激光切割气体出口马赫数对马赫盘的影响

建立了自由射流模型,采用了可压缩流体轴对称N-S方程和RNG k-ε模型,重点分析了出流为欠膨胀波时的马赫盘(MSD)结构.对出口静压为6.145×105Pa的自由喷射外流场进行数值仿真,描述了不同出口马赫数时的射流场结构,分析了马赫盘与喷嘴出口马赫数之间的关系,揭示了随着出口马赫数的增加,马赫盘的宽度呈现出收敛趋势,表明超音速喷嘴设计在保证常用工作压力时不出现过膨胀的情况下应适当提高出口马赫数.揭示了实际切割过程中,随着出口马赫数不断增大,马赫盘将收敛于一固定位置.对求解模型进行流场可视化对比验证,证明了仿真结果的准确性和结论分析的有效性.

Effect of Gas Outlet Mach Number on Mach Shock Disk in Laser Cutting

The structure of Mach shock disk (MSD) is analysed emphatically by constructing free jet model, adopting compressible liquid axial symmetric N-S equation and RNG k-ε model. Through the numerical simulation of free jet outer flow field under the outlet static pressure of 6.145×105 Pa, the paper describes the jet structures of different outlet Mach numbers, analyses the relation between MSD and outlet Mach number of nozzles. It reveals that the width of MSD presents convergent trend with the increasing of Mach number, and indicates that the outlet Mach number should be improved properly by ensuring disappearance of overexpanding waves under the working pressure. It is illuminated that the Mach number will be convergent to a fixed position with the increasing of outlet Mach number. The veracity of simulation results and the validity of conclusion analysis are proved by contrasting validating of flow field visualization to the solved model.