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 pr essure laser cutting is presented. The design is based on the theory o f gas dynamics in that the potential energy of high stagnation pressur e is converted totally into effective velocity energy so that a high m omentum of the exit jet can be obtained for improving the capability o f removing molten debris quickly and minimizing the heat-affected zone of the cut edges. Another purpose is to increase the cutting speed an d minimize gas consumption under high pressure cutting conditions. The behavior of the exit jet under the condition of stagnation gas pressu re ranging from 4 similar to 16 bar are investigated by means of a com puter simulation test. The results of theoretical analysis and of the simulation test show that for a supersonic jet, each sectional diamete r and curve contour of the supersonic nozzle must be designed strictly according to the theory of gas dynamics. An exit jet with high moment um, 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.