponge titanium gradually increase. This work provides a theoretical reference for controlling the density of titanium sponge in industry.

Numerical simulation and experimental investigation of the molten pool evolution and defects formation mechanism of Selective laser melted CuSn20/Diamond composites

Some defects such as small pores, thermal damage of diamond particle and micro-cracks between diamond and metal matrix existed in SLM-fabricated metal-bonded diamond tools. For further application, it is vital to understand the formation mechanism of such defects by SLM-fabricated parameters. In this work, a multiphysics field numerical simulation model based on computational fluid dynamics (CFD) was developed to investigate molten pool evolution and defects formation mechanism for SLM-fabricated CuSn20-bonded diamond composites. From simulation results, the metal particles melt and flow forward under the action of the laser. Also, the presence of diamond particles can obstruct the normal flow of melted CuSn20 fluid. Increasing the laser power can widen and stabilize the molten pool, however, exacerbate the thermal damage of diamond particles. Specially, the migration and marginalisation of the diamond particles during the formation of molten pool were found by simulation and experimental results. Unavoidably, there are obvious gaps in the interfacial bonding region of diamond and CuSn20 due to the comprehensive reasons of thermal gradient, differences in thermophysical properties of two materials and undergo continuous migration and rotational behavior of diamond particles. These findings have potential value for understanding and optimizing the process of SLM-fabricated metal-bonded diamond tools.

Transient behaviour analysis in silicon carbide alpha particle detector using TCAD and SRIM simulation

Time response characteristics of α particle detector are crucial for monitoring radiation fields varied with time and its characterization of pulse radiation field. Here, SRIM-informed TCAD simulation is utilized to visually investigate the transient behaviors of carriers and alpha particles in 4H-SiC Schottky barrier detectors for the time response characteristics. We identified external bias voltage and incident particle energy as key factors to influence transient current pulse broadening. Low-energy alpha particles result in low initial kinetic energy of the ionization-generated carriers, leading to transient current broadening and reduced time resolution characteristics. Conversely, high-energy alpha particles ionize carrier with high drift velocity, preventing the broadening effect. Our simulation provides a planform and valuable guidance for optimizing alpha particle detector, selecting appropriate bias voltages, and enhancing time resolution capabilities.

Inertial focusing of small particles in oscillatory channel flows

This study leverages the immersed boundary-lattice Boltzmann method to investigate the inertial focusing dynamics of a small neutrally buoyant particle in oscillatory channel flows driven by two distinct pressure gradient (PG) waveforms. Through an in-depth analysis of particle behavior, this research delineates the effects of PG waveforms, particle Reynolds number (Rep), and Womersley number (Wo) on the inertial focusing processes, and contrasts these findings with conventional Poiseuille flow-induced inertial focusing. Our results reveal that oscillatory flows induce more intricate focusing patterns than those observed in Poiseuille flow. The streamwise PG oscillation alters the particle focusing positions and introduces minor lateral oscillations in the post-focusing phase. The square PG waveform positions particles closer to the channel wall compared to Poiseuille flow, whereas the sine PG waveform positions particles closer to the channel center. Moreover, an increase in Rep nudges the focusing positions towards the channel center, while a higher Wo pushes them towards the walls. Notably, at Wo ≥ 5, the flow's oscillatory effect dominates over its inertial effect (i.e. Rep) on particle focusing. The study also underscores the capability of oscillatory flows to reduce the required channel length for particle focusing, albeit at the cost of increased focusing time. Contrary to Poiseuille flow, where the focusing length shortens with an increased Rep, oscillatory flow demonstrates an inverse correlation, with an increase in Rep extending the focusing length. Furthermore, while a higher Rep is beneficial in Poiseuille flow, it adversely affects the focusing effect in oscillatory flow. The focusing efficiency peaks at Wo = 3.5 for both waveforms, with the sine PG waveform offering superior efficiency due to the lower lift forces generated. Consequently, for optimal focusing in similar conditions, it is recommended to set Rep and Wo to 0.075 and 3.5, respectively.

Numerical Simulation of Hydrodynamics and Heat Transfer in a Reactor with a Fluidized Bed of Catalyst Particles in a Three-Dimensional Formulation

The hydrodynamics and heat transfer in a reactor with a fluidized bed of catalyst particles and an inert material were simulated. The particle bed (the particle density was 2350 kg/m3, and the particle diameter was 1.5 to 4 mm) was located in a distribution device which was a grid of 90 × 90 × 60 mm vertical baffles. The behavior of the liquefying medium (air) was modeled using a realizable k-ε turbulence model. The behavior of particles was modeled using the discrete element method (DEM). In order to reduce the slugging effect, the particles were divided into four separate horizontal layers. It was determined that with the velocity of the liquefying medium close to the minimum fluidization velocity (1 m/s), slugging fluidization is observed. At a velocity of the liquefying medium of 3 m/s, turbulent fluidization in the lowest particle layer and bubbling fluidization on subsequent particle layers are observed. With an increase in the velocity of the liquefying medium over 3 m/s, entrainment of particles is observed. It was shown that a decrease in the density of the liquefying medium from 1.205 kg/m3 to 0.383 kg/m3 when it is heated from 298 K to 923 K would not significantly affect the hydraulic resistance of the bed. Based on the obtained results, it can be stated that the obtained model is optimal for such problems and is suitable for the further description of experimental data.

