Numerical simulation of powder-gas flow field of inside-beam powder feeding nozzle with changing attitude
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摘要: 光内送粉喷头是一种新型的激光熔覆同轴送粉喷头,具有空心光束、单根粉束指向性好、无干涉、光粉气一体同轴等优势。为了分析喷头倾斜角度和外层准直气流速对粉束汇聚特性的影响,采用FLUENT软件进行模拟计算,对喷头在空间变姿态作业过程中单喷嘴出口粉束的汇聚特性进行了理论分析和实验验证。结果表明,喷嘴出口粉末质量浓度分布沿x方向服从高斯分布,对称轴上沿-y方向质量浓度先基本保持恒定,后逐渐下降为0kg/m3;随喷头倾斜角度的增大,粉末汇聚长度h不断减小,h变化范围为11mm~17mm,偏移量Δx大致呈增大趋势,Δx变化范围为0.0mm~0.4mm;随外层准直气速度增加,汇聚长度h呈轻微上升趋势,h上升幅度为1mm~2mm,而偏移量Δx在不同倾斜角度范围内呈现出不同变化趋势,Δx变化幅度为0.05mm~0.15mm;实验数据与模拟结果变化趋势基本吻合。所建模型和模拟结果对于选择和优化实验工艺参量具有参考价值。Abstract: Inside-beam powder feeding nozzle is a new laser cladding coaxial powder feeding nozzle, which has the advantages of hollow beam, good directivity, no interference and co-axis of light, powder and gas. In order to analyze the influence of nozzle's inclination angle and outer collimating gas velocity on the focusing characteristics of powder, FLUENT software was used for numerical simulation. The focusing characteristics of powder out of a single nozzle with changing attitude were analyzed in theory and verified in experiments. The results show that mass concentration distribution of powder nozzle is consistent with Gaussian distribution along the x direction and it remains constant firstly and then decreases to zero gradually along the -y direction of the symmetry axis. When the inclination angle of the head increases, the powder focusing length h decreases in the range of 11mm~17mm and the deviation Δx increases in the range of 0.0mm~0.4mm substantially. When the outer collimating gas velocity increases, the powder focusing length h increases slightly in the range of 1mm~2mm and the deviation Δx presents different trend in the range of 0.05mm~0.15mm. The experimental data and simulation results are basically consistent. The built model and the simulation results have reference value for the selection and optimization of experimental parameters.
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