A self-developed forced convection rheoforming （FCR） machine for the preparation of light alloy semisolid slurry was introduced. The microstructure characteristics of 7075 aluminium alloy semisolid slurry at differe...A self-developed forced convection rheoforming （FCR） machine for the preparation of light alloy semisolid slurry was introduced. The microstructure characteristics of 7075 aluminium alloy semisolid slurry at different stirring speeds prepared by the FCR process were analyzed. The experimental results suggest that with the increase of the stirring speed, the mean grain size of the semisolid decreases and the shape factor as well as the number of primary grains increase. Meanwhile, the preparation process of semisolid slurry was numerically simulated. The flow characteristics of the melt in the device and the effect of the stirring speed on temperature field and solid fraction of the melt were investigated. The simulated results show that during the preparation process of semisolid slurry, there is a complex convection within the FCR device that obviously changes the temperature field distribution and solid fraction of the melt. When the convection intensity increases, the scope of the undercooling gradient of the melt is reduced and temperature distribution is improved.展开更多
Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional(3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of...Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional(3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of unsteady flow characteristics on solid-liquid two-phase flow and pump performance were researched under design condition. The results show that clocking effect has a significant influence on the flow in pump, and the fluctuation of flow velocity and pressure is obvious, particularly near the volute tongue, at the position of small sections of volute and within diffuser. Clocking effect has a more influence on liquid-phase than on solid-phase, and the wake-jet structure of relative velocity of solid-phase is less obvious than liquid-phase near the volute tongue and the impeller passage outlet. The fluctuation of relative velocity of solid-phase flow is 7.6% smaller than liquid-phase flow at the impeller outlet on circular path. Head and radial forces of the impeller are 8.1% and 85.7% of fluctuation, respectively. The results provide a theoretical basis for further research for turbulence, improving efficient, reducing the hydraulic losses and wear. Finally, field tests were carried out to verify the operation and wear of slurry pump.展开更多
It is difficult to temporally and spatially track and characterize the slurry viscosity in flowing water during grouting simulation.In this study,a sequential flow and solidification(SFS)method considering the spatial...It is difficult to temporally and spatially track and characterize the slurry viscosity in flowing water during grouting simulation.In this study,a sequential flow and solidification(SFS)method considering the spatial-temporal evolution of slurry viscosity in flowing water in karst conduit is proposed.First,a time-dependent model for the threshold function of slurry viscosity is established.During the grouting process,the spatial-temporal evolution of slurry viscosity is revealed by tracking the diffusion behavior of the slurry injected at different times.This method is capable of describing the gradual solidification process of the slurry during grouting.Furthermore,a physical model of grouting in a karst conduit is developed.Second,the effectiveness of the SFS method in grouting simulation is verified by the experiment of grouting conduit in flowing water.The SFS method enables real-time monitoring of fluid velocity and pressure during grouting in flowing water and provides a feasible calculation method for revealing the grouting plugging mechanism in complex karst conduits at different engineering scales.In addition,it can be used to guide the design of grouting tests in flowing water,improve cost efficiency,and provide theoretical basis for optimizing grouting design and slurry selection.展开更多
The particle simulation method is used to solve free-surface slurry flow problems that may be encountered in several scientific and engineering fields.The main idea behind the use of the particle simulation method is ...The particle simulation method is used to solve free-surface slurry flow problems that may be encountered in several scientific and engineering fields.The main idea behind the use of the particle simulation method is to treat granular or other materials as an assembly of many particles.Compared with the continuum-mechanics-based numerical methods such as the finite element and finite volume methods,the movement of each particle is accurately described in the particle simulation method so that the free surface of a slurry flow problem can be automatically obtained.The major advantage of using the particle simulation method is that only a simple numerical algorithm is needed to solve the governing equation of a particle simulation system.For the purpose of illustrating how to use the particle simulation method to solve free-surface flow problems,three examples involving slurry flow on three different types of river beds have been considered.The related particle simulation results obtained from these three examples have demonstrated that:1) The particle simulation method is a promising and useful method for solving free-surface flow problems encountered in both the scientific and engineering fields;2) The shape and irregular roughness of a river bed can have a significant effect on the free surface morphologies of slurry flow when it passes through the river bed.展开更多
