| Precision seed-metering device is the key component to ensure the implementation of precision seeding and the metering performance is directly related to the quality of seeding. Mechanical seed-metering device has the advantages of simple structure, low cost and is widely used. But it also leads to damage to seeds and can not adapt to high speed operation. The commonly precision seed-metering device is pneumatic seed-metering device. The single seed is usually grabbed from seed chamber and discharged by the air pressure difference. Compared with the mechanical precision seeder, the pneumatic seed-metering device has the advantages of no damage to the seed. And it has good adaption to different seed size.The good versatility and high operating speed can also be achieved. A new type of side positive pressure maize precision seed-metering device was designed in this paper, its filling and metering principle was analyzed. Related experimental analysis was also done. Fluent software was applied to simulate the flow field of seed-metering device. Meanwhile, high-speed photography technology was used to analyze the filling process of seed-metering device. A new design ideas and methods for the metering was provided to ensure the precision seeding. The main research results are as follows:1、In order to study dynamic characteristics and analyze flow field of Zhengdan958seed, the characteristics of granular body was measured, including three shaft size of maize seeds,TKW(Thousand Kernel Weight), seed volume density, particle density and porosity2、Based on the analysis of the lateral positive pressure seed-metering mechanism, the basic structure parameters were designed.3、The uniform design method was applied to study the influencing factors of the side positive pressure seed-metering mechanism. Regression equations were established between the seeding quality index, the reseeding index, leakage seeding index and influencing factors. The factors’influences on the test index were verified according to the response surface generated by Design expert. Design scheme was optimized through the Design Expert. When fan pressure was1.0KPa, speed of planter plate was16r/min, filling hole size was10.5mm, the qualified index was94.61%, the replay index was2.54, leakage sowing index was7.55, which agreed well with the experimental results.4、LES (large eddy simulation) in FLUENT software was firstly used in carrying out numerical simulation of the positive pressure air chamber flow field in side positive pressure seed-metering device. According to the characteristics of the flow field in the seed-metering device, simulation analysis and contrast experiment for positive pressure flow field were performed under different working parameters. Selective analyses of were done to study the characteristics of flow field in seed filling area, seed clearing area and seed carrying area. Velocity field around the filling hole was studied in detail. Simulation analysis and experiment results showed that:seeding performance was better when the plate speed was lower than18r/min.5、Working process of side positive pressure metering device were analyzed by using a high-speed video camera technology. According to the results, the reasons of reseeding and leakage seeding were achieved. The results provided the method for improving metering device. |
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