| Food security is related to national security.As a large agricultural country,China ’s per capita cultivated area is less than 1.5 mu,only about half of the global average.Therefore,in the case of limited available cultivated land resources,it is particularly important to improve grain production.Precision sowing is a new scientific operation mode,which has great advantages in sowing accuracy and sowing quality.Precision seeding technology is mainly realized by seeding machinery.Generally speaking,the working quality of seeding machinery is positively correlated with crop yield.Seedmetering device is the core component of the seeder,and its development is conducive to promoting the development of precision sowing technology.Based on the research of commonly used air-suction seed-metering device,this paper developed a air-suction variable aperture precision metering device to meet the different sowing needs of corn and wheat.Based on the physical characteristics of seeds,the structure design and simulation analysis of the seed-metering device are carried out.Finally,the optimal operating parameters are determined by bench test.The main contents are as follows:（1）Measurement of seed physical characteristics: In order to improve the versatility of seed-metering device,Ludan288 was selected as the research object of corn seed-metering.Jimai22 was selected as the research object of wheat seed-metering,and the main physical characteristics of seeds were measured to provide data support for the design optimization and later simulation analysis of seed-metering device.（2）Structural design of the overall and key components of the seed-metering device: Solid Works software was used to model the overall structure of the seedmetering device.At the same time,the structural design of key components such as seed-metering plate and baffle,suction chamber shell and scraper device with variable aperture combination structure was carried out to improve the stability of the internal flow field of the seed-metering device and the interference effect.（3）Simulation analysis of seed-metering process: Based on Fluent software,the change of internal flow field of seed-metering device was studied by changing the type of suction hole,the rotation speed and aperture of seed-metering plate.The seeds were modeled based on EDEM software,and the motion state of the internal population of the seed-metering device was studied by comparing whether the seed-metering plate had auxiliary seed filling structure.Finally,the seeding process was simulated by Fluent-EDEM coupling simulation to determine the optimal structure size and optimal operating parameter range of the seeding device.（4）Bench test: In order to verify the performance of seed-metering device,experimental research was carried out on the JPS-12 seed-metering device test bench.With qualified rate,reseeding rate and missing rate as test indexes,single-factor tests were carried out on the negative pressure value and the rotation speed of seeding plate that affected the seeding effect to determine the range of values.Secondly,three factors and three levels orthogonal test was carried out to explore the primary and secondary order of each factor affecting the test index,and the optimal combination of operating parameters was obtained.The results showed that when the rotation speed of corn seeding was 12r/min,the negative pressure was-7KPa and the aperture was 4.8mm,the qualified rate was 87.67%,the missing sowing rate was 5.05% and the reseeding rate was 7.16%.When the rotation speed of wheat seeding is 50 r / min,the negative pressure value is-3KPa,and the aperture is 2.6mm,the qualified rate is 97.52%,the missing sowing rate is 0.82%,and the replay rate is 0.78%.The bench test is basically consistent with the simulation results. |
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