Computational fluid dynamics （CFD） combined with detailed chemical kinetics was employed to model the filtration combustion of a mixture of methane/air in a packed bed of uniform 3 mm diameter alumina spherical part...Computational fluid dynamics （CFD） combined with detailed chemical kinetics was employed to model the filtration combustion of a mixture of methane/air in a packed bed of uniform 3 mm diameter alumina spherical particles. The standard k-ε turbulence model and a methane oxidation mechanism with 23 species and 39 elemental reactions were used. Various equivalence ratios （1.47, 1.88, 2.12 and 2.35） were studied. The numerical results showed good agreement with the experimental data. For ultra-rich mixtures, the combustion temperature exceeds the adiabatic value by hundreds of centigrade degrees. Syngas （hydrogen and carbon monoxide） can be obtained up to a mole fraction of 23%. The numerical results also showed that the combination of CFD with detailed chemical kinetics gives good performance for modeling the pseudo-homogeneous flames of methane in porous media.展开更多
TiO2 fibers were prepared via alternatively introducing water vapor and Ti precursor carried by N2 to an APCVD （chemical vapor deposition under atmospheric pressure） reactor at ≤200 ℃. Activated carbon fibers （A...TiO2 fibers were prepared via alternatively introducing water vapor and Ti precursor carried by N2 to an APCVD （chemical vapor deposition under atmospheric pressure） reactor at ≤200 ℃. Activated carbon fibers （ACFs） were used as templates for deposition and later removed by calcinations. The obtained catalysts were characterized by scanning electron micros- copy （SEM）, transmission electron microscopy （TEM）, Brunauer, Emmett and Teller （BET） and X-ray diffraction （XRD） analysis The pores within TiO2 fibers included micro-range and meso-range, e.g., 7 nm, and the specific surface areas for TiO2 fibers were 141 m^2/g and 148 m^2/g for samples deposited at 100 ℃ and 200℃ （using ACFI700 as template）, respectively. The deposition temperature significantly influenced TiO2 morphology. The special advantages of this technique for preparing porous nano-material include no consumption of organic solvent in the process and easy control of deposition conditions and speeds.展开更多
This investigation and morphology analysis of porous structure of some kinds of natural materials such as chicken eggshell, partridge eggshell, pig bone, and seeds of mung bean, soja, ginkgo, lotus seed, as well as th...This investigation and morphology analysis of porous structure of some kinds of natural materials such as chicken eggshell, partridge eggshell, pig bone, and seeds of mung bean, soja, ginkgo, lotus seed, as well as the epidermis of apples, with SEM (Scanning Electronic Microscope) showed that natural structures’ pores can be classified into uniform pores, gradient pores and multi pores from the viewpoint of the distribution variation of pore density, size and geometry. Furthermore, an optimal design of porous bearings was for the first time developed based on the gradient configuration of natural materials. The bionic design of porous structures is predicted to be widely developed and applied in the fields of materials and mechanical engineering in the future.展开更多
Porous biomaterials are widely used as bone replacement materials because of thers high biocompatibility and osteoconductivity property. Understanding of their porous structure (i.e. geometrical and topological charac...Porous biomaterials are widely used as bone replacement materials because of thers high biocompatibility and osteoconductivity property. Understanding of their porous structure (i.e. geometrical and topological characteristic) and studying how to the body fluid flow through them are essential to investigate the degradation behaviour at the surface-liquid interface. This research develops a numerical model to simulate the porous structure of biomaterials based on the stochastic approach in pore size distribution and interconnectivity.展开更多
A 3-dimensional unit cell model is developed for analyzing effective thermal conductivity of xonotlite-aerogelcomposite insulation material based on its microstructure features. Effective thermal conductivity comparis...A 3-dimensional unit cell model is developed for analyzing effective thermal conductivity of xonotlite-aerogelcomposite insulation material based on its microstructure features. Effective thermal conductivity comparisonsbetween xonotlite-type calcium silicate and aerogel as well as xonotlite-aerogel composite insulation material arepresented. It is shown that the density of xonotlite-type calcium silicate is the key factor affecting the effectivethermal conductivity of xonotlite-aerogel composite insulation material, and the density of aerogel has little influence.The effective thermal conductivity can be lowered greatly by composite of the two materials at an elevatedtemperature.展开更多
基金Supported by the National Natural Science Foundation of China （20307007, 50576081） and the Natural Science Foundation of Zhejiang Province （R 107532）, Program for New Century Excellent Talents in University （NCET-07-0761） and a Foundation for the Author of National Excellent Doctoral Dissertation of China （200747）.
