| Due to the irregular shape and large difference in size of large-grained flat seeds,the air-suction metering device has the problems of unstable filling performance and poor seeding effect when seeding flat seeds.Starting from the adsorption posture of flat seeds,this paper proposes to use air blowing disturbance and mechanical posture adjustment mechanism to jointly control the adsorption posture of flat seeds,and designs an air suction seed metering device for flat seeds based on air blowing disturbance.The watermelon and corn were selected as the representatives of flat seeds,and the material characteristics such as triaxial size,1000-grain weight,density and friction angle of seeds were measured.Through the pre-test of flat seed air-suction metering device,the influence of flat seed adsorption attitude on seeding performance was explored.An air-blowing seeding test platform was built,and high-speed cameras are used to study and analyze the boiling intensity,motion trajectory,and posture changes of seeds,clarifying that the main factors affecting the stability of flat seed suspension posture were the speed and angle of the blowing seeding airflow.Based on fluid mechanics and rigid body dynamics theory,the motion equations of flat seeds under the combined action of air disturbance sowing flow and negative pressure adsorption flow,as well as the dynamic model of seed adsorption moment.The velocity and pressure distribution of the composite flow field around the suction hole in the seed chamber were simulated and analyzed by Fluent software,and the optimal aerodynamic structure parameters were obtained.A physical prototype of the air-blowing seeding suction-type seeder was manufactured and compared with a traditional seeder,showing that air-blowing seeding can improve the adsorption posture of seeds,significantly enhance the seeding performance of flat seeds,but there is still room for improvement in high-speed adhesion performance.To further optimize the adsorption posture of flat seeds,a tilted convex platform-type posture control structure was designed above the suction hole,and the posture control process of the tilted convex platform was theoretically analyzed and designed.Discrete element simulation comparison experiments of three types of seeding discs showed that the tilted convex platform has strong disturbance ability on the population,increases the degree of population dispersion,and enhances the intensity of seed posture changes.Simulation analysis clarified the principle of posture control of seeds by the tilted convex platform,increasing the parallel adhesion probability between the flat surface of the seed and the suction hole surface.A physical prototype was manufactured and indoor bench and field tests were conducted to verify that the tilted convex platform posture control structure can effectively adjust the adsorption posture of flat seeds,improve adhesion stability and seeding performance.A combined seeding system was designed by integrating air-blowing seeding and tilted convex platform design,and the adsorption posture was coupled and controlled by aerodynamic and mechanical means.A three-factor three-level orthogonal combination test plan was designed to conduct seeding performance tests,and variance analysis of the test results showed that the operating speed,airflow velocity,and negative pressure significantly affected the qualified rate and missing rate,and there were interactive effects between factors.Regression equations were established there were interactive effects between factors.Regression equations were established was used to comprehensively optimize the regression equation to obtain the optimal working parameter: forward speed of 9.71km/h,airflow velocity of 5.14m/s,and negative pressure of 3.21 k Pa,with qualified rate of 97.99% and missing rate of 0.67%.This paper controls the adsorption posture of flat seeds through the coupling of air and mechanical forces,improve the adsorption performance of air suction seeder,solves the technical problem of high-speed precision seeding of flat seeds,and provides new ideas,structures,and theoretical references for researchers at home and abroad to carry out precision seeding technology research. |
