Simulation Analysis And Experiment Of Seed Delivery Of Pneumatic Seeder Based On Discrete Element Method(DEM)

In this paper,the poor uniformity of seed spacing of 2BMQ-8 precision planter fed back by the market of YTO Group Corporation is studied.The movement process of corn seeds in the seed guide tube is simulated and analyzed by using the discrete element software edem.According to the simulation analysis results,the structural layout of seed metering device and seed guide tube is optimized,and the field performance test is carried out to improve the uniformity of sowing plant spacing.The main research work of this paper is as follows:(1)The basic physical properties of maize seeds were measured.The modeling of corn seed particle model is realized by using multi ball combination filling method,and the simulation parameters of particle model are calibrated in edem;The corn seed delivery process of the two seed metering systems was simulated and analyzed,and the trajectory diagram,velocity change curve and first collision reflectance diagram of corn seed in the seed guide tube were drawn.(2)The seed trajectory is optimized by comparative analysis.According to the simulation results,the seeds slide and roll in the seed guide tube.Under the condition of uniform speed operation,the uniformity of plant spacing depends on the movement time of adjacent seeds in the seed guide tube and the position and angle of seeds out of the seed guide tube.The seed will collide with the seed guide tube for 2 ～ 5 times during the falling process,resulting in the variation of seed trajectory with the ejection position,angle and plant spacing in the seed guide tube;The collision increases the horizontal velocity component of seeds,which is conducive to the formation of zero speed seed dropping.According to the calculation of zero speed seed dropping theory,the design value range of the angle between the end of the curve of the seed guide tube and the horizontal plane is 53 ° ～ 68 °.(3)Summarize the law of incidence angle and reflection angle of air suction and finger clip seed metering system,and clarify that the excessive incidence angle of air suction seed metering system is the main reason for many inflection points and unsmooth trajectory of corn in air suction seed guide tube,and finally lead to the deterioration of the uniformity of sowing plant spacing.When the incidence angle of the first collision between the seed and the seed guide tube is controlled at 4 ° ～ 6.5 °,the seed will not collide and separate from the seed guide tube,only roll and slide along the curve of the seed guide tube,the movement time interval of the seed in the seed guide tube is the same,and the plant spacing is uniform.(4)The arrangement of seed guide tube is optimized and the structure of seed pressing wheel is added.The incidence angle of the first collision between the improved seed and the seed guide tube is 4.1 ° ～ 4.4 °,and the included angle between the end of the circular arc section of the seed guide tube and the horizontal plane is61 °.The seed delivery simulation and field performance test of the improved structure are carried out.The simulation results show that the seed motion trajectory is to slide down along the wall of the seed guide tube and shoot out along the tangent direction of the circular arc section at the end of the seed guide tube.The field test results show that the qualified index of grain spacing is increased by 7% ～ 12%,and the variation coefficient of qualified grain spacing is less than 30%,which meets the requirements of national standard,the improvement is effective,and the performance of planter is greatly improved.