为解决飞机结构损伤激光在线快速修复过程中同轴送粉喷嘴气体保护效果不佳的问题,利用粒子图像测速(PIV)、烟雾流动显示技术和Fluent软件对喷嘴保护气体流场进行了研究。系统分析了喷嘴气流速度变化、侧吹气流速度对喷嘴气体冲击射流场的影响。结果表明,当喷嘴三个喷口气流速度接近一致时,湍流扩散区消失,流场稳定。当喷嘴中心气流速度小于外环气流速度时,工件表面出现旋涡,破坏了流场的稳定性。侧风对喷嘴气体保护范围影响较大,随着侧风速度增大,气流轴线偏离喷嘴轴线距离增大。当侧风速度超过喷嘴气流速度50%时,喷嘴保护气流混入空气,完全失去对金属熔池的保护。

Using particle image velocimetry (PIV),smoke flow visualization technology and Fluent software,shielding gas flow fields of coaxial powder feeder nozzle are researched in order to improve the shielding effect of gas flow on laser on-line rapid repair of aircraft structure damage. Influences of gas velocity from nozzle,crosswind velocity are systematically analyzed on gas impacting jet flow field. The results show that when the velocities of three-section gas flow are nearly consistent,the turbulent diffusion area disappears and a stable flow field can be obtained. When the gas velocity from center nozzle is smaller than that from outer ring,a vortex is generated and disturbs the stability of gas flow field. The crosswind produces prominent interfere to the gas protective range. With the increase of velocity of crosswind,the axis of shielding gas fields and nozzle get apart. When the velocity of crosswind surpasses 50% of the velocity of gas from nozzle,the shielding gas fails to protect molten pool totally because ambient air is mixed.