Pneumatic separation on separating unit of a combine harvester.
1988
Chung C.J. | Nam S.I.
This study was attempted to investigate the pneumatic separation on separating unit of a combine harvester. The aerodynamic characteristics of threshed materials were analyzed by experiments. The air velocity distribution within the separation chamber was measured for various speeds of the winnower and suction fans to find out the operational and design conditions of the separating unit which would serve for reducing the grain loss from chaff outlet. Based on the separation curve of threshed materials analyzed, it was shown that three different kinds of materials-kernels, straw chaff, and leaf chaff were as a whole able to be separated pneumatically, regardless of varieties. However, a small amount to the separation grain loss may be expected to occur if the complete separation between kernels and straw chaff would be undertaken because some portion of their separation curves were overlapping. It was shown that a large portion of grain loss from chaff outlet may occur when the kernels may bump against a portion of separation chamber wall and those kernels thus scattered into the discharging region were sucked by the suction fan. It was accordingly recommended that a new design of the wall of separation chamber so as to bump down kernels may be necessary to reduce grain loss from the chaff outlet.
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