建立了激光熔覆中由粉嘴输出的保护气体-金属粉末两相流场计算模型,应用FLUENT软件进行计算。该模型中考虑了两相流中动量和质量的传输。分析了金属粉末流场的水平方向和中心线上的速度分布规律,以及粉嘴内外粉末流的速度矢量分布规律。计算结果表明,中心线处粉末流速度分布先呈现微小的增大减小过程,而后单调递增,大约从粉嘴下方100 mm后呈线性递增; 速度水平分布先在中心线附近达到最大而后在径向距离6～11 mm区间内线性递减至零。在相同的工艺参数下,应用数字粒子图像测速(DPIV)技术对同一流场进行检测,计算值和测量值吻合较好。结果表明,所建立的保护气体-金属粉末流速度场模型是可靠的,该模型对掌握流场参数分布和进一步指导粉嘴尺寸设计有一定的参考作用。

A numerical model of velocity distribution of shielding gas-metal powder two phases flow field output from the nozzle in laser cladding is established, and it is calculated by FLUENT software. In this model, the influences of momentum and mass transmission on the two phases flow are taken into consideration. The metal powder flow field velocity distribution on horizontal and center line is analyzed, as well as the velocity vector distribution of powder flow inside or outside the nozzle. The results show that powder velocity magnitude on center line increases first, then decreases, finally it keeps linearly increasing from the stand-off distance 100 mm below the nozzle; powder velocity magnitude on horizontal line reaches its maximum near the center line, then linearly decreases to 0 from the radial distance 6 mm to 11 mm. Under the same process parameters, the same flow field is measured with digital particle image velocity (DPIV) technique. The calculated result agrees well with the measured result, which indicates that the established model is reliable. The model can be used to obtain flow field parameters and further design the nozzle size.