Test and Optimization of Oilseed Rape (Brassica napus L.) Threshing Device Based on DEM

Gridded concave plate sieves are usually used for threshing operations of grain and oilseed crops. In response to the problems of high threshing loss rate and grain breakage rate when threshing oilseed rape, this research modified the threshing concave plate of oilseed rape (Brassica napus L.) harvesters to improve the performance and efficiency of oilseed rape separation. The improved threshing concave plate adopts a 360° wrap angle, and a guide plate with an adjustable inflow angle is designed on the inner side of the concave plate. The optimal combination of parameters for the threshing device is determined by simulation analysis and field testing. Single-factor simulations of the threshing cylinder speed and guide plate angle are carried out using EDEM, which showed that both are influencing factors for the force and speed of the oilseed rape particles. A three-factor and three-level orthogonal experiment was undertaken to validate the simulation analysis further. The threshing cylinder speed, concave plate speed, and guide plate angle were influencing factors. The threshing loss rate and grain breakage rate are evaluation indicators. The field validation tests are carried out on concave plates with 180° wrap angle and 360° wrap angle, the results showed that the concave plate with 360° wrap angle reduces the threshing loss rate by 4.25%, the grain breakage rate by 0.93%, and improved the harvesting efficiency by 0.31 km/h when the threshing cylinder speed was 81.89 rad/s, concave plate speed was 9.34 rad/s, and guide plate angle was 40°. This study demonstrates that the concave plate with a 360° wrap angle has better performance and operational efficiency, and it provides design ideas for threshing devices for other crop combine harvesters.