Design And Experiment On Flexible Threshing Device For Corn

Maize mechanized harvesting includes corn harvesting and grain harvesting.Among them,corn harvesting is used to complete the maize picking and peeling operations,and then the corn transporting,drying and threshing operations are also needed,which belongs to the initial stage of mechanized maize harvesting.Grain harvesting is a one-time process of harvesting,threshing and cleaning with corn harvester.This method has the characteristics of high efficiency and low loss,and is the inevitable trend of the development of corn harvester.Huang-Huai-Hai region is one of the main corn producing areas in China.In 2015, the corn planting area was 1.7577×10~8 hm~2,accounting for 46.1%of the corn planting area in China,and the total yield was 8.69×10~8t,accounting for 38.7%of the whole country.Spring corn matures in late July,summer corn matures in late September.The moisture content of corn grain is about 30%at harvest time.Therefore,in the process of grain harvesting,corn was liable to break or crack under the action of extrusion,impact and rubbing of threshing elements.The risk of infection with aflatoxin poses a great threat to the grain quality and food safety of corn.Therefore,reducing grain damage during corn threshing has become a problem restricting the development of corn grain harvesting in Huang-Huai-Hai region.In order to solve the problem that corn grains are easily damaged in threshing process,it is necessary to study the technology of flexible threshing under high moisture content in order to improve the existing problems in the process of corn grain harvesting in China.In this paper,a transverse axial flow corn flexible threshing device was designed,which combines flexible tooth and elastic short rasp bar to reduce the damage rate of corn grains on the premise of ensuring the un-threshed rate.The feasibility of the flexible threshing method was verified by theoretical analysis and discrete element simulation.Based on the bench test,the optimum combination of working parameters of the device was obtained,and the threshing performance of the device was verified.The device achieves the operation effect of reducing corn grain damage on the premise of guaranteeing the un-threshed rate.It shows that the device has certain potential for direct harvesting of corn,and provides a reference for the technology of corn grain harvesting in China.The main contents of this paper are as follows:(1)Compressibility tests of corn grains and ears were carried out,and the mechanical properties of corn grains and ears were obtained,which provided a basis for the design of key components of the transverse axial flow corn flexible threshing device.(2)A transverse axial flow corn flexible threshing device test bench has been designed independently.The test bench is mainly divided into conveying device and transverse axial flow corn flexible threshing device.The conveying device is used to transport corn ears.The transverse axial flow corn flexible threshing device uses flexible tooth and elastic short rasp bar to complete corn threshing operation.The threshing operation is assisted by accessories such as guide plate,concave and concave adjusting mechanism.The test bench provides important support for the optimization of the working parameters of the flexible threshing device.(3)Based on Hertz contact theory,a contact mechanics model of flexible tooth and corn ear was established.The theoretical analysis shows that flexible tooth has the potential to reduce grain damage.Based on rigid-flexible coupling theory,a collision mechanics model of elastic short rasp bar and corn ear was established,and the elastic short rasp bar was analyzed by mechanical analysis.The mechanical analysis shows that the elastic short rasp bar has the potential to reduce grain damage.(4)Based on image processing,the discrete element model of corn ear was established.The transverse axial flow corn flexible threshing device was simulated and analyzed by the discrete element simulation software.The contact force between the threshing element and the ear was analyzed.The results showed that the threshing device could reduce the grain damage during threshing.(5)The bench test of the designed transverse axial flow corn flexible threshing device was carried out.Through the key parameters test of the threshing device,the optimum combination of working parameters was determined:the feeding amount was 8 kg/s,the rotational speed of the cylinder was 450 r/min,and the clearance between the concave was40 mm.The rationality of the flexible threshing was verified.Under this condition,the breakage rate was 2.75%and the un-threshed rate was 0.59%.It provided a reference for corn flexible threshing and had a certain technical potential for corn grain harvesting.