Design And Test Of Single Axial Flow Threshing Drum For Corn Grain Harvester

Corn is an important grain crop in China.Corn planting area is wide and the yield is high.Threshing is an important part of corn harvest,and the threshing process determines the quality and efficiency of the operation.The moisture content of corn was higher at harvest time,and the change gradient was larger with time,which affected the physical properties of corn at harvest time.During the threshing process,the material is rubbed and hit by the threshing drum and threshing parts.If the design of threshing drum and threshing part is not reasonable,the damage rate and stripping rate of corn will be affected and the economic loss will be large.Axial flow threshing technology is a new technology vigorously promoted in China.However,there are still some general technical problems such as unclear mechanism and bad parameters.Therefore,this paper carried out the physical property test of maize during harvest,the analysis of threshing mechanism of single axial flow threshing drum,the design and simulation of threshing drum,bench test and field verification test.The main research content is as follows:Material property test.The moisture content of maize decreased gradually with time.The decreasing speed shows the changing rule of slow and fast.The size of ears and grains of maize changed little with moisture content.The moisture content of maize was 24~28% during the harvest period,the compression resistance of maize was better.The moisture content is 26~30%,the shear characteristics are better.At harvest time,the resistance of corn seeds to compression decreased with the increase of moisture content under different placement modes.The ability to resist compression when seeds are laid flat is obviously better than that when they are laid vertically or laterally.The resistance to compression is about the same when the seeds are placed vertically and laterally.Analysis of threshing mechanism.Based on the structure of single axial flow threshing drum,the threshing process and mechanism of the drum were analyzed.The forms and causes of damage loss in different threshing processes are expounded.Based on Hertz contact theory,the contact model between ear and threshing drum was established,and the factors affecting the critical fracture speed of corn ear were analyzed.The contact model between grain and grain was established to analyze the factors affecting the maximum contact force and the contact deformation.Design single axial flow threshing drum.The improved design of single axial flow threshing drum was carried out.Increase the intermediate threshing section of mixed arrangement of threshing bar and threshing nail tooth interval.Determine the size parameters of the screw conveyor head,determine the length and diameter of the threshing drum.Design threshing bar and nail teeth,determine the size,arrangement and spacing of the threshing bar and nail teeth.The mode simulation analysis of single axial flow threshing drum shows that the drum does not produce resonance and the deformation is small.The reliability of the threshing drum is verified by modal analysis.Single axial flow threshing drum bench test and field validation test.Based on the threshing drum stand,the corn threshing stand test was carried out.The single factor experiment of maize threshing showed that the optimal parameter interval was: drum speed is 350~550 r/min,threshing clearance is 40~65 mm,feeding capacity is 6~11 kg/s.The orthogonal test is designed and carried out in the operation interval of the better parameter.It was found that the combination of optimal operation parameters of maize threshing rate,damage rate and comprehensive index.The regression models of threshing rate,damage rate and two-factor response surface were constructed were constructed from orthogonal test data.Field experiments show that the regression model of threshing is reliable.