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Analytical and experimental modeling of raw material pressure profile in tops

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In the article the influence of technological parameters and design features of grinding screw machines on the formation of the pressure field in the screw channel is studied, which determines the quality and energy intensity of the processes of movement, extrusion, and cutting of the crushed material. It is proved that the main parameters limiting the achieved pressure levels of raw materials at the output of the shredder are the geometric parameters of the screw, the body, the knife, the thickness of the output lattice, the number and diameter of holes in it, as well as the physical and mechanical characteristics of the product. It is shown that the objects for the mathematical description are zones and processes in which the largest share of power is spent. At the same time, the non-trivial screw nature of the movement of the crushed product from the entrance to the body of the screw shredder as it moves to the exit determines the complexity of the structure of the pressure formation along the spiral trajectory. It is the complexity of the analytical description of this process that has led to the simplified consideration of either individual technological zones of existing designs of grinders or the use of insufficiently substantiated assumptions. The principal feature of the design of screw devices, complicating the modeling, is the presence of the anti-skid bars on the inner surface of the body, excluding the rotation of raw materials, as well as providingthe translational motion of the product and the formation of the pressure required for extrusion, which forced to use for the mathematical description of the process hydrodynamic equations of motion in the Euler form. Thus, the analytical definition of the law of pressure distribution in the tops along the length of the helix, depending on the design and technological parameters of the top and physical and mechanical characteristics of the crushed material, is the aim of the study. The solution of such a problem under the conditions of not only the braking forces of passive friction, but also under the active resistance forces of the anti-skid mechanical elements, distinguishes it from the existing approaches fundamentally. As a result of the mathematical description, the analytical dependence of the intra-screw pressure on sixteen influencing factors, including the length of the helix, which allows to justify the parameters of the structural elements and to form the necessary pressure for raw materials with different physical andmechanical properties at the output of the grinder, based on the conditions of ensuring the quality of the product at the output and the minimum energy intensity of the process.

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