The nanometer particles of TiO_2 and TiO_2/SiO_2 oxides wereprepared by sol-gel supercritical fluid drying method. The propertiesof TiO_2 and TiO_2/SiO_2 were characterized by means of BET(Brunner-Emmett- Teller metho...The nanometer particles of TiO_2 and TiO_2/SiO_2 oxides wereprepared by sol-gel supercritical fluid drying method. The propertiesof TiO_2 and TiO_2/SiO_2 were characterized by means of BET(Brunner-Emmett- Teller method), TEM (transmission electronmicroscopy), SEM (scanning electron microscopy), XRD (X-ray diffrac-tion) and FTIR (Fourier transform-infrared) techniques. The effectsof different preparation route, prehydrolysis and non-prehydrolysis,on the properties of TiO_2/SiO_2 oxide were also examined.展开更多
The hydrodynamic behavior of fine powders in jet-fluidized beds was studiednumerically and experimentally. The starting point of numerical simulation was the generalizedNavier-Stokes (N-S) equations for the gas and so...The hydrodynamic behavior of fine powders in jet-fluidized beds was studiednumerically and experimentally. The starting point of numerical simulation was the generalizedNavier-Stokes (N-S) equations for the gas and solids phases. The κ-ε turbulence model was used forhigh-speed gas jets in fluidized beds. Computation shows that a suitable turbulence model isnecessary to obtain agreement between the simulation and literature experimental data for ahigh-speed gas jet. The model was applied to simulating the fluidization of fine powders influidized beds with an upward or a downward air jet. An empirical cohesion model was obtained bycorrelating the cohesive force between fine particles using a cohetester. The cohesion model wasembedded into the two-fluid model to simulate the fluidization of fine powders in two-dimensional(2-D) beds. To study the fluidization behavior of fine and cohesive powders with a downward jet,experiments were performed in a 2-D bed. Agreement between the computed time-averaged porosity andmeasured data was obtained. With an upward jet in the bed center, the measured and computedporosities show a dilute central core, especially at very high jet velocities. Based on ourexperiments and computations, a downward jet located inside the bed is recommended to achieve bettermixing and contacting of gas and solids.展开更多
For patients with lung disease,dry powder inhalers(DPI)are profoundly beneficial.The current study introduces and develops a series of dry powder inhalers(DPIs).A capsule-based(size 0)active DPI was considered.The stu...For patients with lung disease,dry powder inhalers(DPI)are profoundly beneficial.The current study introduces and develops a series of dry powder inhalers(DPIs).A capsule-based(size 0)active DPI was considered.The study aims to investigate whether swirling flow and outlet capillary diameter(dc_out)affect the percentage of emitted doses(ED)released from the capsule.Spiral vanes were added to the capillary inlet to produce a swirling flow.Computational fluid dynamics(CFD)was applied to simulate the problem.The results were compared with previous in vitro and numerical studies to validate the results.Based on the derived results,the small swirl parameter(SP)enhances the secondary flow and recirculation zone.It increases the central jet flow,which increases the ED value by about 5–20%compared to no-swirl flow.However,as the airflow rate increases,the recirculation zone enlarges,vorticities become dominant,and asymmetrical flow patterns emerge.Consequently,ED%drops significantly(more than 50%).As d_(c_out)decreases,the vorticities around the outlet capillary become more potent,which is undesirable.Indeed,the emptying of the capsule does not happen ideally.The research provides a perspective on the device's design and DPI performance.展开更多
Based on computational fluid dynamics method,the effect of atomization gas pressure on the atomization efficiency of Laval nozzle was studied,and then a discrete phase model was established and combined with industria...Based on computational fluid dynamics method,the effect of atomization gas pressure on the atomization efficiency of Laval nozzle was studied,and then a discrete phase model was established and combined with industrial trials to study the effect of a new type of assisted gas nozzles(AGNs)on powder size distribution and amorphous powder yield.The results show that increasing the atomization pressure can effectively improve the gas velocity for the Laval nozzle;however,it will decrease the aspiration pressure,and the optimal atomization pressure is 2.0 MPa.Compared with this,after the application of AGNs with the inlet velocity of 200 m s^(-1),assisted gas jet can increase the velocity of overall droplets in the break-up and solidification area by 40 m s^(-1) and the maximum cooling rate is increased from 1.9×10^(4) to 2.3×10^(4) K s^(-1).The predicted particle behavior is demonstrated by the industrial trails,that is,after the application of AGNs,the median diameter of powders d50 is decreased from 28.42 to 25.56 lm,the sphericity is increased from 0.874 to 0.927,the fraction of amorphous powders is increased from 90.4% to 99.4%,and only the coercivity is increased slightly due to the accumulation of internal stress.It is illustrated that the AGNs can improve the yield of fine amorphous powders,which is beneficial to providing high-performance raw powders for additive manufacturing technology.展开更多
Coprecipitation supercritical fluid drying technology has been employed to synthesize calcia-stabilized zirconia ultrafine powder with low-cost inorganic salts as the starting materials. The sintering behaviors of the...Coprecipitation supercritical fluid drying technology has been employed to synthesize calcia-stabilized zirconia ultrafine powder with low-cost inorganic salts as the starting materials. The sintering behaviors of these powders were also investigated. The results showed that supercritical fluid drying could effectively alleviate the hard agglomeration of grains during the gel drying process, and the morphology of the powder retained the network texture of the original gel. The resulting particles were characterized by small particle size (5-20 nm), better monodispersity and high surface area, which gave rise to high activity and sinterability. Consequently, these powders could readily be compacted into the desired shape and their densification could be carried out in shorter time and at lower temperatures. For instance, nanometer-sized powder calcined at 600癈 for 2 h could be cold-pressed into a green body and sintered at 1100?for 0.5 h to attain a dense body with bulk density of 5.9718 g/cm3 and specific pore volume of 0.0008 cm3/g.展开更多
基金Supported by PetroChina Company Limited (990801-21-2).
