Study On Key Technology And Equipment Of Green Chinese Onion Precision Seeding

China is the main planting country of green Chinese onion,its output accounts for 23%of the world’s total output.At present,artificial seeding as Chinese planting method of green Chinese onion,which has many disadvantages,such as wasting seeds and time.Based on the reaserch of agronomic requirements,physical and mechanical characteristics of green Chinese onion,a green Chinese onion precision seeding equipment was developed.The main contents of this paper are as follows:(1)The overall design scheme of green Chinese onion precision seeding equipment was determined by SolidWorks software.(2)Design of key components.In order to provide references for the parameter design of seed metering device,the physical and mechanical characteristics of green Chinese onion seeds were studied,and the air-suction seed metering device for uncoated and coated green Chinese onion seeds were designed.The simulation module of SolidWorks software was used to check the strength of hollow shaft.The results showed that hollow shaft meets the practical requirements.With the help of FLUENT software,a internal flow field of positive pressure airflow assisted seed dropping device was simulated under different parameter combinations.The optimum combination of flow velocity uniformity in the tube flow field of the positive pressure assisted seed dropping device was determined as the diameter of blowhole was 4 mm,the diameter of intake pipe was 30 mm,and the intake mode was the intermediate intake.(3)Analysis of precision seeding process of green Chinese onion.The stress of green Chinese onion seeds in the flow field before seed suction hole was investigated preliminarily.It was found that reasons for "multi-grain" adsorption of onion seeds.Stress analysis was carried out on the process of green Chinese onion seed suction,the upper and lower limits of negative pressure in uncoated seeds suction drum were 71.78 MPa and 281 Pa respectively,the upper and lower limits of negative pressure in coated seeds suction drum were 28.4 MPa and 502 Pa respectively.The displacement equation of the unloading process of green Chinese onion seeds was established,and it was found that appropriate height of the green Chinese onion seeds and the appropriate rotational speed of the drum had a direct impact on the position of the green Chinese onion seeds.The equation of nude seed movement assisted by positive pressure airflow was established.When the rotational speed of the drum,the angle of unloading,the number of seed suction holes on the drum,the diameter of the air blower and the theoretical plant distance were unchanged,the effect of uncoated seed dropped mainly depend on the positive pressure of blowing,the angle of blowing and the height of blowing.(4)Bench test of seed metering device.The results showed that the qualified index was 90.64%,multiple index was 8.50%and missing index was 0.98%under the conditions of hole diameter as 1 mm,negative pressure as-8kPa,seeding height as 100mm,and rotation speed as 15 r/min.The single seed absorption rate was 81.67%,multiple seed absorption rates was 12.78%,and missing absorption rates was 5.58%under the conditions of hole diameter as 0.6 mm,negative pressure as-10kPa and rotation speed as 16 r/min on bare seed drum.The qualified index was 83.05%,the multiple index was 12.71%,and the missing index was 4.24%under the conditions of the blowing height as 62mm,blowing angle as 51° and positive pressure as 0.08kPa.(5)Field test.The qualified index of field experiment of coated seed was 81.75%,multiple index was 10.58%,missing seeding index was 7.67%;The qualified index of uncoated seed field experiment was 72.52%,the multiple index was 17.83%,and the missing index was 9.57%;The operating width of the two sets of machines was 1 m,and the production efficiency of the two sets of machines was 0.11hm2/h for coated seed and 0.12hm2/h for uncoated seed,respectively,which meet the project requirement of 0.09～0.13hm2/h for the productivity.