| China is a traditional agricultural country and corn thresher is widely used. Improvingthe corn thresher’s performance has great significance for ensuring the quality of corn grainand increasing farmers’incomeIn this paper, a collision style corn thresher is designed, and its performance is tested onthe bench. The threshing process is simulated and analyzed by self-developed softwarenamed AgriDEM which is based on discrete element method. The results of the simulationand the experiments are compared and analyzed. The design of the threshing roller isoptimized. The main work and results of this paper are as follows.(1)A collision style corn thresher is designed. The threshing rollers have threedifferent lengths. A generic intaglio is designed, which can be equipped with severaldifferent threshing rollers. Two observation windows are designed, and the windows made oforganic glass (Acrylic). When the thresher works, the threshing process can be observed inreal time from the axial and radial. A partition gate is designed, which divided the spacebelow the gravure into several grain collection ranges.(2)A bench test of the threshing process is carried out. The test factors include therotary speeds of threshing roller, the lengths of threshing roller, the corn varieties, the cornear feeding, and the corn moisture content. The performance indicators include the grainthreshed rate, the grain crushed rate, the axial distribution curve, and the threshing time.Conclusions are as follows.The grain threshed rate test results show that the threshing roller rotary speed ishigher, the higher the threshed rate, but when the threshing roller rotary speed reaches acertain value the threshed rate is stabilized. The lengths of threshing roller, the corn varieties,and the corn ear feeding have little effect on the grain threshed rate within a certain range.The corn moisture content has great influence on the threshed rate. The moisture content islower, the higher the threshed rate;The grain crushed rate test results show that the threshing roller rotary speed hasgreat influence on the crushed rate. The threshing roller rotary speed is higher, the higher thegrain crushed rate. The length of threshing roller has some influence on grain crushed rate,but the effect is not obvious. The grain crushed rates of two corn varieties have largedifferences. When the threshing roller rotary speed is344.9r/min, the grain crushed rate ofthe Xianyu335corn is higher by0.9percentage points than Baidan678. With the increase inthe corn ear feeding, the grain crushed rate has a tendency to increase. The corn ear feedingis lower, the lower the crushed rate. But on the whole, this trend is not obvious. The cornmoisture content has great influence on the crushed rate also. The crushed rate of the moisture content of10.47%is6%, which is higher by1.6percentage points than moisturecontent of14.85%;The axial distribution curve test results show that It has a less threshed kernelsdistribution axially in different rotary speed of the roller. There are a little different betweenthe slope of the axial distribution of those three different lengths off the threshing roller,which shows little relationship between the axial distribution curve and the length ofthreshing roller. When testing different varieties of corn ear, it shows that the threshedkernels distribution axially of the Xianyu335is higher than Baidan678at No.1and2locations of the rollers, indicating that just entered the thresher that time, the Xianyu335earsare easier threshed than Baidan678. The corn ear feeding have little effect on the axialdistribution curve within a certain range.The threshing time test results show that the roller has great influence on thethreshing time when the roller rotary speed is low, but when the threshing roller rotary speedreaches a certain value the threshing time is stabilized. The lengths of threshing roller arelonger, the longer the threshing time. The corn varieties and the corn moisture content havegreat influence on the threshing time.(3)The threshing process is simulated and analyzed by self-developed software.Those three-dimensional discrete element analysis models of Xianyu335ear and thresher areestablished. The results of the simulation and the experiments are compared and analyzed.Conclusions are as follows.The threshing roller rotary speed is higher, the higher the threshed rate of simulation.When the threshing roller rotary speeds are344.9r/min,462.6r/min,580.9r/min, and817.3r/min, the threshed rates between the bench test results and the simulation results arevery similar, and the maximum relative error is only0.93%, which shows that the simulationresults under different rotation speed of threshed rate with high reliability;The threshing roller rotary speed is higher, the higher the simulation crushed rate.When the threshing roller rotary speeds are107.4r/min, the simulation crushed rate is thelowest. As the rotary speed increase to817.3.3r/min, the grain crushed rate increase from2.18to5.54%, and this change is obvious. When the threshing roller rotary speeds are344.9r/min, and817.3r/min the simulation crushed rates between the bench test results and thesimulation results are very similar. When the threshing roller rotary speed is462.2r/min, thesimulation crushed rate is higher by0.87percentage points than experiment crushed rate.It has a less threshed kernels distribution axially in all rotary speed of the roller. Thechange of the axial distribution curve is obvious at the first two segments of the rollers. Butthe change becomes flattens at the behind three segments. Simulation curves andexperimental curves have some differences. The maximum error reach15.94%, but theoverall trend is similar.(4)The design of the threshing roller is optimized. The primary and secondary factorsof the threshing roller structure parameters affecting the threshing rate were roller diameter, spike tooth height and spike tooth pitch. And the optimal parameters from the simulationresults were70mm of the roller diameter,85mm of the spike tooth pitch and20mm of thespike tooth height. Change the threshing roller’s cylinder teeth into plate teeth, and thosethreshing process of two styles roller are simulated and analyzed. When the threshing rollerrotary speeds are225.3r/min, the threshed rates of plate teeth style reach98.72%, which ishigher by6.01percentage points than cylinder teeth style, and the crushed rate of plate teethstyle is1.67%, which is lower by0.95percentage points than cylinder teeth style. When thethreshing roller rotary speeds are650r/min, the threshed rates of plate teeth style reach100%,which is higher by0.78percentage points than cylinder teeth style, and the crushed rate ofplate teeth style is2.03%, which is lower by2.97percentage points than cylinder teeth style.So the performance of the plate teeth style is superior. |
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