Calculation of rational modes of plasma torches for plasma arc furnaces

The method of universal arc characteristics developed for calculating the electrical and thermal characteristics of the cylindrical part of the Mecker model column allows simple algebraic methods to calculate the characteristics of the arc column at a distance from the cathode and, thereby, to concretize the mathematical model of Mecker. The proven conservativeness of the arc as a result of the formation of a spatial layer with increased volumetric viscosity on the surface of the column allows, in accordance with the provisions of the boundary layer theory, to apply a boundary condition of the third kind to the surface of the cylindrical part of the arc column. The method of universal arc characteristics also helps to link the boundary value of the linear heat flux density on the surface of the cylindrical part of the column with the temperature profile of the column and, thereby, to specify the dependence of the electrical, geometric and thermal characteristics of the column plasma on the conditions of arc heat exchange in the working space of the installation with electric arc heating. The proposed method makes it possible, based only on the external voltage characteristics of the arc, to identify the Mecker heat exchange model and calculate by a simple algebraic method the structure and values of the heat fluxes generated by the arc during heat exchange with the plasma torch gas jet in the melting space of the plasma arc furnace. Examples of arc characteristics are given when working on different gases for different stages of melting — at the beginning of melting and during the melting of the charge.