| The high efficiency and cost-saving technology of direct harvesting of corn kernels is an inevitable trend for the development of mechanized corn harvesting.So far,the mechanized harvest of corn is still dominated by direct ear harvesting,and only the northeast and northwest regions have begun to apply the direct harvest technology of corn kernels in a small area.The direct harvesting and threshing device for corn has problems such as unclear threshing mechanism and poor working parameters,resulting in a higher rate of kernel damage and a lower rate of ear removal during the threshing process.The application of direct harvesting technology for corn is restricted by the moisture content of the kernels during harvest Especially serious.In order to further explore the threshing mechanism of corn ears and optimize the working parameters of the threshing device,a high efficiency was designed to solve the problems of high kernel damage rate and low ear removal rate caused by the unclear threshing mechanism and poor working parameters of the threshing device,Low-damage corn grain direct harvesting and threshing device,through simulation analysis and experimental research to verify the reliability and superiority of the equipment,to provide a reference for the research on corn grain direct harvesting technology in my country.The main research contents are as follows:(1)The material characteristics of corn ears with high moisture content were studied.The omni-directional measurement of the triaxial size of the ear was carried out,which provided data support for the establishment of the three-dimensional model of the ear;the compression and shear characteristics of the grain were tested,and the compression and shear characteristics of the grain were obtained as a function of the moisture content;The mechanical properties test of the stalk of the grain was carried out,and the change law of the mechanical properties of the stalk of the grain with the moisture content was obtained.(2)Developed a test bench for a vertical and axial flow corn grain direct harvesting and threshing device.Based on the longitudinal axial flow threshing form,the drum,concave screen and threshing element and other key components of the threshing device are theoretically analyzed and the working parameters are calculated;based on the finite element analysis method,the drum,concave screen and other components are modal analysis to obtain The eighth-order vibration shape cloud diagram and natural vibration frequency of the drum and the concave screen are used to verify the reliability of the drum and the concave screen;the dynamic balance analysis of the drum is carried out based on the dynamic analysis method,and the excellent dynamic balance performance of the drum is verified.(3)The discrete element simulation analysis of the threshing device was carried out.Based on the Hertz theory,the contact collision model between the ear and the threshing element was established,and the discrete element model of the ear was established using EDEM discrete element analysis software.The threshing process was simulated and analyzed.The effect of the change of the plate gap on the stress and movement state of the ears,it is finally determined that the performance of the combined threshing drum is better than that of the round-head nailtooth threshing drum.(4)The bench test of the corn grain direct harvest threshing device was carried out.Based on the evaluation index of the grain damage rate and the unremoved rate,the influence of the three factors of drum speed,concave plate gap and feeding amount on the performance of the threshing device was explored,and the best combination of working parameters was determined according to the results of orthogonal experiments: The drum speed is 410.330r/min,the recessed plate gap is 48.944 mm,and the feed rate is 9.18kg/s.The predicted best response value is: the kernel damage rate is 4.031%,and the unclean rate is 0.871%. |
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