Design And Experiment On Pneumatic Cone Disk Type Wide Seedling Strip Wheat Precision Metering Device

Wheat is an important crop in China.Wide seedling strip planting is a new type of wheat cultivation technology.Practice has proved that its yield-increasing effect is obvious.At present,the wide seedling strip sowing of wheat is mainly based on the traditional outer groove wheel metering device with the uniform device of seed tube,which has the problems of strong randomness and poor uniformity of seeds distribution in rows.To improve the quality of wheat sowing,this paper developed a pneumatic wide seedling strip wheat precision metering device with a conical seed disc based on the principles of seed self-weight sowing and pressure suction seeds.Theoretical research,simulation analysis,bench tests,and field tests were conducted.The main content includes:(1)Based on the characteristics of wheat materials and the agricultural requirements of wide seedling strip planting,a pneumatic wide seedling strip wheat precision metering device with one machine for four rows was proposed.The main structure design including the conical seeding plate,the seed hopper,the air chamber,and the seed outlet,was carried out.The diameter range of the suction hole was determined to be 1.6～2.0mm.Through theoretical calculation the number of suction holes per row was set to 40.The taper angle of the conical seeding plate was determined to be 45 degrees by using EDEM simulation analysis.(2)A mechanical model of the three processes of seed-filling,seed-carrying,and seed-sowing under the action of the pneumatic conical seeding plate was constructed,and the critical negative pressure expressions required for sucking in each process were determined.The impact of the structural and operational parameters of metering device on the seed transport process was analyzed.The theoretical analysis showed that the critical negative pressure values required for seed-filling and seed-carrying were related to the taper angle α of the conical seeding plate,the seed mass m,the three-axis dimensions of the seed,the diameter D of the seed suction hole,the rotation speed ω of the seeding plate,and the pitch circle diameter of the seeding hole.(3)A simulation test of the metering device was conducted.The movement of seeds in the driving layer,static layer,and trailing layer of the seed population was analyzed through simulation tests of the impact of different taper angle seeding plates on the degree of population dispersion.It was found that the 45-degree taper angle seeding plate has the advantages of good disturbance performance and low transport resistance.Meanwhile,Fluent simulation analysis was conducted on the gas chamber flow area and the seed suction hole flow area of the metering device.The variation law of surface flow velocity of different seed suction holes was clarified,and the conclusion with the highest surface flow velocity of seed hole was obtained through orthogonal experiment,which was when the diameter of the negative pressure suction port was 25 mm,the diameter of the seed suction hole was 1.8mm,and the thickness of the seeding plate was 1.8mm.(4)The seeding performance test of pneumatic cone disk type wide seedling strip wheat precision metering device was conducted.Through the study of the seeding structure parameters,it was determined that when the type of suction hole was a vertical hole with a diameter of 1.8mm,the variation coefficient of four rows seeding quantity uniformity was 2.34%,the variation coefficient of total seeding quantity stability was1.22%,and the variation coefficient of four rows seeding uniformity was 11.78%.Through the study of the seeding working parameters,it was determined that when the working speed was 30r/min and the negative pressure was-5200 pa,the variation coefficient of four rows seeding quantity uniformity was 1.93%,the variation coefficient of total seeding quantity stability was 1.26%,and the variation coefficient of four rows seeding uniformity was 9.52%.Through field comparison test of wheat planting,it was concluded that pneumatic cone disk type wide seedling strip wheat precision metering device had a seeding uniformity of 11.77% inside the seedlings,while the seeding uniformity of the outer groove wheel seeder was 22.51%.Compared with the outer groove wheel seeder,the seeding uniformity was significantly improved,which could meet the requirements of wheat wide seedling strip planting.