It is of vital significance to investigate mass transfer enhancements for chemical engineering processes.This work focuses on investigating the coupling influence of embedding wire mesh and adding solid particles on b...It is of vital significance to investigate mass transfer enhancements for chemical engineering processes.This work focuses on investigating the coupling influence of embedding wire mesh and adding solid particles on bubble motion and gas-liquid mass transfer process in a bubble column.Particle image velocimetry(PIV)technology was employed to analyze the flow field and bubble motion behavior,and dynamic oxygen absorption technology was used to measure the gas-liquid volumetric mass transfer coefficient(kLa).The effect of embedding wire mesh,adding solid particles,and wire mesh coupling solid particles on the flow characteristic and kLa were analyzed and compared.The results show that the gas-liquid interface area increases by 33%-72%when using the wire mesh coupling solid particles strategy compared to the gas-liquid two-phase flow,which is superior to the other two strengthening methods.Compared with the system without reinforcement,kLa in the bubble column increased by 0.5-1.8 times with wire mesh coupling solid particles method,which is higher than the sum of kLa increases with inserting wire mesh and adding particles,and the coupling reinforcement mechanism for affecting gas-liquid mass transfer process was discussed to provide a new idea for enhancing gas-liquid mass transfer.展开更多
The influences of solid particles in leach solution on the formation of the third phase crud during solvent extraction of copper were studied. Analyzed from the point of view of pH value and surface tension, the study...The influences of solid particles in leach solution on the formation of the third phase crud during solvent extraction of copper were studied. Analyzed from the point of view of pH value and surface tension, the study results showed that the solid particle is one of the most important contributors for the formation of the third phase crud. During solvent extraction, if the pH value was greater than 2.30, the number of solid particles in the mother solution increased, in which case the possibility of forming the third phase crud could also increase, and the interface tension value might grow in pace with the quantity of the third phase crud.展开更多
Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type mi...Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type microemulison region, so it is the proper system to prepare Ce0.6Zr0.4O2 solid solution ultrafine particle. Some physical-chemical techniques such as TG/DTA, XRD, BET, and HRTEM are used to characterize the resultant powders. The results show that the fluorite cubic Ce0.6Zr0.4O2 solid solution is obtained at 400 ℃. The surface area is (146.7 m^2·g^-1), which is higher than the surface area for sol-gel prepared sample (59.5m^2·g^-1). HRTEM images indicated that the Ce0.6Zr0.4O2 solid solution ultrafine particle is well-crystallized, narrow size distribution, less agglomeration, within mean size of 5 -7 nm.展开更多
The forces on rigid particles moving in relation to fluid having been studied and the equation of modifications of their expressions under different flow conditions discussed, a general form of equation for discrete p...The forces on rigid particles moving in relation to fluid having been studied and the equation of modifications of their expressions under different flow conditions discussed, a general form of equation for discrete particles' motion in arbitrary flow field is obtained. The mathematical features of the linear form of the equation are clarified and analytical solution of the linearized equation is gotten by means of Laplace transform. According to above theoretical results, the effects of particles' properties on its motion in several typical flow field are studied, with some meaningful conclusions being reached.展开更多
The paper presents the experimental research findings for the patterns of collisions of water droplets with pressed tableted samples used as substrates and with small particles of a pyrolyzing solid fuel.Brown coal sa...The paper presents the experimental research findings for the patterns of collisions of water droplets with pressed tableted samples used as substrates and with small particles of a pyrolyzing solid fuel.Brown coal samples were used.Droplet-substrate interactions were studied when varying the droplet diameter in the range from 1 to 4 mm and velocity from 0.5 to 4 m/s.That corresponded to the Weber number range of 7-830.The coal tablet surface temperature was varied from 20 to 700℃.In the interactions of water droplets(0.7-1.5 mm in diameter,pre-collision velocity from 1 to 3 m/s)with coal particles(with a size of 0.2-1 mm,pre-collision velocity 0.7-2 m/s),the temperature of the latter was varied in the range of 330-480℃.The following regimes of the interaction of droplets with solid particles during chemical reactions and phase transformations were distinguished:spreading/agglomeration and break-up/separation.Differences in the characteristics of the interaction of water droplets with coal particles at varying temperatures were identified.Droplet-particle interaction regime maps for B(We),We(Oh)and We(Ca)were constructed.The collision regime boundaries were described using fitted curves that can be utilized to develop the existing mathematical models of droplet-particle collisions in gas.It was established that the gaseous volatile production in coal pyrolysis has a modest effect on the regimes and characteristics of the droplet destruction in the temperature range under consideration(20-700℃).展开更多
