A comparative study on the performance of gas atomized(GA)and rotating-disk atomized(RDA)aluminum alloy powders produced on industrial scale for laser directed energy deposition(L-DED)process was carried out.The powde...A comparative study on the performance of gas atomized(GA)and rotating-disk atomized(RDA)aluminum alloy powders produced on industrial scale for laser directed energy deposition(L-DED)process was carried out.The powder characteristics,the printing process window,and the quality,microstructure,and mechanical properties of printed parts were taken into account for comparison and discussion.The results demonstrate that the RDA powder is superior to the GA powder in terms of sphericity,surface quality,internal defects,flowability,and apparent density,together with a larger printing process window during the L-DED parts fabrication.Besides,the resultant parts from the RDA powder have higher dimensional accuracy,lower internal defects,more uniform and finer microstructure,and more favorable mechanical properties than those from the GA powder.展开更多
Combustion dynamics are a critical factor in determining the performance and reliabilityof a chemical propulsion engine.The underlying processes include liquid atomization,evaporation,mixing,and chemical reactions.Thi...Combustion dynamics are a critical factor in determining the performance and reliabilityof a chemical propulsion engine.The underlying processes include liquid atomization,evaporation,mixing,and chemical reactions.This paper presents a high-fidelity numerical study of liquidatomization and spray combustion under high-pressure conditions,emphasizing the effects of pres-sure oscillations on the flow evolution and combustion dynamics.The theoretical framework isbased on the three-dimensional conservation equations for multiphase flows and turbulent combus-tion.The numerical solution is achieved using a coupling method of volume-of-fluid and Lagran-gian particle tracking.The Zhuang-Kadota-Sutton(ZKS)high-pressure evaporation model andthe eddy breakup-Arrhenius combustion model are employed.Simulations are conducted for amodel combustion chamber with impinging-jet injectors using liquid oxygen and kerosene as pro-pellants.Both conditions with and without inlet and outlet pressure oscillations are considered.Thefindings reveal that pressure oscillations amplify flow fluctuations and can be characterized usingkey physical parameters such as droplet evaporation,chemical reaction,and chamber pressure.The spectral analysis uncovers the axial variations of the dominant and secondary frequenciesand their amplitudes in terms of the characteristic physical quantities.This research helps establisha methodology for exploring the coupling effect of liquid atomization and spray combustion.It alsoprovides practical insights into their responses to pressure oscillations during the occurrence ofcombustion instability.This information can be used to enhance the design and operation ofliquid-fueled propulsion engines.展开更多
The so-called close-coupled gas atomization process involves melting a metal and using a high-pressure gas jet positioned close to the melt stream to rapidly break it into fine,spherical powder particles.This techniqu...The so-called close-coupled gas atomization process involves melting a metal and using a high-pressure gas jet positioned close to the melt stream to rapidly break it into fine,spherical powder particles.This technique,adapted for blast furnace slag granulation using a circular seam nozzle,typically aims to produce solid slag particles sized 30–140μm,thereby allowing the utilization of slag as a resource.This study explores the atomization dynamics of liquid blast furnace slag,focusing on the effects of atomization pressure.Primary atomization is simulated using a combination of the Volume of Fluid(VOF)method and the Shear Stress Transport k-ωturbulence model,while secondary atomization is analyzed through the Discrete Phase Model(DPM).The results reveal that primary atomization progresses in three stages:the slag column transforms into an umbrella-shaped liquid film,whose leading edge fragments into particles while forming a cavity-like structure,which is eventually torn into ligaments.This primary deformation is driven by the interplay of airflow velocity in the recirculation zone and the guide tube outlet pressure(Fp).Increasing the atomization pressure amplifies airflow velocity,recirculation zone size,expansion and shock waves,though the guide tube outlet pressure variations remain irregular.Notably,at 4.5 MPa,the primary deformation is most pronounced.Secondary atomization yields finer slag particles as a result of more vigorous primary atomization.For this pressure,the smallest average particle size and the highest yield of particles within the target range(30–140μm)are achieved.展开更多
This review summarizes recent progress in the study of impinging-jet dynamics and atomization,with a focus on liquid sheet formation,instability mechanisms,and the influence of key parameters such as fluid properties,...This review summarizes recent progress in the study of impinging-jet dynamics and atomization,with a focus on liquid sheet formation,instability mechanisms,and the influence of key parameters such as fluid properties,Weber number,and Reynolds number.Special attention is given to atomization behaviors under high pressure and external perturbations.Representative experimental and numerical approaches are introduced,and critical findings under complex conditions are highlighted.In addition,practical applications of impinging-jet technology in aerospace propulsion,biomedical devices,and energy science are discussed.This review aims to serve as a concise reference for researchers interested in multiphase flow dynamics and engineering applications of impinging jets.展开更多
