In order to reveal the intrinsic fluid-dynamic mechanisms of a pressure-swirl nozzle used for Si3N4 dry granulation,and effectively predict its external spray characteristics,the dynamics of air-atomized liquid two-p...In order to reveal the intrinsic fluid-dynamic mechanisms of a pressure-swirl nozzle used for Si3N4 dry granulation,and effectively predict its external spray characteristics,the dynamics of air-atomized liquid two-phase flow is analyzed using a VOF(Volume of Fraction)method together with the modified realizable k-εturbulence model.The influence of nozzle orifice shape on velocity distribution,pressure distribution is studied.The results show that the pressure difference in a convergent conical nozzle is the largest with a hollow air core being formed in the nozzle.The corresponding velocity of atomized liquid at nozzle orifice is the largest.Using a self-designed atomization experiment platform,the velocity and pressure of atomized liquid and the spray cone angle are measured for three nozzles with different orifice shapes.The micro-morphology of Si3N4 particles is also determined.These data confirm the correctness of numerical simulation.Considering atomization performance of the nozzle,the contraction conical nozzle is more suitable for the atomization of Si3N4 in practical production based on the dry granulation approach.展开更多
Radioactive tritium leakage from high-pressure storage vessels is a common nuclear leakage event.Different leakage conditions have different effects on tritium diffusion,resulting in different degrees of radioactive h...Radioactive tritium leakage from high-pressure storage vessels is a common nuclear leakage event.Different leakage conditions have different effects on tritium diffusion,resulting in different degrees of radioactive hazards.This study focuses on tritium leakage from high-pressure storage vessels and analyzes the influence of different leakage orifice shapes,leakage positions,and the presence of obstacles in the scene space on tritium leakage diffusion.The results show that there is little difference in the radial diffusion velocity of tritium gas along the jet axis between circular and square leakage orifices.The radial diffusion velocity of tritium gas in the long-axis direction of the rectangular leakage orifice is larger than that in the short-axis direction,and the larger the aspect ratio of the rectangle is,the greater the difference is in the diffusion velocity.In addition,leakage from the storage vessel below the air inlet is beneficial to the dilution of tritium,whereas leakage from the air vents leads to a slow decrease in the tritium concentration.The obstacles present in the tritium scene space hinder the migration of tritium gas and prolong the time for the tritium concentration to reach stabilization.This study provides a theoretical basis for the disposal of tritium in tritium leakage accidents by analyzing the influence of different leakage conditions in storage vessels on tritium gas diffusion.展开更多
基金the National Natural Science Foundation of China(Grant:51964022).
文摘In order to reveal the intrinsic fluid-dynamic mechanisms of a pressure-swirl nozzle used for Si3N4 dry granulation,and effectively predict its external spray characteristics,the dynamics of air-atomized liquid two-phase flow is analyzed using a VOF(Volume of Fraction)method together with the modified realizable k-εturbulence model.The influence of nozzle orifice shape on velocity distribution,pressure distribution is studied.The results show that the pressure difference in a convergent conical nozzle is the largest with a hollow air core being formed in the nozzle.The corresponding velocity of atomized liquid at nozzle orifice is the largest.Using a self-designed atomization experiment platform,the velocity and pressure of atomized liquid and the spray cone angle are measured for three nozzles with different orifice shapes.The micro-morphology of Si3N4 particles is also determined.These data confirm the correctness of numerical simulation.Considering atomization performance of the nozzle,the contraction conical nozzle is more suitable for the atomization of Si3N4 in practical production based on the dry granulation approach.
基金supported by the Youth Innovation Team of Shaanxi Universities and the Pre-research Fund(No.50926050408).
文摘Radioactive tritium leakage from high-pressure storage vessels is a common nuclear leakage event.Different leakage conditions have different effects on tritium diffusion,resulting in different degrees of radioactive hazards.This study focuses on tritium leakage from high-pressure storage vessels and analyzes the influence of different leakage orifice shapes,leakage positions,and the presence of obstacles in the scene space on tritium leakage diffusion.The results show that there is little difference in the radial diffusion velocity of tritium gas along the jet axis between circular and square leakage orifices.The radial diffusion velocity of tritium gas in the long-axis direction of the rectangular leakage orifice is larger than that in the short-axis direction,and the larger the aspect ratio of the rectangle is,the greater the difference is in the diffusion velocity.In addition,leakage from the storage vessel below the air inlet is beneficial to the dilution of tritium,whereas leakage from the air vents leads to a slow decrease in the tritium concentration.The obstacles present in the tritium scene space hinder the migration of tritium gas and prolong the time for the tritium concentration to reach stabilization.This study provides a theoretical basis for the disposal of tritium in tritium leakage accidents by analyzing the influence of different leakage conditions in storage vessels on tritium gas diffusion.
