Numerical Simulation And Experimental Study On Maize Air-and-screen Cleaning Device

In China maize is an important food that is widely planted. Maize mainly harvest by stripper mode at the present stage. But the direct grain harvest pattern reduced the snap harvest process by this kind of maize harvester was gradually attended, it also has good prospects for development. The air-and-screen cleaning device is an important part of maize threshing harvester. The motion of maize mixture group in the cleaning device is complex. Its is most import in the whole combine harvester. To study the distraction of airflow in the cleaning device, to analysis the motion law of maize mixture, and explore the influence of machine running parameters on its cleaning performance, not only provides the cleaning principle basis for the air-and-screen cleaning device, but also for the optimization the operating parameters of the cleaning reference selection device.This article summarized the research situation of the maize harvester at home and abroad, analyst the development of cleaning device and its application situation, founding that currently there has no reports about that the the maize mixture cleaned by maize harvester. Therefore this article through surveying the physics features of maize mixture, according to the distribution of the airflow and the movement of maize mixture in the cleaning device, using the method of theoretical analysis, combined simulation and experiment method to study the movement condition of maize mixture, and the multi-factor experiment was conducted to study the effect of inlet airflow velocity, vibration frequency and mass of maize mixture feed to the cleaning performance of the cleaning device, the main research work was as follows:(1) The mass percent content of maize mixture of each component was obtained according to research and test research, and the physics features of maize mixture were measured, through the EDEM software to establish maize model, cob model and straw model.(2)Study the distribution of airflow and the motion of the maize mixture in the cleaning device based on CFD-DEM, the moving law of maize mixture as well as the increase of inlet airflow velocity also was obtained.(3)By cloth arrangement method to obtained the distribution of airflow in the cross section on the cleaning device, and through the MATLAB software to fit out the airflow velocity distribution, the results were consistent with simulation. Using high-speed camera video technology on Maize mixture group at the upper screen and at the front between the screen of the cleaning device, the distribution of maize mixture group was obtained which consistences with the simulation results.(4)In order to verify the movement of maize mixture equivalent to inspection the cleaning performance of the cleaning device. Measuring the cleaning rate and losing rate of the cleaning device, the test results show that the simulation of maize grain cleaning rate and losing rate in accordance with the simulation result.(5)In order to obtain the optimal parameter combination of cleaning device for cleaning maize mixture, taking losing rate of maize ans cleaning rate of maize as target. Designated chooses the inlet airflow velocity, the frequency of vibrating screen, the mass of maize mixture fed as factor, Using multi-factor experimental design, the Design-Expert 8.0.6 was used to process and optimization the test data, getting that the inlet airflow velocity had the most influence on the losing rate and cleaning rate of cleaning device, the influence of frequency of vibrating screen was stronger than the influence of mass of maize mixture fed.