Uneven Distribution Of Particles Research Articles

Neutralizing coffee-ring effect using gradual structures for uniform particle distribution

The coffee-ring effect is a process that takes place when a tiny drop of liquid-containing particles disappears, resulting in a distinct deposit around the edge of the spill resembling a ring. One of the primary causes of this effect is the uneven distribution of particles due to dissimilar evaporation rates on the droplet surface and contact line pinning effects. In this research, a microwell with a gradual structure has been developed to regularize the slippery Wenzel wettability of the surface and control the particle distribution. The mobility and pinning of droplet contact lines during the evaporation process are greatly influenced by this structure. The uniform curvature of the sidewall structure is predisposed to contact line depinning and thus helps the sliding of droplets to further neutralize the coffee-ring effect. Contact line pinning is predominantly observed at the corners of the structure, which are encircled by the ends and bottoms of the microwell's sidewalls. The curvature changes at this point, enhancing van der Waals' forces and resulting in a uniform monolayer of sediment being deposited at the microwell's bottom. The restraining efficacy of microwells of gradual structure on coffee rings with polystyrene spheres was confirmed, and the impact of microwell diameter, particle diameter, and loading efficacy on particle deposition distribution was investigated. The results show that the gradient configuration permits a single layer and even distribution of particles, enabling the sediment's dimensions to be anticipated and evaluated.

A Low-Cost, Tabletop LOD-EPR System for Nondestructive Quantification of Iron Oxide Nanoparticles in Tissues.

Iron oxide nanoparticles (IONPs) have wide utility in applications from drug delivery to the rewarming of cryopreserved tissues. Due to the complex behavior of IONPs (e.g., uneven particle distribution and aggregation), further developments and clinical translation can be accelerated by having access to a noninvasive method for tissue IONP quantification. Currently, there is no low-cost method to nondestructively track IONPs in tissues across a wide range of concentrations. This work describes the performance of a low-cost, tabletop, longitudinally detected electron paramagnetic resonance (LOD-EPR) system to address this issue in the field of cryopreservation, which utilizes IONPs for rewarming of rat kidneys. A low-cost LOD-EPR system is realized via simultaneous transmit and receive using MHz continuous-wave transverse excitation with kHz modulation, which is longitudinally detected at the modulation frequency to provide both geometric and frequency isolation. The accuracy of LOD-EPR for IONP quantification is compared with NMR relaxometry. Solution measurements show excellent linearity (R2 > 0.99) versus Fe concentration for both measurements on EMG308 (a commercial nanoparticle), silica-coated EMG308, and PEG-coated EMG308 in water. The LOD-EPR signal intensity and NMR longitudinal relaxation rate constant (R1) of water are affected by particle coating, solution viscosity, and particle aggregation. R1 remains linear but with a reduced slope when in cryoprotective agent (CPA) solution, whereas the LOD-EPR signal is relatively insensitive to this. R1 does not correlate well with Fe concentration in rat kidney sections (R2 = 0.3487), while LOD-EPR does (R2 = 0.8276), with a linear regression closely matching that observed in solution and CPA.

Pore structure regulation of hierarchically porous TiO2 ceramics derived from printable foams

Titanium dioxide (TiO2) is widely used as pollutants degradation material because of the effective photocatalytic capacity, while broad applications are limited due to their traditional forms for application involving as-received powders or coating on carrier. Herein, a novel method for hierarchically porous TiO2 ceramics with designable pores has been put forward, that is direct ink writing of printable particle-stabilized foams. The uneven particle distribution or low solid loading caused weak areas of particle self-assembly on pore wall during foaming, leading to fracture to form interconnected pore structure once grain growth happened during following sintering process. Both open and closed pore structure could be well controlled by adjusting powder composition, sintering temperature and solid loading. The prepared porous TiO2 ceramics possess homogeneous pores, high porosity of 81.76%, bulk density of 0.78 g/cm3 and compressive strength of 11.8 MPa, which can be readily exploited in filter component, catalyst supports, biological scaffolds, especially those with sophisticated shape.

