Design And Experiment Of Positive-negative Pressure Type Seed-metering Device For Wide Seedling-width Wheat Planting

Wheat was one of the important food crops in China,which played an important role in agricultural production.Reasonable wheat planting technology could promote the improvement of wheat yield and quality,reduce farmers’ planting burden,and increase farmers’ income,which was of great significance to promote the development of agricultural economy in China.The precision seeding technology of wide seedling-width(wide width)wheat planting was proposed and successfully studied by Academician Yu Songlie.It was a high-yield comprehensive cultivation technology for wheat.This technology promoted uniform wheat sowing by expanding the row spacing,increasing the width of the seedling belt and controlling the sowing amount.And it could solve the problems such as seedling shortage,ridge breaking,poor seeding uniformity and more seeds used during seeding in drill operations.Precision seed-metering device was the key component to achieve precision seeding of crops,which was mainly promoted and applied on seed-metering devices of cultivating crops(soybeans,corn)and was divided into mechanical type and pneumatic type.At present,there was a lack of precision seed-metering device for Wide Seedling-width Wheat Planting.Most of the seed-metering device for wide seedling-width wheat planting on the market mainly adopted grooved-wheel type seed-metering devices,which cooperated with disperser to achieve wide seedling-width planting.It had problems such as poor seeding uniformity,large amount of seed and high seed damage rate.In this paper,a positive-negative pressure type seed-metering device for wide seedling-width wheat planting was designed.Wheat seeds were absorbed on the seed holes of the drum under the effect of negative pressure,and followed the rotation of the drum.After reaching the planting area,the seeds fell into seeding belt under the effect of positive pressure and gravity.At the same time,the positive pressure also could remove impurities in the seed holes.The main research contents were as follows:(1)Taking Liangxing 99 wheat as the research object,according to the agronomic requirements of precision seeding of wide seedling-width wheat planting,the overall design of the seed-metering device was completed,and the three-dimensional model of the seed-metering device was established.The seed-metering device adopted a drum structure combined with of positive-negative pressure.(2)According to the stress conditions of wheat seeds in different areas,model was established and mechanical analysis was carried out.The influence of different parameters(drum diameter,diameter,shape and number of seed hole,cross-section shape of positive and negative pressure type,diameter of central pipe shaft,seed suction negative pressure and speed of seed-metering device)on seed-metering performance and power consumption of fan was analyzed.The outer diameter of drum was 180 mm,and the outer diameter of the central pipe shaft was 25 mm,and there were 5 rows of straight seed holes distributed in the circumferential direction of the drum,and the distance between the rows of holes was 20 mm.(3)The internal flow field of the seed-metering device was simulated by Fluent software.Through pressure cloud diagram and flow velocity vector diagram,and the influence of structure parameters(suction negative pressure,diameter of seed hole and number of seed hole in each row)on seeding performance(pressure and velocity in seed holes)was analyzed.The better parameters were obtained as follows:diameter of seed hole was 2.0 mm,the number of seed holes in each row was 28,and the pressure range of seed suction was-4.0～-2.5 kPa.The movement of wheat particles was simulated by EDEM-Fluent coupling method.By observing the adsorption of seeds in the seed holes,the influence of rotation speed of seed-metering device on the seeding performance(seeding qualification rate,repeat-sowing rate,leak-sowing rate)was analyzed.(4)The seeding performance test bench was built with JPS-12 test bench,and carried out single factor test and response surface test.The influence of different operating parameters(suction negative pressure,seed metering speed and seeding height)on seeding performance(qualification rate,repeat-sowing rate and leak-sowing rate)were analyzed,and a better parameter combination was obtained:suction negative pressure was-3.5 kPa,seed metering speed was 19 r/min,seeding height 180 mm.After parameter optimization,the test results of the seed-metering device were as follows:the qualification rate was 80.62%,the repeat-sowing rate was 9.22%,and the leak-sowing rate was 10.16%.The result reached the index requirements in JB/T 10293-2013 Specifications for single seed drills(precision drills).Experimental studies had shown that the seed-metering device adopted a drum structure combined with positive-negative pressure,which had the advantages of good seeding uniformity,seed saving and no damage to seeds.The seed-metering device met the agronomic requirements of precise sowing of wide seedling-width wheat planting,and laid foundation for large-scale demonstration and popularization of precision seeding technology for wide seedling-width wheat planting.