THEORETICAL JUSTIFICATION FOR THE SPEED LIMIT OF THE SCREEN
It is known that the cleaning efficiency of the sieve depends on the kinematic parameters of the screen. It has been experimentally established that with increasing sieve velocity to the optimum value (limiting speed of the screen), the cleaning efficiency increases linearly to a maximum. A further increase in the sieve velocity results in the fact that the efficiency of the lattice cleaning sharply decreases. There is also a theoretical notion of the critical speed of grain, the excess of which leads to the fact that the grain flies over the hole, without having time to stock it. The absence of a connection between the critical grain speed and the limiting speed of the screen is established, since the velocity of the individual particles of the flow can not be measured during the experiment. It is shown that the critical grain velocity is determined by the size of the sieve hole (structural parameters of the screen) and the particle size of the grain flow (parameters of the grain heap), the value of the limiting speed of the screen is determined empirically. It has been established that the critical grain velocity and the limiting speed of the screen are special cases (maximum values) of grain speeds and screening, respectively. The relationship between grain speed and screen speed using differential equations Letoshneva for harmonic vibrations of the sieve is investigated to relate two concepts (theoretical and empirical). The established relationship is verified using a computer screening model that can take into account the dimensions of individual grains; measure their position, speed at any time. As a result of theoretical studies and computer simulation, a dependence was obtained that takes into account the relationship between the kinematic and structural parameters of the screen, the parameters of the grain (dimensions, type of culture, the angle of dynamic friction, etc.), and for small sieve loads and a small section of its length determines the limiting speed of the screen.