| Straw returning is a method to directly apply or apply upon stacking and decomposition the straws(including wheat,maize,and rice straws)that should not be directly used as feed.The agricultural production is also an energy conversion process,and the crop growth is accompanied with unceasing energy consumption and replenishment,as well as the content adjustment of water,fertilizer,gas and heat in the soil.In particular,the straw is rich in fresh organic materials,which can be converted into organic matters and available nutrients when the straws are returned to the farmland and upon a certain period of decomposition.This not only improves the physical and chemical properties of soil,but also provides certain quantity of potassium and other nutrients.Straw returning accelerates agricultural water and cost saving,as well as production and efficiency increase,to which full attention shall be paid in environmental protection and agricultural sustainable development.Straw returning can be categorized into direct and indirect returning by the approach.Straw returning by shredding and scattering is one of the most significant approaches for direct straw returning,its working device shall be further researched and well matched with the existing combine harvesters used in China.This paper studies the straw shredding and scattering technology in terms of three links,namely,straw shredding,bran scattering,and straw shredding,and the corresponding working devices and the regulating mechanism for each part of device are designed.With respect to the key parts,fatigue analysis is made with ANSYS simulation software,and a manually and electrically adjustable horizontal double-regulating mechanism for spreading board is designed.Through bench test and field test,the feasibility and reliability of devices designed in the paper are verified.According to the analysis of test data,the actual working effects of straw shredding device and spreading board are studied.Main contents of this paper include:(1)straw returning approaches and the current research of domestic and overseas straw shredding and scattering technologies;(2)straw shredding device and its overall structure design,fatigue life analysis of key parts on moving knife roll,as well as the influence of moving and fixed knife clearance on the straw shredding effect;(3)bran scattering device and its overall structural design,and the methods to regulate the height of the scattering wheel to the ground;(4)spreading board for shredded straws and its overall structural design,the optimum arrangement mode of spreading board,and the research and design of corresponding regulation mechanism of the spreading board;(5)the actual working effect of the designed straw shredding device and shredded straw scattering device through bench test and field test.Main achievements of this paper:(1)the domestic and overseas straw shredding and scattering technologies and working devices are studied,the existing deficiencies in the supporting working devices in China,and the development trend of straw returning by scattering is summarized;(2)amoving and fixed knife combined straw shredding device is designed,manufactured in a trail and matched with the combine harvester,its working feasibility and stability is verified through ANSYS software simulation,bench test and field test,and the straw shredding yield is increased;(3)a bran dual-scattering wheel mechanism is designed,manufactured in a trial and matched with the working machines and tools,and the residual returning by scattering is realized on the perforated plate;(4)a spreading board for shredded straws is designed and manufactured in a trial and a manually and electrically adjustable horizontal double-regulating mechanism for spreading board is designed according to its adjustment mode,and through bench test and matching with the combine harvester,the working reliability of the device is verified,and the straw returning quality by scattering is improved. |
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