A test study on 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has been carried out in a specially designed discharge cabinet. A mechanical sieve is set up for sifting differen...A test study on 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has been carried out in a specially designed discharge cabinet. A mechanical sieve is set up for sifting different solid particles into the discharge space uniformly. The lightning impulse voltage according with international electro-technical commission (IEC) standard is applied to the electrodes inside the discharge cabinet by the rule of up-down method in a total of 40 times. The results showed that the 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has its own features and is much different from that in air.展开更多
In order to solve the fouling problems in boiling processes,a boiling system was designedby adding solid particles to the boiling liquid In this paper.both theoretical analyses andexperimental studies on the boiling h...In order to solve the fouling problems in boiling processes,a boiling system was designedby adding solid particles to the boiling liquid In this paper.both theoretical analyses andexperimental studies on the boiling heat transfer in such a three-phase flow boiling were carried out.Based on the analysis of heat transfer characters of this three-phase flow boiling,a mathematical mod-el for the heat transfer coefficient of flow boiling was developed.The experiments show that,in thepresence of particles the boiling heat transfer is enhanced and is about 2 times that of the vaporliquid two phase one with better flow stability.The fluidized particles rub the heat transfer wall toprevent and to clean the fouling.展开更多
Sand production is one of the main obstacles restricting gas extraction efficiency and safety from marine natural gas hydrate(NGH)reservoirs.Particle migration within the NGH reservoir dominates sand production behavi...Sand production is one of the main obstacles restricting gas extraction efficiency and safety from marine natural gas hydrate(NGH)reservoirs.Particle migration within the NGH reservoir dominates sand production behaviors,while their relationships were rarely reported,severely constrains quantitative evaluation of sand production risks.This paper reports the optical observations of solid particle migration and production from micrometer to mesoscopic scales conditioned to gravel packing during depressurization-induced NGH dissociation for the first time.Theoretical evolutionary modes of sand migration are established based on experimental observations,and its implications on field NGH are comprehensively discussed.Five particle migration regimes of local borehole failure,continuous collapse,wormhole expansion,extensive slow deformation,and pore-wall fluidization are proved to occur during depressurization.The types of particle migration regimes and their transmission modes during depressurization are predominantly determined by initial hydrate saturation.In contrast,the depressurization mainly dominates the transmission rate of the particle migration regimes.Furthermore,both the cumulative mass and the medium grain size of the produced sand decrease linearly with increasing initial methane hydrate(MH)saturation.Discontinuous gas bubble emission,expansion,and explosion during MH dissociation delay sand migration into the wellbore.At the same time,continuous water flow is a requirement for sand production during hydrate dissociation by depressurization.The experiments enlighten us that a constitutive model that can illustrate visible particle migration regimes and their transmission modes is urgently needed to bridge numerical simulation and field applications.Optimizing wellbore layout positions or special reservoir treatment shall be important for mitigating sand production tendency during NGH exploitation.展开更多
The failure of spur gears operating in highly contaminated media was studied. In fact, the effect of the presence of solid particles in gear mechanisms during surface tooth contact was observed. It is shown that the s...The failure of spur gears operating in highly contaminated media was studied. In fact, the effect of the presence of solid particles in gear mechanisms during surface tooth contact was observed. It is shown that the solid contaminants lead to significant wear in the first few operating cycles, in zones with a high rate of sliding. The scanning electron microscopy(SEM) images show clearly that the wear is more significant for a dry contact in the presence of larger size particles. Indeed, the presence of contaminants leads to an increase in friction, and therefore raises the temperature and the vibration levels when the operation of gear mechanism becomes very severe especially for a dry contact under the effect of larger size particles. On the other hand, we have tried to obtain a better understanding and a good description of wear debris distributions in gear mechanisms by using unimodal, single distribution models(Weibull and three-parameter Weibull).展开更多
The spatial stability equation of moving jet containing dense suspended solid particles was derived out by means of the continuum phase-coupled model. The stability curves of moving jet far different downstream distan...The spatial stability equation of moving jet containing dense suspended solid particles was derived out by means of the continuum phase-coupled model. The stability curves of moving jet far different downstream distances, Reynolds number of flow-field, particle properties and velocities of jetting device are got by the finite difference method based on the asymptotic method and the Eulerian conservative difference scheme. Founded on the analysis of the obtained stability curves it is found that the positive velocity of jetting device widens the unstable frequency range of flow-field hut the effect of the negative one is contrary. In addition, particles existing in the flow-field curb the instability of flow-field and the effect enhances with the decrease of Reynolds number of flow-field. These conclusions benefit learning the development of moving two-phase jet.展开更多