To realize the technology of fabricating the rheologic semi-solid slurry of ZL112Y aluminum alloy via continues electromagnetic stirring process,ANSYS software was used to simulate electromagnetic force field and flui...To realize the technology of fabricating the rheologic semi-solid slurry of ZL112Y aluminum alloy via continues electromagnetic stirring process,ANSYS software was used to simulate electromagnetic force field and fluid velocity field in the alloy melt in a crucible tube in three coils.In the first section of the paper,eletromagnetic force field and fluid velocity field caused by single coil were simulated.The result of this simulation gives an average velocity of 3.2 cm/s and it is called critical velocity because a fluid velocity over it will cause a fine and spherical structure of solid primary a in a semi-solid melt.And,from this result,a reasonable temperature of semi-solid of the alloy and an electrical current intensity were established.The electrical current intensity of the result of this simulation corresponded to the current intensity used in a practice experiment,in which the primaryαwas obviously refined and sphericized.Based on this simulation of single coil electromagnetic stirring,in the second section of the paper,eletromagnetic force field and fluid velocity field caused by three coils were simulated.The result of the simulation shows that,1)there is a semi-solid zone of 32 mm from bottom of the crucible tube to the upper;2)the electrical current intensities of three coils of 400 A,600 A,and 400 A,which were set to top range,middle range and bottom range of the tube,respectively,were the optimum parameters of electromagnetic current intensity under the condition of this investigation;and 3)under effect of these electromagnetic current intensity,the fluid velocities of the melt in the tube were 6.3 cm/s in top range,3.75 cm/s in middle range,and 3.9 cm/s in bottom range of it,respectively.展开更多
X-ray fluorescence （XRF） in combination with partial least-squares （PLS） regression was employed to analyze the ore slurry grade. Using the Monte Carlo simulation code PENELOPE, X-ray fluorescence spectra of ore s...X-ray fluorescence （XRF） in combination with partial least-squares （PLS） regression was employed to analyze the ore slurry grade. Using the Monte Carlo simulation code PENELOPE, X-ray fluorescence spectra of ore samples were obtained. Good accuracy was achieved when this method was used to analyze elements with concentrations of several percent or above. It was demonstrated that the more the number of X-ray fluorescence spectra used to calibrate, the better the obtained accuracy. In this method detector resolution was found to have little or no effect on the results of quantitative analysis. The effect of the concentration of water was investigated as well, and it was found to have little influence on the results.展开更多
Aspen plus software was employed to simulate process. The system concludes gasification scrubbing system the opposed multi-burner gasifier （OMB） methanol production and purification shift system. The distributions o...Aspen plus software was employed to simulate process. The system concludes gasification scrubbing system the opposed multi-burner gasifier （OMB） methanol production and purification shift system. The distributions of ammonia con- centration in streams were obtained. The study demonstrates that ammonium crystallization problem caused by ammonia ac- cumulation, and if the process has ammonia exports its concentration will greatly reduced and the ammonia salt problem will effectively alleviate. Aspen plus simulation is a useful tool strengthening the ammonia recycling use and reducing pollutant for improving water quality, maintaining stable production, emissions.展开更多
The research on the multiphase flow characteristics of hydrate slurry is the key to implementing the risk prevention and control technology of hydrate slurry in deep-water oil and gas mixed transportation system.This ...The research on the multiphase flow characteristics of hydrate slurry is the key to implementing the risk prevention and control technology of hydrate slurry in deep-water oil and gas mixed transportation system.This paper established a geometric model based on the high-pressure hydrate slurry experimental loop.The model was used to carry out simulation research on the flow characteristics of gas-liquid-solid three-phase flow.The specific research is as follows:Firstly,the effects of factors such as slurry flow velocity,hydrate particle density,hydrate particle size,and hydrate volume fraction on the stratified smooth flow were specifically studied.Orthogonal test obtained particle size has the most influence on the particle concentration distribution.The slurry flow velocity is gradually increased based on stratified smooth flow.Various flow patterns were observed and their characteristics were analyzed.Secondly,increasing the slurry velocity to 2 m/s could achieve the slurry flow pattern of partial hydrate in the pipeline transition from stratified smooth flow to wavy flow.When the flow rate increases to 3 m/s,a violent wave forms throughout the entire loop.Based on wave flow,as the velocity increased to 4 m/s,and the flow pattern changed to slug flow.When the particle concentration was below 10%,the increase of the concentration would aggravate the slug flow trend;if the particle concentration was above 10%,the increase of the concentration would weaken the slug flow trend,the increase of particle density and liquid viscosity would weaken the tendency of slug flow.The relationship between the pressure drop gradients of several different flow patterns is:slug flow>wave flow>stratified smooth flow.展开更多
Slurry jets in a static uniform environment were simulated with a two-phase mixture model in which flow-particle interactions were considered. A standard k-e turbulence model was chosen to close the governing equation...Slurry jets in a static uniform environment were simulated with a two-phase mixture model in which flow-particle interactions were considered. A standard k-e turbulence model was chosen to close the governing equations. The computational results were in agreement with previous laboratory measurements. The characteristics of the two-phase flow field and the influences of hydraulic and geometric parameters on the distribution of the slurry jets were analyzed on the basis of the computational results. The calculated results reveal that if the initial velocity of the slurry jet is high, the jet spreads less in the radial direction. When the slurry jet is less influenced by the ambient fluid （when the Stokes number St is relatively large）, the turbulent kinetic energy k and turbulent dissipation rate e, which are relatively concentrated around the jet axis, decrease more rapidly after the slurry jet passes through the nozzle. For different values of St, the radial distributions of streamwise velocity and particle volume fraction are both self-similar and fit a Gaussian profile after the slurry jet fully develops. The decay rate of the particle velocity is lower than that of water velocity along the jet axis, and the axial distributions of the centerline particle streamwise velocity are self-similar along the jet axis. The pattern of particle dispersion depends on the Stokes number St. When St = 0.39, the panicle dispersion along the radial direction is considerable, and the relative velocity is very low due to the low dynamic response time. When St = 3.08, the dispersion of particles along the radial direction is very little, and most of the particles have high relative velocities along the streamwise direction.展开更多
