Double-nozzle control of a subsonic gas flow in the conditions of gas-laser cutting

Abstract

The peculiarities of subsonic jet in narrow channels geometrically similar to a laser cut have been studied experimentally and theoretically. To organize the jets, both single sonic nozzles with conic or cylindrical heads and a double nozzle with an additive coaxial ring channel were used. The experimental procedure based on the CCD-camera registration of the viscous-liquid flow by the channel walls was used to visualize the gas flows.Vortex formations have been found on the gas stream input and output from the channel. The strongest vortex at the channel output is able to gain and accumulate the liquid flowing down by the channel walls. The vortex formations have been founded numerically. As the experiments have shown, the vortexes can be cancelled through the pressure increase in the external ring nozzle. The stable, vortex-free and separation-free gas flow forms there.In the experiments of laser cutting of the low-carbon steel with a single nozzle it has been established that, at the increased cutting rate, some part of melt does not go out from the channel, but remains in the channel’s bottom section. This may result from the gas flow peculiarities. According to the experiments, in the case of a second concentric nozzle application, the melt goes out more effectively, and the walls are clean. The increased effectiveness of the melt removal may be caused by the fact that the second nozzle applied changes the gas flow pattern and enables to produce the vortex-free flow.The peculiarities of subsonic jet in narrow channels geometrically similar to a laser cut have been studied experimentally and theoretically. To organize the jets, both single sonic nozzles with conic or cylindrical heads and a double nozzle with an additive coaxial ring channel were used. The experimental procedure based on the CCD-camera registration of the viscous-liquid flow by the channel walls was used to visualize the gas flows.Vortex formations have been found on the gas stream input and output from the channel. The strongest vortex at the channel output is able to gain and accumulate the liquid flowing down by the channel walls. The vortex formations have been founded numerically. As the experiments have shown, the vortexes can be cancelled through the pressure increase in the external ring nozzle. The stable, vortex-free and separation-free gas flow forms there.In the experiments of laser cutting of the low-carbon steel with a single nozzle it has been established that, at the increased cutting ...