Lithium(Li)metal is considered the most promising anode material for the next generation of secondary batteries due to its high theoretical specific capacity and low potential.However,the application of Li anode in re...Lithium(Li)metal is considered the most promising anode material for the next generation of secondary batteries due to its high theoretical specific capacity and low potential.However,the application of Li anode in rechargeable Li metal batteries(LMBs)is hindered due to the short cycle life caused by uncontrolled dendrite growth.In this work,a dendrite-free anode(Li–Sn/Cu)is reinforced synergistically by lithophilic alloy,and a 3D grid structure is designed.Li^(+)diffusion and uniform nucleation are effectively induced by the lithophilic alloy Li_(22)Sn_(5).Moreover,homogeneous deposition of Li^(+)is caused by the reversible gridded Li plating/stripping effect of Cu mesh.Furthermore,the local space electric field is redistributed throughout the 3D conductive network,whereby the tip effect is suppressed,thus inhibiting the growth of Li dendrites.Also,the volume expansion of the anode during cycling is eased by the 3D grid structure.The results show that the Li–Sn/Cu symmetric battery can stably cycle for more than 10,000 h at 2 mA.cm^(-2)and 1 mAh.cm^(-2)with a low overpotential.The capacity retention of the LiFePO_(4)full battery remains above 90.7%after 1,000 cycles at 1C.This work provides a facile,low-cost,and effective strategy for obtaining Li metal batteries with ultra-long cycle life.展开更多
The propagation characteristics of flexural waves in periodic grid structures designed with the idea of phononic crystals are investigated by combining the Bloch theorem with the finite element method. This combined a...The propagation characteristics of flexural waves in periodic grid structures designed with the idea of phononic crystals are investigated by combining the Bloch theorem with the finite element method. This combined analysis yields phase constant surfaces, which predict the location and the extension of band gaps, as well as the directions and the regions of wave propagation at assigned frequencies. The predictions are validated by computation and experimental analysis of the harmonic responses of a finite structure with 11 × 11 unit cells. The flexural wave is localized at the point of excitation in band gaps, while the directional behaviour occurs at particular frequencies in pass bands. These studies provide guidelines to designing periodic structures for vibration attenuation.展开更多
The title compound [Cu（bix）2（NO3）z·H2P]n 1 （bix = 1,4-bis（imidazole-1-ylme-thyl） benzene） has been synthesized by hydrothermal method. Its crystal structure is of monoclinic, space group P1^- with a = 8.3...The title compound [Cu（bix）2（NO3）z·H2P]n 1 （bix = 1,4-bis（imidazole-1-ylme-thyl） benzene） has been synthesized by hydrothermal method. Its crystal structure is of monoclinic, space group P1^- with a = 8.3075（13）, b = 9.4725（13）, c = 10.0192（13） A, α = 91.088（4）, β = 104.063（6）, γ = 101.88（1）, V = 746.5（3） A^3, Z = 1, C28H30N10O7Cu1, Mr = 682.16, Dc = 1.518 g/cm^3, μ = 0.796 mm^-1, F（000） = 353, the final R = 0.0535 and wR = 0.0996 for 2921 observed reflections with I 〉 2σ（I）. Each bix ligand binds two Cu（Ⅱ） ions to form a 2-D（4,4） square grid layer, which is connected by hydrogen bonds showing large channels occupied by solvated water molecules and nitrate anions.展开更多
The herringbone water-sediment separation structure(HWSSS) was developed to prevent debris flows. This paper mainly focuses on evaluating the sediment separation efficiency of HWSSS in debris flow prevention and deter...The herringbone water-sediment separation structure(HWSSS) was developed to prevent debris flows. This paper mainly focuses on evaluating the sediment separation efficiency of HWSSS in debris flow prevention and determining the grid opening width D, a crucial structure parameter for HWSSS design. Theoretical analysis on the total sediment separation rate Pt reveals that the efficiency of sediment separation is much related with sediment grain size distribution(GSD) and grid opening width. The lower limit of Pt is deduced from the perspective of safety consideration by transforming debris flow into sediment-laden flow. Hydraulic model tests were carried out. Based on the regression analysis of the experimental data, the quantitative relationships between Pt and D and GSD characteristic values were finally established. A procedure for determining optimal grid opening width is proposed based on these analyses. These results are of significance in evaluating sediment separation effect by HWSSS in debris flow prevention and contribute to a more explicit methodology for design of HWSSS.展开更多
The reflection characteristics of gird structures are calculated by the spatial network method in the case of normal incidence plane electromagnetic wave. The numerical result shows that the grid panels without electr...The reflection characteristics of gird structures are calculated by the spatial network method in the case of normal incidence plane electromagnetic wave. The numerical result shows that the grid panels without electromagnetic wave absorbing foams are not ideal. However, the absorbing ability can be achieved as low as -25 dBsm from 8 GHz to 12 GHz when the grid cells are filled with foam absorbers. Also it is noted from computation that the foam filled grid structures with larger cell size, higher and thinner ribs will improve the absorbing abilities, which illustrates that they can be used as the effective light-weight stealth structures for aeronautical application.展开更多
