Analysis And Experiment On The Adsorption Mechanism Of The Perturbation Pneumatic Precision Seed Metering Device For Rapeseed

Rapeseed is the best crop for the combination of planting and breeding in the Jianghuai area.Its mechanized direct seeding has many advantages such as labor-saving and time-saving,cost-saving and increased efficiency,and suitable for mechanized harvesting.The seed metering device is the core component of the rape seeding machine,which directly affects the seeding quality of rapeseed.Aiming at the problem of increased operating speed of rapeseed pneumatic seeder,which is likely to cause leakage and affect seeding performance,a kind of perturbation pneumatic precision seeder for rapeseed was designed.The particle dynamics theory,EDEM numerical simulation,Fluent simulation analysis,high-speed camera technology,orthogonal test design and response surface analysis were combined to study the perturbation adsorption mechanism.The main conclusions are as follows:(1)The structure composition and working principle of seed metering device were explained.Combined with the requirements of rape agronomic planting and the theory of particle dynamics,the structural parameters of key components of seed metering device were analyzed and determined.The mechanical model of interaction between seed and seed disturbing mechanism was established,and the key factors affecting adsorption performance were identified.Three types of air distributor are designed: cylindrical annular type,cone-column annular type and cone-column cone type(2)The EDEM software was used to simulate the perturbation of different types of seed plates to the population,with the number of groove-tooth and the thickness of the groove-tooth as the test factors.The average velocity of the population in the forced disturbance area is proposed as an evaluation index of the performance of the population perturbation.The simulation results show that the average velocity of the population in the forced disturbance area increases with the increase of the number of groove teeth,and first increases and then decreases with the increase of the groove tooth thickness.The Fluent software was used to simulate the internal airflow field of different types of air distributors,and the negative pressure loss was taken as the evaluation index.The results show that the negative pressure loss of the cone-column annular air distributor is the smallest,and different outlet negative pressure on the cone-column annular air distributor were simulated,which shows that the loss under each negative pressure is relatively stable.(3)The single performance test of the seed metering device shows that the thickness of the groove-tooth,the number of groove-tooth,the rotation speed of the seed plate and the working dynamic pressure are the key factors affecting the adsorption performance,and the average velocity of the population in the forced disturbance area is negatively correlated with the missing rate.The groove-tooth structure parameters of the seed plate with the best seed filling performance are as following: the number of groove-tooth is 18,and the thickness of the groove-tooth is 1.0 mm.The optimal seed plate was selected as the test object,The quadratic rotation orthogonal test was carried out with the seed plate rotation speed and working dynamic pressure as test factors,and the cavity rate and the qualified rate of the seed’s number in the hill as evaluation indexes.Through the analysis of variance,the regression equation of the cavity rate and the qualified rate of the seed’s number in the hill were obtained.Multi-objective optimization results are obtained as following: when the seed plate rotation speed is 40 r/min and the working negative pressure is-2392 Pa,the cavity rate is 0.40%,and the qualified rate of the seed’s number in the hill is 97.48%(4)The optimization test of air distributor shows that the cone-column annular air distributor is better overall,The regression equations of the seed plate rotation speed,working static negative pressure and the average seeding volume of each row and the coefficient of variation of seed quantity consistency in each row were established.The best matching combination of seed plate rotation speed and static negative pressure were obtained through multi-objective optimization.Field experiments shows that the average plant spacing of rapeseed is 53.12 mm,the cavity rate is 4.6%,the qualified rate of the seed’s number in the hill is 90.54%,and the coefficient of variation of plant distribution uniformity in each row is 10.87%.