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在激光金属直接制造过程中,实际的粉末汇聚不是自由射流,而是受阻射流。为了获得受阻射流工艺参数对粉末汇聚特性的影响规律,提高激光直接制造精度,应用FLUENT软件中的离散相模型模拟了工艺参数对粉末汇聚浓度分布的影响。结果表明:在自由射流时,粉末汇聚浓度随着送粉量的增加而增大,随着载气速度的增大而明显降低,保护气速度的增大对粉末汇聚浓度影响不明显。在受阻射流时,随着送粉量增加粉末汇聚浓度显著增大,且粉末汇聚点位置相比自由射流时出现少量上移,随着载气速度增大熔覆点处的粉末浓度显著下降,保护气速度的增加对熔覆点处粉末浓度影响较小。熔覆点处的粉末浓度随着堆积宽度的增大而显著增大,粉末汇聚点位置基本稳定,堆积层高度的增加对粉末浓度的影响较小。
In the direct manufacturing of laser metals, the actual powder pool is not a free jet, but a blocked jet. In order to get the influence law of the obstructed jet flow parameters on powder convergence characteristics and improve the laser direct manufacturing accuracy, the influence of process parameters on the powder concentration distribution was simulated by discrete phase model in FLUENT software. The results show that the concentration of powder increases with the increase of feed rate and decreases with the increase of carrier gas velocity. The increase of shield gas velocity has no significant effect on the concentration of powder. At the hindered jet flow, with the increase of powder feeding volume, the concentration of powder agglomeration increased significantly, and the position of powder agglomeration point increased slightly compared with that of free jet. As the carrier gas velocity increased, the powder concentration at the cratering point decreased significantly, The increase of shielding gas velocity has little effect on the powder concentration at the cladding point. The concentration of the powder at the cladding point increases significantly with the increase of the deposition width, and the position of the powder aggregation point is basically stable. The increase of the deposition height has little effect on the powder concentration.