Study Of Grain Vertical Air Separation Based On DEM-CFD Coupling

With the development of science and technology and the progress of the times,the grain processing industry is not only closely related to agriculture,but also to the machinery industry,especially the grain manufacturing,packaging,and retail industries.As the first process in the grain processing process,the quality of the impurity-removal work directly affects the value of the grain product,and the improvement of the work performance of the impurity-removal equipment will bring about the improvement of the grain processing quality.The vertical airflow separation device is a commonly used grain secondary cleaning device.Since the cleaning process involves a gas-solid two-phase flow field,it is difficult to describe its complicated working state by conventional methods.Computational fluid dynamics or distribution point measurement can only reflect the characteristics of airflow field,but cannot describe the change rule of material movement state under the influence of airflow and the change rule of airflow field distribution under the influence of materials.The DEM(discrete element method)-CFD(computational fluid dynamics)coupling method is a new technique to simulate the process of grain separation in the impurity-removal equipment.The technology simulates and calculates the fluid phase and the particle phase in different environments,and then transmits information through the coupling interface,so as to simultaneously describe the airflow field environment and particle movement behavior.In this paper,Solidworks,EDEM,FLUENT and other software were used as research tools,DEM-CFD coupling method was used as research method,simulated the separation process of grain-stalk mixed particle system in vertical airflow separation device,and explain the separation mechanism of grain in vertical airflow.In addition,using the control variable method,simulated the cleaning process under different working parameters.Studies have shown that at a low wind speed range(5,6,7,8 m/s),increasing the wind speed can improve the volume concentration of grains after the winnowing.When v=8m/s,the volume concentration of grains reaches 100%.At high wind speed range(11,12,13,14 m/s),when v=13m/s,grain loss occurs,and the increase of wind speed leads to a large loss rate.When v=6m/s,the initial volume fraction of grain-stalk mixed particles remains the same,and there are differences in airflow distribution in the wind channel between different feeding amounts.The smaller the amount of feeding,the higher the grain volume concentration and the higher the cleaning rate after the winnowing.On the premise of ensuring the bestimpurity-removal effect,the maximum grain quality that can be processed by the vertical airflow separator studied in this paper is 0.99 kg within 10 s.Finally,the test bench was successfully built and tested by designing parts,processing and manufacturing,and the simulation results under low wind speed range,high wind speed range and different feed rates were verified.The work done in this paper can promote the mechanization of removing impurities in the rice processing industry and provide a new idea and method for the research and development of the grain secondary cleaning device.