To obtain the performance characteristics of hydrodynamic tractor-retarder assembly under traction work condition,a numerical simulation model of flow channel was established and tetrahedron unstructured grids were ad...To obtain the performance characteristics of hydrodynamic tractor-retarder assembly under traction work condition,a numerical simulation model of flow channel was established and tetrahedron unstructured grids were adopted in the meshing stage.The racing rotating speed of the brake wheels was calculated by computational fluid dynamics（CFD） calculation and interpolation,and then accurate boundary condition was applied to the CFD simulation to study the pressure and velocity distribution of internal flow field in hydrodynamic tractor-retarder assembly.Finally,the original characteristics were calculated by CFD post-processing analysis.Comparison of experimental data and flow field analysis results showed that the calculation tolerance of the torque ratio K and the efficiency η was less than 5%,and the calculation tolerance of the pump torque coefficient λ was less than 10%.展开更多
Dielectrophoresis(DEP)describes the motion of suspended objects when exposed to an inhomogeneous electric field.It has been successful as a method for parallel and site-selective assembling of nanotubes from a dispers...Dielectrophoresis(DEP)describes the motion of suspended objects when exposed to an inhomogeneous electric field.It has been successful as a method for parallel and site-selective assembling of nanotubes from a dispersion into a sophisticated device architecture.Researchers have conducted extensive works to understand the DEP of nanotubes in aqueous ionic surfactant solutions.However,only recently,DEP was applied to polymer-wrapped single-walled carbon nanotubes(SWCNTs)in organic solvents due to the availability of ultra-pure SWCNT content.In this paper,the focus is on the difference between the DEP in aqueous and organic solutions.It starts with an introduction into the DEP of carbon nanotubes(CNT-DEP)to provide a comprehensive,in-depth theoretical background before discussing in detail the experimental procedures and conditions.For academic interests,this work focuses on the CNT-DEP deposition scheme,discusses the importance of the electrical double layer,and employs finite element simulations to optimize CNT-DEP deposition condition with respect to the experimental observation.An important outcome is an understanding of why DEP in organic solvents allows for the deposition and alignment of SWCNTs in low-frequency and even static electric fields,and why the response of semiconducting SWCNTs(s-SWCNTs)is strongly enhanced in non-conducting,weakly polarizable media.Strategies to further improve CNT-DEP for s-SWCNT-relevant applications are given as well.Overall,this work should serve as a practical guideline to select the appropriate setting for effective CNT DEPs.展开更多
基金Supported by the National Key Laboratory of Vehicular Transmission (9140C3405020905)the National Natural Science Foundation of China(50905016)
文摘To obtain the performance characteristics of hydrodynamic tractor-retarder assembly under traction work condition,a numerical simulation model of flow channel was established and tetrahedron unstructured grids were adopted in the meshing stage.The racing rotating speed of the brake wheels was calculated by computational fluid dynamics（CFD） calculation and interpolation,and then accurate boundary condition was applied to the CFD simulation to study the pressure and velocity distribution of internal flow field in hydrodynamic tractor-retarder assembly.Finally,the original characteristics were calculated by CFD post-processing analysis.Comparison of experimental data and flow field analysis results showed that the calculation tolerance of the torque ratio K and the efficiency η was less than 5%,and the calculation tolerance of the pump torque coefficient λ was less than 10%.
基金S.Flavel acknowledges support from the Deutsche Forschungsgemeinschafts Emmy Noether Program under grant number FL 834/1-1.
文摘Dielectrophoresis(DEP)describes the motion of suspended objects when exposed to an inhomogeneous electric field.It has been successful as a method for parallel and site-selective assembling of nanotubes from a dispersion into a sophisticated device architecture.Researchers have conducted extensive works to understand the DEP of nanotubes in aqueous ionic surfactant solutions.However,only recently,DEP was applied to polymer-wrapped single-walled carbon nanotubes(SWCNTs)in organic solvents due to the availability of ultra-pure SWCNT content.In this paper,the focus is on the difference between the DEP in aqueous and organic solutions.It starts with an introduction into the DEP of carbon nanotubes(CNT-DEP)to provide a comprehensive,in-depth theoretical background before discussing in detail the experimental procedures and conditions.For academic interests,this work focuses on the CNT-DEP deposition scheme,discusses the importance of the electrical double layer,and employs finite element simulations to optimize CNT-DEP deposition condition with respect to the experimental observation.An important outcome is an understanding of why DEP in organic solvents allows for the deposition and alignment of SWCNTs in low-frequency and even static electric fields,and why the response of semiconducting SWCNTs(s-SWCNTs)is strongly enhanced in non-conducting,weakly polarizable media.Strategies to further improve CNT-DEP for s-SWCNT-relevant applications are given as well.Overall,this work should serve as a practical guideline to select the appropriate setting for effective CNT DEPs.