Responses of colonization and development of periphytic biofilms to three typical tire wear particles with or without incubation-aging in migrating aqueous phases

Understanding the behavior of tire wear particles (TWPs) and their impact on aquatic environments after aging is essential. This study explored the characteristics of TWPs generated using different methods (rolling friction, sliding friction, and cryogenic milling) and their transformation after exposure to environmental conditions mimicking runoff and sewage, focusing on their effects on river water and periphytic biofilms. Laboratory experiments indicate that at low exposure levels (0.1 mg/L), TWPs promoted biofilm growth, likely due to zinc release acting as a nutrient and the aggregation of particles serving as biofilm scaffolds. However, at higher concentrations (100 mg/L), TWPs inhibited biofilm development. This inhibition is linked to toxic byproducts like N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone and environmentally persistent free radicals, which reduce biofilm biomass, alter algal diversity, and decrease the production of essential biofilm components such as proteins and polysaccharides, consistent with the inhibitory behavior of TWPs on bis-(3′-5′)-cyclic diguanosine monophosphate and quorum sensing signals, including acyl-homoserine lactone and autoinducer-2. Aging processes, particularly after simulated sewage treatment, further affect ecological impacts of TWPs, reducing the benefits observed at low concentrations and intensifying the negative effects at high concentrations. Contribution of here lies in systematically revealing the impact of TWPs on the development of aquatic biofilms, emphasizing the logical relationship between their aging characteristics, environmental behavior, and ecological risks. It assesses not only the release effects of typical additives and conventional size effects but also highlights the emerging photochemical toxicity (persistent free radicals), thus providing valuable insights into the aquatic ecological risk assessment of TWPs.

Effect of vibration and airflow on separation of 6–1 mm fine coal in compound dry separation bed

The segregation behaviour of solid particles are affected by airflow and vibration in a compound dry separation bed. The distribution characteristics of airflow field on the bed surface have been systematically investigated by a novel method of regional air distribution, and the movement and segregation behavior of fine coal particles have been observed under different gas velocity. Meanwhile, the spatial distribution characteristics and ash variation of fine coal particles during the process of segregation and stratification were analyzed. The obtained results show that the airflow velocity of the bed showed a zonal air distribution characteristic of gradual decrease from the separation area to the clean coal section and the gangue section. The segregation and stratification of particles in the Y-axis and Z-axis directions of the bed surface can be enhanced by vibration. When the vibration frequency is 34 Hz, the probable error (E) is 0.08 g/cm3. The bed inclination and the bed grid height have a certain influence on the segregation behavior of fine coal.

Effects of external field and potential on non-relativistic quantum particles in disclinations background

In this work, we investigate the behavior of non-relativistic quantum particles immersed in a cosmic string space-time background. Our study involves the examination of these particles as they interact with a range of influences, including potential, magnetic, and quantum flux fields. We employ analytical methods to solve the associated wave equation, leading to the derivation of eigenvalue solutions for this quantum system. Subsequently, we leverage these eigenvalue solutions to scrutinize several potential models. For each model, we present and engage in a thorough discussion of the corresponding eigenvalue solutions. In an extension of our investigation, we explore the thermodynamic and magnetic properties of the quantum system when it is exposed to non-zero temperature conditions, denoted by [Formula: see text]. Our analysis encompasses the calculation of essential parameters such as the partition function for the system and other pertinent functions. Following these calculations, we meticulously examine and interpret the outcomes, shedding light on the system’s behavior and characteristics in the presence of temperature variations. Furthermore, we calculate entropic information to investigate the location of particles in the system.

Achieving fully equiaxed grains with minor Sc addition of a novel Al-Li alloy fabricated by laser direct energy deposition

In this study, a novel Al-Li alloy with minor Sc addition was fabricated by laser directed energy deposition (LDED), resulting in a fully equiaxed grain structure. The precipitation behavior of primary Al3Sc particles was studied based on transient nucleation theory, and the results showed that sufficient heterogeneous nuclei by primary Al3Sc particles could preferentially form at initial solidification stage and induce into equiaxed grains. Besides, a large number of acicular T1 (Al2CuLi) phases and spherical Al3Sc phases, as well as rod-shaped TB (Al7Cu4Li) phases and quasicrystalline T2 (Al6CuLi3) phases, were distributed in as-built alloy that served as primary strengthening phases by thermal cycling. However, the specific nucleation behavior of α-Al grains on primary Al3Sc particles and subsequent growth behavior during rapid solidification need to be further investigated.