本研究旨在建立一种高效、快速、选择性测定食品中痕量汞的方法。通过溶剂热法及后续的巯基化修饰,成功制备了一种新型巯基功能化磁性介孔二氧化硅(Thiol-functionalized Magnetic Mesoporous Silica,记为mSS@Fe_(3)O_(4))吸附剂。将该...本研究旨在建立一种高效、快速、选择性测定食品中痕量汞的方法。通过溶剂热法及后续的巯基化修饰,成功制备了一种新型巯基功能化磁性介孔二氧化硅(Thiol-functionalized Magnetic Mesoporous Silica,记为mSS@Fe_(3)O_(4))吸附剂。将该吸附剂用于磁性固相萃取(MSPE),结合原子荧光光谱法(AFS),构建了一种分析食品中痕量汞的新方法。通过X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)等手段对材料进行了表征,证实了巯基已成功接枝到磁性介孔二氧化硅表面。系统优化了萃取过程中的关键参数,包括样品pH值、吸附时间、吸附剂用量、洗脱液组成和上样体积。结果表明,归因于材料的介孔结构和高比表面积,吸附平衡在1 min内即可达到,实现了对Hg^(2+)的快速富集。在最优条件下,该吸附剂对Hg^(2+)的理论最大吸附容量(qm)为67.89 mg/g;在回收率保持>90%时,最大上样体积为200 mL,预浓缩因子可达200。该方法具有较宽的pH值(1~13)适用范围和优异的抗基质干扰能力。方法线性范围为0.10~4.0μg/L(相关系数r=0.9996),方法检出限(MDL)为0.012μg/kg,对空白样品进行7次平行测定的相对标准偏差(RSD)为2.4%(n=7)。通过对国家标准物质和多种实际样品(草鱼、大米等)的加标回收实验,验证了方法的准确性和可靠性,回收率在94.0%~106%。该方法集快速、高效、高选择性与高灵敏度于一体,为食品中痕量汞的常规监测提供了有力的技术支持。展开更多
基金supported by the National Natural Science Foundation of China(No.52074157)Department of Education of Guangdong Province,China(No.2023KTSCX121)Shenzhen Science and Technology Programs,China(Nos.JSGG20210802154210032,JCYJ20210324104608023,JSGG20180508152608855)。
文摘A comparative study on the performance of gas atomized(GA)and rotating-disk atomized(RDA)aluminum alloy powders produced on industrial scale for laser directed energy deposition(L-DED)process was carried out.The powder characteristics,the printing process window,and the quality,microstructure,and mechanical properties of printed parts were taken into account for comparison and discussion.The results demonstrate that the RDA powder is superior to the GA powder in terms of sphericity,surface quality,internal defects,flowability,and apparent density,together with a larger printing process window during the L-DED parts fabrication.Besides,the resultant parts from the RDA powder have higher dimensional accuracy,lower internal defects,more uniform and finer microstructure,and more favorable mechanical properties than those from the GA powder.
基金supported by the National Natural Science Foundation of China(Nos.U23B6009 and 12272050)。
文摘Combustion dynamics are a critical factor in determining the performance and reliabilityof a chemical propulsion engine.The underlying processes include liquid atomization,evaporation,mixing,and chemical reactions.This paper presents a high-fidelity numerical study of liquidatomization and spray combustion under high-pressure conditions,emphasizing the effects of pres-sure oscillations on the flow evolution and combustion dynamics.The theoretical framework isbased on the three-dimensional conservation equations for multiphase flows and turbulent combus-tion.The numerical solution is achieved using a coupling method of volume-of-fluid and Lagran-gian particle tracking.The Zhuang-Kadota-Sutton(ZKS)high-pressure evaporation model andthe eddy breakup-Arrhenius combustion model are employed.Simulations are conducted for amodel combustion chamber with impinging-jet injectors using liquid oxygen and kerosene as pro-pellants.Both conditions with and without inlet and outlet pressure oscillations are considered.Thefindings reveal that pressure oscillations amplify flow fluctuations and can be characterized usingkey physical parameters such as droplet evaporation,chemical reaction,and chamber pressure.The spectral analysis uncovers the axial variations of the dominant and secondary frequenciesand their amplitudes in terms of the characteristic physical quantities.This research helps establisha methodology for exploring the coupling effect of liquid atomization and spray combustion.It alsoprovides practical insights into their responses to pressure oscillations during the occurrence ofcombustion instability.This information can be used to enhance the design and operation ofliquid-fueled propulsion engines.
基金the Tangshan University Doctor Innovation Fund(Project Number:1402306).
文摘The so-called close-coupled gas atomization process involves melting a metal and using a high-pressure gas jet positioned close to the melt stream to rapidly break it into fine,spherical powder particles.This technique,adapted for blast furnace slag granulation using a circular seam nozzle,typically aims to produce solid slag particles sized 30–140μm,thereby allowing the utilization of slag as a resource.This study explores the atomization dynamics of liquid blast furnace slag,focusing on the effects of atomization pressure.Primary atomization is simulated using a combination of the Volume of Fluid(VOF)method and the Shear Stress Transport k-ωturbulence model,while secondary atomization is analyzed through the Discrete Phase Model(DPM).The results reveal that primary atomization progresses in three stages:the slag column transforms into an umbrella-shaped liquid film,whose leading edge fragments into particles while forming a cavity-like structure,which is eventually torn into ligaments.This primary deformation is driven by the interplay of airflow velocity in the recirculation zone and the guide tube outlet pressure(Fp).Increasing the atomization pressure amplifies airflow velocity,recirculation zone size,expansion and shock waves,though the guide tube outlet pressure variations remain irregular.Notably,at 4.5 MPa,the primary deformation is most pronounced.Secondary atomization yields finer slag particles as a result of more vigorous primary atomization.For this pressure,the smallest average particle size and the highest yield of particles within the target range(30–140μm)are achieved.
基金supported by the National Natural Science Foundation of China(Grant Nos.U23B6009 and 12272050).
文摘This review summarizes recent progress in the study of impinging-jet dynamics and atomization,with a focus on liquid sheet formation,instability mechanisms,and the influence of key parameters such as fluid properties,Weber number,and Reynolds number.Special attention is given to atomization behaviors under high pressure and external perturbations.Representative experimental and numerical approaches are introduced,and critical findings under complex conditions are highlighted.In addition,practical applications of impinging-jet technology in aerospace propulsion,biomedical devices,and energy science are discussed.This review aims to serve as a concise reference for researchers interested in multiphase flow dynamics and engineering applications of impinging jets.
