Microfluidic assisted 90%loading CL-20 spherical particles:Enhancing self-sustaining combustion performance

The performance of the chemical fuel determines the altitude,range and longevity of spacecraft in air and space exploration.Promising alternatives(e.g.,hypergolic ionic liquids or high-energy composites)with high-energy density,heat of formation and fast initial rate are considered as potential chemical fuels.As the high-energy density material,hexanitrohexaazaisowurtzitane(CL-20)often serves as secondary explosive with poor self-propagating combustion behaviors.Herein,90%loading CL-20 microspheres with uniform particle sizes are precisely prepared by microfluid method,which exhibit unique hierarchical structure.The morphology,thermal behaviors,as well as combustion performance were further investigated.The results demonstrated that as-prepared spherical particles exhibit prominent thermal compatibility,and the enhanced self-sustaining combustion performance.This work provides an efficient method achieving the uniform high-energy density particles with excellent self-sustaining combustion performance.

Effective Elastic Properties of 3-Phase Particle Reinforced Composites with Randomly Dispersed Elastic Spherical Particles of Different Sizes Dedicated to Professor Karl Stark Pister for his 95th birthday

Higher-order multiscale structures are proposed to predict the effective elastic properties of 3-phase particle reinforced composites by considering the probabilistic spherical particles spatial distribution,the particle interactions,and utilizing homogenization with ensemble volume average approach.The matrix material,spherical particles with radius a1,and spherical particles with radius a2,are denoted as the 0th phase,the 1st phase,and the 2nd phase,respectively.Particularly,the two inhomogeneity phases are different particle sizes and the same elastic material properties.Improved higher-order(in ratio of spherical particle sizes to the distance between the centers of spherical particles)bounds on effective elastic properties of 3-phase particle reinforced proposed Formulation II and Formulation I derive composites.As a special case,i.e.,particle size of the 1st phase is the same as that of the 2nd phase,the proposed formulations reduce to 2-phase formulas.Our theoretical predictions demonstrate excellent agreement with selected experimental data.In addition,several numerical examples are presented to demonstrate the competence of the proposed frameworks.

THE MOTION OF A SPHERICAL PARTICLE IN THE STOKES FLOW OUTSIDE A CIRCULAR ORIFICE

For any study ofa suspension entering a pore, the knowledge of the force and moment exerted on a solute particle in an arbitrary position outside the pore is essential, 'This paper for the first lime presents approximate analytical expressions (in closed form) of all the twelve force and moment coefficienis for a sphere outsied a circular orifice, on the basis of a number of discrete data computed by Yan et al(1987).These coefficients are then applied to calculate the trajectory and angular velocity of a spherical particle approaching the pore at zero Reynolds number. The trajectory is in excellent agreement with the available experimental results. An analysis of the relative importance of the coefficients shows that the rotation effect cannot be neglected near the pore opening or near the wall, and that the lateral force effect must be taken into account in the neighborhood of the edge of the pore opening. It is due to neglecting these factors that previous theoretical results deviate from the experimental ones near the pore opening. The effects of the ratio of the particle to pore radii as well as the influences of the graritytbuoyance on the particle trajectory, velocity distribution and rotation are discnssed in detail. It is pointed out that in the experiments of neutrally-buoyant suspensions, the restriction on the density of the particle is most demanding for a large particle size.The expressions of forces and moments presenled herein are complete, relatively accurate and convenient, thus providing a good prerequisite for further studies of any problems involving the entrance of particles to a pare.

Preparation of Spherical Tungsten Particles Assisted by Hydrothermal Method

We presented a strategy to prepare spherical tungsten powder by the combination of hydrothermal method and H2reduction process.In hydrothermal process,the micelle of tetraethylammonium bromide(TEAB)act as spherical templates for the deposition of tungsten oxide,whereas the excessive TEAB inhibit the formation of spherical tungsten oxide due to the dense molecular layer of TEAB on the tungsten oxide particles.Citric acid(CA)can control the formation rate and structure of the tungsten oxide when its concentration is more than 0.2 mol/L,because of its ability to coordinate with tungsten atoms.The synergistic effect of TEAB and CA facilitates the formation of spherical tungsten oxide with nanorod crown.After being treated by H_(2)at 600 and 650℃,the tungsten oxide particles are reduced to tungsten particles,which maintain the spherical structure of tungsten oxide and have porous structure.

Efficient approaches of determining the motion of a spherical particle in a swirling fluid flow using weighted residual methods

The motion of a spherical particle released in a swirling fluid flow is studied employing the least-squares method and method of moments. The governing equations are obtained and solved employing the two methods. The accuracy of the results is examined against the results of a fourth-order Runge-Kutta numer- ical method. The effects of various parameters, namely the initial radius, initial radial velocity, initial angular velocity, and drag-to-inertia ratio, on the non-dimensional velocity profiles and particle position distribution are considered. The results show that the radial velocity increases over time while the angular velocity decreases, and that an increase in the initial radial velocity increases the particle radial distance and angular velocity but decreases the radial velocity profile.