In this paper,based on Fluent software,a five-nozzle gasifier reactor was established to simulate the gasification process of oil-based drill cuttings coal-water slurry.The influence of concentration and oxygen/carbon...In this paper,based on Fluent software,a five-nozzle gasifier reactor was established to simulate the gasification process of oil-based drill cuttings coal-water slurry.The influence of concentration and oxygen/carbon atomic ratio on the gasification process of oil-based drill cuttings coal-water slurry was investigated.The results show that when the oxygen flow is constant,the outlet temperature of gasifier decreases,the content of effective gas increases,and the carbon conversion rate decreases with the increase of concentration;When the ratio of oxygen to carbon atoms is constant,the effective gas content rises and the temperature rises with the increase of the concentration,and the carbon conversion rate reaches the maximum value when the concentration of oil-based drill cuttings coal-water slurry is 65%;When the concentration is constant,the effective gas content decreases and the outlet temperature rises with the increase of the oxygen/carbon atom ratio,and the carbon conversion rate reaches 99.80%when the oxygen/carbon atom ratio is 1.03.It shows that this method can effectively decompose the organic matter in oilbased drill cuttings and realize the efficient and cooperative treatment of oil-based drill cuttings.展开更多
The hot cracking tendency of 7075 semi-solid alloy under different conditions was studied by critical diameter method.The experiment and simulation results show that the dendrite arms of the rod grow from the edge to ...The hot cracking tendency of 7075 semi-solid alloy under different conditions was studied by critical diameter method.The experiment and simulation results show that the dendrite arms of the rod grow from the edge to the center.The smaller the diameter of the rod is,the more obvious the directional growth of dendrite is,and the greater the tendency of hot cracking is.Compared with ordinary melt,for semi-solid slurry,increasing mould temperature or decreasing pouring temperature can significantly decrease hot cracking tendency of 7075 alloy,decreasing hot cracking grade from 256 to 100 mm^2.Furthermore,based on the RDG criterion,the effects of solidification conditions on the hot cracking tendency were discussed combined with simulation.At the same time,the application and development of RDG criterion were also researched.展开更多
A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether （DME） from syngas, considering both the influence of part inert c...A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether （DME） from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows： diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger （Ф 38×2 mm）, and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.展开更多
The computational fluid dynamics （CFD）-population balance equations （PBE） coupled model is employed to investigate the hydrodynamics in a gas-slurry internal loop reactor with external slurry circulation. The pred...The computational fluid dynamics （CFD）-population balance equations （PBE） coupled model is employed to investigate the hydrodynamics in a gas-slurry internal loop reactor with external slurry circulation. The predicted radial profiles of local gas holdup and bubble diameter are in good agreement with the corresponding experimental data. The spatio-temporal velocity profile of the gas phase reveals that the upward movement of gas is slowed down and the residence time of gas is prolonged by the downward momentum of the slurry, introduction of the external slurry can greatly improve the uniformity of gas holdup distribution in the reactor, especially in the downcomer-tube action region. Moreover, the interaction between the downward slurry and upward gas can lead to small bubble size and high interfacial area as well as good mass and heat transfer. The above results suggest the function of external slurry circulation for the internal loop reactor and would be helpful for optimizing the design and scale up of reactors.展开更多
Preparation of semisolid slurry using a cooling slope is increasingly becoming popular,primarily because of the simplicity in design and ease control of the process.In this process,liquid alloy is poured down an incli...Preparation of semisolid slurry using a cooling slope is increasingly becoming popular,primarily because of the simplicity in design and ease control of the process.In this process,liquid alloy is poured down an inclined surface which is cooled from underneath.The cooling enables partial solidification and the incline provides the necessary shear for producing semisolid slurry.However,the final microstructure of the ingot depends on several process parameters such as cooling rate,incline angle of the cooling slope,length of the slope and initial melt superheat.In this work,a CFD model using volume of fluid(VOF) method for simulating flow along the cooling slope was presented.Equations for conservation of mass,momentum,energy and species were solved to predict hydrodynamic and thermal behavior,in addition to predicting solid fraction distribution and macrosegregation.Solidification was modeled using an enthalpy approach and a volume averaged technique for the different phases.The mushy region was modeled as a multi-layered porous medium consisting of fixed columnar dendrites and mobile equiaxed/fragmented grains.The alloy chosen for the study was aluminum alloy A356,for which adequate experimental data were available in the literature.The effects of two key process parameters,namely the slope angle and the pouring temperature,on temperature distribution,velocity distribution and macrosegregation were also studied.展开更多
The motion forms（deformation） of the sliding soil along the slope include inviscid particle flow,viscous particle flow,and mass sliding.The motion forms were mainly influenced by the mechanical properties of the vis...The motion forms（deformation） of the sliding soil along the slope include inviscid particle flow,viscous particle flow,and mass sliding.The motion forms were mainly influenced by the mechanical properties of the viscous mud medium filling.The effect of the medium filling on the motion forms of the sliding soil is worth discussing.The sliding soil can be seen as the mixture which is composed of the medium filling and coarse particles.The Chengdu clay with different moisture contents were selected as the medium filling.Their mechanical parameters were experimentally measured for simulating the moving process of the sliding soil.Different motion forms of the sliding soil were numerical simulated based on PFC3D by changing the specific mechanical parameters.The mechanical parameters of the Chengdu clay are experimentally determined.The numerical results show that with the moisture content of the filling slurry medium in the range of 〉302%,101%~182%,and 〈80%,the motion form of the sliding soil belongs to the inviscid particles flow（similar with the sliding sand）,viscous particles flow（seen as the viscous flows）;and masssliding（seen as the block sliding along the slope surface）,respectively.展开更多
