Design and characteristic analysis of supersonic nozzles for high gas pressure laser cutting

A new method for the design of a supersonic nozzle tip for high gas pressure laser cutting is presented. The design is based on the theory of gas dynamics in that the potential energy of high stagnation pressure is converted totally into effective velocity energy so that a high momentum of the exit jet can be obtained for improving the capability of removing molten debris quickly and minimizing the heat-affected zone of the cut edges. Another purpose is to increase the cutting speed and minimize gas consumption under high pressure cutting conditions. The behavior of the exit jet under the condition of stagnation gas pressure ranging from 4 ∼ 16 bar are investigated by means of a computer simulation test. The results of theoretical analysis and of the simulation test show that for a supersonic jet, each sectional diameter and curve contour of the supersonic nozzle must be designed strictly according to the theory of gas dynamics. An exit jet with high momentum, good uniform and a tidy boundary can be obtained and the tolerance of the working distance between the nozzle tip and the workpiece can be increased.