为了设计一种适用于大功率的宽带激光熔覆同轴送粉喷嘴, 采用FLUENT软件中的离散相模型, 对送粉喷嘴的送粉道在不同倾角和不同出口间隙条件下的粉末汇聚特性和浓度分布特性进行了研究。分析了其它条件不变时, 外层保护气流速对粉末汇聚的影响, 得到了较优的结构尺寸, 并利用设计研制的宽带同轴送粉喷嘴装置, 进行了送粉和熔覆实验。结果表明, 宽带激光同轴送粉喷嘴的焦点浓度在汇聚中心的径向和轴向都近似服从高斯分布; 随着倾角的增大, 出口间隙对焦距的影响也越来越大, 且出口间隙越小, 焦距越大; 当倾角为70°, 出口间隙为3.5mm时粉末汇聚性较好, 粉末利用率较高; 在其它条件不变时, 外层保护气体流速过大或过小均不利于粉末汇聚, 当外层保护气体流速略小于载气速率时, 送粉喷嘴的粉末汇聚特性最佳。表面熔覆质量达到了预期要求, 验证了该结构的合理性。所设计的宽带同轴送粉喷嘴对后续宽带激光熔覆的研究与应用具有重要意义。

In order to design a coaxial powder feeding nozzle for high power broad laser cladding, powder convergence property and concentration distribution for broad laser coaxial powder feeding nozzles were analyzed at different inclination angles and exit gap of the powder feeding channel by using the discrete phase model in FLUENT software. And when other conditions were fixed, the effect of outer protective gas velocity on powder convergence was analyzed and the better structure size was obtained. The experiments of powder feeding and cladding were carried out by using the designed and developed broad coaxial powder feeding nozzle. The experimental results show that, the focal point concentration of the coaxial powder nozzle is approximately obeyed by Gaussian distribution in radial direction and axial direction. With the increase of feeding angle, the effect of exit gap on focal length becomes more and more important.The smaller the exit gap, the greater the focal length. When feeding angle is 70°and exit gap is 3.5mm, powder convergence is better and utilization ratio of powder is high.When the other conditions are constant, the fact that outer protective gas velocity is too fast or too slow is not beneficial to powder convergence. When outer protective gas velocity is slightly less than carrying gas velocity, the characteristics of powder convergence of powder feeding nozzle is the best. The quality of surface cladding reaches the expected requirement, and the rationality of the structure is verified. The designed nozzle has a great significance for the research and application of subsequent broad laser cladding.