In order to study the settling mechanism of particles in an air-solid magnetically stabilized fluidized bed(MSFB) for separation,we carried out free settling and quasi-zero settling tests on the tracing particles.The ...In order to study the settling mechanism of particles in an air-solid magnetically stabilized fluidized bed(MSFB) for separation,we carried out free settling and quasi-zero settling tests on the tracing particles.The results show that the main resistance forces as the tracing particles settled in an air-solid MSFB were motion resistance force and yield force.The motion resistance and yield forces greatly hindered the free settling of the particles by greatly decreasing the acceleration for settling process of the particles.The acceleration decreased from 3022.62 cm/s 2 to zero in 0.1 s,and in the end,the particles stopped in the air-solid MSFB.The yield force on particles increased with increasing the magnetic field intensity,resulting in decrease of the quasi-zero settling displacement.However,the yield force on particles decreased with increasing the fluidized air velocity,leading to increase of the quasi-zero settling displacement.When the structure and operating parameters of the air-solid MSFB were set up,the yield stress on particles stopped in an air-solid MSFB was a function of diameter and density of particles.The settling displacements of equal diameter particles increased with increasing their densities,and the settling displacements of equal density particles increased with increasing their diameters.展开更多
Ultrafine particles prepared by evaporating pure Fe in CH4 atmosphere using arc-dischargeheating method, were found to consist of Fe-C solid solution, γ-Fe and Fe3C phases. EfFect of annealing temperature on phase tr...Ultrafine particles prepared by evaporating pure Fe in CH4 atmosphere using arc-dischargeheating method, were found to consist of Fe-C solid solution, γ-Fe and Fe3C phases. EfFect of annealing temperature on phase transformation and hyperfine interactions has been investigated by Mossbauer spectroscopy, X-ray diffraction (XRD), differential thermal analysis and thermogravimetry (DTA-TG), transmission electron microscopy (TEM), oxygen determination and vibrating sample magnetometer (VSM) measurements. It was observed that phase transformation of γ-Fe to α-Fe occurs during annealing in vacuum. The mechanism causing the change of hyperfine interactions with annealing temperature differs for Fe-C solution and interstitial compounds. DifFerence of hyperfine interactions of Fe-C solid solution in the starting sample and its annealed samples is ascribed to the improvement of activation of interstitial carbon atoms. Stress-relieving in structure of annealed Fe3C particle can result in a weak influence on hyperfine interactions. Parameters fitted to the Mossbauer spectra show the existence of superparamagnetism in all the samples. Absorbed and combined oxygen on particle surface of the starting sample were determined.展开更多
Many researchers in academia and industries are interested in reducing particle sizes from few submicrometers to nano-meter levels.These nano-particles find application in several areas including ceramics,paints,cosme...Many researchers in academia and industries are interested in reducing particle sizes from few submicrometers to nano-meter levels.These nano-particles find application in several areas including ceramics,paints,cosmetics,microelectronics,sensors,textiles and biomedical,etc.This article reviews the present state of the art for solid state synthesis of mineral nano-particles by wet milling,including their operating variables such as ball size,solid mass fraction and suspension stability.This article concludes and recommends with a critical discussion of nano-particles synthesis and a few common strategies to overcome stability issues.展开更多
The stability equation of interface of two-phase jet and the corresponding particle-gas disturbance velocity ratio equation are derived by means of the phase-coupled model. The stability nares of interface of two-phas...The stability equation of interface of two-phase jet and the corresponding particle-gas disturbance velocity ratio equation are derived by means of the phase-coupled model. The stability nares of interface of two-phase jet for different particle properties and the corresponding particle-gas disturbance velocity ratio curves are given out through numerical computation. Further, several important conclusions on effect of particle property on growth and propagation of disturbance of interface of two-phase jet and particle disturbance property me presented on the basis of analyses of the obtained stability curves and particle-gas disturbance velocity ratio curves. These important conclusions can play a guiding role in studying development of two-phase jet and executing artificial controls over it in project practice.展开更多
By considering the effect of suspended solid particles in the ordinary equations for two-dimension inviscid incompressible mixing layer, the Rayleigh equation and the modified Rayleigh equation are obtained. And then,...By considering the effect of suspended solid particles in the ordinary equations for two-dimension inviscid incompressible mixing layer, the Rayleigh equation and the modified Rayleigh equation are obtained. And then, by solving the corresponding eigen-value equations with numerical computational method, the relation curves between perturbation frequency and spacial growth rate of the mixing layer for the varying particle loading, ratio of particle velocity to fluid velocity and Stokes number are got. Sever al important conclusions on the effect of suspended solid particles on unstability of the mixing layer are presented in the end by analyzing all the relation curves.展开更多