文摘Computational fluid dynamics （CFD） combined with detailed chemical kinetics was employed to model the filtration combustion of a mixture of methane/air in a packed bed of uniform 3 mm diameter alumina spherical particles. The standard k-ε turbulence model and a methane oxidation mechanism with 23 species and 39 elemental reactions were used. Various equivalence ratios （1.47, 1.88, 2.12 and 2.35） were studied. The numerical results showed good agreement with the experimental data. For ultra-rich mixtures, the combustion temperature exceeds the adiabatic value by hundreds of centigrade degrees. Syngas （hydrogen and carbon monoxide） can be obtained up to a mole fraction of 23%. The numerical results also showed that the combination of CFD with detailed chemical kinetics gives good performance for modeling the pseudo-homogeneous flames of methane in porous media.
基金Project (No. 20477006) supported by the National Natural ScienceFoundation of China
文摘TiO2 fibers were prepared via alternatively introducing water vapor and Ti precursor carried by N2 to an APCVD （chemical vapor deposition under atmospheric pressure） reactor at ≤200 ℃. Activated carbon fibers （ACFs） were used as templates for deposition and later removed by calcinations. The obtained catalysts were characterized by scanning electron micros- copy （SEM）, transmission electron microscopy （TEM）, Brunauer, Emmett and Teller （BET） and X-ray diffraction （XRD） analysis The pores within TiO2 fibers included micro-range and meso-range, e.g., 7 nm, and the specific surface areas for TiO2 fibers were 141 m^2/g and 148 m^2/g for samples deposited at 100 ℃ and 200℃ （using ACFI700 as template）, respectively. The deposition temperature significantly influenced TiO2 morphology. The special advantages of this technique for preparing porous nano-material include no consumption of organic solvent in the process and easy control of deposition conditions and speeds.
文摘This investigation and morphology analysis of porous structure of some kinds of natural materials such as chicken eggshell, partridge eggshell, pig bone, and seeds of mung bean, soja, ginkgo, lotus seed, as well as the epidermis of apples, with SEM (Scanning Electronic Microscope) showed that natural structures’ pores can be classified into uniform pores, gradient pores and multi pores from the viewpoint of the distribution variation of pore density, size and geometry. Furthermore, an optimal design of porous bearings was for the first time developed based on the gradient configuration of natural materials. The bionic design of porous structures is predicted to be widely developed and applied in the fields of materials and mechanical engineering in the future.
基金Funded by"973" project which serial number is G19990 6 4 70 1
文摘Porous biomaterials are widely used as bone replacement materials because of thers high biocompatibility and osteoconductivity property. Understanding of their porous structure (i.e. geometrical and topological characteristic) and studying how to the body fluid flow through them are essential to investigate the degradation behaviour at the surface-liquid interface. This research develops a numerical model to simulate the porous structure of biomaterials based on the stochastic approach in pore size distribution and interconnectivity.
基金supported by the National Natural Science Foundation of China (No.50806021)Program for Changjiang Scholars and Inn ovative Researeh Team in University (PCSIRT0720).
文摘A 3-dimensional unit cell model is developed for analyzing effective thermal conductivity of xonotlite-aerogelcomposite insulation material based on its microstructure features. Effective thermal conductivity comparisonsbetween xonotlite-type calcium silicate and aerogel as well as xonotlite-aerogel composite insulation material arepresented. It is shown that the density of xonotlite-type calcium silicate is the key factor affecting the effectivethermal conductivity of xonotlite-aerogel composite insulation material, and the density of aerogel has little influence.The effective thermal conductivity can be lowered greatly by composite of the two materials at an elevatedtemperature.
