在激光沉积制造时, 粉末汇聚性是保证成形质量的关键因素。为了改善粉末的汇聚性, 采用气固两相流理论对载气式同轴送粉喷嘴纵吹气帘气压力大小对粉末汇聚性影响进行了数值模拟, 应用FLUENT软件中的离散相模型计算了粉末流场速度和浓度分布规律及汇聚特性。模拟结果表明, 纵吹气压力较小(0.3 MPa)时会导致粉末流充满整个流场域, 汇聚性极差; 气压力较大(0.7 MPa)时同样粉末汇聚性较差, 影响沉积制造成形质量; 气压力为0.5 MPa时汇聚性良好, 且在焦点到焦点以下10 mm的汇聚区进行激光沉积制造能形成较好的熔池, 成形质量较好同时提高了粉末利用率。试验结果验证了模拟结果的合理性, 数值模拟结果对同轴送粉喷嘴设计和结构优化具有较大的参考价值, 并解决了现有喷嘴粉末汇聚性较差问题。

In the laser deposition manufacturing, the convergence of powder is the key factor to ensure the forming quality. Gas-solid two phase flow theory is used to simulate the effect of vertical inflatable curtain of coaxial powder feeding nozzle with carrying gas on the convergence of powder to improve the convergence of the powder. The discrete phase model of FLUENT software is used to calculate the powder flow field rate and concentration distribution and convergence properties. The simulation results show that: the smaller vertical blowing pressure (0.3 MPa) will lead to the powder flow full of the whole flow field, resulting in poor convergence; the greater vertical blowing pressure (0.7 MPa) result in poorer convergence similarly, will affect deposition manufacturing forming quality; when the vertical blowing pressure is 0.5 MPa, the convergence of powder is good. It can form a better molten pool for laser deposition manufacturing in the focus and convergence zone 10mm following the focus, forming quality is better and improve the utilization rate of powder. The experimental results verify the rationality of the simulation results which has great reference value for coaxial powder feeding nozzle design and structure optimization, and solve the problem of poor convergence of the nozzle powder.