Optimization of Lightly Calcined MgO Fluidized-Bed Roaster Jet Feed Structure Parameters

This work aims to improve the material segregation, bottom-of-furnace aggregation, and uneven particle distribution in the feeding area of a lightly calcined MgO airflow hearth roaster. A feeding structure type based on the jet is proposed, and a large cold experimental device with an 85 mm inner diameter and 3500 mm height is established based on the jet. Then the effects of different parameters on the flow characteristics of magnesite particles in the jet-feeding device of the lightly calcined MgO furnace are investigated. The experimental results indicate that the feeding structure based on the jet could not only improve the fluidization gas velocity and material segregation in the feeding area but also completely solve the bottom of furnace aggregation, enhancing the gas–solid mixing efficiency and improving the particle distribution uniformity. The optimized key structural parameters reveal that the best scheme for the jet feeding device is as follows: the nozzle distance is 225 mm, the nozzle diameter is 16 mm, and the length–diameter ratio is <2.

Effect of strain rate on fractography texture descriptor of AA6063/(Si3N4)x/(Cu(NO3)2)y (x=12%, y = 2–6%)composite after multiple ECAP passes: second order statistical texture analysis conjunction with regression analysis

The tensile strength of the ECAP processed composite of AA6063/(Si3N4)x/(Cu(NO3)2)y (x=12%, y=2-6%) at various strain rates from 0.0001 to 1s-1 with an increment of 10 was examined in relation to the seven-fracture image texture descriptor through void features such as void size and distribution. In order to measure the matrices of voids on the fracture surface created through the coalescence of void results to enhance the material hardening as strain rate increases, the second order statistical texture analysis has been used. With respect to the rising strain rate, it was observed that the composite fracture image feature parameter correlation, homogeneity improved by 6 %, and 20.74% for AA6063/12%Si3N4/6%Cu(NO3)2 after I passes as compared to AA6063/12% Si3N4 after III pass. The contrast was reduced by around 58.643% when reinforcement went from a single reinforcement of 12% Si3N4 with I Pass to a composite of two reinforcements (Si3N4, Cu(NO3)2) that had 6% Cu(NO3)2 with I Pass. After three passes on AA6063/12%Si3N4/2%Cu(NO3)2, the maximum entropy was seen due to the material's increased plastic deformation, which led to an uneven particle distribution. As strain rate and copper nitrate percentage grew from 0 to 6 percent, the tensile strength of the composite improved by 34.69%. To assess the importance of fracture image features in relation to tensile strength with respect to strain rate, a regression model was developed. In order to get information about the fracture studies from fractography, the contrast with varying strain rate was nevertheless the aspect, which had the greatest influence.

Comparative study on gas-particle transport characteristics subjected to the central and annular coaxial jets

The gas-particle transport characteristics subjected to the central and annular coaxial jets were investigated using particle image velocimetry (PIV) and optical fiber probe technologies. The powder transport behaviors, the distributions of particle velocity, concentration, fluxes, and turbulence properties, as well as the spatial variations of vortex structures and vorticity, were measured with various jet velocities. The results showed that the injection patterns significantly influence the transport characteristics of the gas-particle two-phase coaxial jets. Compared with the annular coaxial jets, the powder jet subjected to the central coaxial jets exhibits better momentum transfer and particle dispersion characteristics, leading to the acceleration and fluctuation in the axial and radial velocities of particles. Correspondingly, the vortex structures formed in the shear layer of the annular coaxial jets do not undergo pairing, coalescing, and breaking up into small-scale eddies as rapidly as the central coaxial jets, which significantly decreases the entrainment and turbulence intensity. The combing interactions of the recirculating entrainment and the wall effect result in the particle accumulation near the wall ( r / R = 0.83– 1). Although the uneven distribution of particles was observed in both coaxial jets, the radial profiles of particle concentration are more uniform in the central coaxial jets than in the annular coaxial jets. • The injection patterns showed a significant effect on powder transport behaviors. • The turbulence properties and the evolution of coherent structures were captured. • The central coaxial jet exhibited better momentum transfer and particle dispersion. • The near-wall accumulation of particles increases with gas jet velocity.

