Development Of CFD-DEM-based Wind Sorting Device For Wolfberry Picking Platform

Chinese wolfberry as a typical medicinal food functional characteristic woody plants,has a strong medicinal value,is the special economic crop of Ningxia.But the current harvesting method of Chinese wolfberry to manual harvesting,low production efficiency,labor intensity,seriously restrict the sustainable development of Chinese wolfberry industry.Therefore the use of mechanized harvesting equipment to complete the harvesting of Chinese wolfberry is very necessary,but there are many impurities in the fruit of Chinese wolfberry after the completion of mechanical harvesting,which seriously affects the subsequent drying,storage and other processing procedures.Therefore,it is important to develop efficient scavenging equipment to remove impurities from wolfberries after mechanical harvesting.In this paper,the fruit and leaves of Chinese wolfberry were used as the object of study,the discrete element boundary parameters of the leaves are obtained through discrete element simulation calibration and test,and then the motion of the leaves in the sorting chamber is investigated by coupled simulation based on computational fluid dynamics and discrete unit method.The main research contents of this paper are as follows:(1)Study of discrete element boundary parameters of Wolfberry fruit leaves.In this paper,the stacking angle and sliding tangent angle are used as the research phenomena,and the intrinsic parameters,some contact parameters,stacking angle and sliding tangent angle of the fruit leaf of wolfberry are obtained by reviewing the literature and physical tests.Secondly,using EDEMpy as a bridge,the discrete element simulation software EDEM was used for the virtual calibration of the boundary parameters of goji fruit leaves.In the calibration test,the relationship between water content and surface energy of wolfberry leaves was investigated,and the regression model of water content and surface energy of wolfberry was established."Hertz-Mindlin with Johnson-Kendall-Roberts" cohesive contact model in EDEM was selected,and the discrete element simulation parameters were calibrated for the fresh fruit and leaves of wolfberry after harvesting,and the collision recovery coefficient between wolfberry and wolfberry was obtained as 0.18,static friction coefficient as 0.506,and dynamic friction coefficient as 0.506.and 0.064 for kinetic friction;0.15,0.5 and 0.05 for the collision recovery coefficient between wolfberry and leaf;0.225,0.9 and 0.105 for the collision recovery coefficient between wolfberry and steel plate;0.12,0.8 and 0.1 for the collision recovery coefficient between leaf and leaf;the coefficient of collision recovery between leaf-plate is 0.31,the coefficient of static friction is 0.4,and the coefficient of dynamic friction is 0.15;the surface of wolfberry can be 0.048J/m2,and the surface of leaf can be 0.05J/m2.(2)Simulation and validation experimental study of the cleaning chamber of the wolfberry wind sorting device.This paper combines the boundary parameters of the discrete element calibration of wolfberry,and carries out the simulation test and verification of the cleaning chamber of wolfberry wind sorting device based on CFD-DEM coupling method.The results show that the flow velocity distribution in the cleaning chamber can meet the expected requirements based on the analysis of the flow field in the cleaning chamber,and the structural design of the cleaning chamber is reasonable.The accuracy of the previous calibration of the boundary parameters of wolfberry leaves was demonstrated by visualization of the simulation tests,and it was determined that the feeding rate and wind speed were the main factors affecting the cleaning rate and loss rate of wolfberry leaves,and that the cleaning rate of wolfberry leaves was higher and the loss rate was lower when the fan speed was about 2800 rpm(the inlet wind speed ranged from 5 m/s to 10 m/s)and the feeding rate was about 60 g/s.(3)The fruit and leaf of Chinese wolfberry wind sorting test bench validation test research.In this study,according to the simulation and validation test results of Chinese wolfberry wind sorting device,using the self-developed Chinese wolfberry fruit and leaf wind sorting test bench,using the cleaning rate and loss rate of Chinese wolfberry fruit and leaf after cleaning as evaluation index to design single-factor test,then according to the single-factor test change law,select the wind speed,feeding volume,feeding angle as zero level point to design multi-factor test,using Design-Expert software The regression model was established and ANOVA and response surface optimization analysis were performed to obtain the best combination of working parameters for the wind sorting of wolfberry leaves:feeding angle 37.16°,feeding volume 79.66 g/s and wind speed 7.02 m/s,which resulted in a cleaning rate of 98.36%and a loss rate of 1.77%.This paper is based on CFD-DEM for the development of the winnowing device of the wolfberry harvesting platform,the test results obtained can provide theoretical support and data support for the subsequent development of the wolfberry harvesting platform clearing device.