C spin-lattice relaxtion times for polystyrene nanolatex particles have been investigated. It was found that the dramatic increase at 80℃ annealing temperature is well below the Tg temperature of bulk polystyrene, t...C spin-lattice relaxtion times for polystyrene nanolatex particles have been investigated. It was found that the dramatic increase at 80℃ annealing temperature is well below the Tg temperature of bulk polystyrene, the increase of relaxation time of aromatic carbons is larger than that of for aliphatic carbons at transition annealing temperature.展开更多
A test device with rectangular channel is developed to study the combustion performance of solid propellant in high temperature particles erosion.The flowfields in this newdevice and a test device with circular channe...A test device with rectangular channel is developed to study the combustion performance of solid propellant in high temperature particles erosion.The flowfields in this newdevice and a test device with circular channels are simulated numerically.The particle erosion experiments in these two devices are carried out under different particle concentrations.The results showthat the test device with rectangular channel can effectively improve the clarity and precision of combustion diagnosis image and can be used for research on combustion performance of solid propellant under lowconcentration particle erosion;the circular channel device has good particle convergent effect,provides high concentration particle erosion,and can be used for research on the combustion performance of solid propellant under high concentration particle erosion.The experiment data indicates that the propellant burning rate does not change obviously in lower particle concentration;the propellant with lower static burning rate increases remarkably under particle erosion,while the propellant with high static burning rate is not sensitive to the particle erosion.展开更多
An electronic particle size analyzer (Coulter Counter ZM) was utilized to quantitate the particulate microemboli, varying from 15 to 80μin size, during cardiopulmonary bypass. We confirmed the main causes of microemb...An electronic particle size analyzer (Coulter Counter ZM) was utilized to quantitate the particulate microemboli, varying from 15 to 80μin size, during cardiopulmonary bypass. We confirmed the main causes of microemboli were banked blood, cardiotomy reservoirs and oxygenators. Electronic microscopic examination showed that a large number of solid particles more than 20μin size were formed during heart-lung bypass, which obstructed microcirculation and damaged the pulmonary capillary endothelial and alveolar epithelial cells. The degree of histological damage was related to the number and size of microemboli and time of pulmonary microcirculatory obstruction.展开更多
Solid contamination existing as solid particles in power fluid transmission systems may lead to transmission performance reduction,system failures,and component damage.The hydraulic reservoir will deposit the contamin...Solid contamination existing as solid particles in power fluid transmission systems may lead to transmission performance reduction,system failures,and component damage.The hydraulic reservoir will deposit the contamination and store hydraulic fluid.To investigate its purification ability for solid contamination,experiments and simulations for the motion and deposition status of the typical hydraulic system particles are carried out to reveal the interaction of particles and fluid in hydraulic water reservoirs.The results show that the CFD-DEM coupling method could predict the accurate deposition position of iron particles and sand particles when ignoring the small-scale turbulence effect in the flow field.Besides,the particle motion traces and deposition patterns in the reservoir illustrate that the flow development on the bottom surface results in the particles turning,and particles tend to settle in the low flow energy position.The motion of particles is also linked to particles Stokes number,and the same-size sand particles are easily driven by the fluid.The contribution of this paper could provide a guide for predicting the particle motion and deposition pattern in the hydraulic reservoir.展开更多
Virtual mass force is an indispensable component in the momentum balance involved with dispersed particles in a multiphase system.In this work the accelerating motion of a single solid particle is mathematically formu...Virtual mass force is an indispensable component in the momentum balance involved with dispersed particles in a multiphase system.In this work the accelerating motion of a single solid particle is mathematically formulated and solved using the vorticity-stream function formulation in an orthogonal curvilinear coordinate system.The total drag coefficient was evaluated from the numerical simulation in a range of the Reynolds number(Re)from 10 to 200 and the dimensionless acceleration(A)between2.0 to 2.0.The simulation demonstrates that the total drag is heavily correlated with A,and large deceleration even drops the drag force to a negative value.It is found that the value of virtual mass force coefficient(CV)of a spherical particle is a variable in a wide range and difficult to be correlated with A and Re.However,the total drag coefficient(CDV)is successfully correlated as a function of Re and A,and it increases as A is increased.The proposed correlation of total drag coefficient may be used for simulation of solid–liquid flow with better accuracy.展开更多
基金supported by the Key Research and Development Plan of Shandong Province(the Major Scientific and Technological Innovation Projects,2021ZDSYS13)the Natural Science Foundation of Shandong Province(ZR2021MB135)Natural Science Foundation of Shandong Province(ZR2021ME224).