Texture analysis and physicochemical characteristics of fermented soymilk gel by different lactic acid bacteria

The high hardness and low water holding capacity (WHC) characteristics of fermented soymilk limit the consumer acceptance of its products. In this study, 4 strains were screened from 126 strains of lactic acid bacteria (LAB) for the fermentation of pure soymilk. The soymilk fermented by the 4 strains had different hardness and WHC levels but similar springiness and kinetic viscosity. Effect of the LAB hydrolyzing protein subunits (7S and 11S) on the particle size, zeta potential, microstructure and intermolecular force of fermented soymilk gel was studied. The results showed that the different degree of protein subunit hydrolysis would affect the particle distribution, zeta potential and intermolecular force in gel, resulting in the difference of microstructure and texture. Hydrophobic protein subunit (7S β subunit, 11S basic subunit) degraded by the LAB enhanced the electrostatic repulsion in the gel, resulting in uneven particle distribution and rough microstructure, which reduced WHC of the gel. When the contribution of hydrophobic force in gel was far greater than that of hydrogen bond, it was unfavorable to the WHC of gel. Hydrolysis of 11S subunit increased the cross-linking sites to raise the content of 20 μm particles and increased the large clusters in the microstructure of gel thus improving the hardness of gel. This study has explained the difference in hardness and WHC of soymilk gel fermented by LAB from a new perspective of protein subunit hydrolysis, and it will help to screen out LAB through protease characteristics to ferment soymilk with low hardness and high WHC.

CPFD Simulation of Gas-Solid Flow in Dense Phase Zone of Pant-Leg Fluidized Bed with Secondary Air

Aggregation of fluidization media may appear at the dense phase region of the pant-leg fluidized bed near the incline walls. When the particles flow along the inclined wall, the friction and drag force will cause the particles to accumulate on the inclined wall, resulting in an uneven distribution of particles. The stagnant zones can be minimized by correctly arranging secondary air. Computational particle fluid dynamics (CPFD) method was used to simulate the gas-solid two-phase flow pattern in the dense phase region of pant-leg fluidized bed. Cold tests were performed on a benchtop pant-leg fluidized bed. A high speed imaging technology was used to monitor the flow pattern in the dense phase area, whereas the bubble size and residence time were compared to verify the accuracy of the simulation. The gas-solid flow patterns under various models were simulated. The influence of different secondary air velocities on the reduction of stagnant zone in the dense phase zone of the fluidized bed were predicted. The results indicated that the introduction of secondary air could effectively promote the mixing of particles, and weaken the accumulation of particles on the inclined wall surface. Moreover, secondary air can effectively promote the flow between the gas-solid two-phases and improve the combustion characteristics in the furnace.

Dehydrated cement paste improves compressive strength of alkali-activated coal gangue

In this study, dehydrated cement paste (DCP) was used as a calcium source and solid dispersant for alkali-activated coal gangue (CG). The reaction mechanism of alkali-activated CG-DCP was revealed by detecting the compressive strength and microscopic properties of alkali-activated CG-DCP. The molecular structure characteristics of alkali-activated CG-DCP combined with the molecular dynamics were analysed. The results show that using DCP as the solid dispersant of CG could refine the particle size of CG, and improve problems of bonding and uneven distribution of particles caused by grinding. The addition of DCP could increase the calcium content in alkali-activated CG-DCP and promote the generation of more calcium silicate hydrate gel, thereby increasing its compressive strength. The secondary calcination of the CG-DCP composites could promote the release of calcium in the composites and increase the attraction force between particles in the alkali-activated CG-DCP molecular structure. The secondary calcination temperature of more than 900°C can lead to attraction force decrease and molecular structure instability in the molecular structure of alkali-activated CG-DCP, resulting in decreasing compressive strength.

