Abstract: The implementation of laser cutting is the interaction result of laser beam and assistant gas, so the inner shape of nozzles and their flow field is one of the key factors of affecting laser cutting quality and efficiency. Based on the axial symmetric N-S equation of compressible fluid, structure network and finite volume method with second order accuracy are adopted to analyze the relationship between the structure of jet flow field and the turning angle of throat section, and the influence of the length of divergence section on state parameters of flow field is studied. Through rationally planning the turning angle of throat section and the length of divergence section, short oblique line is used to replace the complex curve so as to simplify the structure of supersonic nozzle. The simulation results show that the improved nozzle can obtain a jet flow field with rational assistant gas outlet parameters and good dynamic performance.

Key words: Jet flow, Supersonic nozzle, Throat section