This paper presents an improved unstructured grid immersed boundary method.The advantages of both immersed boundary method and body fitted grids which are generated by unstructured grid technology are used to enhance ...This paper presents an improved unstructured grid immersed boundary method.The advantages of both immersed boundary method and body fitted grids which are generated by unstructured grid technology are used to enhance the computation efficiency of fluid structure interaction in complex domain.The Navier-Stokes equation was discretized spacially with collocated finite volume method and Euler implicit method in time domain.The rigid body motion was simulated by immersed boundary method in which the fluid and rigid body interface interaction was dealt with VOS(volume of solid) method.A new VOS calculation method based on graph was presented in which both immersed boundary points and cross points were collected in arbitrary order to form a graph.The method is verified with flow past oscillating cylinder.展开更多
The increasing grid data in CFD simulation has brought some new difficulties and challenges,such as high storage cost,low transmission efficiency.In order to overcome these problems,a novel method for compressing and ...The increasing grid data in CFD simulation has brought some new difficulties and challenges,such as high storage cost,low transmission efficiency.In order to overcome these problems,a novel method for compressing and saving the structured grid are proposed.In the present method,the geometric coordinates of the six logical domains of one grid block is saved instead of all grid vertex coordinates to reduce the size of the structured grid file when the grid is compressed.And all grid vertex coordinates are recovered from the compressed data with the use of the transfinite interpolation algorithm when the grid is decompressed.Firstly,single-block grid cases with different edge vertexes are tested to investigate the compression effect.The test results show that a higher compression ratio will be obtained on a larger grid.Secondly,further theoretical analysis is carried out to investigate the effects of parameters on grid compression.The analysis on single-block grid compression shows that the compression ratio is proportionate to the cubic root of the number of total vertexes.The highest compression ratio of single-block grid is obtained when the numbers of vertexes in three logical directions are equal.The analysis on multi-block grid compression shows that a higher compression ratio will be obtained when a larger difference of total vertexes number exists among the grid blocks.Finally,multi-blockgrids of two industrial aircraft configurations are compressed to validate the method.The compression results demonstrate that the present method has an excellent ability on structured grid compression.For a million-vertex structured grid,more than 80 percent disk space can be saved after compression.展开更多
Liquid crystalline multi-block copolymers poly[1,6-bis(4-oxybenzoyl-oxy)hexane terephthalate]-b-bisphenol A polycarbonate (PHTH-6-b-PC) with different segments of polycarbonate (PC) and thermotropic polyester PHTH-6 w...Liquid crystalline multi-block copolymers poly[1,6-bis(4-oxybenzoyl-oxy)hexane terephthalate]-b-bisphenol A polycarbonate (PHTH-6-b-PC) with different segments of polycarbonate (PC) and thermotropic polyester PHTH-6 were synthesized in tetrachloroethane at 144 similar to 146 degrees C. The influence of segment length on the resulting phase structure and thermal behavior of block copolymers was also discussed. It is demonstrated by TEM and DMA that the resulting block copolymers show a considerable microphase separation. The degree of phase separation and the thermal behavior of the block copolymers are strongly dependent on the molecular weight of the segments incorporated.展开更多
Based on a control grid network and in combination with a remote total station and digital camera,the distribution of steel nodes and deflection curve of a steel grid structure can be obtained easily.The measurement r...Based on a control grid network and in combination with a remote total station and digital camera,the distribution of steel nodes and deflection curve of a steel grid structure can be obtained easily.The measurement result shows that this method is effective and utilitarian.展开更多
The section of electric power is the foundation of national economy. The paper analyzes the relation between industrial structure and grid load in Shanxi province, and finds out that electricity demand and grid load r...The section of electric power is the foundation of national economy. The paper analyzes the relation between industrial structure and grid load in Shanxi province, and finds out that electricity demand and grid load relate linearly to value added of industry. In the end, the paper predicts electricity demand and grid load via the model.展开更多
