The purpose of the work is to reveal the influence of conical directing agents on the speed and trajectory of particles movement in the vertical pneumatic conduit of the sowing machine and to establish their rational parameters. With the help of numerical modeling the particle flight trajectories in the air flow were obtained. The carried out researches have shown expediency of application of the conical directing agent, allowing to take away a longitudinal stream of particles from walls of a pneumatic conduit and to centre their trajectories of movement along an axis of a pneumatic conduit. Particles are focused to the center of the distributor when the distributor covers the area of pneumatic conduit cross-section close to 25%.
The aim of the study is to develop a mathematical model of linear calculation of the pneumatic system of a seeder with a pneumatic sowing system, implemented in the MathCAD computer algebra system. The description of the pneumatic transport system of a typical seeder with pneumatic sowing is presented, its design scheme is given. Based on the provisions of the mechanics of continuous media, a methodology for calculating the parameters of a pneumatic system to verify the adopted design decisions has been developed. A computer model of a pneumatic transport system with series-parallel arrangement of sections has been developed. Linear calculations with structurally implemented recounting of indicators were performed. The obtained value of the standard deviation between the calculated average values and the velocities of the flow core in the sections does not exceed 14% for the values of the velocities and 0.5% for the pressure over the sections. When implementing the proposed analytical modeling in the MathCAD 8.0 system, the error in mass flow rate is 1.152×10-14%, which allows limiting the number of conversion cycles of indicators to two – three cycles.
Seed drills with a seed metering device and a pneumatic system of flow stream and distribution of grain seeds to the coulters of the seeder with pneumatic sowing have become widespread in the sphere of agriculture. The aim of this study was to establish the functional dependence of the aero-product stream flow nature in the pipeline and in the grain seeder distributor. The research method involved numerical studies of the developed 3D model of the seeder pneumatic system. The influence of the geometric features of the internal cavity of the distributor top of the seeder pneumatic system, the flow rate in the pipeline in the range from 15 to 25 m/s, the concentration of seeds in the flow stream from 0.52 to 1.57 kg/kg air were taken into account. The values of static, dynamic and total pressure, pressure losses by sections, rates of flow streams in the areas, areas of intense mechanical impact (surface wear) were studied. The regression equations of these indicators have been obtained the factors studied being taken into consideration. The greatest pressure losses have been observed in the distributortops with a cap having the shape of a concave hemisphere. The flat surface of the cap makes it possible to achieve intermediate pressure losses in the distributor top. The smallest pressure loss is observed in the distributor top with a convex cone-shaped cap.
In the course of the study, methods for ensuring the centeringof particlesofbulkmaterialintheairflowmovinginthepneumaticductofthe seeder were investigated. To solve this problem, it is proposed to use a conical confusor. The aim of the study was to obtain the functional dependences of the movement of particles in a conical airflow guide (confusor) for the conditions of transportation of the sown particles on the basis of force analysis and to identify the nature of the movement of the sownparticlesinataperingairflow.Duringthestudy,todescribethemotion of particles in a vertical tapering pipe, a system of expressions was substantiated. The developed mathematical model of particle motion in a conical air flow, implemented in the MathCAD mathematical package, allowscalculatingboththeparticletrajectoryandthevelocityparametersof the air flow and the particles to be sown. The digital calculation results in the MathCAD program are in good agreement with the finite element calculations. The magnitude of the error in air velocity is less than 1%. The differences in the velocities of the transported particles in the calculation options do not exceed 7%. The installation of a conical guide helps tofocus the flow of particles in the central part of the narrowed air line. In this case, part of the particles in the central part of the guide will retain the initial longitudinaltrajectory.Theangleattheapexoftheconeandtheparameters of the particles affect the speed and angle of the tangent contact of the particle with theguide.
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