CFD modeling of particle dispersion behavior in the MIKE 3 apparatus

A simulation investigation on the flow domain and particle movement pattern in the dispersion stage of dust explosion experiment were conducted using CFD simulation based on Euler–Lagrange approach. A new solver that couples two phases was developed based on the default solver rhoPimpleFoam from the OpenFOAM tool kit. Three sizes of particles 25 μm, 125 μm and 250 μm were simulated and studied. The simulation results of dust front propagation were evaluated by the experiment data. Particles with smaller diameters tended to move slower. Due to the high turbulence, flow vortices in the lower part of the dispersion domain were identified. These vortices gradually became larger with time and the decrease of inflow velocity. Uneven distribution of particles along with the equipment and high concentration of particles between the discharge electrodes were found in the simulation. Furthermore, particles with higher velocity favored the middle position in the tube. These facts suggested that the ignition delay time for particles larger than 125 μm should be higher than 60 ms.

Determination of Total Saccharide Content in Auricularia auricula Based on Near-Infrared Spectroscopy

In this paper, the content of total saccharide in Auricularia auricula from different regions was determined. Then, near-infrared (NIR) technology was used to collect the spectral information of the samples. The sample data were divided into calibration set and validation set. The best quantitative model of the total saccharide content of A. auricula was established by selecting the parameters such as spectral range, pretreatment method, and partial least square method (PLS) main factor number of the calibration set data. The validation set data were used to verify the reliability of this model. In this model, the original spectrum was used to preprocess by standard normal variate (SNV) + second derivative (SD) to eliminate the scattering effect caused by uneven particle distribution and the influence of noise on spectral data. The spectrum range was 4000–10000 cm−1, and the final choice of PLS main factor number was 11. Under this condition, the calibration set Rc2 of the model was 0.9092, the root mean square error of calibration (RMSEC) was 1.405, the root mean square error of prediction (RMSEP) was 1.507, and the residual predictive deviation (RPD) was 3.32. The validation samples were used to test the model, and the result showed that Rv2 = 0.9048 of the validation set. The result proved that the predicted value of the validation samples had a good linear relationship with the measured value. According to the T-test of the two sets of data in the validation set, the difference between the predicted value and the chemical value was not significant ( P ≥ 0.05). The results were in line with the expected objectives. The established NIR quantitative model can be used to predict the total saccharide content of the black fungus sample to be tested.

Numerical analysis and optimization of key parts in the stirred tank based on solid-liquid flow field

In order to further improve the mixing performance of the mixing device, the structure of the agitator was optimized, and the effects of the diameter and pitch of the agitator on the solid-liquid suspension characteristics were analyzed by single factor method. Multiple reference frame (MRF), computational fluid dynamics, Euler multiphase flow model and standard K- ε turbulence model were used to investigate the effect of the height from the bottom of the agitator on the suspension characteristics of particles in the agitator was studied. The results show that reducing the height from the bottom of the agitator can promote the suspension of particles at the bottom of the tank, but too low height from the bottom will easily produce mixing dead zone at the bottom of the tank, and cause the accumulation of particles. Reducing the height of the agitator from the bottom will enlarge the clear liquid area of the flow field, cause uneven particle distribution and increase the stirring torque. With the increase of agitator diameter, the critical suspension speed of the flow field decrease, but the stirring power required by the flow field increase. Increasing the blade spacing in a certain range can promote the suspension of particles and make the distribution of particles in the flow field more uniform. Therefore, the mixing power and the uniformity of particle concentration distribution need to be considered together in order to make the mixing device more efficient and energy-saving.

On taking into account the scattering angle when assessing the uneven distribution of particles in a high-speed two-phase flow by the laser sheet method

On taking into account the scattering angle when assessing the uneven distribution of particles in a high-speed two-phase flow by the laser sheet method

Synthesis and characterization of pyrite mineral from rock deposits in Bantimurung Maros Regency of South Sulawesi

