【摘要】 在激光金属直接制造过程中,为获得较小特征尺寸和组织致密的熔覆零件,采用气固两相流理论对载气式同轴送粉喷嘴的内外流场进行了数值模拟,应用FLUENT软件中的离散相模型计算了粉末的流场浓度分布规律及汇聚特性.计算结果表明,同轴送粉喷嘴的焦点浓度在径向和轴向都近似服从高斯分布,在同轴送粉喷嘴锥角不变时,锥环间隙越小,粉末流场焦点处的浓度越大,聚焦半径和焦距越小,汇聚特性就越好.在同轴送粉喷嘴锥环间隙不变时,锥角过大或过小均不利于粉末汇聚,选择最佳锥角有利于获得最佳汇聚特性.在其他条件不变时,外层保护气体流速过大或过小也不利于粉末汇聚,当外层保护气体流速为6 m/s时,同轴送粉喷嘴粉末的汇聚特性最佳.因此,所建模型和模拟结果对同轴送粉喷嘴的设计和结构优化具有参考价值.更多还原

【Abstract】 In the laser metal direct manufacturing,gas-solid two-phase flow theory is considered to simulate the inside and outside flow field of coaxial powder nozzle with carrying gas to obtain cladding parts of less characteristic size and compact structure.The separate model in FLUENT is used to evaluate the concentration distribution and the powder focusing characteristics of the powder flow field.The computed results indicate that the focal point concentration of the coaxial powder nozzle in radial direction and axial direction is approximately obeyed by the Gaussian distribution.When the cone angle of a coaxial powder nozzle is invariable,the cone ring gap is smaller,the focal point concentration in the powder flow field is bigger,the focus radius smaller,the focal distance also smaller,the gathering characteristic better.When the cone ring gap of the coaxial powder nozzle is invariable,the cone angle getting too big or too small is harmful for powder gathering,choosing the best cone angle facilitates obtaining the best gathering characteristics.When other conditions are invariable,too large or too small protect gas velocity is harmful for powder gathering.When the protect gas velocity approaches to 6 m/s,the gathering characteristic of the coaxial powder nozzle achieves the best.更多还原