Settling behavior of spherical particles in vertical annulus:Experimental study and model development

Coiled tubing(CT)drilling technology offers significant advantages in terms of cost and efficiency for exploitations of unconventional oil and gas resources.However,the development of CT drilling technol-ogy is restricted by cuttings accumulation in the wellbore due to non-rotation of the drill string and limited circulating capacity.Cuttings cleaning becomes more difficult with the wall resistance of pipe-wellbore annulus on the cutting transport.Accurate description of particle transport process in the pipe-wellbore annulus is,therefore,important for improving the wellbore cleanliness.In this study,high-speed cam-era is used to record and analyze the settling process of particles in the transparent annulus filled with power-law fluids.A total of 540 tests were carried out,involving dimensionless diameters of 0.10-0.95 and particle Reynolds Numbers of 0.01-12.97,revealing the effect of the dimensionless diameter and particle Reynolds number on the annulus wall effect,and the wall factor model with an average relative error of2.75%was established.In addition,a dimensionless parameter,Archimedes number,independent of the settling velocity,was introduced to establish an explicit model of the settling velocity of spherical particles in the vertical annulus,with the average relative error of 7.89%.Finally,a calculation example was provided to show how to use the explicit model of settling velocity in annulus.The results of this study are expected to provide guidance for field engineers to improve the wellbore cleanliness of coiled tubing drilling.

3D CFD modeling of acetone hydrogenation in fixed bed reactor with spherical particles

Acetone hydrogenation in a fixed bed reactor packed with spherical catalyst particles was simulated to study the effects of inlet gas velocity and particle diameter on hydrogenation reaction. Computational results show that the catalyst particles in the reactor are almost isothermal, and the high isopropanol concentration appears at the lee of the particles. With the increase of inlet velocity, the outlet isopropanol mole fraction decreases, and the total pressure drop increases drastically. Small diameter catalyst particles are favorable for acetone hydrogenation, but result in large pressure drop.

Motion of a spherical particle in a fluid forced vortex by DQM and DTM

In this study, coupled equations of the motion of a particle in a fluid forced vortex were investigated using the differential transformation method （DTM） with the Pad6 approximation and the differential quadrature method （DO_M）. The significant contribution of the work is the introduction of two new, fast and efficient solutions for a spherical particle in a forced vortex that are improvements over the previous numerical results in the literature. These methods represent approximations with a high degree of accuracy and minimal computational effort for studying the particle motion in a fluid forced vortex. In addition, the velocity profiles （angular and radial） and the position trajectory of a particle in a fluid forced vortex are described in the current study.

Prediction of interphase drag coefficient and bed expansion using a variational model for fluidization of small spherical particles

In this study,we applied the variational model to fluidization of small spherical particles.Fluidization experiments were carried out for spherical particles with 13 diameters between dp=0.13 and 5.00 mm.We propose a generalized form of our variational model to predict the superficial velocity U and interphase drag coefficientβby introducing an exponent n to describe the different dependences of the drag force Fd on fluid velocity for different particle sizes(different flow regimes).By comparing the predictions with the experimental results,we conclude that n=1 should be used for small particles(dp<1 mm)and n=2 for larger particles(dp>1 mm).This conclusion is generalized by proposing n=1 for particles with Ret<160 and n=2 for particles with Ret>160.The average mean absolute error was 5.49%in calculating superficial velocity for different bed voidages using the modified variational model for all of the particles examined.The calculated values ofβwere compared with values of literature models for particles with dp<1.0 mm.The average mean absolute error of the modified variational model was 8.02%in calculatingβfor different bed voidages for all of the particles examined.

Light scattering based analyses of the effects of bovine serum proteins on interactions of magnetite spherical particles with cells

Information concerns endocytosis and autophagic effects of magnetite particles is crucial for understanding the particle-cell interactions. In this work, we investigated the effects of bovine serum proteins on the endocytosis of magnetite spherical particles（MSPs）. Autophagic effects of MSPs in breast cancer cells were studied. Light scattering based flow cytometry and microscopy were used for evaluating the uptake potential of MSPs by cells and the cellular autophagosome accumulation. Results showed bovine serum proteins significantly reduced the endocytosis of MSPs by decreasing their adsorption to cell membranes. Additionally, serum proteins had influences on the endocytic mechanisms of MSPs.Autophagosome accumulation could be caused by the internalized MSPs rather than the particles associated with cell membrane. Above fundamental findings promote our understandings upon the interactions of MSPs with cells. Light scattering based methods were proved to be simple and effective.The present work may promote their application in studies upon endocytosis of metallic particles in the future.