An overset grid methodology is developed for the fully coupled analysis of fluid-structure interaction (FSI) problems. The overset grid approach alleviates some of the computational geometry difficulties traditionally...An overset grid methodology is developed for the fully coupled analysis of fluid-structure interaction (FSI) problems. The overset grid approach alleviates some of the computational geometry difficulties traditionally associated with Arbitrary-Lagrangian-Eulerian (ALE) based, moving mesh methods for FSI. Our partitioned solution algorithm uses separate solvers for the fluid (finite volume method) and the structure (finite element method), with mesh motion computed only on a subset of component grids of our overset grid assembly. Our results indicate a significant reduction in computational cost for the mesh motion, and element quality is improved. Numerical studies of the benchmark test demonstrate the benefits of our overset mesh method over traditional approaches.展开更多
Based on the first-order upwind and second-order central type of finite volume (UFV and CFV) scheme, upwind and central type of perturbation finite volume (UPFV and CPFV) schemes of the Navier-Stokes equations were de...Based on the first-order upwind and second-order central type of finite volume (UFV and CFV) scheme, upwind and central type of perturbation finite volume (UPFV and CPFV) schemes of the Navier-Stokes equations were developed. In PFV method, the mass fluxes of across the cell faces of the control volume (CV) were expanded into power series of the grid spacing and the coefficients of the power series were determined by means of the conservation equation itself. The UPFV and CPFV scheme respectively uses the same nodes and expressions as those of the normal first-order upwind and second-order central scheme, which is apt to programming. The results of numerical experiments about the flow in a lid-driven cavity and the problem of transport of a scalar quantity in a known velocity field show that compared to the first-order UFV and second-order CFV schemes, upwind PFV scheme is higher accuracy and resolution, especially better robustness. The numerical computation to flow in a lid-driven cavity shows that the under-relaxation factor can be arbitrarily selected ranging from (0.3) to (0.8) and convergence perform excellent with Reynolds number variation from 10~2 to 10~4.展开更多
In order to solve the problem of excessive noise and vibration during the operation of the hydraulic transformer,an optimization method of valve plate damping hole structure is proposed to alleviate the phenomenon of ...In order to solve the problem of excessive noise and vibration during the operation of the hydraulic transformer,an optimization method of valve plate damping hole structure is proposed to alleviate the phenomenon of pressure shock.Firstly,the mathematical model of oil pressure gradient in the plunger cavity is established,and the incremental equation of pressure change is derived.Secondly,a kind of buffering structure is proposed,the corresponding relationship between the pressure change and the envelopment angle of the buffering hole and the aperture size is determined by analyzing the oil pressure change curve in the plunger cavity.Finally,the flow field models with buffering holes are established,and the transient simulation of the pressure change process under the optimal solution is carried out with ANSYS software and the flow field pressure distribution contours are obtained.Through the analysis of simulation results,it is concluded that the optimal envelope angle of the three buffer holes ofA-T-B-Ais 5°,and the optimal aperture is 1.8 mm,1.6 mm,and 1.7 mm,respectively.The buffer hole can achieve a better-buffering effect in the range of variable pressure angle[0°,101°].The buffer hole structure can effectively alleviate the pressure shock and reduce the noise level,which lays a foundation for the design and theoretical research of hydraulic transformers.展开更多
There are various construction methods of long-span steel structure. In this paper, sap2000 is used to analyze the overall lifting technology of a 72*144m long-span steel structure. The grid structure is divided into ...There are various construction methods of long-span steel structure. In this paper, sap2000 is used to analyze the overall lifting technology of a 72*144m long-span steel structure. The grid structure is divided into two areas for lifting, and there are four different areas for different repair welding areas and lifting methods. By analyzing the indexes of stress, deformation and internal force of structure construction under different construction zoning schemes, the best construction scheme can be selected. The calculation results show that the construction deformation of the second scheme is the smallest, with the final deformation of 49.164mm, the maximum stress ratio of the components after construction being 0.204, and the stress ratio of the components under the load of 1.3D+1.5L being 0.8098, which is basically the same as the stress ratio of 0.80 obtained by the one-time loading design, so the second scheme is finally selected.展开更多
