毛坯基体形态对再制造同轴送粉粉流场影响规律分析#br#

 在激光增材再制造中，气粉流冲击基体表面的反射情况是影响成形质量和效率的重要因素。由于加工基体形态各不相同，粉末撞击基体后粉流场的变化情况不尽相同，以气固两相流为理论基础，采用EDEM与FLUENT软件耦合仿真，分别对规则基体边界、薄壁基体厚度及弧面基体曲率三种基体变化情况下的气粉流场分布特性进行了研究及实验验证。结果表明：在喷嘴中心轴线远离边界的过程中，壁面接触部分气流场，紊流现象显著，侧壁低速区缩小，负压范围减小，有效加工范围内颗粒数量呈指数趋势减小；随着薄壁基体宽度的增加，气流场范围向两侧发展明显，加工中心点颗粒的体积浓度逐渐降低，有效加工范围颗粒数量先增加然后维持稳定；随着弧面曲率的增大，凸面基体径向颗粒的体积浓度增大，焦点范围减小，粉流有极好的汇聚效果，凹面基体粉流集聚性较差。

Analysis of Influence Laws of Blank Substrate Morphology on Powder Flow Field of Remanufacturing Coaxial Powder Feeding#br#

The reflection of gas-powder impinging on the substrate surface was an important factor to affect the forming quality and efficiency for laser additive remanufacturing. Due to the various substrate shapes, the changes of the powder flow field were different after the powder impinging on the substrates. Gas-solid two-phase flow was taken as the theoretical basis, coupled simulation of EDEM and FLUENT software was used to study the gas-powder flow field distribution characteristics under three kinds of substrate changes, namely, regular substrate boundary, thin-wall substrate thickness and globoidal substrate curvature, and experimental verification was carried out. Results show that the turbulence of the gas field in the contact areas with the substrate increases as the nozzle is far away from the boundary, and the low-speed areas as well as the negative pressure range decreases. Meanwhile, the number of effective particles decrease exponentially. The gas field developes to the both sides obviously and the concentration of the machining centers decreases gradually with the increase of the thin-walled substrate width. And the powder flow rate in the effective ranges increases first and then remains. With the increase of the absolute curvature of substrates, the radial concentration of the convex substrate increases, and the focus range decreases, and the powder flow has a better convergence than that of concave substrates.