Motion of Grain on the Screen Surface under Reciprocating Motion (I)

Abstract

It was found from previous experimental results that the most suitable frequency of the screening existed over the range of centrifugal effect values K=1-2.5, and that the screening characteristic was affected by the motion of grain on the screen surface.
This paper deals with the moving characteristics of a grain which repeated sliding or both sliding and jumping movements on the horizontal reciprocating screen surface with the projection angle of 45° (degree). The four-bar linkages were adopted to oscillate the screen in the reciprocating motion. The motiom of a grain on the screen was experimentally studied from the pictures of stroboscope and the oscillogram of acceleration and phase angle, in addition to the the theoretical analysis.
The main results were as follows.
1) When the frequency of the screen was small, the grain slided along the screen surface; when the frequency of the screen exceeded the sliding limits, the grain jumped on the screen. In these cases the motion of grain may be more or les influenced by the friction and its shape.
2) In the rolling motion of grain (paddy), the experimental value of the mean velocity of grain was slightly greater than the theoretical value.
3) The flowing velocity of grain was increased with the increasing of the value of K and gradually decreased with the increasing of the coefficient of friction of grain.
4) The flowiug which was calculated based on the value of the maximum acceleration of the screen, velocity of grain on the screen with the quick return motion was nearly equal to the experimental value without the rolling motion of grain.