New insights into the effects of powder injector inner diameter and overhang length on particle accelerating behavior in cold spray additive manufacturing by numerical simulation
New insights into the effects of powder injector inner diameter and overhang length on particle accelerating behavior in cold spray additive manufacturing by numerical simulation
复制标题
通过数值模拟研究粉末喷射器内径和悬伸长度对冷喷涂增材制造中颗粒加速行为的影响的新见解
DOI：
10.1016/j.surfcoat.2022.128670
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发表时间：
2022-07-05
影响因子：
5.4
通讯作者：
Zhang, Zhengmao
中科院分区：
文献类型：
--
作者：
Wan, Wenpeng;Li, Wenya;Zhang, Zhengmao
应用要求，特别是添加剂制造，迫使冷喷涂技术加强对颗粒行为的精确控制，并优化喷枪以适应长时间工作。我们最近的研究表明，喷粉器作为喷枪内部的一个小部件，对喷枪内的流场和颗粒的撞击参数有很大的扰动。建立了专门用于流体力学数值计算的模型，该模型考虑了喷粉器参数变化的影响以及进粉气体和主要工作气体之间的混合效应，使数值模拟更加准确，对颗粒加速过程有了更深入的了解。模拟结果表明，颗粒直径、喷粉器内径以及进粉气体与主要工作气体之间的初始压差对喷嘴喉部附近和基片前方的颗粒分布有显著影响。采用较低的压差和较小的喷粉器内径，不仅可以使颗粒更加集中在喷嘴轴线附近，减少喷嘴堵塞的可能性，而且可以提高颗粒的冲击速度。同时，为了提高冷喷涂添加剂的制造精度，应考虑粒径为20-40微米的颗粒。此外，进粉气体和主要工作气体之间的相互作用对颗粒的撞击速度和温度影响很大，对颗粒直径为15~45微米的颗粒更加敏感。此外，两种气体的混合状态对喷嘴上游的流场有显著影响，而对喷嘴出口附近的影响不大。在喷粉器伸入喷嘴喉部的情况下，由于喷粉器端部气体流动的明显扰动，对流场的影响很大。
Application requirements, especially additive manufacturing, have forced cold spray technology to strengthen the precise control of particle behavior and optimize the spray gun for long working hours. Our recent studies show that the powder injector, as a small component inside the spray gun, greatly disturbs the stream fields and the impact parameters of particles. A model dedicated to the hydrodynamic numerical calculation was established which takes into account the influence of changed parameters of powder injector and the mixing effect between the powder feeding gas and main working gas, enabling more accurate simulations and greater insight into the particle acceleration procedure. Simulation results reveal that the particle distributions near the nozzle throat and in front of the substrate are significantly influenced by the particle diameter, the inner diameter of powder injector, and the original pressure discrepancy between the powder feeding gas and main working gas. Employing lower differential pressure and a smaller inner diameter of the powder injector can not only make the particles more concentrated near the nozzle axis, to reduce the possibility of nozzle clogging, but also improve the particle impact velocity. At the same time, for higher precision of cold spray additive manufacturing, particles with diameters of 20-40 mu m should be considered. Besides, the impact velocity and temperature of particles are extremely affected by the interaction between the powder feeding gas and the main working gas, which is more sensitive to the particle diameter of 15-45 mu m. In addition, the mixing state of the two gases shows significant effects on the stream fields in the upstream of the nozzle, but little influence around the nozzle exit. In the case of the powder injector extending into the nozzle throat, the flow field is greatly influenced because of the obvious disturbance of gas flow at the powder injector end.