Experiment And Parameter Optimization Of Vertical Corn Threshing Device

Direct harvesting of corn kernels is the key to reducing harvest losses,reducing production costs,and improving the level of mechanization of corn harvesting in China.As the core technology of grain combine harvesters,threshing has an important impact on the operation quality and efficiency of the harvester.Threshing technology is mainly divided into tangential flow type and axial flow type according to the movement form of the ear in the threshing device,and the axial flow type is further divided into two types: horizontal and vertical axial flow type.When corn harvesting machines are operating in small plots such as hilly and mountainous areas in China,the tangential and transverse axial flow threshing devices are limited by the width of the machine body,while the longitudinal axial flow threshing device extends the drum without widening the machine body,increasing the threshing time.However,due to the reverse threshing of ears,the rate of grain breakage is high,Therefore,controlling the size of threshing device while ensuring threshing quality has guiding significance for improving the adaptability of threshing machinery.Aiming at this problem,this paper designs a new type of vertical corn threshing device,analyzes the threshing mechanism,and explores its threshing performance through bench tests.The main contents are as follows:(1)Research on the physical and mechanical properties of corn.Measure the size characteristics of corn ears and grains;Apply loading to different parts of grains with different moisture contents to test their compressive performance,and obtain the variation pattern of compressive strength with moisture content;Apply loads in different directions to grains with different moisture contents to test their threshing force with the grain handle,identify the direction of force and moisture content of the grains at the minimum threshing force,and provide data support for determining the structural parameters of the vertical axial flow threshing device.(2)Develop a vertical corn threshing test bench.Based on the self-designed vertical corn threshing device,the mechanism of vertical axial flow threshing was analyzed.The bow tooth was selected as the threshing element.Based on Hertz elastic contact mechanics theory,the contact mechanics model of corn grain and threshing element was established.The critical speed,maximum contact force and maximum deformation during grain crushing were explored.It was concluded that the diameter and bending radius of bow tooth would affect the impact strength of the grain,The structural parameters of the arch teeth have been determined.The structural parameters of key components such as the threshing drum,outer cylinder,and gap adjustment device have also been determined.(3)Conduct discrete element simulation analysis of the threshing device.Using the EDEM simulation software,the kinematics simulation of the corn ear threshing process in the threshing device under different threshing elements,different element diameters and different drum lengths was carried out,and the movement time,movement trajectory,collision times,collision contact force and other data of the ear in the threshing device were obtained.The bow tooth threshing element was selected,and the optimal structural parameters of the threshing element were determined,Provide reference for the optimization design of subsequent threshing devices through simulation.(4)Vertical corn threshing bench test and parameter optimization.Based on a vertical corn threshing test bench,a single factor experiment was conducted using corn ears with three moisture contents of 17.8%,21.1%,and 25.5%.The experimental factors selected were drum speed,threshing gap,feeding amount,and arch tooth bending radius.The impact of each factor on threshing performance was explored using grain crushing rate and non threshing rate as experimental indicators,and a single factor analysis of variance was conducted to obtain drum speed The factors such as threshing interval and feeding amount have a significant impact on the experimental indicators.The parameter optimization of the threshing gap of the vertical threshing device was carried out to reduce the uncleaned rate during operation of the vertical threshing device.