| With the increase in demand of the notoginseng market,many places in Yunnan Province have been planted.By 2017,the planting area of notoginseng has exceeded 100 million mu.At present,the planting of notoginseng is mainly done by hand.,and the labor intensity is high,the sowing quality is not balanced.In order to realize high-quality and high-efficiency sowing in notoginseng,the implementation of mechanized sowing has become an urgent matter.Compared with the mechanical metering device,the air-blowing metering device is very important for notoginseng due to the large difference in the shape and size of the notoginseng seeds and the easy breakage of the seeds.Compared with the traditional mechanical seed metering device,the air-blowing precision seed-metering device can easily divide the seeds into single grain and realize the precision seeding of the seeds.Based on the literature review both at home and abroad,this paper designs an air-blowing notoginseng precision metering device.Theoretical calculations and numerical simulations are performed on key structures and operating parameters,and optimized the structure and working parameters.At the same time,based on the planting requirements of notoginseng,made the improvement on the basis of the single-row seed meter design,and a 3-row air-blow metering device was developed.The optimum operating parameter range of the metering device was verified through experiments,so that to meet the sowing requiements of notoginseng.The main contents of this paper are as follows:(1)The air blowing seed metering scheme is determined,based on the agricultural requirements of notoginseng and the structure and working principle of the air blowing type metering device.This metering device is mainly based on the principle of flow separation,and the pressure is formed when the gas flow through holes due to seed in the hole.In order to removal and arrange the seeds,the air flow can also assist the filling and improve seed filling performance.A mathematical model of the clearing process was established and the minimum range of wind pressure for clearing was determined.(2)The flow field characteristics of the two types of air nozzles were compared and analyzed by FLUENT software.It was found that the grid-shaped gas outlet was better than the circular gas outlet.Based on the previous theoretical analysis,simulation simulations were used to determine the range of wind pressure needed to achieve single grain fine sowing,which provided a reference for subsequent selection of experimental wind pressure.Aiming at the structural parameters of the seed hole,a test plan was developed to find the optimal structural parameters.The working process of the metering device was simulated by EDEM-FLUENT coupling,and the flow field and seed particle movement in the air-blowing metering device were discussed.Based on theoretical analysis,the simulation experiment was conducted.The best structural parameters were determined.(3)The effects of seed height,operation speed and air pressure on qualified index,miss seeding index and replay index were studied to identify the range of variables based on the single factor test method.The order of primary and secondary factors that affect seed metering performance were determined as follow seed layer height,operation speed and seed cleaning pressure based on the orthogonal test of three factors and four levels.Design-Expert 8.061 software was used to analyze and test data and optimize the parameter combination.When the operation speed is 0.6m/s,the seed height is 90 mm,and the seed pressure is 0.5kPa,the qualified index of the grain spacing is 90.48,the miss seeding index is 4.24,and the replay index is 5.28.(4)In order to meet the planting requirements of Panax notoginseng,the structure of the single-row seed meter was improved,and a 3-row air-blowing metering device was designed.FLUENT software was used to analyze the position of 3-row air nozzle clearing,and the distribution of flow field in the clearing area under different air nozzle angles and different nozzle distances was compared and analyzed to obtain the best seed clearing effect.(5)Bench tests are performed on 3-row seed metering devices,nozzle angle,nozzle relative distance,and forward speed as influencing factors,qualified index,missing index,and multiple index as the objective indexes,and used quadratic rotation orthogonal combination test method.The regression model between each factor and experimental index was established to optimize the parameter range in addition to each factor,when the forward speed is 0.6m/s,the air nozzle angle is 18~24°,and the air nozzle relative distance is 38~42mm,the qualified index was greater than 91.6,the missing index was less than 4.1,and the multiple index was less than 4.3.By comparing the effect of notoginseng seed grading on the seed metering performance of the air blow metering device,it is concluded that the air blow metering device is not strict for the size and shape of seeds,and suitable for planting notoginseng seeds. |