Unsteady sedimentation analysis of spherical particles in Newtonian fluid media using analytical methods

Unsteady settling behavior of solid spherical particles falling in water as a Newtonian fluid is investigated using a drag coefficient of the form given by Ferreira et al.Differential transformation method(DTM),Galerkin method(GM),collocation method(CM),and numerical methods are applied to analyze the characteristics of particles motion.The influence of physical parameters on terminal velocity is discussed and moreover,comparing the techniques,it is showed that GM and CM are very efficient for solving the governing equation and DTM with Padéapproximation has the best agreement with numerical results.The novelty of this work is introducing three simple and exact analytical method for solving the nonlinear equation of sedimentation and applied it in many industrial and chemical applications。

Behaviors of Spherical and Nonspherical Particles in a Square Pipe Flow

The lattice Boltzmann method(LBM)for multicomponent immiscible fluids is applied to the simulations of solid-fluid mixture flows including spherical or nonspherical particles in a square pipe at Reynolds numbers of about 100.A spherical solid particle is modeled by a droplet with strong interfacial tension and large viscosity,and consequently there is no need to track the moving solid-liquid boundary explicitly.Nonspherical(discoid,flat discoid,and biconcave discoid)solid particles are made by applying artificial forces to the spherical droplet.It is found that the spherical particle moves straightly along a stable position between the wall and the center of the pipe(the Segr´e-Silberberg effect).On the other hand,the biconcave discoid particle moves along a periodic helical path around the center of the pipe with changing its orientation,and the radius of the helical path and the polar angle of the orientation increase as the hollow of the concave becomes large.

Spherical YAG∶Ce^(3+) Phosphor Particles Prepared by Spray Pyrolysis

Spherical YAG：Ce^3＋ phosphor particles with narrow size distribution were prepared by spray pyrolysis. The effects of the concentration of solution, the flow rate of cartier gas and the annexing temperature on the phosphor morphology were studied. The productivity of precursor particles shows a trend of drop after rising with the increase of concentration Raising the flow rate of nitrogen can improve the productivity of the precursor particles. Phosphor prepared by spray pyrolysis has obviously higher emission intensity than that synthesized by solid state reaction, spray pyrolysis makes Ce^3＋ ions well distributed in the crystal lattice as the luminescent centers, and phosphor particles have regular sphericity and narrow size distribution.

Blockage of the Deep-Sea Mining Pump Transporting Large Particles with Different Sphericity

The present study aims to plumb blockage of the deep-sea mining pump transporting large particles with different shapes. A numerical work was performed through combining the computational fluid dynamics(CFD) technique and the discrete element method(DEM). Six particle shapes with sphericity ranging from 0.67 to 1.0 were selected. A velocity triangle is built with the absolute, relative, and circumferential velocities of particles. Velocity triangles with absolute velocity angles ranging from 90° to 180° prevail in the first-stage impeller. With declining sphericity, more particles follow the velocity triangle with absolute velocity angles ranging from 0° to 90°, which weakens the ability of particles to pass through the flow passage. Furthermore, the forces acting on the particles traveling in the impeller passage are analyzed. Large particles, especially non-spherical ones, suffer from high centrifugal force and therefore move along the suction surface of the impeller blades. Non-spherical particles undergo great drag force as a result of large surface area. The distribution of drag force angles is featured by two peaks, and one vanishes due to blockage.As particle sphericity declines, both magnitude and angle of the pressure gradient force decrease. Variation of the drag force and the pressure gradient force causes clockwise deflection of the centripetal force, resulting in deflection and elongation of particle trajectory, which increases the possibility of blockage.

THE EFFECTIVE MODULI OF COMPOSITE REINFORCED BY SPHERICALCOATING PARTICLES

The effective moduli of composite reinforced by spherical coating particles are investigated by the four phase spheroidal model and the theory of equivalent media. The theoretical predicting formulae of bulk modulus and shear modulus have been derived for this kind of composite in this paper. These formulae can reduce to the results of three phase spheroidal model which had been obtained by others for composite reinforced by particles.

A simple formula for predicting settling velocity of sediment particles

Based on the general relationship described by Cheng between the drag coefficient and the Reynolds number of a particle, a new relationship between the Reynolds number and a dimensionless particle parameter is proposed. Using a trial-and-error procedure to minimize errors, the coefficients were determined and a formula was developed for predicting the settling velocity of natural sediment particles. This formula has higher prediction accuracy than other published formulas and it is applicable to all Reynolds numbers less than 2× 10^5.

