SIMULATION OF THE DISTRIBUTION OF AIR FLOWS AND FUEL COMBUSTION PRODUCTS IN A CHANNEL OF A TUNNEL KILN

A characteristic problem of the operation of tunnel kilns with high overlap is the output of products with low quality and a decrease in the energy efficiency of the burning process as a whole. Therefore, the object of research is the process of the flow of kiln gases through the channel of the tunnel kiln, the change in velocity of which was studied depending on the geometric parameters of the tunnel. In the course of studies of the dependence of the velocity distribution of the flow of kiln gases along the channel of the kiln on its geometric characteristics, a numerical simulation method in a simplified 2D formulation using the OpenFoam open code using the k--shear stress turbulence model is used. The velocity fields of kiln gases are obtained for three options for the height of the channel: the base with a vault height of 2 m, with a reduced vault height along the entire length of the tunnel and with a reduced tunnel height only in the burning zone. Analysis of changes in flow rates shows that the most effective would be to reduce the height along the entire kiln length, while changing the arch height in the burning zone will hardly affect the uniformity of velocities in the heating zone. Reducing the arch height also minimizes the likelihood of a return air flow in the cooling zone in the area from burning to the place of air extraction for drying. A lower overlap in the cooling section will increase the intensity of heat removal and, accordingly, reduce its loss with the product in order to use it for drying products. The presented simulation results make it possible to note that a change in the height of the overlap will lead to an increase in aerodynamic drag and, consequently, a pressure drop. This will require additional energy costs for driving draft engines and the possibility of increasing temperatures in the space under the cars