导流管长度和雾化压力对气体回流影响的数值模拟及实验研究

Numerical simulation and experimental study on the influence of the length of guide tube and atomization pressure on gas reflux

金属3D打印专用球形粉末普遍采用气雾化法制备,无坩埚电极感应气雾化技术(EIGA)制备的金属粉末具有氧增量低、细粉收得率较高、球形度高、流动性好等优点。实验对雾化喷嘴导流管底端的气流场进行了数值模拟,研究导流管长度和雾化压力对气体回流的影响,并通过雾化实验对模拟结果进行了验证。结果表明:导流管长度存在一临界值,当长度低于临界值时,雾化喷嘴环缝外侧气体的流速高于内侧气体的流速,气体易回流进入导流管内部,导致较多缺陷粉产生;长度高于临界值时,环缝内侧气体的流速高于外侧气体的流速,气体回流现象消失,缺陷粉数量大幅减少。雾化压力主要影响粉末的粒径,雾化压力越大,粉末粒径越小。

Spherical powder for metal 3D printing is generally prepared by the technology of atomization,the met-al powder prepared by electrode induction-melting gas atomization(EIGA)without crucible has the advantages of low oxygen increment,high fine powder yield,high sphericity and good fluidity.In this paper,a numerical simula-tion of the airflow field at the bottom end of the guide tube of the atomizing nozzle is carried out,and the influence of the length of the guide tube and the atomization pressure on the gas reflux is studied,and the simulation results are verified by the atomization experiment.The results show that there is a critical value for the length of the guide tube.When the length is lower than the critical value,the flow velocity of the gas outside the annular seam of the atomizing nozzle is higher than that inside,and the gas is easy to return to the inside of the guide tube,resulting in more defective powders.When the length is higher than the critical value,the flow velocity of the gas inside the annular seam is higher than that outside,the gas reflux disappears,and the number of defective powders is greatly reduced.The atomization pressure mainly affects the particle size of the powder.The greater the atomization pres-sure,the smaller the powder particle size.