Design And Experiment Of Air-suction Precision Seed Metering Device For Wheat

Wheat,as one of the widely cultivated grasses all over the world,the caryopsis is important the staple food of mankind."wheat flour can complement deficiency,strengthen skin and body,thick intestines and stomach,and strengthen strength".The B vitamins and a large number of mineral elements contained in the caryopsis grains are beneficial to human health.Wheat is a relatively important staple food in the north of China,and by 2021 China’s wheat sown area and production were 23568.4 thousand hectares and 136.95 million tonnes respectively,both ranked first in the world.At present,the mechanisation of wheat sowing is highly popular,but at present mainly mechanical seed rowers are used for strip sowing,the uniformity of the row cannot be guaranteed,which is not conducive to wheat growth and affects the final yield.Therefore,improving the mechanical wheat seed discharger is an important task to improve the uniformity of sowing and bring into play the yield potential of wheat.In this paper,according to the material characteristics of wheat seed,combined with foreign small-seed precision seeders,an air-absorbing precision seeder suitable for wheat sowing is developed,with the following main research.(1)The physical and intrinsic parameters of the seeds and the contact parameters between the seeds and the seeds,aluminium alloy and 45 steel were determined using Chuan Mai 104 wheat seeds as the research object.The wheat seed model was established by reverse engineering technology,and the wheat seed particles were modelled in EDEM and calibrated for the seed particle intrinsic parameters.Based on the calibrated wheat seed particle model,the contact parameters between the relevant materials were tested and compared.The results showed that the collision recovery coefficients between wheat seed and seed,aluminium alloy and 45 steel were 0.297,0.316 and 0.418 respectively,with error rates of 3.571%,4.819% and4.784% from the physical test results.The coefficients of dynamic friction were 0.0966,0.0723 and 0.0595 respectively,with error rates of 1.226%,4.993% and 6.151% compared to the physical test results.The static friction coefficients were 0.686,0.453 and 0.471,with error rates of 0.587%,7.346% and 4.900% compared to the physical test results.The discrete element simulation tests of wheat seed contact parameters were in general agreement with the physical test results.(2)Based on the physical characteristics of wheat seeds,the kinetic analysis of the seed discharge process clarifies how to achieve the boundary conditions for seed suction,and the structure of the seed discharge disc is clarified by combining theoretical equation calculations.The 3D model of the air-suction wheat precision seed discharger was completed in Solid Works.Experiments on the seed disturbance performance of the seed box with and without the seed stirring shaft and the seed sparing performance of different shapes of seed saving stubs were carried out in EDEM.The results showed that,after comparison of the tests,a seed stirring shaft is required in the seed box and the seed saving stubs are of the non-rounded type.The results show that the optimum structural parameters for the seed tray are cylindrical holes with a thickness of 1.5 mm,the optimum structural parameters for the negative pressure chamber are15 mm airflow slot width,2.3 mm hole diameter and 36 holes.(3)A single-factor test was conducted on a test stand to investigate the effect of different factors(negative hole pressure,seeding disc speed and tilt angle)on the seeding performance of the seed disperser designed in this paper.A three-factor quadratic regression rotational combination orthogonal test was carried out with the test rig using three factors: negative pressure of the type hole,rotational speed of the seeding disc and tilt angle as the test factors,and the pass index,reseeding index and missed seeding index as the test index.The tilt angle had no significant effect on the test index compared to the other factors.The tilt angle is 0°,the disc speed is 43.8～47r/min and the negative pressure of the hole is 960～1040Pa,the ideal optimisation results can be obtained: the pass index is more than 89%,the miss-sowing index and the reseeding index are less than 5.5%.