| Potato is the fourth largest food crop in China, has the characteristics of grain and vegetables. China is the largest country of potato growing area and production. In recent years, the technology application of potato detoxication and rapid propagation has solved the potato quality degradation and accelerated the industrial development. Disease-free mini-tuber has gradually replaced the conventional slicing potato to become field planting potato seed. So as to, potato production and commodity rates are increased significantly. Potato agronomic changes require promoting a complete study of the mechanization of sowing techniques. Therefore, this paper takes the disease-free mini-tuber as the investigation object to study a precision metering technology and device which is adapted to disease-free mini-tuber.Based on the current state and appliance of potato mechanical planting technology summarized, this paper has a comparative analysis of mechanical and pneumatic different types of metering devices, and develops a disease-free mini-tuber air-suction metering device. The disease-free mini-tuber air-suction metering device dynamics calculation, the gas chamber flow simulation and the metering device experimental study have been carried out.The major points are as follows:(1) Study the disease-free mini-tuber mechanical and physical properties, these parameters could be used as the basis of designing metering device. Three varieties of disease-free mini-tuber geometric physical and granular properties are focus tested; also the compression characteristics and shear properties are tested. The results show that compression yield load of different varieties of disease-free mini-tuber is significantly different; shear maximum hardness is not significantly different. Average of extrusion yield load is19.612N, and maximum hardness average is43.98N.(2) The disease-free mini-tuber chain-spoon and inner seed-filling mechanical styles metering devices are designed and experimental studied. There is a conclusion that mechanical metering principle is seriously injury to disease-free mini-tuber, not adaptive to mechanical and physical properties, and as a basis to determine the air-suction principle for the study target. Then, the overall design and the main parameters of seed plate holes and the air chamber structure of metering device are carried out. (3) Rely on the space three-dimensional natural coordinate system established, analysis the disease-free mini-tuber dynamics characteristics of the metering device working process, establish mathematical model between metering device key parameters with the pressure of hole rupture plane, and establish calculation model of the negative pressure area flow field rupture pressure and the gas pipeline flow using computational fluid dynamics method.(4) Simulate and analyze the gas chamber fluid flow of the metering device in different operating parameters through computational fluid dynamics simulation software ANSYS/CFX. The clearly detailed characteristics of the whole vacuum chamber fluid field can be obtained, the main factors of the impact of flow field pressure distribution can be fixed, which is the seed plate hole pattern. Compared with conical hole, the gas chamber pressure is evenly distributed at the cylindrical hole, and has large rupture pressure to adsorb disease-free mini-tuber, also the flow velocity and uniformity was significantly greater than conical hole.(5) Design and develop a metering device test bench and seed charge detecting system, also the air-suction metering device performance test is carried out. The influencing law of metering device structure and operational parameters on the test index are studied. The results show that the metering device speed and test angle and their interactions have significantly affected on eligible index and miss index. The eligible index first increases with the increase of metering device speed and then decreases, also increases with the increase of test angle. The highest eligible index can be obtained when metering device speed is40r/min and test angle is60°... |
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