Optimization Simulation And Experimental Research Of Inside-Filling Air-blowing Maize Precision Seed-metering Device

At present,the sowing precision of the existing mechanical precision seed-metering device is not good enough to adapt to high speed operation.The vacuum precision seed-metering device has some drawbacks in sowing un-spherical seeds such as maize,it also has problems of complex structure and large power consumption.Both of these seed-metering devices are difficult to meet the actual production needs.Accordingly,developing one kind of seed-metering device with simple structures and high-speed precision seeding has become an important project.The first generation of inside-filling air-blowing seed-metering device was researched and developed based on the good filling performance of mechanical inside-filling seed-metering device.The single rate of inside-filling air-blowing seed-metering device was achieved by using air-blowing seed-metering device to clean seeds at high speed of airflow and pneumatic seed metering device to keep seeds with differential pressure.To ensure the single rate when the cleaning process was finished,the inside-filling air-blowing seed-metering device relies on the combined gas nozzles to make the single seed in the hole stability.The seeding plate with half structure was used to achieve well investment under seed's gravity.Simultaneously,the mechanical structure was applied to protect seeds from vibration in the field,and the seed-metering device has high reliability.According to the present situation of the sowing effect of first generation inside-filling air-blowing seed-metering device for flat seeds is better than circles,the main work of this paper is to further optimize the structure and working performance of the seed-metering device.To break the conventional method used in the research and development process of seed-metering device,such as drawing design,prototype manufacturing,test research,data collection and improved design,and then repeat testing,improving and making finished products.A non-spherical cohesive particle model that accords with the shape characteristics of maize seeds is established with the help of simulation software Engineering discrete element method EDEM.The mechanical properties of maize cohesive particles are studied.The influence of particle radius,bonding radius and contact radius on bonding force is analyzed,and the optimum coupling simulation parameters of maize bonding particles are determined.The simulation models of CFD field and particle field in inside-filling air-blowing seed-metering device were built respectively.Gas-solid bidirectional coupling simulation of inside-filling air-blowing seed-metering device is carried out based on DEM-CFD.First,the influence of the installation position of gas nozzle on the working performance of seed-metering device was analyzed.The relationship between filling limiting velocity and qualified rate of the seed-metering device under different installation positions of gas nozzle was explored,and the best structure and installation position of gas nozzle were determined.Mechanical models of seeds during cleaning and pressing process were established.The influencing factors of cleaning and pressing performance of seed-metering device were evaluated.The drag force and differential pressure of evaluation indicators were extracted and analyzed based on DEM-CFD coupling analysis method when different structures of seeding plates were used.A new theoretical method and train of thought was supplied for the study of precision seed-metering mechanism in this paper.On the basis of the above research,the different structures of gas nozzles and seeding plates were processed and tested on the bench,and the optimal structure and working parameters were selected for field test.By repeatedly optimizing and simulation analysis,the installation position of gas nozzle is determined to be in the middle position and the best structure of seeding plate is plate C.Based on cleaning and pressing performance analysis of different seeding plates,the drag force and pressing force in the hole of plate C were both larger than the other three.And due to the volume of seed filling in the holes was increased compared with other plates,the effect of plate C sowing circle and mixed seed were both better through coupling simulation.The full factorial experiments were conducted on the seed disc with block slot with forward speed of 4-12 km/h and working pressure of 4 to 8 kPa,experimental results show that the qualified rate increases gradually with the increase of forward speed and working pressure,the qualified rate is close to 96%and leakage rate is less than 1%when working pressure is above 6 kPa.Field experiments of plate C were carried out when the installation position of gas nozzle was middle based on the bench test.The results showed that the qualified rate of seed-metering device could reach over 90%under all forward speeds.