文摘It is of vital significance to investigate mass transfer enhancements for chemical engineering processes.This work focuses on investigating the coupling influence of embedding wire mesh and adding solid particles on bubble motion and gas-liquid mass transfer process in a bubble column.Particle image velocimetry(PIV)technology was employed to analyze the flow field and bubble motion behavior,and dynamic oxygen absorption technology was used to measure the gas-liquid volumetric mass transfer coefficient(kLa).The effect of embedding wire mesh,adding solid particles,and wire mesh coupling solid particles on the flow characteristic and kLa were analyzed and compared.The results show that the gas-liquid interface area increases by 33%-72%when using the wire mesh coupling solid particles strategy compared to the gas-liquid two-phase flow,which is superior to the other two strengthening methods.Compared with the system without reinforcement,kLa in the bubble column increased by 0.5-1.8 times with wire mesh coupling solid particles method,which is higher than the sum of kLa increases with inserting wire mesh and adding particles,and the coupling reinforcement mechanism for affecting gas-liquid mass transfer process was discussed to provide a new idea for enhancing gas-liquid mass transfer.
基金This study is financially supported by the "973" National Basic Research of China (No. 2004CB619206).
文摘The influences of solid particles in leach solution on the formation of the third phase crud during solvent extraction of copper were studied. Analyzed from the point of view of pH value and surface tension, the study results showed that the solid particle is one of the most important contributors for the formation of the third phase crud. During solvent extraction, if the pH value was greater than 2.30, the number of solid particles in the mother solution increased, in which case the possibility of forming the third phase crud could also increase, and the interface tension value might grow in pace with the quantity of the third phase crud.
文摘Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type microemulison region, so it is the proper system to prepare Ce0.6Zr0.4O2 solid solution ultrafine particle. Some physical-chemical techniques such as TG/DTA, XRD, BET, and HRTEM are used to characterize the resultant powders. The results show that the fluorite cubic Ce0.6Zr0.4O2 solid solution is obtained at 400 ℃. The surface area is (146.7 m^2·g^-1), which is higher than the surface area for sol-gel prepared sample (59.5m^2·g^-1). HRTEM images indicated that the Ce0.6Zr0.4O2 solid solution ultrafine particle is well-crystallized, narrow size distribution, less agglomeration, within mean size of 5 -7 nm.
文摘The forces on rigid particles moving in relation to fluid having been studied and the equation of modifications of their expressions under different flow conditions discussed, a general form of equation for discrete particles' motion in arbitrary flow field is obtained. The mathematical features of the linear form of the equation are clarified and analytical solution of the linearized equation is gotten by means of Laplace transform. According to above theoretical results, the effects of particles' properties on its motion in several typical flow field are studied, with some meaningful conclusions being reached.
