Design And Test Of Corn Flexible Threshing Device

As the first staple grain crop in China,corn has the largest planting area and production in China.Due to the restriction of planting system and variety,corn has a high moisture content at harvest in most parts of China.The corn grain harvesting by the traditional combined harvester is likely to cause the damage of the corn grain.Therefore,the method of segment harvesting is generally adopted.However,the segment harvesting is low efficiency and large grain loss.To solve the above problems,a flexible corn threshing device was designed based on the structural basis of the World DC60 wheeled combine harvester.The finite element strength analysis and the contact between threshing device and corn grain verify that the flexible threshing device can meet the strength requirement of the threshing process and improve the threshing effect.The flexible threshing device is processed and assembled on a prototype for field trials.The experimental results show that the flexible threshing device can thresh corn grain with moisture content of 29%-32%.The flexible threshing device has the advantages of high work efficiency,small harvest loss,and good versatility.The main contributions are as follows:(1)The basic physical and mechanical properties of Zhengdan 958 corn were determined and analyzed.The morphological dimensions,density,mass and moisture content of the corn were measured by corresponding measuring instruments,and the links between the data were analyzed.Through the texture analyzer,the corn stalk connection strength,the corn kernel crushing strength and the corn cob crushing strength were measured,and the differences and relations between the damage processes of the materials in different directions were analyzed.It provides the basis for the impact simulation between corn and threshing device,the determination of the structure size and working parameters of the flexible threshing device.(2)Theoretically analyze the feasibility of flexible threshing method and design a flexible threshing device.Based on the Hertz contact theory,the impact process between the flexible threshing device or the rigid threshing device and corn ear was comparatively analyzed.The flexible threshing device reduces the rate of grain breakage and trash content by reducing the maximum contact force on corn,and increases the rate of threshing of corn grain by increasing the impact time and area of action on corn grain.A flexible threshing device was designed based on the World DC60 wheeled combine harvester.The material and structure dimensions were determined.(3)Analysis the impact between the threshing device and corn ear,and the strength of flexible threshing device.The pre-processing software HyperMesh,solver LS-DYNA and post-processing software HyperView were used to analyze the impact between the flexible threshing device and the corn ear to compared with the rigid threshing device.The simulation results are consistent with the Hertz contact theory analysis results: the maximum pressure,contact area,stress and strain caused by the flexible threshing device on the corn ear are all smaller than those of the rigid threshing device,and the contact time is longer than that of the rigid threshing device.The ANSYS was used to apply a load to the designed flexible threshing device to verify that the designed flexible device meets the strength requirements of the threshing process.(4)Comparative analysis of field trials of flexible threshing device and rigid threshing device.The flexible threshing device was processed and assembled.Test prototypes were equipped with flexible threshing devices and rigid threshing devices for field comparison tests.Analysis of the sampling results showed that the grain breakage rate of the flexible threshing device and the rigid threshing device were 3.97% and 7.24%,respectively,and the under-threshing rate were 0.12% and 0.33%,respectively,and the impurity rate was 2.36% and 3.37%,respectively.For corn with a moisture content of 29%-32%,the flexible threshing device performs better than the rigid threshing device.(5)Optimize the operation parameters of the prototype equipped with flexible threshing device.The optimum operation parameters of the flexible threshing device are as follows: the flow-cutting drum speed is 350r/min,the front of clearance is 30 mm,the end of clearance is 15 mm,and the forward speed is 0.97m/s.The grain crushing rate was 2.47%,the under-threshing rate was 0.084%,and the impurity rate was 0.94%.The rotation speed of the inflowing roller has the greatest influence on the grain breaking rate and the impurity rate,and the forward speed has the greatest influence on the under-threshing rate.