Concave design for high-moisture corn ear threshing

Abstract

In a threshing device, identifying the optimum balance between grain damage and grain loss during threshing is highly relevant while harvesting high-moisture corn ears. The qualitative performance indicators of a threshing device depend on the corn ear properties and process parameters as well as the device's design. Comparative experimental trials of two concaves (control and experimental) of a tangential threshing device were conducted under laboratory conditions by threshing high-moisture corn ears. The control concave's surface line corresponded to a circular arc, whereas that of the experimental concave corresponded to a portion of Archimedes' spiral. The clearance between the crossbars and cylinder rasp bars in the first section of the control concave length increased, whereas in the second section, it decreased. For the experimental concave, the clearance along the entire concave length consistently decreased. The experimental concave yielded approximately half the grain loss of the control during separation in the concave. A rational clearance between the experimental concave crossbars was validated because the portion of damaged grain did not exceed 3% at that point. With clearance l equal to 62.5 mm in the control concave, the grain threshing loss was 2.2%, whereas for the experimental concave, the loss was virtually independent of q and did not exceed the acceptable 0.3% limit. In general, the trials demonstrated that for high-moisture corn ear threshing, the surface line of the concave should correspond to a portion of Archimedes' spiral and the clearances between adjacent crossbars should be 62.5 mm.