In order to reduce the problems of high grain breakage rate and uncleaned material rate in the threshing and separating device of longitudinal axial flow corn, a threshing device of "front flexible nail tooth + rear pressure spring elastic short grain rod" was designed and the threshing elements were arranged spirally on the conical threshing drum. Discrete element method and field test were used to verify the feasibility of threshing drum design, and EDEM simulation software was used to obtain

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... the appropriate guide plate Angle parameter range. Single factor test was carried out on each experimental factor under high and low water content conditions, and four factors suitable working range was obtained.On this basis, four factors and three levels orthogonal test were carried out on grain breakage rate and undepurated rate, rotational speed of roller, feeding rate, cylinder-concave clearance and deflector angle as experimental factors. Range and variance analysis were used to analyze the rotational speed of roller, feeding rate, cylinder-concave clearance and deflector angle. The results showed that:Under the conditions of low water content, the threshing effect is the best under the conditions of feeding rate of 8kg/s,rotational speed of roller of 450 r/min, cylinder-concave clearance of 45 mm, and deflector angle of 70°.Under the conditions of high water content,the best threshing effect was achieved under the conditions of feeding rate of 7kg/s, rotational speed of roller of 450 r/min, cylinder-concave clearance of 40 mm and deflector angle of 75°. Compared with the conventional threshing separation device, the grain breakage rate of low moisture content decreased by 39.4% and the uncleaned material rate decreased by 63.9%.The grain breakage rate of high moisture content was reduced by 45.5%, and the uncleaned material rate was reduced by 66.7%, which was better than the conventional longitudinal axial flow threshing separation device. The research results can provide reference for the design and optimization of longitudinal axial flow corn harvester.