面向播种过程离散元仿真的玉米颗粒建模方法OA北大核心CSTPCD

The discrete element method is widely used in the analysis and improvement of agriculture machinery performance.To realize digital reproduction of maize seeding process based on discrete element method and improve seeding performance of seeding machinery,the corresponding maize grain assembly model needs to be constructed.In this paper,maize grain shape and size distribution of 10 common varieties in Northeast China were statistically analyzed,and a general shape classification method of maize grains was proposed.That is,the actual assembly of maize grains could be considered as a collection of horse-tooth,spherical-cone,and spheroid maize grains.On this basis,the corresponding assembly modelling of maize grains was constructed based on the sphere filling method and discrete element method.Namely,a single maize grain model was used as a template,the main size was randomly generated according to a normal distribution,the other feature sizes were calculated from the main size to generate each maize seed model,and this was repeated;In addition,the corresponding number of maize seeds was generated according to the percentage of quantity,so that the characteristics of generated maize grain assembly model should be closer to the actual maize grain.The number of filling spheres was optimized through the stacking test and sieve test with the two varieties of maize.The results showed that when the number of filling spheres in the maize grain model was 10-14,18,and 1 for horse-tooth,spherical-cone,and spheroid maize grain models respectively,the population characteristics of the maize grain discrete element method model were consistent with those of the actual maize grains,which preliminarily proved the validity of the proposed maize grain assembly modelling method.Further,a discrete element method simulation of the seed discharging process of the inner nest hole rower was carried out based on the established maize grain assembly model,and the rotation speed of the seed discharging wheel was optimized,and the optimization result(30 r/min)was consistent with the experimental one,which further demonstrated the validity of the proposed maize grain assembly modelling method.Finally,with the increase of the rotational speed of the seed discharge wheel,the single grain rate was the first to rise and then fall,the double grain rate was the first to fall and then rise,and when the rotational speed was 30 r/min,the single grain rate reached a maximum of 88％,and the double grain rate was the minimum of 11％.Cavity rate was the first to fall rapidly after the basic stability in the vicinity of 1％.This is because when the row of seed wheel speed gradually increased,the particles in the row of seed wheel under the perturbation of the centrifugal inertia force gradually increased,when the rotation speed of the seed discharging wheel was less than 30 r/min,the single particles could reliably rotated with the row of seed wheels,while more than the particles fell back to the bottom of the seed chamber due to the size limitations of the holes,the role of their gravity,and other factors.However,when the rotational speed of the seed discharge wheel was greater than 30 r/min,the centrifugal inertial force dominating the maize seed made it difficult for the excess particles to fall back to the bottom of the seed chamber and rotate with the seed discharge wheel's nest hole,which led to a decrease in the single grain rate.The results of this paper can provide a certain reference for the digital design of maize-seeding machinery.