The numerical simulation program of PFC2D(Particle Flow Code in 2 Dimension)particle flow based on the flow-solid coupling principle and,on its built-in FISHTANK function library and FISH language,defines the flow equ...The numerical simulation program of PFC2D(Particle Flow Code in 2 Dimension)particle flow based on the flow-solid coupling principle and,on its built-in FISHTANK function library and FISH language,defines the flow equation and pressure equation of fluid domain respectively,and carries out numerical simulation calculations on the diffusion process and,on the morphology and particle displacement of slurry during the slurry injection process.By adjusting the parameters of hist,n_bond,s_bond and measure in the PFC command flow,the tracking of granular body displacement changes is achieved,and the mesoscopic mechanism such as the diffusion law of soil slurry at different depths and the change of formation porosity is revealed.The numerical calculations show that:the grouting pressure has a significant effect on the alteration and destruction of the formation structure,and the fracturing effect becomes gradually worse with increasing adhesive strength,while the porosity increases significantly with increasing grouting pressure.Based on the elastic-plastic theory of the Mohr-Colomb criterion to theoretically derive the stress field of the soil around the borehole,it is pointed out that the mechanical mechanism of annular tension and radial compression is the fundamental reason for the appearance of fracturing grouting action mode.The increase of slurry viscosity is beneficial to improve the grouting effect of fracturing-compacting grouting,while the increase of friction coefficient has little effect on the grouting effect.The comparative analysis of the laboratory tests shows that the PFC2D simulation of the grouting process is feasible.展开更多
The suspension characteristics of ultrafine powder slurry in the stirred vessel were simulated by using computational fluid dynamics.The results show that the Rushton disk turbine impeller is more conducive to maintai...The suspension characteristics of ultrafine powder slurry in the stirred vessel were simulated by using computational fluid dynamics.The results show that the Rushton disk turbine impeller is more conducive to maintaining suspended homogeneity and circulation of slurry compared with the pitch blade turbine pumping up impeller and the pitch blade turbine pumping down impeller.And the increase in stirring speed enhances turbulent fluctuation and anisotropic velocity of the fluid at the cost of more power consumption,which improves dispersibility and suspensibility of the particles.Meanwhile,the change of impeller clearance has a weak influence on the flow pattern,and the impeller clearance of 0.32T(T is the diameter of the bottom of the reactor)can achieve better dispersivity and suspensibility of the particles with lower power consumption and larger axial velocity.The experiments of surface coating modification of ultrafine titanium dioxide(TiO2)were carried out under the same conditions for those of the simulation system.The surface film morphology and photocatalytic properties of the modified TiO2 were analyzed,and the obtained data are well consistent with the simulation results.展开更多
Erosion in slurry pumps presents a persistent challenge in industrial applications.This study examines the erosion of the static components of a 150ZJ-C42 centrifugal slurry pump,currently in operation at a beneficiat...Erosion in slurry pumps presents a persistent challenge in industrial applications.This study examines the erosion of the static components of a 150ZJ-C42 centrifugal slurry pump,currently in operation at a beneficiation plant,under varying particle conditions.Utilizing high-precision three-dimensional reverse engineering,the pump’s flow passage geometry was reconstructed to facilitate detailed erosion analysis.Focusing on the front and rear baffles of the pump chamber,as well as the volute,erosion patterns were analyzed for different particle volume concentrations and sizes.The results reveal that the highest erosion damage consistently occurs near the volute tongue,with wear being most severe in regions adjacent to the partition plate near the rear cover.Erosion damage intensity in this area correlates positively with particle diameter.Notably,the average erosion rate in the volute surpasses that of the front and rear chamber liners,reaching a value as high as 6.03×10^(-7)kg·m^(-2)·s^(-1)at a particle concentration of 9%and diameter of 0.1 mm,adversely impacting pump stability.For the pump chamber baffles,increased erosion is observed at a particle diameter of 0.05 mm under constant volume concentration conditions,while higher particle concentrations exacerbate localized erosion.展开更多
基金Project (2011CB606302-1) supported by the National Basic Research Program of ChinaProject (2013AA031001) supported by Hi-Tech Research and Development Program of China
文摘A self-developed forced convection rheoforming （FCR） machine for the preparation of light alloy semisolid slurry was introduced. The microstructure characteristics of 7075 aluminium alloy semisolid slurry at different stirring speeds prepared by the FCR process were analyzed. The experimental results suggest that with the increase of the stirring speed, the mean grain size of the semisolid decreases and the shape factor as well as the number of primary grains increase. Meanwhile, the preparation process of semisolid slurry was numerically simulated. The flow characteristics of the melt in the device and the effect of the stirring speed on temperature field and solid fraction of the melt were investigated. The simulated results show that during the preparation process of semisolid slurry, there is a complex convection within the FCR device that obviously changes the temperature field distribution and solid fraction of the melt. When the convection intensity increases, the scope of the undercooling gradient of the melt is reduced and temperature distribution is improved.
