激光制造中载气式同轴送粉粉末流场的数值模拟

NUMERICAL SIMULATION OF COAXIAL POWDER FLOW WITH CARRYING GAS IN LASER MANUFACTURING

应用气固两相流理论对载气式同轴送粉系统中粉末流出送粉喷嘴后的粉末流场进行模拟计算,研究分析粉末流场浓度分布规律及粉末流参数(聚焦焦距和聚焦半径)的变化规律,计算结果与数字粒子图像测速的试验结果吻合较好。结果表明,载气式同轴送粉系统中,送粉喷嘴结构参数一定时,粉末流浓度和粉末流参数受送粉量及送粉气流量的影响。送粉气流量主要影响送粉喷嘴出粉口处粉末流的速度,对粉末流浓度分布和粉末流聚焦参数影响较小;送粉量增加,聚焦点处浓度值增大,粉流聚焦焦点略微下移,焦距处半径增大,聚焦焦深减小。建立粉末流简化物理模型,所建模型对同轴送粉喷嘴的设计和性能优化具有参考价值。

Gas-solid two-phase flow theory is used to simulate the powder flow from coaxial nozzle in coaxial powder feeder system with carrying gas, which is the key technology in laser manufacturing. The concentration distributing of powder flow and powder parameters （focus distance to nozzle exit and focus radius of powder flow） varying is simulated and analyzed. The numerical simulation result is well consistent with the result of measurement by digital particle image velocimetry （DPIV）. It is shown that the concentration of powder flow and powder parameters is also influenced by gas flux and feeding powder amount. It can be found that the gas flux mainly affects the powder velocity and the powder concentration or focus parameters hardly change with various gas fluxes and constant feeding powder amount. The powder concentration tends to increase with increasing powder feed amount, The focus distance and powder stream radius at the focus point also increase and focus depth decreases with increasing the feeding powder. The powder flow simple model is also presented. The conclusion will benefit for coaxial nozzle designing and performance improving.