Design And Experiment Of Mechanism Of Throwing Impurity In Cleaning Device Of Maize Grain Harvester

As the second largest grain crop,maize is widely planted,and its production value plays an irreplaceable role in the national economy in China.With the improvement of Agricultural Mechanization,the technology of direct harvesting of maize plays an important role in the development of Agricultural Mechanization in China.With the increases of maize yield year by year,in order to meet the requirements of high cleaning rate and low loss rate of maize in the cleaning device,most of the literatures rely on improving the movements or structures parameters of the plane reciprocating vibration screen in the air-screen cleaning device.The mechanism of throwing impurity,which is installed in the upper space of cleaning screen to make maize mixture disperse in the horizontal direction and layer in the vertical direction,is invented to meet requirements of the increasing feeding quantity.The CFD-DEM coupling method was used to simulate the delamination of maize mixture with the help of mechanism of throwing impurity in the vertical direction.Relying on the National Natural Science Foundation of China(51475090),Heilongjiang Science Foundation(E2017004),the National Key Research and Development Program(2018YFD0300103)and the Key Laboratory of Heilongjiang Province for Modern Agricultural Equipment in Northern Cold Areas,the main research work is as follows:(1)Analysis of movement characteristics of maize mixture in cleaning device with mechanis-m of throwing impurity.The kinematics model of maize mixture was established,and the effect of mechanism of throwing impurity on the displacement of maize mixture in horizontal direction was explored.Through the kinematics and dynamics research on the whole throwing process of maize mixture(the movement of maize mixture leaving tossing board before arriving at raking finger,the movement of maize mixture on raking finger,the movement of maize mixture thrown in the wind),the installation position of mechanism of throwing impurity and the shape of raking finger were determined.(2)The single-factor simulation tests are implemented to simulate the movements of maize trajectory with the help of mechanism of throwing impurity with CFD-DEM coupling method.The CFD-DEM coupling method is used to simulate single factor test.Based on the movement analysis of maize mixture on raking finger of mechanism of throwing impurity,the numbers of raking finger in circumferential direction,the rotation radii of raking finger,the spacing between fingers axially and the angular velocity of roll were selected as the experimental factors.In the horizontal direction,the farther the impurities are thrown,the greater the chances of maizes screening and the higher the cleaning rate of the mazies;the smaller the overlap displacement between the impurities and the maizes,the smaller the carrying effect of the impurities on the maizes and the lower the loss rate of the mazies.Therefore,the horizontal displacement of impurity threw and the overlaping displacement of maize mixture in the horizontal direction were taken as the performance indicators.The affecting ranges of parameters of each factor are determined by single factor simulation test.(3)In order to obtain the combination of optimum parameters of the throwing performance of mechanism of throwing impurity,the quadratic orthogonal rotational-combinational simulation test was designed.The test results were analyzed by response surface methodology.The numbers of raking finger in circumferential direction had the most significant effect on the horizontal displacement of impurity threw,followed by the angular velocity of roll,then the spacing between fingers axially,finally the rotation radii of raking finger and the numbers of raking finger in circumferential direction had the most significant effect on the overlapping displacement of maize mixture in the horizontal direction,followed by the spacing between fingers axially,then the angular velocity of roll,finally the rotation radii of raking finger.The optimized parameters of the mechanism of throwing impurity were the numbers of raking finger in circumferential direction 8,the rotation radii of raking finger of 80.2 mm,the spacing between fingers axially of 12.5 mm and the angular velocity of roll of 15.4 rad/s.(4)Based on the the shape of raking finger and the results of optimization parameters of simulation,mechanism of throwing impurity with the numbers of raking finger in circumferential direction of 8,the rotation radii of raking finger of 80.18 mm and the spacing between fingers axially of 12.44 mm was processed.The test bench of the air-screen cleaning device was improved,and mechanism of throwing impurity was installed in the corresponding position of the cleaning device.Bench test showed that under the condition of inlet velocities of 12.8 m/s and direction angle of the inlet of 25 degree,when the feed quantity of maize mixture at the entrance of cleaning device was 5 kg/s,the cleaning rate and the loss rate of maize without mechanism of throwing impurity in cleaning device were 97.08% and 2.26%,the cleaning rate and the loss rate of maize with mechanism of throwing impurity in cleaning device were 98.74% and 1.65% respectively.When the feed quantity of maize mixture at the entrance of cleaning device was 6~7 kg/s,the cleaning rate of maize with mechanism of throwing impurity in cleaning device can reach 97.91% and the loss rate of maize can reach 1.74%,which can meet the requirements of technical specification for quality evaluation of screening under the condition of large feed quantity.In this paper,a mechanism of throwing impurity is installed in the upper space of the vibrating screen of the air-screen cleaning device.The movement characteristics of maize mixture in the cleaning device with a mechanism of throwing impurity are analyzed.The influence of the numbers of raking finger in circumferential direction,the rotation radii of raking finger,the spacing between fingers axially and the angular velocity of roll on the horizontal displacement of impurity threw and the overlapping displacement of maize mixture in the horizontal direction,which provides a reference for the design of the auxiliary separation components in the air-screen cleaning device.