文摘The nanometer particles of TiO_2 and TiO_2/SiO_2 oxides wereprepared by sol-gel supercritical fluid drying method. The propertiesof TiO_2 and TiO_2/SiO_2 were characterized by means of BET(Brunner-Emmett- Teller method), TEM (transmission electronmicroscopy), SEM (scanning electron microscopy), XRD (X-ray diffrac-tion) and FTIR (Fourier transform-infrared) techniques. The effectsof different preparation route, prehydrolysis and non-prehydrolysis,on the properties of TiO_2/SiO_2 oxide were also examined.
基金supported by the National Natural Science Foundation of China(NNSFC,No.20476065)the Scientific Re-search Foundation for the Retumed Overseas Chinese Scholars of State Education Ministry(SRF for ROCS,SEM)Multi-Phase Reaction Laboratory(MPR)at the Institute of Process Engineering(IPE),Chinese Academy of Sciences(CAS).
文摘The hydrodynamic behavior of fine powders in jet-fluidized beds was studiednumerically and experimentally. The starting point of numerical simulation was the generalizedNavier-Stokes (N-S) equations for the gas and solids phases. The κ-ε turbulence model was used forhigh-speed gas jets in fluidized beds. Computation shows that a suitable turbulence model isnecessary to obtain agreement between the simulation and literature experimental data for ahigh-speed gas jet. The model was applied to simulating the fluidization of fine powders influidized beds with an upward or a downward air jet. An empirical cohesion model was obtained bycorrelating the cohesive force between fine particles using a cohetester. The cohesion model wasembedded into the two-fluid model to simulate the fluidization of fine powders in two-dimensional(2-D) beds. To study the fluidization behavior of fine and cohesive powders with a downward jet,experiments were performed in a 2-D bed. Agreement between the computed time-averaged porosity andmeasured data was obtained. With an upward jet in the bed center, the measured and computedporosities show a dilute central core, especially at very high jet velocities. Based on ourexperiments and computations, a downward jet located inside the bed is recommended to achieve bettermixing and contacting of gas and solids.
基金This work was supported the National Natural Science Foundation of China(grant No.12172146).
文摘For patients with lung disease,dry powder inhalers(DPI)are profoundly beneficial.The current study introduces and develops a series of dry powder inhalers(DPIs).A capsule-based(size 0)active DPI was considered.The study aims to investigate whether swirling flow and outlet capillary diameter(dc_out)affect the percentage of emitted doses(ED)released from the capsule.Spiral vanes were added to the capillary inlet to produce a swirling flow.Computational fluid dynamics(CFD)was applied to simulate the problem.The results were compared with previous in vitro and numerical studies to validate the results.Based on the derived results,the small swirl parameter(SP)enhances the secondary flow and recirculation zone.It increases the central jet flow,which increases the ED value by about 5–20%compared to no-swirl flow.However,as the airflow rate increases,the recirculation zone enlarges,vorticities become dominant,and asymmetrical flow patterns emerge.Consequently,ED%drops significantly(more than 50%).As d_(c_out)decreases,the vorticities around the outlet capillary become more potent,which is undesirable.Indeed,the emptying of the capsule does not happen ideally.The research provides a perspective on the device's design and DPI performance.
基金funded by Key research and development project of Shandong province in China(Grant Number 2018TSCYCX-10).
文摘Based on computational fluid dynamics method,the effect of atomization gas pressure on the atomization efficiency of Laval nozzle was studied,and then a discrete phase model was established and combined with industrial trials to study the effect of a new type of assisted gas nozzles(AGNs)on powder size distribution and amorphous powder yield.The results show that increasing the atomization pressure can effectively improve the gas velocity for the Laval nozzle;however,it will decrease the aspiration pressure,and the optimal atomization pressure is 2.0 MPa.Compared with this,after the application of AGNs with the inlet velocity of 200 m s^(-1),assisted gas jet can increase the velocity of overall droplets in the break-up and solidification area by 40 m s^(-1) and the maximum cooling rate is increased from 1.9×10^(4) to 2.3×10^(4) K s^(-1).The predicted particle behavior is demonstrated by the industrial trails,that is,after the application of AGNs,the median diameter of powders d50 is decreased from 28.42 to 25.56 lm,the sphericity is increased from 0.874 to 0.927,the fraction of amorphous powders is increased from 90.4% to 99.4%,and only the coercivity is increased slightly due to the accumulation of internal stress.It is illustrated that the AGNs can improve the yield of fine amorphous powders,which is beneficial to providing high-performance raw powders for additive manufacturing technology.
基金the National Natural Science Foundation of China under grant No.20133040
文摘Coprecipitation supercritical fluid drying technology has been employed to synthesize calcia-stabilized zirconia ultrafine powder with low-cost inorganic salts as the starting materials. The sintering behaviors of these powders were also investigated. The results showed that supercritical fluid drying could effectively alleviate the hard agglomeration of grains during the gel drying process, and the morphology of the powder retained the network texture of the original gel. The resulting particles were characterized by small particle size (5-20 nm), better monodispersity and high surface area, which gave rise to high activity and sinterability. Consequently, these powders could readily be compacted into the desired shape and their densification could be carried out in shorter time and at lower temperatures. For instance, nanometer-sized powder calcined at 600癈 for 2 h could be cold-pressed into a green body and sintered at 1100?for 0.5 h to attain a dense body with bulk density of 5.9718 g/cm3 and specific pore volume of 0.0008 cm3/g.
