The thermal diffusion column represents one method of separating stable isotopes.This method is advantageous for smallscale operations because of the simplicity of the apparatus and small inventory,especially in gas-p...The thermal diffusion column represents one method of separating stable isotopes.This method is advantageous for smallscale operations because of the simplicity of the apparatus and small inventory,especially in gas-phase operations.Consequently,it has attracted attention for its applicability in tritium and noble gas separation systems.In this study,the R cascade was used to design and determine the number of columns.A square cascade was adopted for the final design because of its flexibility,and calculations were performed to separate 20Ne and 22Ne isotopes.All the R cascades that enriched the Ne isotopes by more than 99%were investigated,the number of columns was determined,and the square cascade parameters were optimized using the specified columns.Additionally,a calculation code“RSQ_CASCADE”was developed.A unit separation factor of three was considered,and the number of studied stages ranged from 10 to 20.The results showed that the column separation power,relative total flow rate,and required number of columns were linearly related to the number of stages.The separation power and relative total flow decreased and the number of columns increased as the stage number increased.Therefore,a cascade of 85 columns is recommended to separate the stable Ne isotopes.These calculations yielded a 17-stage square cascade with five columns in each stage.By changing the stage cut,feed point,and cascade feed flow rate,the best parameters for the square cascade were determined according to the cascade and column separation powers.As the column separation power had a maximum value in cascade feed 50,it was selected for separating Ne isotopes.展开更多
A new gas-solid separator dedicated to heavy-oil fast pyrolysis process incorporating inertial and centrifugal separation was designed. Gas and typical fluid catalytic cracking (FCC) catalyst particles (with a dens...A new gas-solid separator dedicated to heavy-oil fast pyrolysis process incorporating inertial and centrifugal separation was designed. Gas and typical fluid catalytic cracking (FCC) catalyst particles (with a density of 1500 kg/m3, and a mean diameter of 45.81 p.m) were used in the study. The inlet gas velocity was kept constant at 13.36 m/s, while the solid loading at the inlet ranged from 0 to 700 g/m3. When the exhaust pipe opening was provided with two narrow-width slots near the inlet without baffles, the solid collection efficiency increased with an increasing solid loading at the inlet and was close to 95% along with a decreasing pressure drop. After increasing the secondary separation structure, the separation efficiency greatly improved. By adjusting the diameter of the secondary exhaust pipe, the separation efficiency and pressure drop could be balanced. Under the experimental conditions, when the diameter of the second exhaust pipe was equal to d=100 mm, the pressure drop was lower than 1400 Pa while the separation efficiency could exceed 99.50%; and when the diameter was equal to d=120 mm, the pressure drop was less than 700 Pa, with the separation efficiency reaching over 99.00%.展开更多
The present study was aimed at the inlet particle spatial distribution of a gas-solid separator with high solid loading and investigated its effects on cyclone performance and the inner flow pattern.The flow fields of...The present study was aimed at the inlet particle spatial distribution of a gas-solid separator with high solid loading and investigated its effects on cyclone performance and the inner flow pattern.The flow fields of a cyclone with different rectangular particle flow areas on the inlet surface were numerically simulated using a four-way coupling method.The simulated results indicate that reducing the inlet particle flow area and lowing the inlet particle position can effectively reduce the scattered particles inside the cyclone separator and enhance the separation performance.Vertically gathering the particles to the centerline can also weaken the particle back-mixing.The particles near the roof account for the swirling particle ceiling phenomenon.The inlet particle spatial distribution affects the pressure drop mainly by affecting the gas tangential velocity in the cylinder body.Moreover,compared to the hori-zontal particle distribution on the inlet surface,the vertical particle distribution has greater effects on cyclone performance.展开更多
We consider the functional separation of variables to the nonlinear diffusion equation with source and convection term: ut = (A(x)D(u)ux)x + B(x)Q(u), Ax ≠ 0. The functional separation of variables to thi...We consider the functional separation of variables to the nonlinear diffusion equation with source and convection term: ut = (A(x)D(u)ux)x + B(x)Q(u), Ax ≠ 0. The functional separation of variables to this equation is studied by using the group foliation method. A classification is carried out for the equations which admit the function separable solutions. As a consequence, some solutions to the resulting equations are obtained.展开更多
The functionally generalized variable separation of the generalized nonlinear diffusion equations ut = A(u, Ux)Uxx + B(u, ux) is studied by using the conditional Lie-Blicklund symmetry method. The variant forms o...The functionally generalized variable separation of the generalized nonlinear diffusion equations ut = A(u, Ux)Uxx + B(u, ux) is studied by using the conditional Lie-Blicklund symmetry method. The variant forms of the considered equations, which admit the corresponding conditional Lie--Biicklund symmetries, are characterized. To construct functionally gener- alized separable solutions, several concrete examples defined on the exponential and trigonometric invariant subspaces are provided.展开更多
