Layer Breakup and Particle Movement on a Chaffer Sieve

Abstract

The breakup of a layer of wheat MOG (material other than grain) and grain on an adjustable chaffer sieve was recorded with a video camera. Several stages of the breakup were described as they happened when the specific air flow rate was increased in steps. For each stage, the required static pressure acting at the bottom of the material layer and the specific air flow rate were determined. A hole was formed at an average specific air flow rate just below 0.8 to 2.0 (m3/s)/m2 for the layer of pure MOG and below 2.6 (m3/s)/m2 for the mixture of grain and MOG. The air pressure below the material layer was proportional to layer thickness for MOG, 3 Pa/cm, and for the mixture more than twice as high. The maximum pressure below the material layer was 45 to 70% of the material load.