基金supported by the Russian Science Foundation (project 18-71-10002-π,https://rscf.ru/en/project/21-71-03001/)。
文摘The paper presents the experimental research findings for the patterns of collisions of water droplets with pressed tableted samples used as substrates and with small particles of a pyrolyzing solid fuel.Brown coal samples were used.Droplet-substrate interactions were studied when varying the droplet diameter in the range from 1 to 4 mm and velocity from 0.5 to 4 m/s.That corresponded to the Weber number range of 7-830.The coal tablet surface temperature was varied from 20 to 700℃.In the interactions of water droplets(0.7-1.5 mm in diameter,pre-collision velocity from 1 to 3 m/s)with coal particles(with a size of 0.2-1 mm,pre-collision velocity 0.7-2 m/s),the temperature of the latter was varied in the range of 330-480℃.The following regimes of the interaction of droplets with solid particles during chemical reactions and phase transformations were distinguished:spreading/agglomeration and break-up/separation.Differences in the characteristics of the interaction of water droplets with coal particles at varying temperatures were identified.Droplet-particle interaction regime maps for B(We),We(Oh)and We(Ca)were constructed.The collision regime boundaries were described using fitted curves that can be utilized to develop the existing mathematical models of droplet-particle collisions in gas.It was established that the gaseous volatile production in coal pyrolysis has a modest effect on the regimes and characteristics of the droplet destruction in the temperature range under consideration(20-700℃).
基金National Natural Science Foundation of China.(No.50237010)
文摘A test study on 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has been carried out in a specially designed discharge cabinet. A mechanical sieve is set up for sifting different solid particles into the discharge space uniformly. The lightning impulse voltage according with international electro-technical commission (IEC) standard is applied to the electrodes inside the discharge cabinet by the rule of up-down method in a total of 40 times. The results showed that the 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has its own features and is much different from that in air.
文摘In order to solve the fouling problems in boiling processes,a boiling system was designedby adding solid particles to the boiling liquid In this paper.both theoretical analyses andexperimental studies on the boiling heat transfer in such a three-phase flow boiling were carried out.Based on the analysis of heat transfer characters of this three-phase flow boiling,a mathematical mod-el for the heat transfer coefficient of flow boiling was developed.The experiments show that,in thepresence of particles the boiling heat transfer is enhanced and is about 2 times that of the vaporliquid two phase one with better flow stability.The fluidized particles rub the heat transfer wall toprevent and to clean the fouling.
基金supported by the Laoshan Laboratory(No.LSKJ LSKJ202203506)the Taishan Scholars Program,and the National Natural Science Foundation of China(Grant No.41976074).
文摘Sand production is one of the main obstacles restricting gas extraction efficiency and safety from marine natural gas hydrate(NGH)reservoirs.Particle migration within the NGH reservoir dominates sand production behaviors,while their relationships were rarely reported,severely constrains quantitative evaluation of sand production risks.This paper reports the optical observations of solid particle migration and production from micrometer to mesoscopic scales conditioned to gravel packing during depressurization-induced NGH dissociation for the first time.Theoretical evolutionary modes of sand migration are established based on experimental observations,and its implications on field NGH are comprehensively discussed.Five particle migration regimes of local borehole failure,continuous collapse,wormhole expansion,extensive slow deformation,and pore-wall fluidization are proved to occur during depressurization.The types of particle migration regimes and their transmission modes during depressurization are predominantly determined by initial hydrate saturation.In contrast,the depressurization mainly dominates the transmission rate of the particle migration regimes.Furthermore,both the cumulative mass and the medium grain size of the produced sand decrease linearly with increasing initial methane hydrate(MH)saturation.Discontinuous gas bubble emission,expansion,and explosion during MH dissociation delay sand migration into the wellbore.At the same time,continuous water flow is a requirement for sand production during hydrate dissociation by depressurization.The experiments enlighten us that a constitutive model that can illustrate visible particle migration regimes and their transmission modes is urgently needed to bridge numerical simulation and field applications.Optimizing wellbore layout positions or special reservoir treatment shall be important for mitigating sand production tendency during NGH exploitation.
文摘The failure of spur gears operating in highly contaminated media was studied. In fact, the effect of the presence of solid particles in gear mechanisms during surface tooth contact was observed. It is shown that the solid contaminants lead to significant wear in the first few operating cycles, in zones with a high rate of sliding. The scanning electron microscopy(SEM) images show clearly that the wear is more significant for a dry contact in the presence of larger size particles. Indeed, the presence of contaminants leads to an increase in friction, and therefore raises the temperature and the vibration levels when the operation of gear mechanism becomes very severe especially for a dry contact under the effect of larger size particles. On the other hand, we have tried to obtain a better understanding and a good description of wear debris distributions in gear mechanisms by using unimodal, single distribution models(Weibull and three-parameter Weibull).