The study has successfully obtained the mineral pyrite (iron pyrite persulfide) and Hematite (Fe2O3) of the natural resources in the Bantimurung District, Maros, South Sulawesi. The method used in this purification is the hydrothermal method. Based on the characterization results, it was obtained pyrite mineral with high purity (more than 90%). Based on the analysis, this material has a cubic structure P a -3 with lattice parameters a = 5.4167 Å and a space structure for the hematite group -R 32 c with lattice parameters a = 5.048 Å, b = 5.048 Å, and c = 13,762 Å. These results are consistent with the surface morphology characterized using SEM with various magnifications showing uneven particle distribution with a particle size of 5 µm-100 nm. The results of characterization and analysis of XRF and XRD show that the degree of crystallization and homogeneity of natural material deposits in Bantimurung are rich in iron, magnesium (Mg), sulfur (S), which appear with a high percentage, and high value minerals such as molybdenum (Mo) and neodymium with a low percentage. With this composition, the materials in Bantimurung have the potential to be used as photovoltaic coatings in solar cell applications, production of sulfur dioxide, paper industry, manufacture of sulfuric acid, semiconductor materials, and applications in sodium and lithium batteries.

Devising a model of the airflow with dust particles in the intake system of a vehicle’s internal combustion engine

This paper considers the mechanism of malfunction of internal combustion engines that implies the accelerated local wear of parts in individual cylinders as a result of uneven distribution of dust particles that pass through the air filter in the intake system. In order to acquire quantitative data on the effect of the structure of the intake system on the redistribution of dust in engine cylinders, the two-phase flow of air with dust particles in the standard elements of the intake system was mathematically modeled. ANSYS software package was used to solve the problem. A simulation technique was devised in which the airflow was first calculated to determine the boundary conditions for dust, after which the flow of air with particles was calculated. The calculations were carried out in a range of air velocities of 5‒20 m/s in branching channels with diversion angles of 45°, 90°, and 135° for the most characteristic particle sizes of 5‒30 µm. It has been estimated that dust particles deviate from the air streamlines by inertia and can slip through the lateral drain the stronger the larger particle size, diversion angle, and velocity of air. The comparison of the simulation results with experimental data confirmed that in the intake system of some engines, due to uneven particle distribution, there is local abrasive wear in one or more cylinders, which can significantly reduce the resource. This paper shows the need to take into consideration the centrifugation and redistribution of dust in the intake systems during the design, modernization, expert studies to determine the causes of faults associated with faulty operating conditions, as well as to clarify the regulations for the maintenance of existing engines.

Parallel load-balancing for combustion with spray for large-scale simulation

An asynchronous task-based Eulerian-Lagrangian approach for efficient parallel multi-physics simulations that can scale for arbitrary large number of particles and non-uniformly distributed particles is presented. The parallel methodology is based on a task-based partitioning of the multi-physics problem, where each single-physics problem is considered as a task and carried out using its own set of processes. This allows the two problems to solve their governing equations concurrently; therefore, hiding the computational cost incurred of solving an additional physical solver. Applications to complex breakup mechanism leading to highly dynamic computational loading and three-dimensional swirl combustion chamber with reacting flow/spray with extremely uneven particle distribution demonstrate the improved parallel efficiency and great potential of the presented approach.

Design and operation of a multi-stage reactor system for chemical looping combustion process

A chemical looping combustion (CLC) system with a multi-stage fuel reactor (FR) and a two-stage air reactor (AR), was constructed and operated in an experimental study and simulated via the computational particle fluid dynamics (CPFD) method. Hydrodynamic results with a bubble-based EMMS drag model agreed well with the experimental measurements. The wall effect in the small-scale AR led to an uneven particle distribution and irregular fluidization at a small NAR. The bubble size and velocity were limited in the FR, thereby significantly boosting the gas-solid contact. The particle residence time in the FR was prolonged, resulting in a high carbon capture rate. With the increase in fluidization number in FR and AR, the mass flux increased, but the residence time decreased. Adding a secondary gas flow in the FR has a positive impact on the solid circulation rate. The results in the thermal test indicated that a high CO2 capture rate and a low oxygen demand were achieved; thus the proposed reactor design improved the fuel conversion in the CLC process.