Influence of Coherent Vortex Rolls on Particle Dynamics in Unstably Stratified Turbulent Channel Flows

This work investigates the dynamics of heavy particles dispersed in turbulent channel flows under unstable thermal stratification conditions using point-particle direct numerical simulations (PP-DNS), to quantify the influence of large-scale coherent vortex rolls, arising from the combined effects of shear and buoyancy, on the spatial distribution and preferential sampling behavior of inertial particles. We examined three particle Stokes numbers (St+=0.6,60,120) and two friction Richardson numbers, Riτ=0.272 and Riτ=27.2, which exemplify the regimes below and above the critical condition for vortex roll formation, respectively. The results indicate that the flow reorganization into large-scale longitudinal vortices significantly alters the topological features of small scales in the near-wall region impinged by the thermal plumes, resulting in a prevalence of vorticity-dominated topologies. The interplay between this phenomenon and the tendency of particles to preferentially sample strain-dominated topologies leads to a distinctive asymmetric particle distribution in the near-wall planes. Inertial particles markedly accumulate in the strain-dominated regions where the coherent thermal plumes emerge from the walls, while avoiding the vorticity-dominated impingement zones. This peculiar particle response to the vortex rolls is most pronounced when the particle response time matches the characteristic timescale of the large-scale coherent motions in the cross-stream planes.

Hydrodynamic behavior of Janus particles in a finite inertial flow

Hydrodynamic behavior of Janus particles in a finite inertial flow is studied numerically using the lattice Boltzmann method (LBM) in the range of Reynolds number 0.05 ⩽ Re⩽ 10 and swimming parameter −3 ⩽ β ⩽ 3. Some results are validated by comparing with the existing results. The effects of Re, β on the hydrodynamic behavior of Janus particles are analyzed. The results show that the velocity of a pusher (a type of Janus particles) monotonically increases with the increase of Re, while the velocity of a puller (another type of Janus particles) exhibits a non-monotonic change. At high Re, the puller is unstable and presents a lateral displacement, while the pusher remains stable. The power consumption for the pusher and puller, the hydrodynamic efficiency for the pusher increase monotonically with increasing Re, while the hydrodynamic efficiency for the puller exhibits a non-monotonic change. At low Re, the power consumption and hydrodynamic efficiency of Janus particles exhibit symmetry with the variation of surface velocity distribution. This symmetry is disrupted with the increase of Re, similar to the velocity changing with the surface angle.

Fragmentation behavior of diamond particles with different particle size and ratio under high pressure compaction

The fragmentation behavior of mixed diamond particles with different grain sizes under high pressure is important to guide the design of raw material diamond powder ratios and obtain high performance polycrystalline diamond compact (PDC). In this study, five different grain size diamond powders commonly used for the preparation of PDCs were selected, and the single and mixed diamond particles were cold pressed at 7.7 GPa for 60s. The particle size variations of diamond powders with different principal particle sizes and ratios after cold pressing were analyzed by a laser particle size scanner, and the crushing behavior was observed by scanning electron microscopy. The results showed that the larger the initial grain size, the more significant the degree of fragmentation under high pressure. The crushing morphology of fine-grained diamond showed that the majority of grains were locally fractured at the edge, and the peak of the grain size distribution curve was shifted to the left after high pressure. In comparison, the coarse-grained diamond produced a large number of cracks and fractures along the weak grain boundaries under high pressure, which generated a large number of fine grains, and multiple secondary peaks in the particle size distribution curve. The addition of fine-grained diamond as filler particles to coarse-grained diamond could inhibit the crushing phenomenon to some extent. As the proportion of filler particles increased, the crushing of coarse-grained diamond was inhibited more significantly. When the proportion of filler particles was 30 wt%, the crushing under high pressure was greatly limited, especially when the size difference between filler particles and main particles was large. The results of the cold pressing experiments provided preliminary evidence that 30 wt% of filler particles were too high, and that a better ratio should be between 10 wt% and 20 wt%.

Dissolution behaviour of WC particles and evolution of precipitated phases in the plasma transfer arc Ni-based composite coating reinforced by 30 wt% WC particles

Ni-WC composite coating was prepared on Q235 steel substrate by plasma transfer arc (PTA) with welding current ranging from 70 A to 85 A. The results show that the dissolution behaviour of WC particles and the elemental diffusion at the interface promoted by the increased welding current promote the formation and evolution of precipitates, including M7(B, C)3 and M6C. The increased current reduced the volume fraction of WC particles in the coating, but increased that of the precipitates. At welding currents of 75 A and 80 A, dendritic-like M7(B, C)3 presented a regular distribution at the bottom of the coating. At a welding current of 80 A, M6C phase began to form at the bottom of the coating. When the welding current reached 85 A, the dendritic structure was broken, and the M6C phase aggregated and grew. The Ni-WC coating had visible delamination. WC particles at the upper part of the coating dissolved more severely compared to those at the middle and bottom of the coating. Ni3Si compound was formed at the upper and middle of the coating, and it had a crystal orientation relationship of [011]Ni3Si∥[011]γ-Ni, (11-1)Ni3Si∥(11-1)γ-Ni, (−200)Ni3Si∥(-200)γ-Ni, (-11-1)Ni3Si 1.3° from (-11-1)γ-Ni with γ-Ni. The average hardness of the coating decreased slightly due to the dissolution of WC, but the hardness at the interface increased, showing an improved bonding of the interface. The newly formed high hardness precipitates can share the load coming from the friction paired ball, thus reducing CoF and wear loss of the coating.