射频等离子体制备球形粉末的数值模拟  

Numerical simulation on preparation of spherical powder by RF induction plasma

作　　者：王建军[1] 郝俊杰[1] 郭志猛[1] 毛瑞奇 

机构地区：[1]北京科技大学新材料技术研究院,北京100083

出　　处：《中国科技论文》2015年第22期2642-2647,共6页China Sciencepaper

基　　金：高等学校博士学科点专项科研基金资助项目(20120006110007);国家自然科学基金资助项目(51274039)

摘　　要：为了解决射频等离子体球化制粉过程存在的监测困难和成本高问题,提出将射频等离子体视为磁流体(magneto-hydrodynamic,MHD),借助有限元方法分析等离子体的传热与流动。利用计算流体力学(computational fluid dynamics,CFD)软件Fluent,建立球化制粉过程的数值模型,采用k-ε模型计算流场和温度场,通过离散相(discrete phase model,DPM)模型研究颗粒的运动轨迹来探讨球化率和收粉率的问题。结果表明:等离子体炬中心区温度高达10 148K且具有极大的温度梯度,球化处理可以获得球形度高、结构致密的球形粉末;提高送粉率使单位时间内温度场内的颗粒增多,球化率下降;粉末粒径越大,受重力场作用越大,颗粒更趋向沿轴向快速通过等离子炬;湍流作用下粉末的杂乱运动是收粉率低的主要原因。数值模拟可以为等离子体球化制粉技术的推广提供理论指导。To solve the monitoring difficulties and high-cost problems during powder preparation using radio frequency（RF）plasma spheroidizing process,we first propose to treat RF plasma as magneto-hydrodynamic,and then analyze the heat transfer and flow of the plasma by finite element method.The numerical model of RF plasma spheroidization was established by using computational fluid dynamics（CFD）software Fluent.The k-εmodel was used to calculate the flow field and temperature field.And the spheroidization rate and powder collection rate were discussed through the study on particle trajectories simulated by discrete phase model（DPM）.The results show that the temperature at plasma torch center can be as high as 10 148 Kand with great temperature gradient being formed.The spherical powders with good sphericity and dense structure can be obtained after plasma processing.Increasing the feeding rate decreases the powder spheroidization rate due to the particle number increase per unit time in temperature field.The bigger the powder size,the more significant effects by gravity field,and the quicker for particles across the plasma torch along the axialdirection.Under turbulent state,low particle collection rate is caused by disordered movement of the powder.Numerical simulation can provide theoretical guidance for the promotion of the plasma spheroidizing technology.

关 键 词：射频等离子体 数值模拟 颗粒运动轨迹 球化率 

分 类 号：TB383.3[一般工业技术—材料科学与工程]