Experimental study on influence of blade angle and particle size on particle mechanics on a batch-operated single floor of a multiple hearth furnace

In industry,multiple hearth furnaces are used for the thermal treatment of particulate material.The current contribution concentrates on the experimental analysis of particle mechanics for a batch-operated single floor of a multiple hearth furnace.The particles are agitated on the circular floor by a single,rotating rabble arm equipped with three flat rabble blades of 10 mm thickness.The blade angle,defined as the angle,which the blade is inclined against the tangential direction,is varied from 0°to 90°.A single layer of spherical polyoxymethylene(POM)particles with three different diameters(5,10 and 20 mm)is placed on the floor.To analyze the results,two parameters have been extracted from image analysis when the bed of particles is agitated,first,the area not covered by particles and second,the frequency distribution of the mean distance among the particles.The particle free surface area increases with the inclination of the blades.The evolution of the particle free surface area differs for the different particle diameters.In general,the maximum particle free area for all blade angles is the largest for the 5 mm particles followed by the 20 mm particles.For the 10 mm particles,the particle free surface area starts for a blade angle of 0°at larger values than for the 20 mm particles but the values fall below the values for the 20 mm particles for larger blade angles.The reason for this behavior is discussed in detail.The mean distance among the particles is a parameter characterizing the length scales dominating the effects on the floor.The frequency distribution of the mean distance among particles provides infor-mation about the morphology of the particle bulk,for example,whether the free surface area is inter-spersed with particles.

Ray tracing particle image velocimetry-Challenges in the application to a packed bed

Ray tracing Particle Image Velocimetry(RT-PIV)is an optical technique for high resolution velocity measurements in challenging optical systems,such as transparent packed beds,that uses ray tracing to correct for distortions introduced by transparent geometries in the light paths.The ray tracing based correction is a post processing step applied to the raw PIV particle images before classical PIV evaluation.In this study,RT-PIV is performed in the top layer of a body centred cubic(bcc)sphere packing with gaseous flow,where optical access is obtained by the use of transparent N-BK7 glass balls with a diameter of d=40 mm.RT-PIV introduces new experimental and numerical challenges,for example a limited field of view,illumination difficulties,a very large required depth of field and high sensitivity to geometric parameters used in the ray tracing correction.These challenges and their implications are the main scope and discussed in the present work.Further,the validation of the ray tracing reconstruction step is presented and examples for the obtained corrected vector fields in a packed bed are given.The results show the strength of the method in reconstructing velocity fields behind transparent spheres that would not have been accessible by optical measurement techniques without the ray tracing correction.

High Cr(Ⅵ) adsorption capacity of rutile titania prepared by hydrolysis of TiCl4 with AlCl3 addition

Rutile titania(TiO2)was successfully prepared via hydrolysis of TiCl4 in the presence of AlCl3.The powders were characterized by X-ray powder diffraction(XRD),scanning electron microscopy(SEM),and Brunauer-Emmett-Teller(BET)surface area analysis.In the present system,AlCl3 functions as a nucleating agent and induces the formation of rutile TiO2.The influences of HCl and isopropanol concentrations on the purity and morphology of the rutile TiO2 were investigated.The purity of the rutile TiO2 increased with increasing concentration of HCl.Evenly dispersed rutile TiO2 particles with a spherical morphology were obtained when the HCl and isopropanol concentrations were 0.5 and 1 mol·L-1,respectively.Furthermore,the prepared TiO2 powders were used in adsorption tests of the heavy metal pollutant Cr(Ⅵ).Rutile TiO2 sample S-9 demonstrated greater adsorption performance and a removal efficiency that was greater than 99.95%after60 min of adsorption when the Cr(Ⅵ)concentration was 200 mg·L-1.The maximum adsorption capacity on rutile TiO2 was 28.9 mg·g-1.This work provides an easy path to prepare a high-performance rutile TiO2 adsorbent with potential applications in water pollution treatment.

Surface deformation under overlapping impacts of solid particles

To improve the accuracy of erosion prediction,the effect of subsequent particles impacting the same area while the first single particle rebounds from the substrate must be considered.This issue has rarely been considered in studies pertaining to erosion damage.In the present study,the ABAQUS software is used to investigate the erosion crater morphology and stress distribution on a target material subjected to overlapping impacts of spherical particles.Subsequently,the validated model is applied to investigate the effect of the overlapping impacts of particles on the target.Accordingly,the correlation between erosion severity and the impact locations of the two incident particles is quantified.The results show that the horizontal distance between two solid particle impact locations can significantly affect the erosion magnitude and pattern.The interactions of the resulting craters diminish when the horizontal distance exceeds 0.6 times the particle diameter.When the horizontal distance is approximately 0.06 times the particle diameter,the energy loss originating from collisions reaches the maximum,which modifies the crater morphology.The present study is expected to provide in-depth insights into erosion mechanisms and erosion modeling.