A numerical method for simulating nonlinear fluid-rigid structure interaction problems is developed. The structure is assumed to undergo large rigid body motions and the fluid flow is governed by nonlinear, viscous or...A numerical method for simulating nonlinear fluid-rigid structure interaction problems is developed. The structure is assumed to undergo large rigid body motions and the fluid flow is governed by nonlinear, viscous or non-viscous, field equations with nonlinear boundary conditions applied to the free surface and fluid-solid interaction interfaces. An Arbitrary-LagrangianEulerian (ALE) mesh system is used to construct the numerical model. A multi-block numerical scheme of study is adopted allowing for the relative motion between moving overset grids, which are independent of one another. This provides a convenient method to overcome the difficulties in matching fluid meshes with large solid motions. Nonlinear numerical equations describing nonlinear fluid-solid interaction dynamics are derived through a numerical discretization scheme of study. A coupling iteration process is used to solve these numerical equations. Numerical examples are presented to demonstrate applications of the model developed.展开更多
In this study,Computational Fluid Dynamics(CFD)together with a component transport model are exploited to investigate the influence of dimensionless parameters,involving the height of the rectifier grid and the instal...In this study,Computational Fluid Dynamics(CFD)together with a component transport model are exploited to investigate the influence of dimensionless parameters,involving the height of the rectifier grid and the installation height of the first catalyst layer,on the flow field and the overall denitration efficiency of a cement kiln’s SCR(Selective catalytic reduction)denitrification reactor.It is shown that accurate numerical results can be obtained by fitting the particle size distribution function to the actual cement kiln fly ash and implementing a non-uniform particle inlet boundary condition.The relative error between denitration efficiency derived from experimental data,numerical simulation,and real-time system pressure drop ranges from 4%to 9%.Optimization of the SCR reactor is achieved when the rectifier grid thickness ratio k/H≥0.030,the rectifier grid height ratio h/H=0.04,and the spacing between the rectifier grid and the first catalyst layer l/H=0.10.Under these conditions,airflow distribution and particle dispersion upstream of the catalyst result in increased denitration efficiencies of 3.21%,3.43%,and 3.27%,respectively,compared to the least favorable operating conditions.展开更多
Compared with other migration methods, reverse-time migration is based on a precise wave equation, not an approximation, and performs extrapolation in the depth domain rather than the time domain. It is highly accurat...Compared with other migration methods, reverse-time migration is based on a precise wave equation, not an approximation, and performs extrapolation in the depth domain rather than the time domain. It is highly accurate and not affected by strong subsurface structure complexity and horizontal velocity variations. The difference method based on triangular grids maintains the simplicity of the difference method and the precision of the finite element method. It can be used directly for forward modeling on models with complex top surfaces and migration without statics preprocessing. We apply a finite difference method based on triangular grids for post-stack reverse-time migration for the first time. Tests on model data verify that the combination of the two methods can achieve near-perfect results in application.展开更多
基金supported by the National Natural Science Foundation of China(No.52401221)Shandong Provincial Natural Science Foundation,China(No.ZR2022QE014)+1 种基金the Basic Scientific Research Fund for Central Universities(No.202112018)the Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education)。
文摘Lithium(Li)metal is considered the most promising anode material for the next generation of secondary batteries due to its high theoretical specific capacity and low potential.However,the application of Li anode in rechargeable Li metal batteries(LMBs)is hindered due to the short cycle life caused by uncontrolled dendrite growth.In this work,a dendrite-free anode(Li–Sn/Cu)is reinforced synergistically by lithophilic alloy,and a 3D grid structure is designed.Li^(+)diffusion and uniform nucleation are effectively induced by the lithophilic alloy Li_(22)Sn_(5).Moreover,homogeneous deposition of Li^(+)is caused by the reversible gridded Li plating/stripping effect of Cu mesh.Furthermore,the local space electric field is redistributed throughout the 3D conductive network,whereby the tip effect is suppressed,thus inhibiting the growth of Li dendrites.Also,the volume expansion of the anode during cycling is eased by the 3D grid structure.The results show that the Li–Sn/Cu symmetric battery can stably cycle for more than 10,000 h at 2 mA.cm^(-2)and 1 mAh.cm^(-2)with a low overpotential.The capacity retention of the LiFePO_(4)full battery remains above 90.7%after 1,000 cycles at 1C.This work provides a facile,low-cost,and effective strategy for obtaining Li metal batteries with ultra-long cycle life.
