Research On The Simulation Of Seeds “Boiling” Motion And Seeding Experiment Based On Vibration-pneumatic Coupling

With the development of super rice cultivation techniques in China,the area of super rice planting is continuously expanding,and higher requirements are also placed on the seedling device of super rice.To meet the agronomic demand for super rice sowing,to further promote the mechanization of super rice seedlings,to improve the precision and efficiency of super rice seeding,and reduce production costs,the research team has developed an air suction vibration plate type precision seeder using the principle of air suction vibration,which features a low seed damage rate,high seeding accuracy,and is suitable for spot sowing.By vibrating to stimulate the seeds to perform a boiling movement and increase the seed’s degree of dispersion,combined with the suction disk to achieve single-seed suction at a fixed location,it can quickly meet the high precision requirements of super rice seedling sowing.However,the high-intensity excitation of the seed movement through mechanical vibration tables increases the influence of environmental inclination angles,which leads to seed aggregation and difficult for the device to maintain stability under high-intensity vibration,which makes the seed can’t be evenly distributed,resulting in a decrease in seed absorption qualification rate and an increase in miss rate.To solve the above issues,this paper proposes a fluidized vibration method that couples vibration with pneumatic to reduce vibration intensity,and a fluidized vibration seed tray is designed to maintaining a degree of dispersion similar with under high-intensity vibration.The aim is to ensure the long-term stability of seed movement and a high seeding qualification rate.The main research work of this paper are as follows:(1)The analysis of the fluidization vibration process simulation of the seed.Through theoretical calculations,the critical fluidization airflow velocity super rice seed fluidization is 1.22m/s.Using UG and ICEM-CFD software to draw and grid partitioning of seed tray space in 50 mm × 50 mm × 70 mm model size.Analyzed the influence of uniform airflow field on seed motion by the coupling simulation with EDEM-Fluent.The arrangement of air pores in the perforated plate is 2mm in diameter and 6mm apart calculated by the method of stable pressure drop,and the airflow velocity in the air pores should be 13.2m/s at the critical fluidization velocity.Based on the scale of the perforated plate,the model is redrawn and used for coupling simulation in the verification of the fluidization effect under the critical fluidization velocity of 1.22m/s,and analyzed the ditch flow phenomenon in the simulation.Applying 10 Hz with 2mm vibrations and1.22m/s airflow velocity to the same model.The ditch flow phenomenon disappeared.Analyzed the discrete state of the fluidization vibration simulation result,and compare with the vibration simulation.Found that the seeds’ discrete state of 10 Hz and 2mm with1.6m/s airflow velocity is similar to the simulation of vibration with 12 Hz and 4mm.The vibration frequency decreased by 2Hz and the vibration amplitude decreased by 2mm,indicating that applying fluidization can reduce the vibration frequency and amplitude while remains the seed dispersion state.(2)The structural design of the fluidized vibration seed tray.The fluidized vibration seed tray has been designed,including the sidewall shell,the perforated plate with air holes on the surface,and an air pipe group for delivering airflow.The flow field model of the fluidized vibration seed tray is established by the UG software.Using Fluent software to simulate the flow field state,the dual-row intake method was determined to provide uniform airflow.Orthogonal and flow field simulation are conducted by using the average airflow velocity of the pores as the output variable and the number of intake pipes,pipe diameter,and inlet airflow velocity as influencing factors.The result shows that the suitable number of pipes is 4 and the pipe diameter is 18 mm,and the average airflow velocity of the air pores can reach 13.6m/s when the minimum inlet airflow velocity is 21.47m/s,which meets the requirements of fluidization design.The fluidized vibration seed tray is created with two single air chambers,each chamber is400mm×380mm×50mm in scale and has 4 pipes with a diameter of 18 mm.The exhaust performance of the seed tray has been verified,which is similar to the simulation results.(3)The bench test of fluidized vibration seed tray.Designed and installed the fluidized vibration seed tray test bench,using the seed suction pass rate,over rate,and miss rate in the sowing performance of the seeder as the evaluation indicators for seed suction.In the preliminary comparative experiment,the needle-shaped suction port is found more suitable for the seed suction under fluidized vibration.The single-factor experiment has conducted on the fluidized vibration seed tray to obtain the parameter range of five influencing factors: vibration frequency 8-12 Hz,amplitude 1-3mm,inlet airflow velocity 15-24m/s,seed suction height 1-4mm,and seed thickness 6-18 mm.The functional relationships between seed suction performance indicators and vibration frequency,amplitude,inlet airflow velocity,seed suction height,and seed thickness have been established by the orthogonal combination experiment.Using the parameter optimization function of Design Expert software to search for the optimal working parameters.Found the suitable seed suction conditions is vibration frequency 10.0Hz,amplitude 2.2mm,inlet airflow velocity 23.41m/s,seed suction heights 1.88 mm,and seed thickness should maintain between 6mm to 18 mm.Compared with the vibration of12 Hz and 4mm,the vibration frequency of the fluidized vibration table is reduced by2 Hz and the vibration amplitude is reduced by 1.8mm.Using the needle-shaped suction port on the sowing experiment,the sowing time allocation for 1s suction,2.8s carrying,and 1s metering is determined.The results of the continuous seeding experiment show that the average seeding pass rate is 96.26%,the average miss rate is 1.37%,and the seeding efficiency reached 474 trays each hour.The fluidized vibration seed tray can be used for the precision sowing of various crops,saving seeds for factory seedling cultivation,improving sowing quality and long-term stability of the device.The research results provide technical support for the development of precision sowing technology for crops.