基金Project(51375498)supported by the National Natural Science Foundation of China
文摘Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional(3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of unsteady flow characteristics on solid-liquid two-phase flow and pump performance were researched under design condition. The results show that clocking effect has a significant influence on the flow in pump, and the fluctuation of flow velocity and pressure is obvious, particularly near the volute tongue, at the position of small sections of volute and within diffuser. Clocking effect has a more influence on liquid-phase than on solid-phase, and the wake-jet structure of relative velocity of solid-phase is less obvious than liquid-phase near the volute tongue and the impeller passage outlet. The fluctuation of relative velocity of solid-phase flow is 7.6% smaller than liquid-phase flow at the impeller outlet on circular path. Head and radial forces of the impeller are 8.1% and 85.7% of fluctuation, respectively. The results provide a theoretical basis for further research for turbulence, improving efficient, reducing the hydraulic losses and wear. Finally, field tests were carried out to verify the operation and wear of slurry pump.
基金financial support from the National Natural Science Foundation of China(Grant Nos.52022053 and 51879153)the China National Postdoctoral Program for Innovative Talents(Grant No.BX2021172)。
文摘It is difficult to temporally and spatially track and characterize the slurry viscosity in flowing water during grouting simulation.In this study,a sequential flow and solidification(SFS)method considering the spatial-temporal evolution of slurry viscosity in flowing water in karst conduit is proposed.First,a time-dependent model for the threshold function of slurry viscosity is established.During the grouting process,the spatial-temporal evolution of slurry viscosity is revealed by tracking the diffusion behavior of the slurry injected at different times.This method is capable of describing the gradual solidification process of the slurry during grouting.Furthermore,a physical model of grouting in a karst conduit is developed.Second,the effectiveness of the SFS method in grouting simulation is verified by the experiment of grouting conduit in flowing water.The SFS method enables real-time monitoring of fluid velocity and pressure during grouting in flowing water and provides a feasible calculation method for revealing the grouting plugging mechanism in complex karst conduits at different engineering scales.In addition,it can be used to guide the design of grouting tests in flowing water,improve cost efficiency,and provide theoretical basis for optimizing grouting design and slurry selection.
基金Project(11272359)supported by the National Natural Science Foundation of China
文摘The particle simulation method is used to solve free-surface slurry flow problems that may be encountered in several scientific and engineering fields.The main idea behind the use of the particle simulation method is to treat granular or other materials as an assembly of many particles.Compared with the continuum-mechanics-based numerical methods such as the finite element and finite volume methods,the movement of each particle is accurately described in the particle simulation method so that the free surface of a slurry flow problem can be automatically obtained.The major advantage of using the particle simulation method is that only a simple numerical algorithm is needed to solve the governing equation of a particle simulation system.For the purpose of illustrating how to use the particle simulation method to solve free-surface flow problems,three examples involving slurry flow on three different types of river beds have been considered.The related particle simulation results obtained from these three examples have demonstrated that:1) The particle simulation method is a promising and useful method for solving free-surface flow problems encountered in both the scientific and engineering fields;2) The shape and irregular roughness of a river bed can have a significant effect on the free surface morphologies of slurry flow when it passes through the river bed.
文摘To realize the technology of fabricating the rheologic semi-solid slurry of ZL112Y aluminum alloy via continues electromagnetic stirring process,ANSYS software was used to simulate electromagnetic force field and fluid velocity field in the alloy melt in a crucible tube in three coils.In the first section of the paper,eletromagnetic force field and fluid velocity field caused by single coil were simulated.The result of this simulation gives an average velocity of 3.2 cm/s and it is called critical velocity because a fluid velocity over it will cause a fine and spherical structure of solid primary a in a semi-solid melt.And,from this result,a reasonable temperature of semi-solid of the alloy and an electrical current intensity were established.The electrical current intensity of the result of this simulation corresponded to the current intensity used in a practice experiment,in which the primaryαwas obviously refined and sphericized.Based on this simulation of single coil electromagnetic stirring,in the second section of the paper,eletromagnetic force field and fluid velocity field caused by three coils were simulated.The result of the simulation shows that,1)there is a semi-solid zone of 32 mm from bottom of the crucible tube to the upper;2)the electrical current intensities of three coils of 400 A,600 A,and 400 A,which were set to top range,middle range and bottom range of the tube,respectively,were the optimum parameters of electromagnetic current intensity under the condition of this investigation;and 3)under effect of these electromagnetic current intensity,the fluid velocities of the melt in the tube were 6.3 cm/s in top range,3.75 cm/s in middle range,and 3.9 cm/s in bottom range of it,respectively.
