Simulation of High Pressure Gas Flow Field inside a Laser Cut Kerf

摘要

The dynamic behaviours at the entrance, inside and exit of a laser cut kerf of a gas jet from a supersonic nozzle under an inlet stagnation pressure ≥5 bar are investigated by both analytical and numerical simulations. An approximation method is used to locate the detached shock on the top of the cut kerf. A theory of the characteristics for two-dimensional rotational flow is applied in the calculation of the gas flow field distribution. In order to obtain the distribution of the flow field along the cutting front during laser fusion cutting process, the geometrical shapes of the cutting front are yielded using three-dimensional energy balance. The effects of the inlet pressure, the exit diameter of the nozzle and the displacement of the nozzle with the cut kerf upon the distribution of the strength of the gas flow at different locations inside the cut kerf and the cutting quality are analysed for each group of cutting parameters. The mathematical model can help to estimate the cutting parameters for a dross free cut edge.