Investigation of the aerodynamics of a tunnel circular kiln

Abstract

In the modern stage of development of refractory production there are two directions in the creation of highly effective kilns for heat treatment of refractories.The first direction includes further improvement in tunnel kilns and the second the development of tunnel circular kilns [i]. The basic difference between tunnel and tunnel circular kilns is the geometric form of their space.In a tunnel kiln the working space is in a straight line while in a tunnel circular kiln it is a curved ring.In a tunnel circular kiln the energy carriers are the products of combustion of the fuel, atomspheric air, and gaseous mixtures of various compositions.The operating effectiveness of a production kiln depends significantly upon the aerodynamics of the gases in the working space, which influences the intensity and uniformity of heating or cooling of the parts being heat treated.One of the characteristics of the gas aerodynamics is the velocity field in the cross section of the kiln space. The conditions of heat exchange, the uniformity of the temperature field in the cross section, the aerodynamic resistances, and other characteristics depend upon the character of the furnace gas velocity field.In the literature there is no information on the gas aerodynamics in a tunnel circular kiln for heat treatment of refractories and, therefore, a study of the aerodynamics is of much value for the development of tunnel circular kilns.A theoretical analysis of the features of gas aerodynamics of a tunnel circular kiln with the use of elements of the theory of a tunnel kiln and curved working spaces leads to the following results.In a tunnel circular kiln, as in a tunnel one, the charges of parts form with the furnace working space a system of longitudinal and transverse channels of various dimensions.Adjacent charges and parts within the charges have breaks along the axis of the kiln working space, causing local resistances.The resistance of a break in the charges under otherwise similar conditions depends upon the size of the effective cross section of the charge and the length of the break,The length of the break AX across the width of the kiln is a variable increasing from the inner (convex) to the outer (concave) wall while in a tunnel kiln AX is a constant (Fig. i).