Patterns of influence exerted by the side walls of a vibratory sieve on the motion of a loose mixture flow

Abstract

The influence of the side walls of a vibratory sieve on the motion of a loose mixture flow has been investigated. The regularities have been established of the flow motion parameters on the walls’ height, the resistance of their surfaces, the length and distance between them. The condition has been defined for the occurrence, degree, character, as well as the region of the side walls’ influence on the mixture motion over the entire area of a sieve. Increasing the height of the walls, the length and resistance of their surfaces increases the surface density and reduces the longitudinal velocity of a mixture near the near-wall region, causing the occurrence of the transverse velocity component and the uneven distribution of the specific load of the sieve. For the wall’s steady parameters, there is a threshold of distance between them, at which the near-wall regions of uneven loading begin to interact with each other, thereby enhancing their influence on the flow. There occur the under-loaded and over-loaded sites in the sieve that differ in the magnitude of deviations and area. The uneven loading area reaches 83 % of the sieve area while the magnitude of deviations in the specific loading is 26 %. A condition of the influence exerted by the side walls on a flow is exceeding the minimum values of the parameters: a wall height, h >4·10 –3 m; the resistance of a wall surface, C z >2 kg/m 2 ·s; a wall length, l >0.5 m. The side walls’ influence leads to the formation of a near-wall region of the sieve’s under-loaded and over-loaded sites, whose deviations and area are the same. The magnitude of the wall’s region of influence increases in proportion to the sieve length and acquires the shape of a rectangular triangle. To reduce the influence of the side walls, it is necessary to reduce the resistance of their surfaces, the sieve length, and to increase its width, to avoid the threshold distance between the walls and a simultaneous growth of their parameters. The patterns in the side walls’ influence underlie the improvement of vibratory-sieve separators and the substantiation of their operation modes