Effects of solid lubricant fillers on the flexural and shear strength response of carbon fabric-epoxy composites

Multi-layered carbon fabric-epoxy composites (CFEC) encounter certain challenges in expanding their usage mainly due to their low interlaminar shear strength (ILSS) and sensitivity to delamination damage. The present article focuses on evaluating the effectiveness of the fillers molybdenum disulfide (MoS2) and hexagonal boron nitride (h-BN) (2–8 wt%) on the flexural and the shear properties of the CFEC. The filler dispersion in epoxy resin is achieved by ultrasonication and composite fabrication through vacuum-assisted hand lay-up process. The filler surface area, evaluated as per nitrogen adsorption principles, reveals characteristics of hysteresis isotherm and mesoporous structure in both the fillers. Fourier transform infrared analyses on MoS2 reveal the stretch vibration due to molybdenum-sulfur and disulfide bonds whereas, in the h-BN, the transverse stretching and the out-of-plane bending happen due to boron-nitrogen and the boron-nitrogen-boron molecular group, respectively. Further analysis in the atomic force microscope shows more regular filler distribution at the outer surface for 4 and 6 wt% filler loaded CFEC whereas, 8 wt% filler loading results in an uneven particle distribution and attains the minimum surface roughness. The study exhibits the maximum ILSS (43.46 MPa) which is 43% enhancement compared to the neat CFEC for 6 wt% h-BN loaded CFEC. The maximum flexural strength (532 MPa) was noticed in 4 wt% MoS2 loaded CFEC signifying 62% improvement compared to the neat CFEC. The structural property improvements were witnessed because of the regularly distributed filler that strengthens the fiber-matrix interaction zone and reduces the matrix crack. The findings reveal that the proposed enhanced scheme by solid lubricant fillers proves to be more favorable for improving the matrix-dominated properties and the bending stiffness compared to the other particle-reinforced approaches.

Numerical Simulation of the Mixing and Hydrodynamics of Asphalt and Rubber in a Stirred Tank

Computational fluid dynamics (CFD) has been used to analyze the mixing process of Asphalt and Rubber (AR) in a stirred tank with a six flat-blade disc turbine (Rushton), a down-pumping 45° pitched-blade turbine (PBTD-6) and a down-pumping propeller (TXL). The two-phase (solid-liquid) flow in the considered stirred tank has been modelled in the framework of an Eulerian-Eulerian approach, a laminar-flow assumption and a multi-reference frame strategy. The following effects have been investigated: The influence of the impeller speed, impeller type, crumb rubber (CR) particle diameter and initial CR particle loading on the quality of the CR particle’s suspension. The outcomes of the numerical simulations have been found to be in good agreement with the experimental results. The most important findings can be summarized as follows. The flow velocity on the lower part of the stirred tank, induced by the Rushton impeller, is the highest for the three considered mixing systems at the same impeller speed. The suspension quality of CR particles increases with the impeller speed. A larger particle diameter and a higher initial CR particle loading lead to an uneven distribution of particles. The degree of homogeneity in the Rushton impeller system is better than that of the PBTD-6 impeller system and the TXL impeller system at the same impeller speed, while the suspension uniformity of the TXL impeller system is the best possible one for the same power consumption.

A simulation method for particle migration in microfluidic spirals with application to small and medium particle concentrations

This paper treats the separation of particles in microchannels relevant to biological and industrial process engineering. To elucidate the mechanisms creating uneven distribution of particles over the cross section, simulations are conducted with the particles being geometrically resolved and coupled to the fluid by an immersed-boundary method. In a first step, the method is validated for particle focusing in straight channels. Beyond validation, new information not previously available is reported for these cases. Next, an efficient approach is presented to simulate the motion of particles in spiral ducts of small curvature by means of a well-controlled set of approximate equations. It is applied here to situations with spherical particles and validated with reference data for inertial migration in curved channels achieving good agreement. The simulation data provide new rich information on the details of the separation process concerning migration time, particle positioning in the cross section, streamwise particle spacing, and velocity field of the continuous phase. For concentrations smaller than 1%, three different focusing modes are observed: single position, two symmetric positions, and periodic trajectories oscillating between two focusing points. Another set of results is obtained with particle concentrations up to 10% in a curved channel. Here, the spatial distribution of particles is determined in a statistical sense and related to the mean flow of the continuous phase. While focusing is reduced with increasing particle concentration, the distribution of particles is found to be still far from uniform up to the investigated concentration level.