Design And Experiment Of Double-layer Jitter Plates With Holes In Cleaning System Of Maize Grain

The air-and-screen cleaning device with high cleaning efficiency and high cleaning rate of grains is widely used in maize grain combine harvester with jitter plate.With the increase of per unit area yield of maize,working width and working speed of maize grain combine harvester,the feeding mass of the cleaning device is increased year by year.Operational efficiency of mechanized combined harvest are required higher and higher in modern agricultural large-scale production,the maize combine harvester is also developing in the direction of high efficiency and good performance under large-feeding mass maize mixture fed.In the actual production process,maize mixture would accumulate in the front of the vibrating screen when the cleaning device is dealing large-feeding mass maize mixture.To improve the efficiency of cleaning device under the condition of large feeding mass,many scholars studied the fan,structure of vibrating screen and other structures in the cleaning system,there are few reports about the double-layer jitter plates with holes in cleaning system.In the maize grain combine harvester with jitter plate,after threshed and separated by a threshing cylinder,maize mixture fall onto the jitter plate.Under the action of the jitter plate,maize mixture reache the vibrating screen.The CFD-DEM coupling method was used to simulate the movement of maize mixture under the action of jitter plates,this paper proposes and designs the double-layer jitter plates.This paper is based on the maize variety "demeiya 1".The shunt of jitter plates are realized and the ratio of the lower screen used is increased in the cleaning system with double-layer jitter plates.By measuring the vertical distance between the fan and the jitter plate,there is enough space to install the second layer of jitter plate,and the maize leached by the threshing drum has less stalks and will not be blocked at the double layer shaking plate.Through the optimization of the simulation parameters of the jitter plates,the best combination of structural parameters and working parameters of the double-layer jitter plates are determined.The main research is as follows:The kinematics model of maize mixture was established.Through the kinematics and dynamics research on the process of maize mixture after leaving jitter plates before arriving at vibrating screen,the installation position of double-layer jitter plates and vibrating screen were determined,the distribution and size of the sieve holes on the upper jitter plate were determined by referring to the round screen.The CFD-DEM coupling method is used to simulate the airflow in the cleaning system with double-layer jitter plates and the cleaning system with single-layer jitter plate.The results showed that a similar airflow distribution exists in different cleaning systems.In the cleaning system with double-layer jitter plates,the airflow velocity between the end of the upper jitter plate and the front of the vibrating screen is fast and it is beneficial for maize mixture to blow away.A single factor simulation experiment was carried out on the movement of maize mixture in the cleaning system with double-layer jitter plate.The angle of the jitter plates installed,the amplitude and frequency of the jitter plates are chosen as the experimental factors,the time of cleaning maize mixture of the cleaning device are chosen as the direct performance indexes.The cleaning rate and the loss rate of the maize grains are chosen as the indirect performance indexes.Through the single factor simulation test,the influence law of each test factor on the test index is determined,the influence of various factors on the shunt of maize mixture on the jitter plates are explored.Through the single-factor simulation test,the influencing range of each factor are determined:the angle of jitter plates installed is-11°～1°,the frequency of the jitter plates is 3.38～7.38 Hz,the amplitude of jitter plates is 33～48 mm.In order to obtain the best combination of structural parameters and working parameters of the double-layer jitter plates,the quadratic orthogonal rotational-combinational simulation test was designed.The response surface method was used to analyze the experiment results and the regression mathematical modes between factors and indexes were multi-objective optimized by using Design-Expert software.The order of the effect of each factor on the time of cleaning maize mixture of the cleaning device from strong to weak was frequency of the jitter plates,the amplitude of the jitter plates,the angle of the jitter plates installed;the order of the effect of ezch factor on the grain cleaning rate from strong to weak was:frequency of the jitter plates,the amplitude of the jitter plates,the angle of the jitter plates installed;the order of the effect on the grain loss rate from strong to weak:the angle of the jitter plates installed,the frequency of the jitter plates and amplitude of the jitter plates.The optimized parameters of cleaning system with double-layer jitter plates are as follows:the angle of the jitter plates installed is-3.9°,frequency of the jitter plates is 5.6 Hz,the amplitude is 44.8 mm,the time of cleaning maize mixture of the cleaning device is 6.74 s,the cleaning rate of maize grain is 98.36%and the loss rate of maize grain is 1.45%.The performance verification test was carried out indoor and the maize grains were photographed by high-speed camera.The shunt of maize mixture caused by jitter plates was observed.It could be seen from the verification test results:When the feeding mass of maize mixture is 7 kg/s,the cleaning rate and the loss rate of maize grains are 98.25%and 1.56%and the time of cleaning maize mixture of the cleaning device is 6.95 s in the cleaning system with double-layer jitter plates under the condition of airflow velocity of 12.8 m/s and its direction angle of 25° respectively.It is consistent with the simulation results.Compared with the cleaning system with single-layer jitter plate,the cleaning rate of maize grain was reduced by 1.72%,the loss rate of maize grian was reduced by 0.84%and the time of cleaning maize mixture of the cleaning device was shortened by 0.57 s.This paper provides a reference for the research of the cleaning technology of large feeding mass maize mixture.In this paper,the double-layer jitter plates with holes in the cleaning system is designed,and the movement characteristics of maize mixture is analyzed.The effect of the angle of the jitter plates installed,the amplitude and frequency of the jitter plates on grain cleaning rate and loss rate is investigated,which provided a reference for sloving maize mixture accumulate at the front of the vibrating screen at large feeding mass.