文摘The spatial stability equation of moving jet containing dense suspended solid particles was derived out by means of the continuum phase-coupled model. The stability curves of moving jet far different downstream distances, Reynolds number of flow-field, particle properties and velocities of jetting device are got by the finite difference method based on the asymptotic method and the Eulerian conservative difference scheme. Founded on the analysis of the obtained stability curves it is found that the positive velocity of jetting device widens the unstable frequency range of flow-field hut the effect of the negative one is contrary. In addition, particles existing in the flow-field curb the instability of flow-field and the effect enhances with the decrease of Reynolds number of flow-field. These conclusions benefit learning the development of moving two-phase jet.
基金supported by the National Natural Science Foundation of China (Nos. 51134022 and 51174203)the Key Project of Chinese National Programs for Fundamental Research and Development (No. 2012CB214904)+2 种基金the National Natural Science Foundation of China for Innovative Research Group (No. 50921002)the Natural Science Foundation of Jiangsu Province (No. BK2010002)the Fundamental Research Funds for the Central Universities (Nos. 2010QNB11 and 2010ZDP01A06)
文摘In order to study the settling mechanism of particles in an air-solid magnetically stabilized fluidized bed(MSFB) for separation,we carried out free settling and quasi-zero settling tests on the tracing particles.The results show that the main resistance forces as the tracing particles settled in an air-solid MSFB were motion resistance force and yield force.The motion resistance and yield forces greatly hindered the free settling of the particles by greatly decreasing the acceleration for settling process of the particles.The acceleration decreased from 3022.62 cm/s 2 to zero in 0.1 s,and in the end,the particles stopped in the air-solid MSFB.The yield force on particles increased with increasing the magnetic field intensity,resulting in decrease of the quasi-zero settling displacement.However,the yield force on particles decreased with increasing the fluidized air velocity,leading to increase of the quasi-zero settling displacement.When the structure and operating parameters of the air-solid MSFB were set up,the yield stress on particles stopped in an air-solid MSFB was a function of diameter and density of particles.The settling displacements of equal diameter particles increased with increasing their densities,and the settling displacements of equal density particles increased with increasing their diameters.
文摘Ultrafine particles prepared by evaporating pure Fe in CH4 atmosphere using arc-dischargeheating method, were found to consist of Fe-C solid solution, γ-Fe and Fe3C phases. EfFect of annealing temperature on phase transformation and hyperfine interactions has been investigated by Mossbauer spectroscopy, X-ray diffraction (XRD), differential thermal analysis and thermogravimetry (DTA-TG), transmission electron microscopy (TEM), oxygen determination and vibrating sample magnetometer (VSM) measurements. It was observed that phase transformation of γ-Fe to α-Fe occurs during annealing in vacuum. The mechanism causing the change of hyperfine interactions with annealing temperature differs for Fe-C solution and interstitial compounds. DifFerence of hyperfine interactions of Fe-C solid solution in the starting sample and its annealed samples is ascribed to the improvement of activation of interstitial carbon atoms. Stress-relieving in structure of annealed Fe3C particle can result in a weak influence on hyperfine interactions. Parameters fitted to the Mossbauer spectra show the existence of superparamagnetism in all the samples. Absorbed and combined oxygen on particle surface of the starting sample were determined.
文摘Many researchers in academia and industries are interested in reducing particle sizes from few submicrometers to nano-meter levels.These nano-particles find application in several areas including ceramics,paints,cosmetics,microelectronics,sensors,textiles and biomedical,etc.This article reviews the present state of the art for solid state synthesis of mineral nano-particles by wet milling,including their operating variables such as ball size,solid mass fraction and suspension stability.This article concludes and recommends with a critical discussion of nano-particles synthesis and a few common strategies to overcome stability issues.
文摘The stability equation of interface of two-phase jet and the corresponding particle-gas disturbance velocity ratio equation are derived by means of the phase-coupled model. The stability nares of interface of two-phase jet for different particle properties and the corresponding particle-gas disturbance velocity ratio curves are given out through numerical computation. Further, several important conclusions on effect of particle property on growth and propagation of disturbance of interface of two-phase jet and particle disturbance property me presented on the basis of analyses of the obtained stability curves and particle-gas disturbance velocity ratio curves. These important conclusions can play a guiding role in studying development of two-phase jet and executing artificial controls over it in project practice.