基金supported by the Ministry of Science and Technology of China (No.2008EG130243)
文摘X-ray fluorescence （XRF） in combination with partial least-squares （PLS） regression was employed to analyze the ore slurry grade. Using the Monte Carlo simulation code PENELOPE, X-ray fluorescence spectra of ore samples were obtained. Good accuracy was achieved when this method was used to analyze elements with concentrations of several percent or above. It was demonstrated that the more the number of X-ray fluorescence spectra used to calibrate, the better the obtained accuracy. In this method detector resolution was found to have little or no effect on the results of quantitative analysis. The effect of the concentration of water was investigated as well, and it was found to have little influence on the results.
文摘Aspen plus software was employed to simulate process. The system concludes gasification scrubbing system the opposed multi-burner gasifier （OMB） methanol production and purification shift system. The distributions of ammonia con- centration in streams were obtained. The study demonstrates that ammonium crystallization problem caused by ammonia ac- cumulation, and if the process has ammonia exports its concentration will greatly reduced and the ammonia salt problem will effectively alleviate. Aspen plus simulation is a useful tool strengthening the ammonia recycling use and reducing pollutant for improving water quality, maintaining stable production, emissions.
基金supported by the National Natural Science Foundation of China(Grant No.52274061&52004039&51974037)China Postdoctoral Science Foundation(Grant No.2023T160717&2021M693908)+1 种基金The major project of universities affiliated to Jiangsu Province basic science(natural science)research(Grant No.21KJA440001)Jiangsu Qinglan Project,Changzhou Longcheng Talent Plan-Youth Science and Technology Talent Recruitment Project.
文摘The research on the multiphase flow characteristics of hydrate slurry is the key to implementing the risk prevention and control technology of hydrate slurry in deep-water oil and gas mixed transportation system.This paper established a geometric model based on the high-pressure hydrate slurry experimental loop.The model was used to carry out simulation research on the flow characteristics of gas-liquid-solid three-phase flow.The specific research is as follows:Firstly,the effects of factors such as slurry flow velocity,hydrate particle density,hydrate particle size,and hydrate volume fraction on the stratified smooth flow were specifically studied.Orthogonal test obtained particle size has the most influence on the particle concentration distribution.The slurry flow velocity is gradually increased based on stratified smooth flow.Various flow patterns were observed and their characteristics were analyzed.Secondly,increasing the slurry velocity to 2 m/s could achieve the slurry flow pattern of partial hydrate in the pipeline transition from stratified smooth flow to wavy flow.When the flow rate increases to 3 m/s,a violent wave forms throughout the entire loop.Based on wave flow,as the velocity increased to 4 m/s,and the flow pattern changed to slug flow.When the particle concentration was below 10%,the increase of the concentration would aggravate the slug flow trend;if the particle concentration was above 10%,the increase of the concentration would weaken the slug flow trend,the increase of particle density and liquid viscosity would weaken the tendency of slug flow.The relationship between the pressure drop gradients of several different flow patterns is:slug flow>wave flow>stratified smooth flow.
基金supported by the National Natural Science Foundation of China (Grant No. 11172218)the Fundamental Research Funds for the Central Universities (Grant No. 2012206020209)
文摘Slurry jets in a static uniform environment were simulated with a two-phase mixture model in which flow-particle interactions were considered. A standard k-e turbulence model was chosen to close the governing equations. The computational results were in agreement with previous laboratory measurements. The characteristics of the two-phase flow field and the influences of hydraulic and geometric parameters on the distribution of the slurry jets were analyzed on the basis of the computational results. The calculated results reveal that if the initial velocity of the slurry jet is high, the jet spreads less in the radial direction. When the slurry jet is less influenced by the ambient fluid （when the Stokes number St is relatively large）, the turbulent kinetic energy k and turbulent dissipation rate e, which are relatively concentrated around the jet axis, decrease more rapidly after the slurry jet passes through the nozzle. For different values of St, the radial distributions of streamwise velocity and particle volume fraction are both self-similar and fit a Gaussian profile after the slurry jet fully develops. The decay rate of the particle velocity is lower than that of water velocity along the jet axis, and the axial distributions of the centerline particle streamwise velocity are self-similar along the jet axis. The pattern of particle dispersion depends on the Stokes number St. When St = 0.39, the panicle dispersion along the radial direction is considerable, and the relative velocity is very low due to the low dynamic response time. When St = 3.08, the dispersion of particles along the radial direction is very little, and most of the particles have high relative velocities along the streamwise direction.
