Experimental Substantiation of Parameters of Two-Phase «air – Grain» Flow Required to Simulate Operation of the Pneumatic System of the Grain-Cleaning Machine

Abstract

The article gives the results of the comparative tests of wear-resistance and reliability of metal-cutting tools equipped with carbides of ВК8, Т5К10 ,Т15К6, КНТ16 and ТН20 brand marks undergoing linear turning of test cylinders steel-faced with Np-30KhGSA wire. Intense hardness, structural imperfection and ridgeness of the metal coating make its further mechanical processing more difficult. Experimental technique is based on the cutting temperature persistence. Optimum cutting data for the cutting bits equipped with carbides of ВК8, Т5К10, Т15К6, КНТ16 and ТН20 brand marks have been found. Comparative tests proved that wearresistance of the instruments equipped with carbides Т5К10, Т15К6 and КНТ16 is 1,4-1,8 times higher than of those equipped with ВК8 carbide.

Mathematical modeling of the grain material separation in the pneumatic system of the grain-cleaning machine

“…The experimental data were confi rmed by theoretical studies of the mathematical description and modeling in the form of a polydisperse two-phase fl ow with regard to concentration, inertia, relaxation time, resistance coeffi cient. Similar studies were carried out by other scientists, which are refl ected in the works [1][2][3][4][5][6][7][8][9][10][11][12][13]. The adequacy of the model, theoretical and experimental studies is confi rmed by their convergence (reliability is 0.97), which suggests that the possibility of accepting the results is reliable.…”

“…In such fl ows, light particles move (are separated) by the air fl ow due to the aerodynamic drag force, which exceeds the gravitational force, the cause of which is the difference in air velocity and particle. Heavy particles mostly move (separated from the light ones) under the action of gravity, while the aerodynamic drag force acts slightly [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The force of aerodynamic drag is determined by the expression: (1) where C D is the aerodynamic drag coeffi cient of the particle, ρ g is the air density, kg / m 3 (ρ = 1.225 kg / m 3 ); d р -particle diameter, m; U is the air fl ow speed created by the fan, m / s; V -particle velocity, m / s. (6) The aerodynamic drag coeffi cient of spherical particles C D is determined according to the Rayleigh curve depending on the Reynolds number Re (C D = f (Rе)) [1][2][3].…”

“…The equations (6-9) describe the technological process of the fan operation, taking into account the rotating wheel in the coordinate system. The impact of the air fl ow generated by the fan on the grain pile entering the GCM pneumatic system, in general, based on the Navier-Stokes equation, takes the form [13][14]. (10) where is the operator nabla (Hamilton), a vector differential operator whose components are partial derivatives with respect to coordinates; Q p m -mass feed of particles, kg / m 3 •s.…”

“…Due to the imperfection of the design of the pneumatic system, there is an increased dustiness in the service areas and poor-quality separation of the grain pile by the air fl ow [10][11][12]. The development of a new technology for the separation of a heap of grain and more advanced technology for its implementation is diffi cult due to the diversity of crops and methods of separation; the complexity and diversity of the process of interaction of the particles of the separated materials with the air fl ow and the working bodies of the machine; insuffi cient development of the theoretical foundations of separation by air fl ow and methods for substantiating the parameters of machines and the modes of their operation [13][14][15][16][17]. In this regard, it is necessary to improve the theory of separation by air fl ow and the designs of pneumatic systems of grain cleaning machines [18][19][20].…”

“…( Tables 1 and 2 present the main physicomechanical properties and the statistical analysis of the geometric parameters of the seeds of a grain pile. As shown by experimental measurements (table 1 and 2), the grain pile is heterogeneous and has a wide range of both physicomechanical and geometrical parameters [13][14][15][16]. The data obtained are used in a mathematical model describing the technological process of the pneumatic system of a grain cleaning machine for pre-cleaning.…”