基金Project supported by the National Natural Science Foundation of China (Grant No 50875255)
文摘The propagation characteristics of flexural waves in periodic grid structures designed with the idea of phononic crystals are investigated by combining the Bloch theorem with the finite element method. This combined analysis yields phase constant surfaces, which predict the location and the extension of band gaps, as well as the directions and the regions of wave propagation at assigned frequencies. The predictions are validated by computation and experimental analysis of the harmonic responses of a finite structure with 11 × 11 unit cells. The flexural wave is localized at the point of excitation in band gaps, while the directional behaviour occurs at particular frequencies in pass bands. These studies provide guidelines to designing periodic structures for vibration attenuation.
文摘The title compound [Cu（bix）2（NO3）z·H2P]n 1 （bix = 1,4-bis（imidazole-1-ylme-thyl） benzene） has been synthesized by hydrothermal method. Its crystal structure is of monoclinic, space group P1^- with a = 8.3075（13）, b = 9.4725（13）, c = 10.0192（13） A, α = 91.088（4）, β = 104.063（6）, γ = 101.88（1）, V = 746.5（3） A^3, Z = 1, C28H30N10O7Cu1, Mr = 682.16, Dc = 1.518 g/cm^3, μ = 0.796 mm^-1, F（000） = 353, the final R = 0.0535 and wR = 0.0996 for 2921 observed reflections with I 〉 2σ（I）. Each bix ligand binds two Cu（Ⅱ） ions to form a 2-D（4,4） square grid layer, which is connected by hydrogen bonds showing large channels occupied by solvated water molecules and nitrate anions.
基金supported by the National Science and Technology Support Program (2011BAK12B00)
文摘The herringbone water-sediment separation structure(HWSSS) was developed to prevent debris flows. This paper mainly focuses on evaluating the sediment separation efficiency of HWSSS in debris flow prevention and determining the grid opening width D, a crucial structure parameter for HWSSS design. Theoretical analysis on the total sediment separation rate Pt reveals that the efficiency of sediment separation is much related with sediment grain size distribution(GSD) and grid opening width. The lower limit of Pt is deduced from the perspective of safety consideration by transforming debris flow into sediment-laden flow. Hydraulic model tests were carried out. Based on the regression analysis of the experimental data, the quantitative relationships between Pt and D and GSD characteristic values were finally established. A procedure for determining optimal grid opening width is proposed based on these analyses. These results are of significance in evaluating sediment separation effect by HWSSS in debris flow prevention and contribute to a more explicit methodology for design of HWSSS.
基金Funded by the National Natural Science Foundation of China(No.10572012)
文摘The reflection characteristics of gird structures are calculated by the spatial network method in the case of normal incidence plane electromagnetic wave. The numerical result shows that the grid panels without electromagnetic wave absorbing foams are not ideal. However, the absorbing ability can be achieved as low as -25 dBsm from 8 GHz to 12 GHz when the grid cells are filled with foam absorbers. Also it is noted from computation that the foam filled grid structures with larger cell size, higher and thinner ribs will improve the absorbing abilities, which illustrates that they can be used as the effective light-weight stealth structures for aeronautical application.
文摘This paper presents an improved unstructured grid immersed boundary method.The advantages of both immersed boundary method and body fitted grids which are generated by unstructured grid technology are used to enhance the computation efficiency of fluid structure interaction in complex domain.The Navier-Stokes equation was discretized spacially with collocated finite volume method and Euler implicit method in time domain.The rigid body motion was simulated by immersed boundary method in which the fluid and rigid body interface interaction was dealt with VOS(volume of solid) method.A new VOS calculation method based on graph was presented in which both immersed boundary points and cross points were collected in arbitrary order to form a graph.The method is verified with flow past oscillating cylinder.