基金This research was funded by the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(KYCX21_2815).
文摘In this paper,based on Fluent software,a five-nozzle gasifier reactor was established to simulate the gasification process of oil-based drill cuttings coal-water slurry.The influence of concentration and oxygen/carbon atomic ratio on the gasification process of oil-based drill cuttings coal-water slurry was investigated.The results show that when the oxygen flow is constant,the outlet temperature of gasifier decreases,the content of effective gas increases,and the carbon conversion rate decreases with the increase of concentration;When the ratio of oxygen to carbon atoms is constant,the effective gas content rises and the temperature rises with the increase of the concentration,and the carbon conversion rate reaches the maximum value when the concentration of oil-based drill cuttings coal-water slurry is 65%;When the concentration is constant,the effective gas content decreases and the outlet temperature rises with the increase of the oxygen/carbon atom ratio,and the carbon conversion rate reaches 99.80%when the oxygen/carbon atom ratio is 1.03.It shows that this method can effectively decompose the organic matter in oilbased drill cuttings and realize the efficient and cooperative treatment of oil-based drill cuttings.
基金Project(17YF1407100)supported by the Shanghai Sailing Program of ChinaProject(17PJ1408600)supported by Shanghai Pujiang Program of China
文摘The hot cracking tendency of 7075 semi-solid alloy under different conditions was studied by critical diameter method.The experiment and simulation results show that the dendrite arms of the rod grow from the edge to the center.The smaller the diameter of the rod is,the more obvious the directional growth of dendrite is,and the greater the tendency of hot cracking is.Compared with ordinary melt,for semi-solid slurry,increasing mould temperature or decreasing pouring temperature can significantly decrease hot cracking tendency of 7075 alloy,decreasing hot cracking grade from 256 to 100 mm^2.Furthermore,based on the RDG criterion,the effects of solidification conditions on the hot cracking tendency were discussed combined with simulation.At the same time,the application and development of RDG criterion were also researched.
基金This work was supported by the National Basic Research Program of China (2005CB221205)
文摘A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether （DME） from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows： diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger （Ф 38×2 mm）, and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.
基金Financial support from the National Natural Science Foundation of China(51076043 and 51061130538)Program for New Century Excellent Talents in University(NCET-09-0342)+1 种基金Central Universities(12QN02)111 Project(B12034)
文摘The computational fluid dynamics （CFD）-population balance equations （PBE） coupled model is employed to investigate the hydrodynamics in a gas-slurry internal loop reactor with external slurry circulation. The predicted radial profiles of local gas holdup and bubble diameter are in good agreement with the corresponding experimental data. The spatio-temporal velocity profile of the gas phase reveals that the upward movement of gas is slowed down and the residence time of gas is prolonged by the downward momentum of the slurry, introduction of the external slurry can greatly improve the uniformity of gas holdup distribution in the reactor, especially in the downcomer-tube action region. Moreover, the interaction between the downward slurry and upward gas can lead to small bubble size and high interfacial area as well as good mass and heat transfer. The above results suggest the function of external slurry circulation for the internal loop reactor and would be helpful for optimizing the design and scale up of reactors.
文摘Preparation of semisolid slurry using a cooling slope is increasingly becoming popular,primarily because of the simplicity in design and ease control of the process.In this process,liquid alloy is poured down an inclined surface which is cooled from underneath.The cooling enables partial solidification and the incline provides the necessary shear for producing semisolid slurry.However,the final microstructure of the ingot depends on several process parameters such as cooling rate,incline angle of the cooling slope,length of the slope and initial melt superheat.In this work,a CFD model using volume of fluid(VOF) method for simulating flow along the cooling slope was presented.Equations for conservation of mass,momentum,energy and species were solved to predict hydrodynamic and thermal behavior,in addition to predicting solid fraction distribution and macrosegregation.Solidification was modeled using an enthalpy approach and a volume averaged technique for the different phases.The mushy region was modeled as a multi-layered porous medium consisting of fixed columnar dendrites and mobile equiaxed/fragmented grains.The alloy chosen for the study was aluminum alloy A356,for which adequate experimental data were available in the literature.The effects of two key process parameters,namely the slope angle and the pouring temperature,on temperature distribution,velocity distribution and macrosegregation were also studied.
