| With the maturity of soybean harvesting mechanization in China,the demand for on-line detection of soybean harvest cleaning loss is also increasing.At present,most combine harvesters in China detect cleaning loss by installing cleaning loss material detection sensors.Because the distribution law of cleaning loss materials is still in the initial stage,and the installation position and angle of cleaning loss material detection sensors are not clear,the detection of cleaning loss is inaccurate,Therefore,it is necessary to study the distribution law of cleaning loss materials.In this thesis,aiming at the inaccurate detection of cleaning loss of soybean combine harvester,a test-bed for the distribution law of cleaning loss materials with adjustable cleaning operation parameters of typhoon screen cleaning device is designed.The distribution law of cleaning loss materials under different cleaning parameters and the composition of cleaning throw are analyzed,and the bench test is carried out,It provides data reference for the installation position and angle of grain cleaning loss sensor of grain combine harvester.The main research contents include:(1)Experimental study on the physical characteristics of the ejecta behind the cleaning screen: using PS-20 material suspension velocity test-bed,the floating velocity tests of four kinds of ejecta components of soybean grain,pod,light residue,short stem(0 ～ 60mm)and long stem(60 ～ 120mm)were carried out,and the floating velocities were 11.2 ～ 16.8m/s,5.0 ～ 6.0m/s,7.2 ～ 13.0m/s and 8.4 ～ 14.2m/s respectively;The average moisture content of soybean grain and soybean stem were6.1% and 10.3% respectively.(2)Structural design of multi parameter adjustable cleaning loss distribution detection test-bed: in order to study the composition of cleaning discharged materials,the distribution law of cleaning loss grains at the rear of the tail screen of the cleaning screen,and determine the best installation position of grain loss monitoring sensor on the grain combine harvester.A typhoon screen cleaning device with adjustable cleaning operation parameters is designed to detect the distribution law of cleaning loss materials.The device comprises a conveying device,a cleaning device,a cover,a material receiving device,a power input device,a regulating device and other devices;The device can realize the real-time adjustment of test parameters(fan speed,vibrating screen crank speed,fish scale screen opening and tail screen height),which lays an equipment foundation for the distribution law of cleaning lost materials under different cleaning parameters,the composition of cleaning ejecta and bench test.(3)Composition analysis of the ejecta at the rear of the cleaning screen: the ejecta at the rear of the cleaning screen is mainly composed of full grains,pods,miscellaneous residues,short stems(0 ～ 60mm),long stems(60 ～ 120mm),etc.Among them,the long and short stalks fall to the place 0 ～ 100 mm away from the discharge outlet,accounting for 11.7% of the total mass ratio of thrown objects;The light impurities and pods blown 300 mm away from the outlet and behind are classified as impurities,accounting for 84% of the total mass of the ejecta;The loss of soybean seeds from cleaning accounts for only 5% of the total mass of ejecta,which is mainly distributed at 0 ～ 260 mm away from the discharge outlet.(4)Single factor test analysis: four factors including the opening of air door,the opening of fish scale screen,the frequency of vibrating screen and the height of tail screen are selected for single factor test.Most of the lost grains are distributed at a vertical distance of 0 ～ 260 mm from the cleaning discharge outlet,and tend to decrease in the future,and the lost grains are distributed at both sides,that is,at a vertical distance of 0 ～ 130 mm from both ends of the cleaning discharge outlet,and decrease in the middle,That is,the loss of grains is most concentrated at 0 ～ 130 mm on both sides 0 ～ 260 mm after the cleaning discharge outlet.The distribution probability model of grain mass ratio along the x-axis and the distribution probability model of grain mass ratio along the y-axis were determined.Each parameter had no significant effect on grain quality loss.The optimal range of cleaning detection parameters for the optimal operation state of soybean cleaning test-bed and the most concentrated distribution of cleaning loss grains is determined: the fan speed is1400r/min ～ 1600r/min,the frequency of vibrating screen is 320r/min ～ 480r/min,the opening of fish scale screen is 20 °～ 30 °,and the height of tail screen is 15 mm ～25mm.When the rotating speed of the fan is 1500r/min,the frequency of the vibrating screen is 400r/min,the opening degree of the scale screen is 25 °,and the height of the tail screen is 20 mm,the grain loss mass ratio is the lowest under this operating parameter.The distribution of the cleaning loss grain is shifted backward away from the throwing outlet when it is higher than this operating parameter,and the distribution of the cleaning loss grain is shifted forward close to the throwing outlet when it is lower than this operating parameter,and the rotating speed of the fan,the frequency of the vibrating screen,the opening degree of the scale screen The effect of tail screen height on the distribution of grain cleaning loss decreased in turn.(5)Multi factor test analysis: using the box Behnken central composite test design method,the effects of the main operating parameters of soybean cleaning device on the total weight ratio of lost grains,the distribution of peak grain loss and the distribution of peak grain loss were analyzed and studied,and the mathematical model was established.The factors that have great influence on the total mass ratio of lost grains are: the speed of damper,the frequency of vibrating screen and the opening of fish scale screen;The factors that have great influence on the distribution of peak grain loss are: damper speed,vibrating screen frequency,fish scale screen opening;The factors that have great influence on the distribution of grain peak value of shaft loss are damper speed,vibrating screen frequency,fish scale screen opening and tail screen height.Using Design expert 10.0.The quadratic regression equation was optimized and solved for the total mass ratio of lost grains,the distribution of peak grain quantity of shaft loss and the distribution of peak grain quantity of shaft loss.The detection parameters of the optimal cleaning loss distribution were as follows: the rotating speed of fan was 1549r/min,the frequency of vibrating screen was 338 r / min,the opening of fish scale screen was 27 °,and the height of tail screen was 17 mm.At this time,the total weight ratio of grain loss,the distribution of peak grain loss and peak grain loss were 0.26%,0.08% and 0.05% respectively.The experimental results show that the average percentages of the total weight ratio of grain loss,the distribution of peak grain loss and the distribution of peak grain loss are 0.252%,0.07% and 0.04% respectively,and the errors between the optimal value and the experimental value are 1%,0.8% and 0.9%,which are lower than the national standard.(6)High speed photography verification experiment: the high-speed camera is connected with the computer and placed on one side of the ejection port of the test-bed through PCC2.8 the software turns on the high-speed camera and turns on capture recording.During the experiment,the threshing mixture was put into the test-bed manually.After cleaning,the high-speed camera was used to capture and record the movement process of the cleaning loss material being discharged out of the machine.The PCC software was used to analyze the throwing movement law of the cleaning loss grain.Its movement trajectory was similar to a parabola,and the angle of the receiving box was about 45 ° to the horizontal plane.The soybean was discharged out of the machine and rotated at a high speed,with an average speed of14.35 m / s. |
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