Computer simulations were performed to study the dense mixtures of passive particles and active particles in two dimensions.Two systems with different kinds of passive particles(e.g.,spherical particles and rod-like p...Computer simulations were performed to study the dense mixtures of passive particles and active particles in two dimensions.Two systems with different kinds of passive particles(e.g.,spherical particles and rod-like particles)were considered.At small active forces,the high-density and low-density regions emerge in both systems,indicating a phase separation.At higher active forces,the systems return to a homogeneous state with large fluctuation of particle area in contrast with the thermo-equilibrium state.Structurally,the rod-like particles accumulate loosely due to the shape anisotropy compared with the spherical particles at the high-density region.Moreover,there exists a positive correlation between Voronoi area and velocity of the particles.Additionally,a small number of active particles capably give rise to super-diffusion of passive particles in both systems when the self-propelled force is turned on.展开更多
In this article,numerical simulations are performed to investigate the performance of the thermal diffusion column for the separation of n-heptane/benzene mixture.The present work tried to optimize column by analyzing...In this article,numerical simulations are performed to investigate the performance of the thermal diffusion column for the separation of n-heptane/benzene mixture.The present work tried to optimize column by analyzing significant parameters such as feed flow rate,temperature and cut.In order to obtain the hydrodynamic and temperature and mass distribution inside thermal diffusion column,computational fluid dynamic(CFD) method is applied to solve the Navier-Stocks equations.Numerical simulations are conducted to study the main parameters in both stationary and time-dependent conditions.By using the separation work unit as a function of cut,the optimal cut for maximum SWU occurs within a limited range of 0.47-0.5 for feed rate between 0.5 and 4 g min^-1.Our findings reveal that the optimum feed rate in the range of optimum cut is about 1 g min^-1.In transient study,results show that the best cut for reaching to steady-state condition is θ=0.5.展开更多
A turbulent separation-rcattachment flow in a two-dimensional asymmetrical curved-wall diffuser is studied by a two-dimensional laser doppler velocimeter.The turbulent boundary layer separates on the lower curved wall...A turbulent separation-rcattachment flow in a two-dimensional asymmetrical curved-wall diffuser is studied by a two-dimensional laser doppler velocimeter.The turbulent boundary layer separates on the lower curved wall under strong pressure gradient and then reattaches on a parallel channel.At the inlet of the diffuser,Reynolds number based on the diffuser height is 1.2×10~5 and the velocity is 25.2m/s.The re- sults of experiments are presented and analyzed in new defined streamline-aligned coordinates.The experiment shows that after Transitory Detachment Reynolds shear stress is negative in the near-wall backflow region. Their characteristics are approximately the same as in simple turbulent shear layers near the maximum Reynolds shear stress.A scale is formed using the maximum Reynolds shear stresses.It is found that a Reynolds shear stress similarity exists from separation to reattachment and the Schofield-Perry velocity law ex- ists in the forward shear flow.Both profiles are used in the experimental work that leads to the design of a new eddy-viscosity model.The length scale is taken from that developed by Schofield and Perry.The composite velocity scale is formed by the maximum Reynolds shear stress and the Schofield Perry velocity scale as well as the edge velocity of the boundary layer.The results of these experiments are presented in this paper展开更多
To meet the requirements for fast and efficient gas-solid separation at the outlet of a gas-solid concurrent downflow fluidized bed(downer),a new horizontal gas-solid rapid separator was designed based on the joint ac...To meet the requirements for fast and efficient gas-solid separation at the outlet of a gas-solid concurrent downflow fluidized bed(downer),a new horizontal gas-solid rapid separator was designed based on the joint action of centrifugal and inertial forces.Under the same experimental conditions,a fluid catalytic cracking(FCC)catalyst was used as the material(with a particle density of 1500 kg/m3 and a mean particle size of 45.8μm)to experimentally investigate the effects of the insertion length of gas outlet pipe,the bypass cylinder,the gas outlet direction,and the secondary separation structure on the separator performance.The results showed that with an inlet gas flow rate of 14.5 m/s and a gas phase solid content of 60―835 g/m3,the downer system achieved a gas-solid separation efficiency of above 99.5%,with the separator’s pressure drop within 1846 Pa(when the separator included a bypass cylinder and a secondary separation structure with a proper insertion length of gas outlet pipe).展开更多
By using the approximate derivative-dependent functional variable separation approach, we study the quasi-linear diffusion equations with a weak source ut = (A(u)Ux)x + eB(u, Ux). A complete classification of t...By using the approximate derivative-dependent functional variable separation approach, we study the quasi-linear diffusion equations with a weak source ut = (A(u)Ux)x + eB(u, Ux). A complete classification of these perturbed equations which admit approximate derivative-dependent functional separable solutions is listed. As a consequence, some approxi- mate solutions to the resulting perturbed equations are constructed via examples.展开更多