文摘By considering the effect of suspended solid particles in the ordinary equations for two-dimension inviscid incompressible mixing layer, the Rayleigh equation and the modified Rayleigh equation are obtained. And then, by solving the corresponding eigen-value equations with numerical computational method, the relation curves between perturbation frequency and spacial growth rate of the mixing layer for the varying particle loading, ratio of particle velocity to fluid velocity and Stokes number are got. Sever al important conclusions on the effect of suspended solid particles on unstability of the mixing layer are presented in the end by analyzing all the relation curves.
基金This work was supported by National Key Project for Fundamental Research (N.95-11) and National Natural Science Foundation of Ch
文摘C spin-lattice relaxtion times for polystyrene nanolatex particles have been investigated. It was found that the dramatic increase at 80℃ annealing temperature is well below the Tg temperature of bulk polystyrene, the increase of relaxation time of aromatic carbons is larger than that of for aliphatic carbons at transition annealing temperature.
基金Sponsored by the National Nature Science Foundation of China(50976095)
文摘A test device with rectangular channel is developed to study the combustion performance of solid propellant in high temperature particles erosion.The flowfields in this newdevice and a test device with circular channels are simulated numerically.The particle erosion experiments in these two devices are carried out under different particle concentrations.The results showthat the test device with rectangular channel can effectively improve the clarity and precision of combustion diagnosis image and can be used for research on combustion performance of solid propellant under lowconcentration particle erosion;the circular channel device has good particle convergent effect,provides high concentration particle erosion,and can be used for research on the combustion performance of solid propellant under high concentration particle erosion.The experiment data indicates that the propellant burning rate does not change obviously in lower particle concentration;the propellant with lower static burning rate increases remarkably under particle erosion,while the propellant with high static burning rate is not sensitive to the particle erosion.
文摘An electronic particle size analyzer (Coulter Counter ZM) was utilized to quantitate the particulate microemboli, varying from 15 to 80μin size, during cardiopulmonary bypass. We confirmed the main causes of microemboli were banked blood, cardiotomy reservoirs and oxygenators. Electronic microscopic examination showed that a large number of solid particles more than 20μin size were formed during heart-lung bypass, which obstructed microcirculation and damaged the pulmonary capillary endothelial and alveolar epithelial cells. The degree of histological damage was related to the number and size of microemboli and time of pulmonary microcirculatory obstruction.
基金National Key Research and Development Program of China(Grant No.2018YFB2000703)National Natural Science Foundation of China(Grant No.51975507).
文摘Solid contamination existing as solid particles in power fluid transmission systems may lead to transmission performance reduction,system failures,and component damage.The hydraulic reservoir will deposit the contamination and store hydraulic fluid.To investigate its purification ability for solid contamination,experiments and simulations for the motion and deposition status of the typical hydraulic system particles are carried out to reveal the interaction of particles and fluid in hydraulic water reservoirs.The results show that the CFD-DEM coupling method could predict the accurate deposition position of iron particles and sand particles when ignoring the small-scale turbulence effect in the flow field.Besides,the particle motion traces and deposition patterns in the reservoir illustrate that the flow development on the bottom surface results in the particles turning,and particles tend to settle in the low flow energy position.The motion of particles is also linked to particles Stokes number,and the same-size sand particles are easily driven by the fluid.The contribution of this paper could provide a guide for predicting the particle motion and deposition pattern in the hydraulic reservoir.
基金supported by the National Key Research and Development Program(2020YFA0906804)the National Natural Science Foundation of China(22035007,91934301)+1 种基金External Cooperation Program of BIC,Chinese Academy of Sciences(122111KYSB20190032)Chemistry and Chemical Engineering Guangdong Laboratory,Shantou(No.1922006).
文摘Virtual mass force is an indispensable component in the momentum balance involved with dispersed particles in a multiphase system.In this work the accelerating motion of a single solid particle is mathematically formulated and solved using the vorticity-stream function formulation in an orthogonal curvilinear coordinate system.The total drag coefficient was evaluated from the numerical simulation in a range of the Reynolds number(Re)from 10 to 200 and the dimensionless acceleration(A)between2.0 to 2.0.The simulation demonstrates that the total drag is heavily correlated with A,and large deceleration even drops the drag force to a negative value.It is found that the value of virtual mass force coefficient(CV)of a spherical particle is a variable in a wide range and difficult to be correlated with A and Re.However,the total drag coefficient(CDV)is successfully correlated as a function of Re and A,and it increases as A is increased.The proposed correlation of total drag coefficient may be used for simulation of solid–liquid flow with better accuracy.