基金provided by National Natural Science Foundation(Grant No.41372331)the international cooperation project of Ministry of Science and Technology(Grant No.2013DFA21720)Key Laboratory of Mountain Hazards and Earth Surface Processes independent project funding:Dynamic process and buried risk of debris flow in Shenxi gully after Wenchuan earthquake
文摘The motion forms（deformation） of the sliding soil along the slope include inviscid particle flow,viscous particle flow,and mass sliding.The motion forms were mainly influenced by the mechanical properties of the viscous mud medium filling.The effect of the medium filling on the motion forms of the sliding soil is worth discussing.The sliding soil can be seen as the mixture which is composed of the medium filling and coarse particles.The Chengdu clay with different moisture contents were selected as the medium filling.Their mechanical parameters were experimentally measured for simulating the moving process of the sliding soil.Different motion forms of the sliding soil were numerical simulated based on PFC3D by changing the specific mechanical parameters.The mechanical parameters of the Chengdu clay are experimentally determined.The numerical results show that with the moisture content of the filling slurry medium in the range of 〉302%,101%~182%,and 〈80%,the motion form of the sliding soil belongs to the inviscid particles flow（similar with the sliding sand）,viscous particles flow（seen as the viscous flows）;and masssliding（seen as the block sliding along the slope surface）,respectively.
文摘The numerical simulation program of PFC2D(Particle Flow Code in 2 Dimension)particle flow based on the flow-solid coupling principle and,on its built-in FISHTANK function library and FISH language,defines the flow equation and pressure equation of fluid domain respectively,and carries out numerical simulation calculations on the diffusion process and,on the morphology and particle displacement of slurry during the slurry injection process.By adjusting the parameters of hist,n_bond,s_bond and measure in the PFC command flow,the tracking of granular body displacement changes is achieved,and the mesoscopic mechanism such as the diffusion law of soil slurry at different depths and the change of formation porosity is revealed.The numerical calculations show that:the grouting pressure has a significant effect on the alteration and destruction of the formation structure,and the fracturing effect becomes gradually worse with increasing adhesive strength,while the porosity increases significantly with increasing grouting pressure.Based on the elastic-plastic theory of the Mohr-Colomb criterion to theoretically derive the stress field of the soil around the borehole,it is pointed out that the mechanical mechanism of annular tension and radial compression is the fundamental reason for the appearance of fracturing grouting action mode.The increase of slurry viscosity is beneficial to improve the grouting effect of fracturing-compacting grouting,while the increase of friction coefficient has little effect on the grouting effect.The comparative analysis of the laboratory tests shows that the PFC2D simulation of the grouting process is feasible.
基金financially supported by the National Natural Science Foundation of China(Nos.21838003,91834301 and 21878092)the Shanghai Scientific and Technological Innovation Project(No.18JC1410600)+2 种基金the Social Development Program of Shanghai(Nos.17DZ1200900 and 18DZ2252400)the Innovation Program of Shanghai Municipal Education Commissionthe Fundamental Research Funds for the Central Universities(No.222201718002)。
文摘The suspension characteristics of ultrafine powder slurry in the stirred vessel were simulated by using computational fluid dynamics.The results show that the Rushton disk turbine impeller is more conducive to maintaining suspended homogeneity and circulation of slurry compared with the pitch blade turbine pumping up impeller and the pitch blade turbine pumping down impeller.And the increase in stirring speed enhances turbulent fluctuation and anisotropic velocity of the fluid at the cost of more power consumption,which improves dispersibility and suspensibility of the particles.Meanwhile,the change of impeller clearance has a weak influence on the flow pattern,and the impeller clearance of 0.32T(T is the diameter of the bottom of the reactor)can achieve better dispersivity and suspensibility of the particles with lower power consumption and larger axial velocity.The experiments of surface coating modification of ultrafine titanium dioxide(TiO2)were carried out under the same conditions for those of the simulation system.The surface film morphology and photocatalytic properties of the modified TiO2 were analyzed,and the obtained data are well consistent with the simulation results.
基金The authors gratefully acknowledge the filnancial support of the National Natural Science Foundation of China(Grant No.52369018)the Major Training Program of University Research and Innovation Platform of Gansu Provincial Department of Education(No.2024CXPT-09)+1 种基金the Administration of Central Funds Guiding the Local Science and Technology Development,China(Grant No.23ZYQA0320)the Double First-Class Key Program of Gansu Provincial Department of Education,Grant No.GCJ2022-38.
文摘Erosion in slurry pumps presents a persistent challenge in industrial applications.This study examines the erosion of the static components of a 150ZJ-C42 centrifugal slurry pump,currently in operation at a beneficiation plant,under varying particle conditions.Utilizing high-precision three-dimensional reverse engineering,the pump’s flow passage geometry was reconstructed to facilitate detailed erosion analysis.Focusing on the front and rear baffles of the pump chamber,as well as the volute,erosion patterns were analyzed for different particle volume concentrations and sizes.The results reveal that the highest erosion damage consistently occurs near the volute tongue,with wear being most severe in regions adjacent to the partition plate near the rear cover.Erosion damage intensity in this area correlates positively with particle diameter.Notably,the average erosion rate in the volute surpasses that of the front and rear chamber liners,reaching a value as high as 6.03×10^(-7)kg·m^(-2)·s^(-1)at a particle concentration of 9%and diameter of 0.1 mm,adversely impacting pump stability.For the pump chamber baffles,increased erosion is observed at a particle diameter of 0.05 mm under constant volume concentration conditions,while higher particle concentrations exacerbate localized erosion.
