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The influence of a system that forms a gas vapor jet in the focus area of focused laser radiation on the quality and performance of laser melting of powder material during the implementation of Rapid Prototyping technology has been noted by many specialists in this field of research [1-3]. To calculate coaxial nozzles, simple engineering dependencies are usually used, which can not determine the distribution of transverse concentration of powder-puff compositions in the laser treatment zone. That is why the use of numerical simulation of the behavior of a gas-jet stream in the zone of influence of focused laser radiation as an instrument for designing optimal nozzle designs is an urgent task.

In this paper we present the results of the mathematical modeling of the form of a gas-vapor stream for different angles of generating coaxial nozzles. A numerical simulation of the behavior of a gas-jet stream fed into the focus laser-directed beam through coaxial nozzles of various designs was carried out with the help of the Ansys CFX specialized software program using the following algorithm:

-creation of a three-dimensional (parametric) model of a coaxial nozzle;

-creation of a three-dimensional model of the inner cavity of coaxial nozzles and the identification of regions that describe the boundary conditions of the calculation;

-creation of a calculation grid of finite elements of the inner cavity of coaxial nozzles with the designation of boundary conditions in the specified regions;

-direct calculation of the trajectory of the flow of powder and analysis of the results.

To create a three-dimensional parametric model of a coaxial nozzle was used-on CAD system of automatic design. Creation of a network of finite elements with the designation of regions of three-dimensional cavity objects of a coaxial nozzle was carried out with the help of the Meshing module of the Ansys Workbench software program.

According to the results of the research, the following conclusions can be drawn:

On the basis of numerical simulation of the behavior of a gas-jet stream in the space carried out with the help of the Ansys CFX software system, it should be noted that the distribution of the concentration of the powder flow in the cavity perpendicular to the axis of the trajectory of the motion of the n-pow jet depends on the angles of the generators of the external and internal nozzles, namely:

-in increasing the angle of the geometry of the production nozzles there is an increase in the transverse concentration of the powder material in the general case;

- with the increase of the geometry of the generators, the growth of the transverse concentration of the powder composition in the zone of influence of the focused laser radiation is observed, which is explained by the very low distance of the "focus" of the gas jet from the cutoff of the nozzle, due to the large value of the angles of the creation of external and internal nozzles.