Substantiation of concave crossbar shape for corn ear threshing
Keywords:Combine harvester, threshing cylinder, concave, corn ear, grain separation, grain damage
One of the key design parameters of a threshing unit critical for corn ear threshing is the shape, height and number of the concave crossbars. The paper presents the results obtained during the theoretical and experimental research of corn ears threshing process by analysing the crossbars of three different shapes: rectangular, rounded and oblique. The FEM involving the application of curved isoparametric second order finite elements with Serendip type shape functions was adapted to this research. The method of the experiment has been applied for verification of the adequacy of the designed theoretical models The theoretical and experimental analysis has demonstrated that oblique concave crossbars were more efficient during threshing of corn ears that using any of the other two shapes of crossbars. The experimental research has substantiated that a variable radius concave with a working plane tilt angle of the oblique crossbar equal to 45° would be the rational option for corn ear threshing. In this case, the threshing losses and grain damage were least.