Cylinder structures strengthened by internal stiffeners are widely applied in high-speed aircraft and spacecraft that are subjected to harsh environments. However, it is severely challenging to fabricate stiffener structures within a cylinder's restricted space via traditional processes. Techniques that allow for the deposition of metallic structures through zones in difficult-to-access positions, e.g., the inner walls of a cylinder, are quite limited. Laser inside additive manufacturing (LIAM) technology is applied to produce components in the inner walls of thin tubes, whose processing environments are restricted due to their small internal space. Nevertheless, the powder motion behavior driven by the feeding gas and LIAM's operating temperature in the restricted space is not evident. A simulation of the LIAM process as a feasible alternative for application in restricted spaces was investigated in the present study. The effects of the spatial constraints and the carrier gas velocity on the powder flow's aggregation and temperature distribution were studied. It was found that the powder flow was distributed in a convergent shape, which could be divided into an annular area, convergence area, and divergence area. With the increase in the carrier gas velocity, the powder flow concentration was found to decrease gradually. The powder utilization rate of LIAM was found to be as high as 60.5%. Moreover, a higher temperature was achieved in the powder flow for the cylinder substrate due to the difference in the geometric structure and the higher reflection of the cylinder substrate to laser intensity.

由内部加劲肋加强的圆柱结构广泛应用于经受恶劣环境的高速飞机和航天器中。然而，通过传统工艺在圆柱体的受限空间内制造加劲肋结构是一项严峻的挑战。允许金属结构通过难以接近的位置的区域（例如圆柱体的内壁）沉积的技术非常有限。激光内部增材制造（LIAM）技术用于在细管内壁中生产零件，由于内部空间较小，其加工环境受到限制。然而，在有限的空间内，由进料气和LIAM的工作温度驱动的粉末运动行为并不明显。在本研究中，研究了LIAM过程的模拟，将其作为在受限空间中的可行替代方案。研究了空间约束和载气速度对粉末流的聚集和温度分布的影响。发现粉末流呈会聚形状分布，可分为环形区域，会聚区域和发散区域。随着载气速度的增加，发现粉末流量浓度逐渐降低。发现LIAM的粉末利用率高达60.5％。此外，由于几何结构的差异以及圆柱基板对激光强度的更高反射，在圆柱基板的粉末流动中获得了更高的温度。