Research On High Net And Low Loss Cleaning Screen Of Corn Grain Harvester

Corn is one of the three main grain crops,which could be used as grains,economy crops and feed.Corn grain harvesting technology is a new developing technology rapidly in China.However,due to the high loss rate and impurity rate,it has a negative effect on the development and promotion of corn grain harvesting technology.In this paper,based on the analysis of the material properties,the performance of cleaning device was analyzed with different elastic screens using the CFD-DEM gas-solid coupling simulation.In addition,the optimal operating parameters were got.and the simulation results were verified by the cleaning test.The main contents of this paper are as follows:After the material properties of corn extractives were analyzed,and the multi-element particle model was constructed.Material samples were extracted from corn extractives,and the corn grain,corncob and corn stalk were determined as simulation particle model.The physical properties(geometric size,moisture content,density)and mechanical properties(Poisson’s ratio,static friction coefficient and collision recovery coefficient)of the material were measured,which could provide references for the parameter setting of simulation.Moreover,the modeling method was proposed for multi-element particle flow geometric characteristics.Based on the multi-element particle material flow and cleaning gas flow field,a gas-solid coupling modeling method was established.After the theory of multi-element solid particles was analyzed,the contact model was Hertz Mindlin(no-slip)model.According to the air flow field in cleaning room,the cleaning air flow was determined as an incompressible fluid,and the flow state was considered turbulent.The second-order upwind scheme was used in the discrete method,and the algorithm of SIMPLEC was used in iterative solution.Due to the energy exchange for multi-element solid particles and air flow field,the Euler coupling model was used between Fluent and EDEM software.The three-dimensional model was built to simulate the characteristics of cleaning screen.With SolidWorks software,the three-dimensional model of cleaning device was established,and the model was divided into tetrahedral unstructured grids using ICEM-CFD software.The airflow field and device motion parameters were set,and the multi-element particle model was established and verified.The rigid round hole screen was simulated,so the distribution rule of airflow field was got,the size of air pressure,velocity and turbulence were revealed,and the motion trace of materials was revealed in the screen.With the comparison of three screens,the results showed that the cleaning performance of elastic screen was better than that of rigid screen,and the performance of polyurea elastic screen was the best.Simulation Optimization of Operating Parameters of Elastic Cleaning Screen and Bench Verification.The single factor simulation test was carried out on the polyurea elastic screen.The results showed that it had great influence for the wind speed,amplitude and vibration frequency,and the wind angle had little influence on the cleaning effect.The simulation orthogonal test was conducted for cleaning performance evaluation.The wind speed,amplitude and vibration frequency were taken as test factors,and the loss rate and impurity rate were set as indicators.It was also revealed that the wind speed and amplitude all had significant influence on the loss rate,while the vibration frequency has little influence.The wind speed,vibration frequency and amplitude have a decreasing influence on the impurity rate in turn.The optimal combination of operating parameters: wind speed was 12 m/s,amplitude was 30 mm,and vibration frequency was 5 Hz.Under this parameter setting,the loss rate of corn grains was 1.16%,the impurity rate was 1.88%,and the comprehensive index of cleaning performance was 1.52%.According to the optimal combination of parameters,the cleaning bench was built.It was found that the relative error of corn loss rate was 4.20% between bench and simulation test,and the relative error of impurity rate was 3.45%.Therefore,the results of simulation optimization had high authenticity and reliability.