文摘The thermal diffusion column represents one method of separating stable isotopes.This method is advantageous for smallscale operations because of the simplicity of the apparatus and small inventory,especially in gas-phase operations.Consequently,it has attracted attention for its applicability in tritium and noble gas separation systems.In this study,the R cascade was used to design and determine the number of columns.A square cascade was adopted for the final design because of its flexibility,and calculations were performed to separate 20Ne and 22Ne isotopes.All the R cascades that enriched the Ne isotopes by more than 99%were investigated,the number of columns was determined,and the square cascade parameters were optimized using the specified columns.Additionally,a calculation code“RSQ_CASCADE”was developed.A unit separation factor of three was considered,and the number of studied stages ranged from 10 to 20.The results showed that the column separation power,relative total flow rate,and required number of columns were linearly related to the number of stages.The separation power and relative total flow decreased and the number of columns increased as the stage number increased.Therefore,a cascade of 85 columns is recommended to separate the stable Ne isotopes.These calculations yielded a 17-stage square cascade with five columns in each stage.By changing the stage cut,feed point,and cascade feed flow rate,the best parameters for the square cascade were determined according to the cascade and column separation powers.As the column separation power had a maximum value in cascade feed 50,it was selected for separating Ne isotopes.
文摘A new gas-solid separator dedicated to heavy-oil fast pyrolysis process incorporating inertial and centrifugal separation was designed. Gas and typical fluid catalytic cracking (FCC) catalyst particles (with a density of 1500 kg/m3, and a mean diameter of 45.81 p.m) were used in the study. The inlet gas velocity was kept constant at 13.36 m/s, while the solid loading at the inlet ranged from 0 to 700 g/m3. When the exhaust pipe opening was provided with two narrow-width slots near the inlet without baffles, the solid collection efficiency increased with an increasing solid loading at the inlet and was close to 95% along with a decreasing pressure drop. After increasing the secondary separation structure, the separation efficiency greatly improved. By adjusting the diameter of the secondary exhaust pipe, the separation efficiency and pressure drop could be balanced. Under the experimental conditions, when the diameter of the second exhaust pipe was equal to d=100 mm, the pressure drop was lower than 1400 Pa while the separation efficiency could exceed 99.50%; and when the diameter was equal to d=120 mm, the pressure drop was less than 700 Pa, with the separation efficiency reaching over 99.00%.
基金supported by the Key Project of the National Fourteen-Five Year Research Program of China(grant No.2022YFB4100303).
文摘The present study was aimed at the inlet particle spatial distribution of a gas-solid separator with high solid loading and investigated its effects on cyclone performance and the inner flow pattern.The flow fields of a cyclone with different rectangular particle flow areas on the inlet surface were numerically simulated using a four-way coupling method.The simulated results indicate that reducing the inlet particle flow area and lowing the inlet particle position can effectively reduce the scattered particles inside the cyclone separator and enhance the separation performance.Vertically gathering the particles to the centerline can also weaken the particle back-mixing.The particles near the roof account for the swirling particle ceiling phenomenon.The inlet particle spatial distribution affects the pressure drop mainly by affecting the gas tangential velocity in the cylinder body.Moreover,compared to the hori-zontal particle distribution on the inlet surface,the vertical particle distribution has greater effects on cyclone performance.
基金The project supported by National Natural Science Foundation of China under Grant No. 10371098 and the Program for New Century Excellent Talents in Universities under Grant No. NCET-04-0968
文摘We consider the functional separation of variables to the nonlinear diffusion equation with source and convection term: ut = (A(x)D(u)ux)x + B(x)Q(u), Ax ≠ 0. The functional separation of variables to this equation is studied by using the group foliation method. A classification is carried out for the equations which admit the function separable solutions. As a consequence, some solutions to the resulting equations are obtained.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11371293,11401458,and 11501438)the National Natural Science Foundation of China,Tian Yuan Special Foundation(Grant No.11426169)the Natural Science Basic Research Plan in Shaanxi Province of China(Gran No.2015JQ1014)
文摘The functionally generalized variable separation of the generalized nonlinear diffusion equations ut = A(u, Ux)Uxx + B(u, ux) is studied by using the conditional Lie-Blicklund symmetry method. The variant forms of the considered equations, which admit the corresponding conditional Lie--Biicklund symmetries, are characterized. To construct functionally gener- alized separable solutions, several concrete examples defined on the exponential and trigonometric invariant subspaces are provided.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21674078,21474074,21574096,21774091,and 21374073)Overseas Research Program of Jiangsu,China(2019).
