Studies on Grain-Straw Separation by Air Stream for Combine

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In this studies, a new separation system using air stream was devised. It could alternate a conventional straw rack of combine. In the beginning, separation characteristics of straw rack were clarified experimentally. In order to investigate the characteristics of separation by blown up air, basic experiments were conducted by a batch separation system. The basic design parameters for a practical system were obtained. Subsequently, the prototype separation system was developed, and the feasibility of this system was discussed. The summary of results obtained were as follows;In a straw rack, as straws are conveying to the rear end of machine, grains are separated from the grain-straw mixtures. Although a certain amount of straw was required for smooth conveyance, the separation performance became worse as straw amount increased. A crank motion of straw rack could accelerate the separation, but at the same time also might interfere with separation by condensing the straw layer. It was showed that the separation rate of the straw rack was 92.8 - 97.3% at straw feed rate of 2,700 - 5,400kg/h.The developed separation system accelerate the separation by lifting up and loosening the mixture layer which is conveyed by screen conveyer. No vibrating mechanism is used. In near-practical material conditions, reliable separation rate could be obtained. Free-falls at the entrance and the end of screen conveyer were also effective to increase the separation rate. In a trial on the double stage practical system, the separation rate was expected more than 96% at straw feed rate of 3,600kg/h.