基金supported by the National Numerical Windtunnel Project, China
文摘The increasing grid data in CFD simulation has brought some new difficulties and challenges,such as high storage cost,low transmission efficiency.In order to overcome these problems,a novel method for compressing and saving the structured grid are proposed.In the present method,the geometric coordinates of the six logical domains of one grid block is saved instead of all grid vertex coordinates to reduce the size of the structured grid file when the grid is compressed.And all grid vertex coordinates are recovered from the compressed data with the use of the transfinite interpolation algorithm when the grid is decompressed.Firstly,single-block grid cases with different edge vertexes are tested to investigate the compression effect.The test results show that a higher compression ratio will be obtained on a larger grid.Secondly,further theoretical analysis is carried out to investigate the effects of parameters on grid compression.The analysis on single-block grid compression shows that the compression ratio is proportionate to the cubic root of the number of total vertexes.The highest compression ratio of single-block grid is obtained when the numbers of vertexes in three logical directions are equal.The analysis on multi-block grid compression shows that a higher compression ratio will be obtained when a larger difference of total vertexes number exists among the grid blocks.Finally,multi-blockgrids of two industrial aircraft configurations are compressed to validate the method.The compression results demonstrate that the present method has an excellent ability on structured grid compression.For a million-vertex structured grid,more than 80 percent disk space can be saved after compression.
文摘Liquid crystalline multi-block copolymers poly[1,6-bis(4-oxybenzoyl-oxy)hexane terephthalate]-b-bisphenol A polycarbonate (PHTH-6-b-PC) with different segments of polycarbonate (PC) and thermotropic polyester PHTH-6 were synthesized in tetrachloroethane at 144 similar to 146 degrees C. The influence of segment length on the resulting phase structure and thermal behavior of block copolymers was also discussed. It is demonstrated by TEM and DMA that the resulting block copolymers show a considerable microphase separation. The degree of phase separation and the thermal behavior of the block copolymers are strongly dependent on the molecular weight of the segments incorporated.
文摘Based on a control grid network and in combination with a remote total station and digital camera,the distribution of steel nodes and deflection curve of a steel grid structure can be obtained easily.The measurement result shows that this method is effective and utilitarian.
文摘The section of electric power is the foundation of national economy. The paper analyzes the relation between industrial structure and grid load in Shanxi province, and finds out that electricity demand and grid load relate linearly to value added of industry. In the end, the paper predicts electricity demand and grid load via the model.
文摘An overset grid methodology is developed for the fully coupled analysis of fluid-structure interaction (FSI) problems. The overset grid approach alleviates some of the computational geometry difficulties traditionally associated with Arbitrary-Lagrangian-Eulerian (ALE) based, moving mesh methods for FSI. Our partitioned solution algorithm uses separate solvers for the fluid (finite volume method) and the structure (finite element method), with mesh motion computed only on a subset of component grids of our overset grid assembly. Our results indicate a significant reduction in computational cost for the mesh motion, and element quality is improved. Numerical studies of the benchmark test demonstrate the benefits of our overset mesh method over traditional approaches.
文摘Based on the first-order upwind and second-order central type of finite volume (UFV and CFV) scheme, upwind and central type of perturbation finite volume (UPFV and CPFV) schemes of the Navier-Stokes equations were developed. In PFV method, the mass fluxes of across the cell faces of the control volume (CV) were expanded into power series of the grid spacing and the coefficients of the power series were determined by means of the conservation equation itself. The UPFV and CPFV scheme respectively uses the same nodes and expressions as those of the normal first-order upwind and second-order central scheme, which is apt to programming. The results of numerical experiments about the flow in a lid-driven cavity and the problem of transport of a scalar quantity in a known velocity field show that compared to the first-order UFV and second-order CFV schemes, upwind PFV scheme is higher accuracy and resolution, especially better robustness. The numerical computation to flow in a lid-driven cavity shows that the under-relaxation factor can be arbitrarily selected ranging from (0.3) to (0.8) and convergence perform excellent with Reynolds number variation from 10~2 to 10~4.