文摘Computer simulations were performed to study the dense mixtures of passive particles and active particles in two dimensions.Two systems with different kinds of passive particles(e.g.,spherical particles and rod-like particles)were considered.At small active forces,the high-density and low-density regions emerge in both systems,indicating a phase separation.At higher active forces,the systems return to a homogeneous state with large fluctuation of particle area in contrast with the thermo-equilibrium state.Structurally,the rod-like particles accumulate loosely due to the shape anisotropy compared with the spherical particles at the high-density region.Moreover,there exists a positive correlation between Voronoi area and velocity of the particles.Additionally,a small number of active particles capably give rise to super-diffusion of passive particles in both systems when the self-propelled force is turned on.
文摘In this article,numerical simulations are performed to investigate the performance of the thermal diffusion column for the separation of n-heptane/benzene mixture.The present work tried to optimize column by analyzing significant parameters such as feed flow rate,temperature and cut.In order to obtain the hydrodynamic and temperature and mass distribution inside thermal diffusion column,computational fluid dynamic(CFD) method is applied to solve the Navier-Stocks equations.Numerical simulations are conducted to study the main parameters in both stationary and time-dependent conditions.By using the separation work unit as a function of cut,the optimal cut for maximum SWU occurs within a limited range of 0.47-0.5 for feed rate between 0.5 and 4 g min^-1.Our findings reveal that the optimum feed rate in the range of optimum cut is about 1 g min^-1.In transient study,results show that the best cut for reaching to steady-state condition is θ=0.5.
文摘A turbulent separation-rcattachment flow in a two-dimensional asymmetrical curved-wall diffuser is studied by a two-dimensional laser doppler velocimeter.The turbulent boundary layer separates on the lower curved wall under strong pressure gradient and then reattaches on a parallel channel.At the inlet of the diffuser,Reynolds number based on the diffuser height is 1.2×10~5 and the velocity is 25.2m/s.The re- sults of experiments are presented and analyzed in new defined streamline-aligned coordinates.The experiment shows that after Transitory Detachment Reynolds shear stress is negative in the near-wall backflow region. Their characteristics are approximately the same as in simple turbulent shear layers near the maximum Reynolds shear stress.A scale is formed using the maximum Reynolds shear stresses.It is found that a Reynolds shear stress similarity exists from separation to reattachment and the Schofield-Perry velocity law ex- ists in the forward shear flow.Both profiles are used in the experimental work that leads to the design of a new eddy-viscosity model.The length scale is taken from that developed by Schofield and Perry.The composite velocity scale is formed by the maximum Reynolds shear stress and the Schofield Perry velocity scale as well as the edge velocity of the boundary layer.The results of these experiments are presented in this paper
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(21576294 and 21706287).
文摘To meet the requirements for fast and efficient gas-solid separation at the outlet of a gas-solid concurrent downflow fluidized bed(downer),a new horizontal gas-solid rapid separator was designed based on the joint action of centrifugal and inertial forces.Under the same experimental conditions,a fluid catalytic cracking(FCC)catalyst was used as the material(with a particle density of 1500 kg/m3 and a mean particle size of 45.8μm)to experimentally investigate the effects of the insertion length of gas outlet pipe,the bypass cylinder,the gas outlet direction,and the secondary separation structure on the separator performance.The results showed that with an inlet gas flow rate of 14.5 m/s and a gas phase solid content of 60―835 g/m3,the downer system achieved a gas-solid separation efficiency of above 99.5%,with the separator’s pressure drop within 1846 Pa(when the separator included a bypass cylinder and a secondary separation structure with a proper insertion length of gas outlet pipe).
基金Project supported by the National Natural Science Foundation of China(Grant No.10671156)the Natural Science Foundation of Shaanxi Province of China(Grant No.SJ08A05)
文摘By using the approximate derivative-dependent functional variable separation approach, we study the quasi-linear diffusion equations with a weak source ut = (A(u)Ux)x + eB(u, Ux). A complete classification of these perturbed equations which admit approximate derivative-dependent functional separable solutions is listed. As a consequence, some approxi- mate solutions to the resulting perturbed equations are constructed via examples.