基金Supported by the National Natural Science Foundation of China(No.51975164)Outstanding Youth of Pyramid Talent Training Project ofBeijing University of Civil Engineering and Architecture(No.GDRC20220801)。
文摘In order to solve the problem of excessive noise and vibration during the operation of the hydraulic transformer,an optimization method of valve plate damping hole structure is proposed to alleviate the phenomenon of pressure shock.Firstly,the mathematical model of oil pressure gradient in the plunger cavity is established,and the incremental equation of pressure change is derived.Secondly,a kind of buffering structure is proposed,the corresponding relationship between the pressure change and the envelopment angle of the buffering hole and the aperture size is determined by analyzing the oil pressure change curve in the plunger cavity.Finally,the flow field models with buffering holes are established,and the transient simulation of the pressure change process under the optimal solution is carried out with ANSYS software and the flow field pressure distribution contours are obtained.Through the analysis of simulation results,it is concluded that the optimal envelope angle of the three buffer holes ofA-T-B-Ais 5°,and the optimal aperture is 1.8 mm,1.6 mm,and 1.7 mm,respectively.The buffer hole can achieve a better-buffering effect in the range of variable pressure angle[0°,101°].The buffer hole structure can effectively alleviate the pressure shock and reduce the noise level,which lays a foundation for the design and theoretical research of hydraulic transformers.
文摘There are various construction methods of long-span steel structure. In this paper, sap2000 is used to analyze the overall lifting technology of a 72*144m long-span steel structure. The grid structure is divided into two areas for lifting, and there are four different areas for different repair welding areas and lifting methods. By analyzing the indexes of stress, deformation and internal force of structure construction under different construction zoning schemes, the best construction scheme can be selected. The calculation results show that the construction deformation of the second scheme is the smallest, with the final deformation of 49.164mm, the maximum stress ratio of the components after construction being 0.204, and the stress ratio of the components under the load of 1.3D+1.5L being 0.8098, which is basically the same as the stress ratio of 0.80 obtained by the one-time loading design, so the second scheme is finally selected.
文摘A numerical method for simulating nonlinear fluid-rigid structure interaction problems is developed. The structure is assumed to undergo large rigid body motions and the fluid flow is governed by nonlinear, viscous or non-viscous, field equations with nonlinear boundary conditions applied to the free surface and fluid-solid interaction interfaces. An Arbitrary-LagrangianEulerian (ALE) mesh system is used to construct the numerical model. A multi-block numerical scheme of study is adopted allowing for the relative motion between moving overset grids, which are independent of one another. This provides a convenient method to overcome the difficulties in matching fluid meshes with large solid motions. Nonlinear numerical equations describing nonlinear fluid-solid interaction dynamics are derived through a numerical discretization scheme of study. A coupling iteration process is used to solve these numerical equations. Numerical examples are presented to demonstrate applications of the model developed.
基金Anhui Province Key Research and Development Plan of the Ecological Environment Project(No.202104i07020016).
文摘In this study,Computational Fluid Dynamics(CFD)together with a component transport model are exploited to investigate the influence of dimensionless parameters,involving the height of the rectifier grid and the installation height of the first catalyst layer,on the flow field and the overall denitration efficiency of a cement kiln’s SCR(Selective catalytic reduction)denitrification reactor.It is shown that accurate numerical results can be obtained by fitting the particle size distribution function to the actual cement kiln fly ash and implementing a non-uniform particle inlet boundary condition.The relative error between denitration efficiency derived from experimental data,numerical simulation,and real-time system pressure drop ranges from 4%to 9%.Optimization of the SCR reactor is achieved when the rectifier grid thickness ratio k/H≥0.030,the rectifier grid height ratio h/H=0.04,and the spacing between the rectifier grid and the first catalyst layer l/H=0.10.Under these conditions,airflow distribution and particle dispersion upstream of the catalyst result in increased denitration efficiencies of 3.21%,3.43%,and 3.27%,respectively,compared to the least favorable operating conditions.
基金sponsored by National Natural Science Foundation(40474041)National Symposium of 863(2006AA06Z206)+1 种基金National Symposium of 973(2007CB209605)CNPC Geophysical Key Laboratory of the China University of Petroleum (East China) Research Department
文摘Compared with other migration methods, reverse-time migration is based on a precise wave equation, not an approximation, and performs extrapolation in the depth domain rather than the time domain. It is highly accurate and not affected by strong subsurface structure complexity and horizontal velocity variations. The difference method based on triangular grids maintains the simplicity of the difference method and the precision of the finite element method. It can be used directly for forward modeling on models with complex top surfaces and migration without statics preprocessing. We apply a finite difference method based on triangular grids for post-stack reverse-time migration for the first time. Tests on model data verify that the combination of the two methods can achieve near-perfect results in application.
